JPH11120608A - Optical head device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head device capable of surely removing the offset component included in a track error signal. SOLUTION: A photodetector 23 for detecting an off-track signal applied to this optical head device has four photodetecting regions 23a to 23d which detect the off-track signal and are arranged apart from each other. The region irradiated with the light of the high intensity part where all of the zero order diffracted light, first order diffracted light and minus first order diffracted light of the reflected light reflected from an optical disk between these four photodetecting regions is provided with a central photodetecting region consisting of the fifth to eighth photodetecting regions 23e to 23h to remove the offset component included in the off-track signal. As a result, the influence of the offset component included in the off-track signal, i.e., lens shift, on the track error signal is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical head device for recording information on an optical disk as a recording medium and reproducing information from the optical disk.

[0002]

2. Description of the Related Art An optical disk device includes an optical head device having an objective lens for irradiating a recording surface of an optical disk as a recording medium with a light beam having a cross-sectional beam diameter set to a predetermined size. By irradiating the beam, reflected light corresponding to the information recorded on the optical disk is taken out to reproduce the information.

The above-described optical head device has a semiconductor laser device (hereinafter simply referred to as a laser device) as a light source for generating a light beam and a light beam radiated from the laser device on a recording surface of an optical disk as a recording medium. An objective lens for converging and extracting a reflected light beam reflected by the recording surface, a photodetector for photoelectrically converting the reflected light beam extracted by the objective lens and outputting a reproduction signal corresponding to information recorded on the optical disc; Each element is formed by a plurality of optical members or the like constituting an optical path of a light beam.

In the optical head device, an objective lens is mounted on an actuator (movable part) to enable high-speed access, and a laser element, a photodetector, and an optical member constituting an optical path are separated from the actuator. An example of disposing them in a fixed unit (fixed portion) is widely used.

There are various methods for recording information on an optical disk, for example, a pit represented by a music CD. This is such that crater-shaped pits having a predetermined width, depth, and several lengths are formed in advance in a row in the circumferential direction of the optical disk.

In order to always match the center of the light spot focused by the objective lens with the center of the pit row,
The objective lens is moved in the radial direction of the optical disk by the well-known tracking control.

In this case, the amount by which the objective lens should be moved, that is, the tracking control amount, is set based on, for example, a track error signal obtained by using a phase difference method. The light sensing unit applied to the phase difference method has a photodetector divided equally into two rows and two columns by a dividing line along the radial direction and a dividing line along the tangential direction. ing. In this phase difference method, a light beam reflected / diffracted by a groove is received by a photodetector divided into two rows and two columns and is photoelectrically converted, and photoelectrically converted by photodetectors at diagonal positions to each other. In this method, two sets of diagonal sum signals of the obtained signals are generated, the phase difference between the two signals is obtained, and this phase difference is used as a track error amount. The details of the phase difference method are described in, for example, US Pat. No. 4,520,469.

[0008]

However, when a track error signal is obtained by using the above-described phase difference method, it is as if the tracking error occurs even though no tracking error has occurred due to the offset component of the track error signal. There is a problem that a track shift signal such as a shift of the track is output.

That is, when it is necessary to read information at another radial position on the optical disk or to record new information at another radial position, the actuator in which the objective lens is mounted is driven in the radial direction. Further, by appropriately combining and controlling the displacement of the objective lens in the tracking direction, the focused spot is moved at a high speed from the current radial position to the target radial position.

When such control is performed, the light beam reflected and diffracted by the groove of the optical disk is shifted with respect to the dividing line along the radial direction of the photodetector due to the shift of the center of the objective lens, that is, the lens shift. The light enters the respective light receiving portions in an asymmetric positional relationship. Then, a phase difference occurs between two diagonal sum signals obtained by photoelectrically converting the light beam incident on the light receiving unit.

This is because the phase difference obtained from the photodetector does not become 0 even though the converging spot is located at the center of the track to be traced. As a result, the tracking error signal contains an offset component. Occurs.

Further, the occurrence of an offset component in such a tracking error signal brings about a disadvantage that the instability of tracking control is promoted.

Since the above-described lens shift is caused by moving the actuator at a high speed in the radial direction of the optical disk, the lens shift is substantially eliminated from the viewpoint of increasing the speed of reading or writing information. It is difficult. For this reason, there is a problem that the offset component contained in the track shift signal must be reliably removed.

An object of the present invention is to provide an optical head device capable of reliably removing an offset component contained in a track shift signal and obtaining a stable tracking characteristic.

[0015]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above-mentioned problems. According to the first aspect, a light source for emitting a light beam and a light beam emitted from the light source are recorded on a recording medium. A light collecting means for condensing light on the recording surface of the recording medium, and a photoelectric conversion means for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion means is When the condensed spot obtained by being converged by the condensing unit moves in the radial direction of the recording medium, the reflected light beam reflected by the recording medium on the condensing spot is projected onto the photoelectric conversion unit and moves. A region that does not receive a light beam positioned on both sides of a first division line defined in a direction substantially perpendicular to the direction in which the reflected light beam is perpendicular to the first division line. Bi A dead area formed in a rectangular shape shorter than the beam diameter and having a length in a direction parallel to the first division line longer than the beam diameter of the reflected light beam, and located outside the dead area; A dividing line, and a second dividing line that is substantially orthogonal to the first dividing line and substantially equally divides the reflected light beam, and receives the reflected light beams that are substantially equally divided and protrude from the insensitive region. And four light receiving areas, and among the signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, of the signals output from the areas located at diagonal positions to each other. A first and a second diagonal sum signal as two sets of sum signals are generated, and a phase difference signal generated by detecting a phase difference between the first and second diagonal sum signals is generated. The center of a pit row formed in advance on the recording surface of the recording medium and the center An optical head device which is characterized in that the track error signal used for tracking control for moving the focusing means in order to match the center of the light beam passing through the optical means in a direction transverse row of pits is provided.

According to the second aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the condensing unit is disposed in a radial direction of the recording medium. When the recording medium moves, the recording medium is positioned on both sides of a first division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensed spot is projected onto the photoelectric conversion means and moves. A region in which the reflected light beam is not received, wherein a length in a direction orthogonal to the first dividing line is shorter than a beam diameter of the reflected light beam, and a length in a direction parallel to the first dividing line is the reflected light beam. beam A dead area formed in a rectangular shape longer than the beam diameter, and located outside of the dead area, the first division line, and the reflection light beam are substantially equally divided perpendicularly to the first division line. First to fourth light receiving areas for receiving the reflected light beam that is substantially equally divided by the second dividing line and protruding from the insensitive area, and the reflected light beam incident on the first to fourth light receiving areas Generating a first and a second diagonal sum signal, which are two sets of sum signals of signals output from regions located at diagonal positions to each other, among the signals obtained by photoelectrically converting When the center of the pit row formed in advance on the recording surface of the optical disc coincides with the center of the light beam that has passed through the condensing means, the first
The gain of at least one of the first diagonal sum signal and the second diagonal sum signal is adjusted so that the phase difference between the diagonal sum signal and the second diagonal sum signal matches, and The phase difference signal generated by detecting the phase difference between the first diagonal sum signal and the second diagonal sum signal is transmitted to the center of a pit row formed in advance on the recording surface of the recording medium and the condensing means. An optical head device is provided, wherein the optical head device is a track error signal used for tracking control for moving the condensing means in a direction crossing a pit row in order to make the centers of the passed light beams coincide.

According to the third aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium. A photoelectric conversion means for converting the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion means has a condensed spot obtained by condensing by the condensing means with a radius of the recording medium. When the recording medium moves in the direction, the reflected light beam reflected by the recording medium on the condensed spot is projected on the photoelectric conversion means and is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to the moving direction. A region which is located and does not receive the light beam including the intensity center of the 0th-order light component of the reflected light beam from the recording medium, and whose length in the direction orthogonal to the first dividing line is the reflected light beam. A dead area formed in a rectangular shape shorter than the beam diameter of the reflected light beam and having a length in a direction parallel to the first dividing line longer than the beam diameter of the reflected light beam; A light beam mainly composed of a part or all of a light beam in which only a zero-order light component and a first-order light component generated in a pit row radial direction in a light beam reflected from a medium overlap, and reflected on the recording medium. And 0 generated in the radial direction of the pit row of the diffracted light beam.
A light receiving region for receiving the reflected light beam that protrudes from the insensitive region, of the light beam mainly or partially or entirely of the light beam where only the first light component and the −1st order light component overlap, A first dividing line, and first to fourth light receiving regions that are substantially equally divided by a second dividing line substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam; Out of the signals obtained by photoelectrically converting the reflected light beam incident on the fourth to fourth light receiving areas, the first and second signals are sum signals of two sets of signals output from areas located at diagonal positions to each other. Generating a diagonal sum signal, detecting a phase difference between the first diagonal sum signal and the second diagonal sum signal, and forming a phase difference signal generated in advance on a recording surface of the recording medium. The center of the pit row is aligned with the center of the light beam that has passed through the focusing means. An optical head device which is characterized in that the track error signal used for tracking control for moving the focusing means in a direction transverse to the pit row in order is provided.

According to the fourth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting light on the recording surface of the recording medium A photoelectric conversion means for converting the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion means has a condensed spot obtained by condensing by the condensing means with a radius of the recording medium. When the recording medium moves in the direction, the reflected light beam reflected by the recording medium on the condensed spot is projected on the photoelectric conversion means and is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to the moving direction. A region which is located and does not receive the light beam including the intensity center of the 0th-order light component of the reflected light beam from the recording medium, and whose length in the direction orthogonal to the first dividing line is the reflected light beam. A dead area formed in a rectangular shape shorter than the beam diameter of the reflected light beam and having a length in a direction parallel to the first dividing line longer than the beam diameter of the reflected light beam; A light beam mainly composed of a part or all of a light beam in which only a zero-order light component and a first-order light component generated in a pit row radial direction in a light beam reflected from a medium overlap, and reflected on the recording medium. And 0 generated in the radial direction of the pit row of the diffracted light beam.
A light receiving region for receiving the reflected light beam that protrudes from the insensitive region, of the light beam mainly or partially or entirely of the light beam where only the first light component and the −1st order light component overlap, A first dividing line, and first to fourth light receiving regions that are substantially equally divided by a second dividing line substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam; Out of the signals obtained by photoelectrically converting the reflected light beam incident on the fourth to fourth light receiving areas, the first and second signals are sum signals of two sets of signals output from areas located at diagonal positions to each other. A two-diagonal sum signal is generated, and the first diagonal sum is generated when the center of a pit row formed in advance on the recording surface of the recording medium coincides with the center of a light beam that has passed through the condensing means. Signal so that the phase difference between the signal and the second diagonal sum signal matches. It is generated by adjusting the gain of at least one of the diagonal sum signal and the second diagonal sum signal, and detecting the phase difference between the gain-adjusted first diagonal sum signal and the second diagonal sum signal. In order to match the center of the pit array formed in advance on the recording surface of the recording medium with the center of the light beam that has passed through the converging unit, the phase difference signal is moved in the direction crossing the pit array. An optical head device is provided, which is a track error signal used for tracking control for moving.

According to the fifth aspect, a sum signal of the first diagonal sum signal and the second diagonal sum signal is generated, and the sum signal is used as an information signal. An optical head device as described above is provided.

According to the eighth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the condensing unit is disposed in a radial direction of the recording medium. When the recording medium moves, the recording medium is positioned on both sides of a first division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensed spot is projected onto the photoelectric conversion means and moves. And an area for receiving the light beam,
A length in a direction orthogonal to the first dividing line is shorter than a beam diameter of the reflected light beam, and a length in a direction parallel to the first dividing line is longer than the beam diameter of the reflected light beam. The central light receiving region, and the first light dividing line, which is located outside the central light receiving region, and is substantially equal to the second light dividing line substantially orthogonal to the first light dividing line and substantially equally dividing the reflected light beam. Divided, having first to fourth light receiving areas for receiving the reflected light beam protruding from the central light receiving area, at positions respectively adjacent to the first to fourth light receiving areas in the central light receiving area, Fifth to eighth light receiving regions substantially equally divided by the first dividing line and the second dividing line are formed, and are incident on the first to fourth light receiving regions and the fifth to eighth light receiving regions adjacent to each other. The reflected light bee To generate the first to fourth sum signals obtained by photoelectrically converting the two signals. Of the first to fourth sum signals, two sets of sum signals of sum signals output from regions located at diagonal positions to each other are generated. And generate first and second diagonal sum signals
A third signal, which is a sum signal of two sets of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beams incident on the fifth to eighth light receiving areas. And a first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the fourth diagonal sum signal. A second difference signal obtained by subtracting the fourth diagonal sum signal from the second diagonal sum signal including the signal, and detecting and generating a phase difference between the first difference signal and the second difference signal. In order to match the center of the pit array formed in advance on the recording surface of the recording medium with the center of the light beam that has passed through the converging unit, the phase difference signal is moved in the direction crossing the pit array. Light used as a track error signal used for tracking control for moving Head device is provided.

According to the ninth aspect, a light source that emits a light beam, a light condensing unit that condenses the light beam emitted from the light source on a recording surface of a recording medium, and a light source that reflects light from the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the condensing unit is disposed in a radial direction of the recording medium. When the recording medium moves, the recording medium is positioned on both sides of a first division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensed spot is projected onto the photoelectric conversion means and moves. And an area for receiving the light beam,
A length in a direction orthogonal to the first dividing line is shorter than a beam diameter of the reflected light beam, and a length in a direction parallel to the first dividing line is longer than the beam diameter of the reflected light beam. The central light receiving region, and the first light dividing line, which is located outside the central light receiving region, and is substantially equal to the second light dividing line substantially orthogonal to the first light dividing line and substantially equally dividing the reflected light beam. Divided, having first to fourth light receiving areas for receiving the reflected light beam protruding from the central light receiving area, at positions respectively adjacent to the first to fourth light receiving areas in the central light receiving area, Fifth to eighth light receiving regions substantially equally divided by the first dividing line and the second dividing line are formed, and are incident on the first to fourth light receiving regions and the fifth to eighth light receiving regions adjacent to each other. The reflected light bee To generate the first to fourth sum signals obtained by photoelectrically converting the two signals. Of the first to fourth sum signals, two sets of sum signals of sum signals output from regions located at diagonal positions to each other are generated. And generate first and second diagonal sum signals
A third signal, which is a sum signal of two sets of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beams incident on the fifth to eighth light receiving areas. And a fourth diagonal sum signal is generated, and when the center of the pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the light condensing means, the third and fourth diagonal sum signals are generated. The gain of at least one of the third and fourth diagonal sum signals is adjusted so that the phase difference of the fourth diagonal sum signal matches, and the gain of the third diagonal sum signal including the third diagonal sum signal is adjusted. The first difference signal obtained by subtracting the third diagonal sum signal from the one diagonal sum signal, and the fourth diagonal sum signal from the second diagonal sum signal including the gain-adjusted fourth diagonal sum signal. And a second difference signal from which the phase difference between the first difference signal and the second difference signal is calculated. The focusing means is used to match the center of a pit row formed in advance on the recording surface of the recording medium with the center of the light beam passing through the focusing means. An optical head device is provided, which is a track error signal used for tracking control for moving the pit row in a direction crossing the pit row.

According to the tenth aspect, a light source that emits a light beam, a light condensing unit that condenses the light beam emitted from the light source on a recording surface of a recording medium, and a light source that reflects light from the recording surface of the recording medium A photoelectric conversion unit that converts the diffracted reflected light beam into an electric signal, wherein the photoelectric conversion unit is configured such that a condensed spot obtained by being converged by the condensing unit is disposed in a radial direction of the recording medium. When the recording medium moves, the recording medium is positioned on both sides of a first division line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected from the condensed spot is projected onto the photoelectric conversion means and moves. An area in which the light beam is received, wherein a length in a direction perpendicular to the first dividing line is shorter than a beam diameter of the reflected light beam, and a length in a direction parallel to the first dividing line is A central light-receiving region formed in a rectangular shape longer than the beam diameter of the beam, and the first division line, which is located outside the central light-receiving region, and the reflected light beam substantially orthogonal to the first division line. First to fourth light receiving regions that receive the reflected light beam that is substantially equally divided by a second dividing line that divides substantially equally and that protrudes from the central light receiving region; and the first to fourth light receiving regions in the central light receiving region. 4 at the positions adjacent to the respective light receiving areas.
Fifth to eighth light receiving areas substantially equally divided by the dividing line and the second dividing line are formed, and the reflection incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other, respectively. First to fourth sum signals obtained by photoelectrically converting the light beam are generated. Of the first to fourth sum signals, two sets of sum signals output from regions located at diagonal positions to each other are generated. First and second diagonal sum signals, which are sum signals, are generated and the reflected light beams incident on the fifth to eighth light receiving areas are photoelectrically converted. A third and a fourth diagonal sum signal, which is a sum signal of two sets of signals output from the region to be output, are generated, and the third diagonal sum signal is generated from the first diagonal sum signal including the third diagonal sum signal. A first difference signal obtained by subtracting a sum signal, and the second diagonal sum including the fourth diagonal sum signal A second difference signal obtained by subtracting the fourth diagonal sum signal from the signal, and the center of a pit row formed in advance on the recording surface of the recording medium and the center of the light beam passing through the light condensing means. Are matched so that the phase difference between the first difference signal and the second difference signal matches when
Adjusting the gain of at least one of the difference signal and the second difference signal, detecting the phase difference between the gain-adjusted first difference signal and the second difference signal, and recording the phase difference signal generated by the recording. A track used for tracking control for moving the condensing means in a direction crossing the pit row so that the center of the pit row formed in advance on the recording surface of the medium coincides with the center of the light beam passed through the condensing means. An optical head device is provided, which is an error signal.

According to the eleventh aspect, a sum signal of the first diagonal sum signal and the second diagonal sum signal is generated, and the sum signal is used as an information signal. An optical head device as described above is provided.

According to the fourteenth aspect, a light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting light on the recording surface of the recording medium A photoelectric conversion unit that converts a diffracted reflected light beam into an electric signal, wherein the photoelectric conversion unit is converged by the condensing unit. When the condensed spot obtained by moving the recording medium in the radial direction of the recording medium, the recording medium is substantially orthogonal to the direction in which the reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. In a region that does not receive the light beam located on both sides of the first division line defined in the direction in which the light beam is reflected, and the length in the direction orthogonal to the first division line is larger than the beam diameter of the reflected light beam. A dead area formed in a rectangular shape whose length in a direction parallel to the first division line is longer than a beam diameter of the reflected light beam, and located outside the dead area, and the first division line; A first to a fourth light receiving area for receiving the reflected light beam that is substantially equally divided by a second dividing line that is substantially orthogonal to the first dividing line and that substantially divides the reflected light beam and that protrudes from the insensitive area; And among the signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, of the signals output from the areas located at diagonal positions to each other. A first and a second diagonal sum signal as two sets of sum signals are generated, and a phase difference signal generated by detecting a phase difference between the first and second diagonal sum signals is generated. The center of a pit row formed in advance on the recording surface of the recording medium; A signal processing method is provided in which a track error signal used for tracking control for moving the light condensing means in a direction crossing the pit row in order to match the center of the light beam passing through the light condensing means is provided. You.

According to the fifteenth aspect, a light source for emitting a light beam, a condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and a light source for reflecting and reflecting the light beam on the recording surface of the recording medium. A photoelectric conversion unit for converting the diffracted reflected light beam into an electric signal; and a signal processing method for generating a tracking error signal applied to an optical head device, wherein the photoelectric conversion unit is converged by the condensing unit. When the condensed spot obtained by moving in the radial direction of the recording medium, the recording medium is substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. A region which is located on both sides of the first division line defined in the direction and receives the light beam, and whose length in the direction orthogonal to the first division line is the beam of the reflected light beam. A central light-receiving region formed in a rectangular shape having a length shorter than a diameter and having a length in a direction parallel to the first dividing line longer than a beam diameter of the reflected light beam, and located outside the central light-receiving region, A first dividing line and a second dividing line that is substantially orthogonal to the first dividing line and substantially equally divides the reflected light beam, the first dividing line being substantially equally divided and receiving the reflected light beam protruding from the central light receiving region; And a fourth light receiving area, and a fifth light receiving area which is approximately equally divided by the first dividing line and the second dividing line is provided at a position adjacent to the first to fourth light receiving areas in the central light receiving area. First to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving regions and the fifth to eighth light receiving regions adjacent to each other. Generating the second Out of the fourth to fourth sum signals, first and second diagonal sum signals, which are two sets of sum signals output from regions located diagonally to each other, are generated, and the fifth to eighth diagonal sum signals are generated. Third and fourth diagonal sums, which are two sets of sum signals of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam incident on the light receiving area. Generating a signal,
The first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the diagonal sum signal, and the fourth difference signal from the second diagonal sum signal including the fourth diagonal sum signal. A second difference signal obtained by subtracting the diagonal sum signal is generated, and the first difference signal and the second difference signal are generated.
The phase difference signal generated by detecting the phase difference with the difference signal is
Used for tracking control in which the condensing means is moved in a direction crossing the pit row so that the center of a pit row formed in advance on the recording surface of the recording medium coincides with the center of a light beam passing through the condensing means. The signal processing method is characterized in that the signal is a track error signal.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the optical head device according to the present invention will be described below in detail with reference to the drawings.

First, an optical head device according to the first embodiment will be described.

FIG. 1 is a block diagram schematically illustrating an optical disk device in which an optical head device according to an embodiment of the present invention is incorporated.

As shown in FIG. 1, the optical disk device 1
Is an optical head device 3 for recording information on a recording surface of an optical disk D as a recording medium or reading information already recorded on the recording surface, and a signal corresponding to information to be recorded on the optical head device 3. And a control unit 9 that controls a motor 7 that rotates the optical head device 3 and the optical disc D at a predetermined speed. Have.

An external device 99 such as a host computer is connected to the signal processing section 5 via an interface (not shown).

The optical disk D has an information pit row formed at a pitch of about 0.74 μm in the radial direction, that is, in the radial direction, and the shortest length of the information pit is 0.40 to 0.44 μm.

In FIG. 1, the optical head device 3 transmits and receives an electric signal to and from the signal processing unit 5 while controlling the irradiation position of the light beam irradiating the optical disc D by the control signal from the control unit 9. A light beam is exchanged with the optical disc D.

The signal processing unit 5 converts the information read from the optical disk D by the optical head device 3 into an electric signal based on an instruction from the external device 99, and reproduces the information as recorded information. A recording signal is generated to make the information to be recorded correspond to the change in the light intensity of the light beam emitted from the optical head device 3.

The controller 9 controls the light intensity of the light beam emitted from the optical head device 3 to the optical disk D, the position of the light beam on the optical disk, the rotation speed of the optical disk D rotated by the motor 7, and the like.

Hereinafter, the operation of the optical disk device 1 shown in FIG. 1 will be briefly described.

First, the signal processing unit 5 receives a command signal for reproducing or recording information on the optical disk D from the external device 99.

Based on this command signal, the signal processing unit 5
Exchanges electrical signals with the optical head device 3 and transmits control signals to the control unit 9.

On the basis of the transmitted control signal, the control unit 9 controls the optical disk D irradiated by the optical head device 3.
And the rotation speed of the motor 7 are controlled.

As described above, the optical head device 3 transmits and receives a light beam to and from the optical disc D based on the electric signal exchanged with the signal processing unit 5 under the control of the control unit 9. To reproduce or record information.

When the information is reproduced or recorded, the optical head device 3 obtains an electric signal corresponding to the information recorded on the optical disk D and the information on the light beam irradiation position, and converts the electric signal into a signal processing unit. 5 is transmitted.

The signal processing unit 5 sends a control signal for changing the position of the optical head device 3 to the control unit 9 based on the electric signal corresponding to the information on the irradiation position of the light beam from the electric signal, and sends the control signal to the optical disk D. After performing processing such as decoding on the electric signal corresponding to the recorded information, the processed electric signal (reproduced signal) is transmitted to the external device 99.

The external device 99 that has received the reproduction signal from the signal processing unit 5 refers to this reproduction signal and refers to the optical disk device 1.
Then, the instruction signal as the next instruction is transmitted to the signal processing unit 5 again.

The optical disc apparatus 1 reproduces information recorded on the optical disc D or records information on the optical disc D by repeating a series of operations as described above.

Next, the structure of the optical head device 3 will be described with reference to FIGS.

As shown in FIG. 2, the optical head device 3
Are a laser light emitting / receiving unit (hereinafter, referred to as a fixed optical system) 3a fixed on the base 31 and a fixed optical system 3a
And an actuator 3b for irradiating the recording surface of the optical disk D with the laser beam from the optical disk D and guiding the reflected laser beam reflected on the recording surface of the optical disk D again to the fixed optical system 3a.

As shown in FIG. 3, the actuator 3b includes a carriage 33 movably formed on a pair of guide rails 32, 32 extending in the radial direction of the optical disk D, and is integrated with the carriage 33. The guide rails 32, 3 are formed by a pair of radial drive coils 34, 34 formed on the guide rails and a magnetic field supplied from a magnetic field supply mechanism (not shown).
2 is formed so as to be movable in the radial direction of the optical disc D.

The fixed optical system 3a has a housing 10 made of, for example, aluminum, as shown in FIG.

At one end of the housing 10, a predetermined wavelength,
For example, approximately 635 to 650 nanometers (hereinafter, nm)
The laser element (semiconductor laser) 11 for generating a laser beam is fixed.

In the direction in which the laser beam Rf emitted from the semiconductor laser 11 travels, the divergent laser beam Rf
A collimator lens 12 for collimating f is arranged.

In the direction in which the laser beam Rf collimated by the collimator lens 12 is guided, the cross-sectional beam shape of the laser beam Rf emitted as an ellipse is changed from an ellipse to a circle in relation to the aspect ratio specific to the laser beam Rf. An elliptical correction prism 13 to be corrected and a laser beam Rf formed integrally with the elliptical correction prism 13 and having a substantially circular cross-sectional shape are passed toward the actuator 3b, that is, the optical disk D, and are reflected by a recording surface (not shown) of the optical disk D. A beam splitter 14 for separating the reflected laser beam Rr from the laser beam Rf heading for the optical disk D and a laser beam Rf passed through the beam splitter 14 and directed to the actuator 3b to change the direction of the polarization plane from linearly polarized light to circularly polarized light. And reflected on the optical disc D Direction of polarization direction of the polarization plane of the reflected laser beam Rr which the circular polarization to the direction of the plane of polarization of the laser beam Rf directed to actuator 3b is 90
A λ / 4 plate (phase delay plate) 15 for converting into linearly polarized light rotated by ° is arranged in order.

The beam splitter 14 is a polarization beam splitter.

The optical disk D is controlled by the beam splitter 14.
In the direction in which the reflected laser beam Rr separated from the laser beam Rr traveling toward
With two further reflected laser beams Rra and Rrb
Half-mirror type beam splitter 16
Is arranged.

In the direction in which one of the two split laser beams Rra is split by the beam splitter 16, a converging lens 17 for providing the reflected laser beam Rra with predetermined imaging characteristics and convergence is arranged. I have.

In the direction in which the reflected laser beam Rra provided with convergence and predetermined imaging characteristics by the converging lens 17 advances, the reflected laser beam Rra
Lens 1 for improving aberration due to convergence given to lens
8. Reflected laser beam Rra passed through concave lens 18
Next, a cylindrical lens 19 for providing a predetermined imaging characteristic for detecting a focus shift described later, a reflected laser beam Rra given a predetermined imaging characteristic by the cylindrical lens 19, and the reflected laser beam Rra The photodetectors 20 that output output signals corresponding to the light intensities are arranged in order.

In the direction in which the reflected laser beam Rrb split into two by the beam splitter 16 is guided, a mirror 21 for guiding the reflected laser beam Rrb reflected on the optical disk D in a predetermined direction is arranged.

In the direction in which the reflected laser beam Rrb bent by the mirror 21 travels, a converging lens 22 for giving a predetermined convergence to the reflected laser beam Rrb is arranged.

In the direction in which the reflected laser beam Rrb given a predetermined convergence by the converging lens 22 is guided, a photodetector 23 used for detecting a track shift and an offset amount described later is arranged. I have.

The carriage 33 of the actuator 3b has
As shown in FIG. 5, the laser beam Rf emitted from the fixed optical system 3a after passing through the beam splitter 14 and the λ / 4 plate 15 of the fixed optical system 3a is bent so as to be incident on an objective lens described below. A rising mirror 35 is provided.

A predetermined direction of the recording surface of the optical disk D is set between the rising mirror 35 and the optical disk D in a direction in which the laser beam Rf, which is guided by the raising mirror 35 and bent by approximately 90 ° by the raising mirror 35, is directed. An objective lens 36, which is bent by the rising mirror 35 to converge the laser beam Rf and takes out the reflected laser beam Rr reflected by the recording layer of the optical disc D, is disposed on the recording layer (not shown).

The objective lens 36 is moved in a direction parallel to the recording surface of the optical disk D, which will be described in detail later with reference to FIG. 6, by a lens holder described below with reference to FIG. The optical disk D is held so as to be movable in a tracking direction substantially orthogonal to a pit row P formed in advance and in a focus direction orthogonal to a recording surface of the optical disc D.

The objective lens 36 is a semiconductor laser 1
For the wavelength 650 nm of the laser beam emitted by 1,
An aperture ratio of approximately 0.6 is provided.

As shown in FIG. 5, the lens holder 37
Has a bearing portion 37a substantially at the center, and a lens holding surface 37b holding the objective lens 36 on a circumference of a concentric circle having a predetermined radius centered on the bearing portion 37a, and a direction perpendicular to the lens holding surface 37b. A bearing portion 37a is provided on a shaft 39 having a cylindrical surface 37c formed in a partially cut-out cylindrical shape, and extending substantially from the center of a lens holder base 38 fixed at a predetermined position of the carriage 33. By being engaged, it is formed to be rotatable around the shaft 39.

The two sets of coils 4 are provided on the cylindrical surface 37c of the lens holder 37 at positions defined so as to divide the outer periphery of the cylindrical surface 37c into approximately four equal parts along the axis passing through the bearing 37a.
0, 40 and 41, 41 are provided.

The lens holder base 38 has a cylindrical shape at an arbitrary radius whose radius is increased compared to the cylindrical surface 37c of the lens holder 37 with the axis 39 as the center axis and corresponding to the circumference of the concentric circle. A yoke 42 having a notched portion is formed. At a predetermined position on the inner wall of the yoke 42, two sets of magnets 43, 43 and 44, which provide a magnetic field in a predetermined direction toward the cylindrical surface 37c of the lens holder 37,
44 are provided.

The magnets 43, 43 are connected to the objective lens 36.
The N-pole and the S-pole are magnetized in such a manner as to be divided into two parts by a plane orthogonal to the optical axis of the objective lens 36.
The N-pole and S-pole are magnetized in such a manner as to be divided into two by a plane parallel to the optical axis.

Next, the flow of the laser beam in the optical head device 3 described with reference to FIGS. 2 to 5 will be described.

The laser beam Rf emitted from the semiconductor laser 11 is converted into a parallel light beam by the collimator lens 12, the cross-sectional shape is corrected to a substantially circular shape by the elliptic correction prism 13, and the laser beam Rf passes through the beam splitter 14.

The laser beam Rf transmitted through the beam splitter 14 passes through the quarter-wave plate 15 so that the polarization direction is changed from linearly polarized light to circularly polarized light, and is emitted toward the rising mirror 35 of the actuator 3b. Is done.

The laser beam Rf guided to the rising mirror 35 is bent by approximately 90 ° by the rising mirror 35 and guided to the objective lens 36 held by the lens holder 37.

The laser beam Rf is guided to the objective lens 36 and converged, and then radiated to the optical disc D as a spot.

The laser beam R applied to the optical disc D
The reflected laser beam Rr whose f is reflected by the pit array P on the recording surface of the optical disc D is returned to the objective lens 36 and the rising mirror 35 in order, and is again polarized by the quarter-wave plate 15 from circularly polarized light to linearly polarized light. Is converted and guided to the beam splitter 14.

Since the polarization direction of the reflected laser beam Rr is rotated by exactly 90 ° with respect to the polarization direction of the original laser beam Rf emitted from the semiconductor laser 11, the reflected laser beam Rr is The fourteen planes of polarization are now reflected.

The reflected laser beam Rr separated from the laser beam Rf from the semiconductor laser 11 toward the objective lens 36 by the beam splitter 14 is converted by the beam splitter 16 into two reflected laser beams Rra and Rrb having substantially equal light intensities. Is divided.

The reflected laser beam Rra transmitted through the beam splitter 16 is given a predetermined imaging characteristic and convergence by a converging lens 17, then the aberration characteristic is improved by a concave lens 18, and the focus is detected by a cylindrical lens 19. The photodetector 20 is irradiated with the astigmatism for

The reflected laser beam Rra applied to the photodetector 20 is converted by the photodetector 20 into an electric signal having a magnitude corresponding to the light intensity, and is used as a focus error signal and a reproduction signal. In this example, the detection of the focus error signal is a well-known astigmatism method, and a detailed description thereof will be omitted.

On the basis of the focus error signal generated by the photodetector 20, focus control, ie, focusing, for eliminating a deviation between the focus of the spot converged by the objective lens 36 and the optical axis direction of the recording surface of the optical disk D is performed. You. In focusing, the coils 40, 40 are controlled based on the focus error signal.
Is supplied with a current in a predetermined direction, so that the magnets 43, 4
As a result of the attraction or repulsion due to the electromagnetic interaction with the magnetic field provided by 3, the lens holder 37 (objective lens 36) is moved either in a direction toward or away from the recording surface of the optical disc D.

The remaining reflected laser beam Rrb reflected by the beam splitter 16 passes through the optical path 9
It is bent by 0 °, given a predetermined convergence by the converging lens 22, and guided to a photodetector 23 used for detecting a track shift and an offset amount.

FIG. 7 is a plan view of the photodetector.

As shown in FIG. 7, the photodetector 23 has a first dividing line L1 parallel to the radial direction at a predetermined interval and a tangential direction substantially perpendicular to the first dividing line l1. Eight first to eight divided equally into two rows and four columns by a second dividing line L2 and third and fourth dividing lines L3 and L4 parallel to the radial direction symmetrical with respect to the first dividing line L1. Eighth light receiving areas 23a to 23h
have. A central light receiving area including fifth to eighth light receiving areas 23e to 23h is formed at the center of the photodetector 23, and an outside light receiving area including the first to fourth light receiving areas 23a to 23d is formed outside the central light receiving area. A region is formed.

In the outer light receiving area, the first and second light receiving areas 23a and 23b and the third and fourth light receiving areas 23c and 23
d is arranged at a position symmetrical with respect to the first division line L1. Further, the first and third light receiving regions 23a,
3c and the second and fourth light receiving regions 23b and 23d are arranged at positions symmetrical to each other with respect to the second division line L2.

Each of the fifth to eighth light receiving regions 23e to 23h in the central light receiving region has a length along the second division line L2 shorter than the beam radius of the reflected laser beam incident on the photodetector 23, and It is formed in a rectangular shape whose length along the line L1 is sufficiently longer than the beam radius of the reflected laser beam.

Fifth and sixth light receiving regions 23e and 23f
And the seventh and eighth light receiving regions 23g and 23h are arranged at positions symmetrical to each other with respect to the first division line L1.

The fifth and seventh light receiving areas 23e and 23e
3g, the sixth and eighth light receiving regions 23f and 23h,
They are arranged symmetrically with respect to the second division line L2.

The fifth to eighth light receiving regions 23e to 23e
3h, the photodetector 23
A part near the center of the reflected laser beam incident on the light receiving portion is received. On the other hand, these fifth to eighth light receiving regions 23e to 23e
h to the first to fourth light receiving regions 23a to 2
In the outer light receiving region 3d, the light beam of the part protruding from the central light receiving region is received.

The first division line L1 is arranged so as to be substantially parallel to the direction in which the shadow of the pit row P of the optical disc D is projected.

The eight light receiving areas 2 of the photo detector 23
Each of the signals photoelectrically converted by 3a to 23h is used for generating a track shift signal by applying a phase difference method, as will be described in detail later with reference to FIGS.

A track error signal is generated by the signal processing section shown in FIG. 9 based on the track shift signal generated by the photodetector 23, and the focus of the spot converged by the objective lens 36 and the pit on the recording surface of the optical disk D are recorded. Track control or tracking is performed to eliminate the deviation from the center of the row P.

In tracking, a current in a predetermined direction is supplied to the coils 41, 41 based on a track shift signal which is a phase difference between two sets of diagonal sum signals of the light receiving areas at diagonal positions of the photodetector 23. Being done
Attraction or repulsion due to electromagnetic field interaction with the magnetic field provided by magnets 44, 44 results in lens holder 37.
The (objective lens 36) is moved along the recording surface of the optical disc D either toward the center or the outer periphery in the radial direction of the optical disc D in a direction orthogonal to the pit row P.

Incidentally, an optical disk (DVD, pit train P) for high-density digital recording, which has a higher recording density than conventional music optical disks (CDs) and also records video information, has been used today. Although the distance between the pits is approximately 0.74 μm (hereinafter referred to as μm), the offset between adjacent pit rows P is reduced because the distance between the adjacent pit rows P is reduced. From increasing crosstalk with column P,
The offset component included in the track deviation signal must be reliably removed.

For this reason, in this embodiment, as described above, the photodetector 23 is composed of the outer light receiving region composed of the first to fourth light receiving regions 23a to 23d and the fifth to eighth light receiving regions 23e to 23h. A central light receiving area.

More specifically, of the reflected laser beam Rrb applied to the photodetector 23, the 0th-order diffracted light generated in the radial direction of the pit row P has an outer peripheral portion blurred by the objective lens 36. As described above, since the laser beam substantially corresponds to the center of the reflected laser beam Rrb, it forms a high light intensity portion. In the photodetector 23, a central light receiving region including fifth to eighth light receiving regions 23e to 23h is formed at a position where the intensity center region of the zero-order diffracted light is irradiated.

Here, the distance between the third dividing line L3 and the fourth dividing line L4 in the central light receiving region is determined by the specifications of the optical disk D, the wavelength of the laser beam Rf emitted from the semiconductor laser 11, the aperture ratio of the objective lens 36, and It is easily obtained from the imaging characteristics and the optical design specifications of the fixed optical system 3a. For example, the center-to-center (inter-interval) distance of the pit rows P formed on the recording surface of the optical disc D is approximately 0.7.
In the case of 4 μm, it is set to approximately １ ／ of the beam spot diameter of the reflected laser beam reflected by the optical disc D.

FIG. 6 shows a reflected laser beam Rr reflected on the recording surface of a high-density optical disc D for a read-only DVD.
Of the 0-order diffracted light generated in the radial direction of the pit row P,
Each of the first-order diffracted light and the -1st-order diffracted light is the objective lens 3
It is a schematic diagram which roughly explains the state guided to 6.

As shown in FIG. 6, the reflected laser beam Rr reflected by the pit row P on the recording surface of the optical disc D
Are the 0th-order diffracted light that passes through substantially the entire area of the objective lens 36, the 1st-order diffracted light and the -1st-order diffracted light that partially overlap the 0th-order diffracted light, and the 2nd-order diffracted light (not shown) when viewed as diffracted light generated in the radial direction. The objective lens 36 is incident on the objective lens 36 as an aggregate of higher-order diffracted light including the second-order and higher-order diffracted light including the second-order.

As is apparent from FIG. 7, each of the first-order diffracted light and the −1st-order diffracted light has a portion that overlaps with the zero-order diffracted light. That is, as described above, the read-only D
In a high-density optical disc for VD, a well-known music C
D, the distance between adjacent pit rows P is configured to be smaller than that of D, the wavelength is shorter (for example, 780 nm → 650 nm), and the NA of the objective lens is larger (for example, , 0.45 → 0.6) and so on, each of the first-order diffracted light and the −1st-order diffracted light is 0
A part overlaps with the next-order diffracted light, and a part of each other overlaps.

More specifically, since each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light is partially blocked by the opening of the objective lens 36, only a part of the reflected laser beam Rr passes through the objective lens 36. The light is returned to the fixed optical system 3a.

That is, the mid-range region of the intensity of the 0th-order diffracted light is
For example, in a state where the peripheral portion of the reflected laser beam before the incidence on the objective lens 36 is shaved, the photodetector 2 shown in FIG.
Third central light receiving area, that is, fifth to eighth light receiving areas 23
e to 23h. On the other hand, the first order diffracted light and -1
Each of the order diffracted lights is incident on the outer light receiving area of the photodetector 23, that is, the first to fourth light receiving areas 23a to 23d while overlapping with the 0 order diffracted light.

Then, the phase difference between the two sets of diagonal sum signals of the photoelectric conversion signals from the light receiving areas located at diagonal positions of each of the eight light receiving areas is a track shift signal.

That is, a method of processing a photoelectric conversion signal obtained from these eight light receiving regions is as follows.

Regarding the central light receiving area, the sum signal for the photoelectric conversion signals from the light receiving areas located at diagonal positions with respect to each other, that is, the fifth light receiving area and the eighth light receiving area, that is, the first diagonal sum signal, and the sixth light receiving area A sum signal for the photoelectric conversion signals from the area and the seventh light receiving area, that is, a second diagonal sum signal is generated.

Similarly, regarding the outer light receiving area, the sum signal for the photoelectric conversion signals from the light receiving areas located at diagonal positions to each other, that is, the first light receiving area and the fourth light receiving area, that is, the third diagonal sum signal, and A sum signal for the photoelectric conversion signals from the second light receiving area and the third light receiving area, that is, a fourth diagonal sum signal is generated.

Then, the first diagonal sum signal and the third diagonal sum signal are added to generate a fifth diagonal sum signal.

Further, the sixth diagonal sum signal is generated by adding the second diagonal sum signal and the fourth diagonal sum signal.

It is needless to say that the fifth diagonal sum signal and the sixth diagonal sum signal are equal to the signals before the phase difference is observed in the conventional example.

The subtraction of the third and fourth diagonal sum signals from the fifth and sixth diagonal sum signals corresponds to the tracking error signal in the embodiment.

Here, in order to explain the mechanism that enables tracking control by the phase difference method, first, as a preparation, the cause of the occurrence of track off flat at the time of lens shift will be described using a comparative example, that is, a conventional example. FIGS. 18A and 18B show the relationship between the light beam and the photodetector in the comparative example without and with lens shift, respectively.

In FIG. 18, (a) and (b), the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light are shown.
This means diffraction of each number of characters in the radial direction due to a sufficiently long pit. In addition, diffracted light is generated at the front and rear ends of the pit, but is omitted here.

First, let us consider a situation in which a condensed spot traces a pit row in a state where there is no detracking but a lens shift. At this time, as shown in FIG. 18B, the light beam enters the photodetector with a shifted positional relationship. In addition, the intensity center of the light beam is located on the side that occupies a large area, that is, on the light receiving area c and the light receiving area d of the photodetector.

For this reason, the strengths of the two sets of diagonal sum signals (Ia + Id) and (Ib + Ic) for the light receiving regions a to d are dominantly defined by the signals Ic and Id, respectively.

By the way, the first half of the condensed spot in the trace direction receives the intensity change of the diffracted light due to the pit. The light receiving areas of the photo detector facing the front half are a light receiving area a and a light receiving area c. Then, first, the level of Ic fluctuates as a change in the intensity of the diffracted light due to the pits, and then, the level of Id fluctuates.

Therefore, from the above two facts, two sets of diagonal sum signals (Ia + Id) and (I
The phase relationship of (b + Ic) greatly depends on the phase relationship of the signals Ic and Id, and as a result, the two diagonal sum signals are shifted in phase, which corresponds to the track offset.

On the other hand, the state at the time of detracking will be described as follows. Assume that there is no lens shift.

With the detracking, a difference is generated between the intensity of the diffracted light on the inner peripheral side of the pit and the intensity of the diffracted light on the outer peripheral side, and this is two sets of sum signals (Ia + Ib) and (Ic +
Id). For example, it is assumed that the level of the signal (Ia + Ib) is higher than the level of the signal (Ic + Id) as a whole. On the other hand, considering the intensity change of the diffracted light due to the passage of the pit, for example, the phase of the signals Ia and Ic is ahead of the signals Ib and Id.

Therefore, two sets of diagonal sum signals (Ia + I
d) and (Ib + Ic) are the levels of signal I
determined fairly dominantly by a and Ib. Therefore, two sets of diagonal sum signals (Ia + Id) and (Ib + Ic)
Is significantly dominated by the phase difference between signals Ia and Ib, respectively.

However, as described above, since the phase difference of the signal Ia is ahead of the phase difference of the signal Id, as a result, the phase difference of the diagonal sum signal (Ia + Id) is equal to the diagonal sum signal (Ia + Id). A phase difference that the phase is advanced from the phase of Ib + Ic) is generated, and a tracking error signal is generated.

In other words, the difference between the intensity of the overlapping portion of the + 1st-order diffracted light and the 0th-order diffracted light generated in the radial direction by the pit and the intensity of the overlapping portion of the -1st-order diffracted light and the 0th-order diffracted light is referred to as a phase difference. Observed at.
Therefore, if these two regions are secured to some extent, it is possible to generate a tracking error signal by the phase difference method.

The embodiment of the present invention has been made based on the mechanism described above.

FIGS. 8A and 8B show the relative positions of the light beam when there is no lens shift with respect to the photodetector applied to the optical head device of the first embodiment and when there is a lens shift. It is a figure showing a positional relationship.

As shown in FIG. 8B, when there is a lens shift, the light beam enters the photodetector in a shifted state. In other words, the light beam splits in the radial direction and enters each light receiving region in a state where the light beam is shifted with respect to the first division line.

However, as described above, the signal corresponding to the total light amount of the light beam received by all the light receiving areas 23a to 23h of the photodetector 23 is used to determine the central light receiving area 2a.
By generating a tracking error signal based on a signal obtained by subtracting a signal corresponding to the amount of light received at 3e to 23h, the intensity center of the 0th-order diffracted light of the light beam is substantially centered in the light receiving regions 23e to 23h of the photodetector 23.
As long as the inside is shifted, the outer light receiving regions 23a and 23a
There is almost no difference in signal level based on the amount of light received by 3b and the outer light receiving regions 23c and 23d.

On the other hand, the overlapping portions of the + 1st order diffracted light and the 0th order diffracted light and the overlapping portions of the -1st order diffracted light and the 0th order diffracted light generated in the radial direction by the pits are captured by the outer light receiving regions 23a to 23d. As a result, it is possible to generate a tracking error signal by the phase difference method.

Therefore, if there is a converging spot at a position where the center of the converging spot of the laser beam converged on the optical disk D by the objective lens 36 coincides with the center of the pit row P, the radius of the pit row P Since a diffracted light symmetrical in the direction is generated, a first difference signal corresponding to a difference signal between a later-described fifth diagonal sum signal and a third diagonal sum signal based on photoelectric conversion signals from the eight light receiving regions, The signal level difference between the second difference signal corresponding to the difference signal between the sixth diagonal sum signal and the fourth diagonal sum signal is zero. On the other hand, when the center of the converging spot does not coincide with the center of the pit row P, the difference between the signal levels of the first difference signal and the second difference signal is shifted from zero.

As described above, it can be said that the tracking shift signal captures a change in the phase difference between the first-order diffracted light and the -1st-order diffracted light with respect to the 0th-order diffracted light. Therefore, as much as possible, the first-order diffracted light and the -1st-order diffracted light, which greatly contribute to the generation of the tracking shift signal, are taken as much as possible, centering on the portion where the intensity is high. It is important to reduce the track offset as much as possible at the center.

Therefore, as shown in FIG. 7, the light receiving surface of the photodetector 23 has an outer light receiving area for receiving a part where the intensity of the first-order diffracted light is high or a part where the zero-order diffracted light and the first-order diffracted light overlap. First and second light receiving areas 23
a, 23b, third and fourth light receiving regions 23c, 23d of outer light receiving regions that receive a portion where the intensity of the -1st order diffracted light is high or a portion where the 0th order diffracted light and the -1st order diffracted light overlap.
And a portion where the intensity of the 0th-order diffracted light is high or the 0th-order diffracted light,
It has fifth to eighth light receiving regions 23e to 23h of the central light receiving region irradiated with a portion where the first-order diffracted light and the -1st-order diffracted light overlap, which is effective for reducing track offset.

As shown in FIGS. 8A and 8B,
In the photodetector 23 having the structure described above,
The light receiving areas of the first to fourth light receiving areas 23a to 23d for receiving the condensed spot of the reflected laser beam are reduced because the central light receiving areas 23e to 23h are provided between the outer light receiving areas, and the amount of received light is reduced. Reduced, but the first to fourth
The light receiving regions 23a to 23d respectively capture a large amount of first-order diffracted light and minus first-order diffracted light.

The intensity center of the 0th-order diffracted light involved in the generation of the tracking offset component is located at the center light receiving region 23e.
To 23h, the amount of light received by the first to fourth light receiving regions 23a to 23d is obtained by photoelectric conversion while removing a tracking offset by using a first difference signal and a second difference signal described later. A stable tracking signal can be generated by the phase difference between the obtained diagonal sum signals.

Further, as shown in FIG. 8B, the light spot of the photodetector 23 is focused by the lens shift.
Even when the irradiation position of the light is relatively shifted in the radial direction, the center of the intensity of the 0th-order diffracted light is not located in any of the first to fourth light receiving regions 23a to 23d, and the central light receiving regions 23e to 23h It is located in. Therefore, a stable tracking signal can be generated while reducing the tracking offset component even at the time of lens shift.

FIG. 9 is a schematic block diagram showing an example of a signal processing unit and a control unit which can be used for the signal processing unit 5 and the control unit 9 of the optical disc apparatus 1 shown in FIG.

As shown in FIG. 9, the signal processing section 5 is connected to the main control circuit 50, and reproduces information recorded on the optical disk D based on outputs from eight light receiving areas (not shown) of the photo detector 23. The information reproducing circuit 51 is provided. The information reproducing circuit 51 includes, for example, a threshold circuit (not shown), a binarizing circuit, a data decompression circuit, a buffer memory, and the like, and a current-voltage conversion circuit, a differential amplifier, and an adder, which will be described in detail later. The information corresponding to the output from each light receiving area converted into a signal is output to the external device 99 via the main control circuit 50.

On the other hand, the control section 9 comprises a linear motor control circuit 61 for supplying a current in a predetermined direction to the radial drive coil 34 for moving the actuator 3b in the radial direction of the optical disk D, and the objective lens 36 to the recording surface of the optical disk D. A focus error detection circuit 62 for setting a current value to be supplied to the two coils 40, 40 on the cylindrical surface of the lens holder 37 in order to move in a direction perpendicular to the direction of movement of the lens holder 37, and removing a focus error detected by the focus error detection circuit 62. And a focus control circuit 63 for supplying a focus control current to the coils 40 and 40, and a cylindrical surface of the lens holder 37 for moving the objective lens 36 in a direction intersecting the tangent to the pit row P on the recording surface of the optical disc D. A track shift control circuit 64 for setting a current value to be supplied to the two coils 41, 41; The track control circuit 65 that supplies a track control current to the coils 41 and 41 and the light intensity of the laser beam radiated from the semiconductor laser 11 to remove the track shift and the offset output from the rack shift control circuit 64 are adjusted to a predetermined value. A laser drive circuit 66 for setting the intensity is provided. Each circuit is connected to the main control circuit 50.

The focus error detection circuit 62 is connected to each of the four light receiving regions (not shown) of the photodetector 20 and converts the output current output from each light receiving region into a voltage. Vessel 71a
Output from the first and second differential amplifiers 73a and 73b for obtaining a differential output between two predetermined outputs among the voltage signals output from the output signals 71-71d. Is entered.

The information reproduction circuit 51 receives an output signal, that is, an RF signal corresponding to the information signal output from the terminal B via the signal processing circuit 100 connected to each of the eight light receiving regions (not shown) of the photodetector 23. Is done.

Each of the track shift control circuit 64 and the linear motor control circuit 61 has a photodetector 2
The phase difference signal corresponding to the tracking signal output from the terminal A is input via the signal processing circuit 100 connected to each of the eight light receiving regions 23a to 23h.

FIG. 10 is a block diagram schematically showing a configuration of the photodetector 23 and a signal processing circuit 100 for performing signal processing based on the current output from the photodetector 23.

That is, as shown in FIG. 10, the signal processing circuit 100 performs the following signal processing.

That is, the currents output after being photoelectrically converted by the first to eighth light receiving regions 23a to 23h of the photodetector 23 are input to current-to-voltage converters 81a to 81h for current-to-voltage conversion, respectively. Signals Ia to Ih are generated.

Then, a sum signal of voltage signals output from two sets of light receiving areas located at diagonal positions among the eight light receiving areas is generated.

That is, the signals Ia and Ie output from the first light receiving area 23a and the fifth light receiving area 23e are input to an adder 82a that generates a sum signal, and a first sum signal is generated. The signals Ib and If output from the second light receiving area 23b and the sixth light receiving area 23f are input to an adder 82b that generates a sum signal, and a second sum signal is generated.

The third light receiving area 23c and the seventh light receiving area 23g
The signals Ic and Ig output from the above are input to an adder 82c that generates a sum signal, and a third sum signal is generated. The signals Id and Ih output from the fourth light receiving area 23d and the eighth light receiving area 23h are input to an adder 82d that generates a sum signal, and a fourth sum signal is generated.

In the central light receiving region, a sum signal of light receiving regions arranged at diagonal positions is generated. That is, the signals Id and Ih output from the fifth light receiving area 23e and the eighth light receiving area 23h are input to an adder 83a that generates a sum signal, and a fifth sum signal is generated. The signals If and Ig output from the sixth light receiving area 23f and the seventh light receiving area 23g are input to an adder 83b that generates a sum signal, and a sixth sum signal is generated.

Then, the first sum signal and the fourth sum signal are input to an adder 84a for generating a sum signal, and a seventh sum signal is generated. This seventh sum signal corresponds to the sum signal of the signals output from the first, fourth, fifth, and eighth light receiving regions. The second sum signal and the third sum signal are added to an adder 8 for generating a sum signal.
4b, and an eighth sum signal is generated. This eighth sum signal corresponds to the sum signal of the signals output from the second, third, sixth, and seventh light receiving regions.

Then, the seventh sum signal and the fifth sum signal are input to a differential amplifier 85a that generates a difference signal, and a first difference signal is generated. The first difference signal corresponds to a sum signal of the signals output from the first and fourth light receiving regions.

The eighth sum signal and the sixth sum signal are input to a differential amplifier 85b for generating a difference signal, and a second difference signal is generated. This second difference signal corresponds to the sum signal of the signals output from the second and third light receiving areas.

Then, the first difference signal and the second difference signal are inputted to the phase comparator 86 and the differential amplifier 87, respectively, and the difference of the signal level corresponding to the phase difference is detected.
The difference signal corresponding to the signal level difference output from the differential amplifier 87 corresponds to a tracking error signal and is input to the terminal A.

On the other hand, the seventh sum signal and the eighth sum signal are input to an adder 88 for generating a sum signal, and a sum signal is generated. This sum signal corresponds to the sum of the signals output from all the light receiving areas of the photodetector 23, that is, the first to eighth light receiving areas 23a to 23h.
An F signal is formed.

This information signal is input to terminal B.

A track error signal is generated by the signal processing section shown in FIG. 9 based on the signal output to the terminal A.
Track control, that is, tracking, is performed to eliminate a deviation between the focal point of the spot converged by the objective lens 36 and the center of the pit row P on the recording surface of the optical disc D.

In the tracking, the coils 41, 41 have a predetermined direction based on the track shift signal corresponding to the difference signal between the first difference signal and the second difference signal output from the photodetector 23 and the signal processing circuit 100. Is supplied to the lens holder 37 (objective lens 36) as a result of attraction or repulsion due to electromagnetic field interaction with the magnetic field provided by the magnets 44, 44, and the pits are formed along the recording surface of the optical disk D. The optical disc D is moved to either the center or the outer periphery in the radial direction of the optical disc D in a direction orthogonal to the row P.

As described above, according to the optical head device 3 according to the first embodiment, the track shift of the objective lens 36 is substantially equal to the two sets of diagonal positions of the photodetector 23. Is detected as a difference signal of the diagonal sum signal of.

As described above, the tracking control signal is calculated by the track shift control circuit 64 on the basis of the output signal output from the differential amplifier 87, and as if the track shift occurs due to the lens shift of the objective lens 36. It is possible to compensate for the offset amount that acts as an error, that is, the influence of the offset component included in the track shift signal.

Accordingly, stable tracking control can be performed, and crosstalk in a high-density optical disk represented by an optical disk for DVD can be significantly reduced.

Next, a second embodiment will be described.

The optical head device according to the second embodiment has a gain controller for adjusting the signal level in the signal processing circuit 100. Note that the other configuration is substantially the same as that of the first embodiment, and a detailed description is omitted here.

FIG. 11 is a block diagram schematically showing a signal processing circuit applied to the optical head device according to the second embodiment.

That is, in the signal processing circuit 100,
In addition to the signal processing circuit shown in FIG. 10, a gain controller 90a for adjusting the signal level of the output signal output from the fifth adder 83a for generating the fifth sum signal, and a sixth controller for generating the sixth sum signal. Gain controller 90b for adjusting the signal level of the output signal output from adder 83b
And have been added.

These gain controllers 90a, 90
b is, for example, due to a precision error or an assembly error of a component of the optical head device, or a tilt of the optical disk,
Originally, when there is no lens shift, the phase difference between the first difference signal and the second difference signal should be 0,
This is to deal with cases where it does not occur. This allows
The track offset component is reduced more accurately.

Next, a third embodiment will be described.

The optical head device according to the third embodiment also has a gain controller for adjusting the signal level in the signal processing circuit 100, as in the second embodiment. Note that the other configuration is substantially the same as that of the first embodiment, and a detailed description is omitted here.

FIG. 12 is a block diagram schematically showing a signal processing circuit applied to the optical head device according to the third embodiment.

That is, in the signal processing circuit 100,
In addition to the signal processing circuit shown in FIG. 10, the signal level of the output signal output from the differential amplifier 85a that generates the first difference signal, and the differential amplifier 85b that generates the second difference signal
A gain controller 91 that adjusts at least one of the signal levels of the output signal output from the controller is added.
In the example shown in FIG. 12, a gain controller 91 is provided downstream of the differential amplifier 85a so as to adjust the signal level of the first difference signal output from the differential amplifier 85a.

The gain controller 91 adjusts the levels of the fifth and sixth sum signals in accordance with, for example, the type of the optical disc to be reproduced, and thus the effect of reducing the track offset component can be further improved.

In the first to third embodiments described above, although a gain controller is partly included,
After adding the second signal to the first signal, from there the second signal
Although a seemingly meaningless signal operation such as subtraction of a signal is performed, a sum signal obtained by adding the second signal to the first signal is an information signal for obtaining information recorded on the optical disc, that is, an RF signal. In addition to this, there is an advantage that it can be used to check whether a light beam is incident on a photodetector in a predetermined positional relationship when assembling an optical head.

In the case where an RF signal or the like can be generated by another detector, such signal calculation processing can be omitted. Hereinafter, an embodiment of a configuration capable of simplifying the signal arithmetic processing will be described.

Hereinafter, a fourth embodiment will be described.

The optical head device according to the fourth embodiment has a light receiving area having a shape different from that of the photodetector having the light receiving area as shown in FIG. 7 applied in the first to third embodiments. A photodetector is applied.

FIG. 13 is a plan view showing a photodetector according to the fourth embodiment.

As shown in FIG. 13, the photodetector 23 has a first division line L1 perpendicular to the radial direction at a predetermined interval and a second division line parallel to the radial direction substantially perpendicular to the first division line l1. There are four first to fourth light receiving areas 23a to 23d equally divided into two rows and two columns by the line L2. In the center of the photodetector 23, a non-light receiving area is formed, and a dead area 24 that does not receive a light beam is formed.

That is, a light receiving area including the first to fourth light receiving areas 23a to 23d is formed outside the dead area 24 located at the center of the photodetector 23.

More specifically, of the reflected laser beam Rrb applied to the photodetector 23, the 0th-order diffracted light generated in the radial direction by the pit row is blurred by the objective lens 36 at the outer periphery, but will be described below with reference to FIG. As described, the laser beam substantially corresponds to the center of the reflected laser beam Rrb, and thus has a high light intensity. In the photodetector 23, an insensitive region 24 is formed at a position where the central region of the zero-order diffracted light is irradiated.

Here, the width of the dead area 24, that is, the first
The distance between the second light receiving area 23a, 23b and the third and fourth light receiving areas 23c, 23d is the same as in the first embodiment, the specification of the optical disc D, the wavelength of the laser beam Rf emitted from the semiconductor laser 11, and the like. , Which is easily obtained from the aperture ratio and the imaging characteristics of the objective lens 36, the optical design specifications of the fixed optical system 3a, and the like. For example, approximately 1/3 of the beam spot diameter of the reflected laser beam reflected by the optical disk D.
Is set to

As is apparent from FIG. 13, each of the first-order diffracted light and the -1st-order diffracted light generated in the radial direction by the pit row has a portion that overlaps with the zero-order diffracted light. That is, each of the first-order diffracted light and the -1st-order diffracted light is 0
A part overlaps with the next-order diffracted light, and a part of each other overlaps.

More specifically, since each of the 0th-order diffracted light, the 1st-order diffracted light, and the -1st-order diffracted light is partially blocked by the opening of the objective lens 36, only a part of the reflected laser beam Rr passes through the objective lens 36. The light is returned to the fixed optical system 3a.

That is, the intensity center region of the zero-order diffracted light is
For example, the reflected laser beam before entering the objective lens 36 is guided to the dead area 23 of the photodetector 23 shown in FIG.

On the other hand, each of the first-order diffracted light and the -1st-order diffracted light overlaps with the 0th-order diffracted light, and similarly, the first to fourth light-receiving regions 23a to 23d of the photodetector 23 similarly.
It is incident on 3d.

Then, the phase difference between the two sets of sum signals of the photoelectric conversion signals from the two light receiving areas at diagonal positions among these four light receiving areas is a track shift signal.

That is, the processing method of the photoelectric conversion signal obtained from these four light receiving areas is as follows.

That is, the light receiving areas located diagonally to each other, ie, the first light receiving area 23a and the fourth light receiving area 23
a first diagonal sum signal for the photoelectrically converted signal from d.
A second diagonal sum signal is generated for the photoelectric conversion signals from the second light receiving area 23b and the third light receiving area 23c.

The signal corresponding to the phase difference between the first diagonal sum signal and the second diagonal sum signal corresponds to a tracking error signal.

Therefore, if there is a converging spot at a position where the center of the converging spot of the laser beam converged on the optical disc D by the objective lens 36 and the center of the pit row P, the radius of the pit row P Since the diffracted light is symmetrical in the directions, the phase difference of the diagonal sum signals from the four light receiving areas is 0. If they do not match, the intensity of one of the diffracted lights increases, and the phase difference becomes larger. It will deviate from zero.

As described above, it can be said that the tracking shift signal captures the change in the phase difference between the first-order diffracted light and the -1st-order diffracted light with respect to the 0th-order diffracted light. Therefore, as much as possible, the first-order diffracted light and the -1st-order diffracted light, which greatly contribute to the generation of the tracking shift signal, are taken as much as possible, centering on the portion where the intensity is high. It is important to reduce the track offset as much as possible at the center.

Therefore, as shown in FIG. 13, the light receiving surface of the photodetector 23 has first and second light receiving portions that receive a high intensity of the first-order diffracted light or a portion where the zero-order diffracted light and the first-order diffracted light overlap. 2 light receiving areas 23a, 23b,-
Third and fourth light receiving regions 23c and 23d for receiving a portion where the intensity of the first-order diffracted light is high or a portion where the 0th-order diffracted light and the -1st-order diffracted light overlap, and a portion where the intensity of the 0th-order diffracted light is high or 0 It has an insensitive area 24 to which a portion where the first-order diffracted light, the first-order diffracted light, and the -1st-order diffracted light overlap is effective, and is effective in reducing track offset.

FIGS. 14A and 14B show the positional relationship of the reflected laser beam from the optical disk to the photodetector 23 when there is no lens shift and when there is a lens shift, respectively. Things.

The photodetector 2 having the structure described above
In 3, the light receiving area of the first to fourth light receiving areas 23a to 23d for receiving the condensed spot of the reflected laser beam is reduced because the dead area 24 is provided between the light receiving areas, and the amount of received light is reduced. However, the first to fourth light receiving regions 23a to 23d capture the first-order diffracted light and the -1st-order diffracted light, respectively.

Further, since the center of the intensity of the 0th-order diffracted light relating to the generation of the tracking offset component is located in the dead area 24, the tracking offset is removed while removing the tracking offset.
A stable tracking signal can be generated based on the phase difference between the diagonal sum signals obtained by photoelectrically converting the amounts of light received by the first to fourth light receiving regions 23a to 23d.

Further, as shown in FIG. 8B, the photodetector 23 of the condensed spot is shifted by the lens shift.
Even when the irradiation position on the light beam is relatively shifted in the radial direction, the intensity center of the 0th-order diffracted light is not located in any of the first to fourth light receiving regions 23a to 23d, and the insensitive region 24
It is located in. Therefore, a stable tracking signal can be generated while reducing the tracking offset component even at the time of lens shift.

FIG. 15 shows the optical disk device 1 shown in FIG.
3 is a schematic block diagram illustrating an example of a signal processing unit and a control unit that can be used for the signal processing unit 5 and the control unit 9 of FIG.

As shown in FIG. 15, the signal processing section 5 is connected to the main control circuit 50, and reproduces information recorded on the optical disc D based on outputs from four light receiving areas (not shown) of the photo detector 20. Information reproducing circuit 51
have.

The information reproducing circuit 51 includes, for example, a threshold circuit (not shown), a binarizing circuit, a data expanding circuit, a buffer memory, and the like, and a current-voltage converting circuit, a differential amplifier, and an adder, which will be described in detail later. The information corresponding to the output from each light receiving area converted into a voltage signal by the device is output to the external device 99 via the main control circuit 50.

On the other hand, the control section 9 comprises a linear motor control circuit 61 for supplying a current in a predetermined direction to the radial drive coil 34 for moving the actuator 3b in the radial direction of the optical disk D, and the objective lens 36 to the recording surface of the optical disk D. A focus error detection circuit 62 for setting a current value to be supplied to the two coils 40, 40 on the cylindrical surface of the lens holder 37 in order to move in a direction perpendicular to the direction of movement of the lens holder 37, and removing a focus error detected by the focus error detection circuit 62. And a focus control circuit 63 for supplying a focus control current to the coils 40 and 40, and a cylindrical surface of the lens holder 37 for moving the objective lens 36 in a direction intersecting the tangent to the pit row P on the recording surface of the optical disc D. A track shift control circuit 64 for setting a current value to be supplied to the two coils 41, 41; The track control circuit 65 that supplies a track control current to the coils 41 and 41 and the light intensity of the laser beam radiated from the semiconductor laser 11 to remove the track shift and the offset output from the rack shift control circuit 64 are adjusted to a predetermined value. A laser drive circuit 66 for setting the intensity is provided. Each circuit is connected to the main control circuit 50.

The information reproducing circuit 51 is connected to each of four light receiving areas (not shown) of the photodetector 20, and converts the output current output from each light receiving area into a voltage by converting the first to fourth current-voltage converters. The added output of the adder 72 for obtaining the sum of the voltage signals output from each of 71a to 71d is input. By obtaining the sum of these four voltage signals, an information signal, that is, an RF signal is formed.

The focus error detection circuit 62 has the first
And first and second differential amplifiers 73a and 73a for obtaining a differential output between two predetermined outputs among the output voltages output from the fourth to fourth current-voltage converters 71a to 71d.
An output obtained by adding each output of 73b by an adder 74 is input.

Each of the track shift control circuit 64 and the linear motor control circuit 61 has a photodetector 2
The phase difference signal corresponding to the tracking signal output from the terminal A is input to the current output from each of the light receiving regions 23a to 23d of the third through the signal processing circuit 200 via the signal processing circuit 200.

FIG. 16 is a block diagram schematically showing a configuration of the photodetector 23 and a signal processing circuit 100 that performs signal processing based on the current output from the photodetector 23.

That is, as shown in FIG. 16, the signal processing circuit 200 performs the following signal processing.

That is, the currents output after photoelectric conversion in the first to fourth light receiving regions 23a to 23d of the photodetector 23 are input to current-voltage converters 81a to 81d for current-voltage conversion, respectively. Signals Ia to Id are generated.

Then, a sum signal of voltage signals output from two sets of light receiving areas located at diagonal positions of the four light receiving areas is generated. That is, the first light receiving region 23a and the fourth
The signals Ia and Id output from the light receiving region 23d are input to an adder 92a that generates a sum signal, and a first diagonal sum signal is generated. Second light receiving area 23b and third light receiving area 2
The signals Ib and Ic output from the third and third signals 3c are input to an adder 92b that generates a sum signal, and a second diagonal sum signal is generated.

The first diagonal sum signal and the second diagonal sum signal are supplied to a phase comparator 93 and a differential amplifier 94, respectively.
And a signal level difference corresponding to the phase difference is detected. The difference signal corresponding to the signal level difference output from the differential amplifier 94 corresponds to a tracking error signal and is input to the terminal A.

A track error signal is generated by the signal processing unit shown in FIG. 15 based on the signal output to the terminal A, and the focus of the spot converged by the objective lens 36 and the pit row P on the recording surface of the optical disk D are recorded. Control, ie, tracking, to eliminate the deviation from the center of the track.

In the tracking, the coils 41, 41 are output based on the track shift signal corresponding to the difference signal between the first and second diagonal sum signals output from the photodetector 23 and the signal processing circuit 200. Is supplied with a current in a predetermined direction, as a result of attraction or repulsion due to electromagnetic field interaction with a magnetic field provided by the magnets 44, 44, the lens holder 37 (objective lens 36) is moved to the recording surface of the optical disc D. The optical disk D is moved toward either the center or the outer periphery in the radial direction of the optical disk D in the direction orthogonal to the pit row P along the line.

As described above, according to the optical head device 3 according to the fourth embodiment, the track shift of the objective lens 36 is caused by two sets of diagonal sum signals arranged at diagonal positions of the photodetector 23. Is detected as a difference signal.

As described above, the tracking control signal is calculated by the track shift control circuit 64 on the basis of the output signal output from the differential amplifier 94, and as if the track shift occurs due to the lens shift of the objective lens 36. It is possible to compensate for the offset amount that acts as an error, that is, the influence of the offset component included in the track shift signal. Therefore, crosstalk in a high-density optical disk represented by an optical disk for DVD can be significantly reduced.

Next, a fifth embodiment will be described.

The optical head device according to the fifth embodiment includes a gain controller for adjusting the signal level in the signal processing circuit 200. Note that the other configuration is substantially the same as that of the fourth embodiment, and a detailed description thereof is omitted here.

FIG. 17 is a block diagram schematically showing a signal processing circuit applied to the optical head device according to the second embodiment.

That is, in the signal processing circuit 200,
In addition to the signal processing circuit shown in FIG. 16, the signal level of the output signal output from the adder 92a that generates the first diagonal sum signal, and the adder 92b that generates the second diagonal sum signal
A gain controller 95 for adjusting at least one of the signal levels of the output signal output from the control circuit is added.

In the example shown in FIG. 17, a gain controller 95 is provided downstream of the adder 92a so as to adjust the signal level of the first diagonal sum signal output from the adder 92a.

When there is no lens shift due to, for example, an accuracy error or an assembly error of a component of the optical head device or an inclination of the optical disk, the gain controller 95 generates the first diagonal sum signal and the second diagonal sum signal. This is to deal with the case where the phase difference between the diagonal sum signals should be 0 but not 0. Thereby, the effect of reducing the track offset component can be further improved.

According to the above-described fourth and fifth embodiments, the number of light receiving regions is smaller than that of the first to third embodiments, so that the signal calculation processing can be simplified.

FIGS. 19 and 20 show FIGS.
The lens shift amount of 0 mm in the comparative example shown in (a) and (b) and the second embodiment shown in FIG.
The simulation results of the phase difference signals at 0.2 mm and 0.4 mm are shown. The horizontal axis indicates the detrack amount, which is the deviation between the center of the condensed spot and the center of the pit row P, in units of track pitch. Is shown. The vertical axis represents the level of the phase difference signal in units of channel bit time. Note that this simulation was performed under the following conditions. The light source wavelength is 660 nm, the numerical aperture of the objective lens is 0.60, the track pitch of the optical disk is 0.74 μm, and the pit width is 0.4.
0 μm, pit length 0.63 μm, pit depth 70 n
m, the substrate thickness is 0.6 mm.

As shown in FIG. 19, in the comparative example, an offset component, that is, a track offset occurs in the phase difference signal, and the tracking control performance is reduced. It can be seen that the track offset increases as the lens shift amount increases.

On the other hand, as shown in FIG. 20, in the optical head device to which the second embodiment is applied, the occurrence of the offset component is suppressed regardless of the lens shift amount.

As is clear from the comparison between FIGS. 19 and 20, by applying the above-described embodiment,
The effect of reducing the large track offset component was confirmed.

As described above, according to the optical head device of the first embodiment, the light source that emits the light beam and the light source that emits the light beam from the light source onto the recording surface of the recording medium are collected. An optical head device comprising: an optical unit; and a photoelectric conversion unit configured to convert a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion unit is converged by the condensing unit. When the condensed spot obtained by moving in the radial direction of the recording medium, the recording medium is substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. A region which is located on both sides of a first dividing line defined in the direction and receives a light beam,
A central light receiving member formed in a rectangular shape having a length in a direction perpendicular to the dividing line shorter than the beam diameter of the reflected light beam and a length in a direction parallel to the first dividing line longer than the beam diameter of the reflected light beam. The region, located outside the central light receiving region, is substantially equally divided by the first dividing line, and a second dividing line substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam, First to fourth light receiving areas for receiving the reflected light beam protruding from the central light receiving area, and the first light receiving area is located at a position adjacent to the first to fourth light receiving areas in the central light receiving area. Fifth to eighth light receiving areas substantially equally divided by the dividing line and the second dividing line are formed, and the reflection incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other, respectively. Photoelectric light beam The first to fourth sum signals obtained by the conversion are generated, and the first to fourth sum signals are two sets of sum signals output from regions located at diagonal positions to each other. Generating first and second diagonal sum signals;
Third and fourth signals which are two sets of sum signals of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam incident on the eighth to eighth light receiving areas. Generating a diagonal sum signal, including a first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the fourth diagonal sum signal; Generating a second difference signal obtained by subtracting the fourth diagonal sum signal from the second diagonal sum signal, and detecting a phase difference between the first difference signal and the second difference signal; Tracking for moving a signal in a direction traversing the pit row so that the center of the pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the condensing section. Since it is a track error signal used for control, the Generation of click offset can be greatly reduced.

Further, according to the optical head device of the second embodiment, the light source for emitting the light beam and the light condensing means for condensing the light beam emitted from the light source on the recording surface of the recording medium are provided. A photoelectric conversion unit for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion unit is obtained by being converged by the condensing unit. When the condensed spot moves in the radial direction of the recording medium, the recording medium is defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion unit and moves. The first division line is located on both sides of the first division line and receives a light beam, and the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam; A central light receiving area formed in a rectangular shape having a length in a direction parallel to the direction of the reflected light beam longer than the beam diameter of the reflected light beam, the first dividing line being located outside the central light receiving area, and the first dividing line; A first to a fourth light receiving area for receiving the reflected light beam which is substantially equally divided by a second dividing line which is substantially orthogonal to the line and which substantially divides the reflected light beam, and which protrudes from the central light receiving area. At positions respectively adjacent to the first to fourth light receiving regions in the central light receiving region, fifth to eighth light receiving regions substantially equally divided by the first division line and the second division line are formed, Generating first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving regions and the fifth to eighth light receiving regions adjacent to each other,
Generating first and second diagonal sum signals, which are two sets of sum signals output from regions located diagonally to each other, among the first to fourth sum signals; Third and fourth signals which are two sets of sum signals of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam incident on the eighth to eighth light receiving areas. A diagonal sum signal is generated, and when the center of a pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam that has passed through the light condensing means, the third and fourth pairs are generated. The gain of at least one of the third and fourth diagonal sum signals is adjusted so that the phase difference of the angle sum signals matches, and the first diagonal including the gain-adjusted third diagonal sum signal is adjusted. A first difference signal obtained by subtracting the third diagonal sum signal from the sum signal;
A second difference signal is generated by subtracting the fourth diagonal sum signal from the second diagonal sum signal including the gain-adjusted fourth diagonal sum signal, and the first difference signal and the second difference signal are generated. The phase difference signal generated by detecting the phase difference with the center of the pit row formed in advance on the recording surface of the recording medium and the center of the light beam passed through the light condensing means, Since the track error signal is used for tracking control for moving the light condensing means in the direction crossing the pit row, the occurrence of track offset at the time of lens shift can be significantly reduced.

Further, according to the optical head device of the third embodiment, the light source for emitting the light beam, the light condensing means for condensing the light beam emitted from the light source on the recording surface of the recording medium, A photoelectric conversion unit for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion unit is a condensed light obtained by being converged by the condensing unit. When the light spot moves in the radial direction of the recording medium, the recording medium is defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion means and moves. A region located on both sides of the first dividing line and receiving a light beam, wherein the length in a direction orthogonal to the first dividing line is shorter than the beam diameter of the reflected light beam;
A central light receiving region formed in a rectangular shape having a length in a direction parallel to the first dividing line longer than a beam diameter of the reflected light beam, and the first dividing line being located outside the central light receiving region; And a first to fourth light receiving units that receive the reflected light beam that is substantially equally divided by a second dividing line that is substantially orthogonal to the first dividing line and that substantially divides the reflected light beam, and that protrudes from the central light receiving area. 5th to 8th light receiving portions, which are substantially equally divided by the first dividing line and the second dividing line, are provided at positions adjacent to the first to fourth light receiving regions in the central light receiving region. Regions are formed, and generate first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving regions and the fifth to eighth light receiving regions adjacent to each other,
Generating first and second diagonal sum signals, which are two sets of sum signals output from regions located diagonally to each other, among the first to fourth sum signals; Third and fourth signals which are two sets of sum signals of signals output from areas located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam incident on the eighth to eighth light receiving areas. Generating a diagonal sum signal, including a first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the fourth diagonal sum signal; A second difference signal obtained by subtracting the fourth diagonal sum signal from the second diagonal sum signal is generated, and passes through the center of a pit row formed in advance on a recording surface of the recording medium and the condensing means. The phase difference between the first difference signal and the second difference signal is matched when the center of the light beam matches. A gain of at least one of the first difference signal and the second difference signal is adjusted, and a phase difference signal generated by detecting a phase difference between the gain-adjusted first difference signal and the second difference signal is generated. A tracking control for moving the light condensing means in a direction crossing the pit row in order to make the center of the pit row formed in advance on the recording surface of the recording medium coincide with the center of the light beam passing through the light condensing means. Since the track error signal is used, the occurrence of track offset at the time of lens shift can be significantly reduced.

Further, according to the optical head device of the fourth embodiment, the light source for emitting the light beam and the light condensing means for condensing the light beam emitted from the light source on the recording surface of the recording medium are provided. A photoelectric conversion unit for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion unit is obtained by being converged by the condensing unit. When the condensed spot moves in the radial direction of the recording medium, the recording medium is defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion unit and moves. In the region not receiving the light beam located on both sides of the first dividing line, the length in the direction orthogonal to the first dividing line is shorter than the beam diameter of the reflected light beam, and flat A dead region length direction is formed in a long rectangular shape than the beam diameter of the reflected light beam such, while located outside of the dead region, the first dividing line,
A first dividing line that is substantially equally divided by a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and that receives the reflected light beam protruding from the insensitive area;
To a fourth light receiving area, and among signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, signals output from areas located at diagonal positions to each other are output. A phase difference signal generated by generating first and second diagonal sum signals, which are two sets of sum signals, and detecting a phase difference between the first and second diagonal sum signals. Tracking control for moving the light condensing means in a direction crossing the pit row in order to make the center of the pit row formed in advance on the recording surface of the recording medium coincide with the center of the light beam having passed through the light condensing means. To be used as a track error signal for
The occurrence of track offset at the time of lens shift can be greatly reduced.

According to the optical head device of the fifth embodiment, the light source for emitting the light beam and the light condensing means for condensing the light beam emitted from the light source on the recording surface of the recording medium are provided. A photoelectric conversion unit for converting a reflected light beam reflected and diffracted on the recording surface of the recording medium into an electric signal, wherein the photoelectric conversion unit is obtained by being converged by the condensing unit. When the condensed spot moves in the radial direction of the recording medium, the recording medium is defined in a direction substantially orthogonal to the direction in which the reflected light beam reflecting the condensed spot is projected onto the photoelectric conversion unit and moves. In the region not receiving the light beam located on both sides of the first dividing line, the length in the direction orthogonal to the first dividing line is shorter than the beam diameter of the reflected light beam, and flat A dead region length direction is formed in a long rectangular shape than the beam diameter of the reflected light beam such, while located outside of the dead region, the first dividing line,
A first dividing line that is substantially equally divided by a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and that receives the reflected light beam protruding from the insensitive area;
To a fourth light receiving area, and among signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, signals output from areas located at diagonal positions to each other are output. A first and a second diagonal sum signal, which is a sum signal of two sets of signals, are generated, and a center of a pit row formed in advance on a recording surface of the recording medium and a center of a light beam passing through the light condensing unit The gain of at least one of the first diagonal sum signal and the second diagonal sum signal is such that the phase difference between the first diagonal sum signal and the second diagonal sum signal coincides when And a phase difference signal generated by detecting a phase difference between the first diagonal sum signal and the second diagonal sum signal whose gain has been adjusted is previously formed on a recording surface of the recording medium. In order to match the center of the pit row with the center of the light beam that has passed through the focusing means, To the track error signal used for tracking control for moving the optical means in a direction transverse row of pits, the occurrence of the track offset during lens shift can be significantly reduced.

[0218]

As described above, according to the present invention,
An optical head device capable of reliably removing an offset component included in a track error signal can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an optical disk device having an optical head device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of an optical head device incorporated in the optical disk device shown in FIG.

FIG. 3 is a schematic diagram illustrating an example of an actuator applied to the optical head device illustrated in FIG. 2;

FIG. 4 is a schematic view showing an example of a fixed optical system applied to the optical head device shown in FIG.

FIG. 5 is a schematic view illustrating a lens holder of the actuator shown in FIG. 3 and its vicinity.

FIG. 6 is a schematic diagram illustrating a state of a reflected laser beam from an optical disk returned to an objective lens of the actuator shown in FIGS. 3 and 5;

FIG. 7 is a schematic diagram showing a light receiving area of a photodetector used for detecting a track shift capable of detecting an offset component included in the reflected laser beam shown in FIG. 6 in the fixed optical system shown in FIG. 4; It is a top view.

FIGS. 8A and 8B are diagrams showing a relative positional relationship of a light beam when there is no lens shift with respect to the photodetector shown in FIG. 7 and when there is a lens shift;

FIG. 9 is a schematic block diagram illustrating an example of a signal processing unit and a control unit that can be used in the signal processing unit and the control unit of the optical disc device illustrated in FIG. 1;

FIG. 10 is a schematic block diagram illustrating a configuration of a signal processing circuit applied to the signal processing unit and the control unit illustrated in FIG. 9;

FIG. 11 is a schematic block diagram showing a configuration of a modification of the signal processing circuit shown in FIG. 10;

FIG. 12 is a schematic block diagram showing a configuration of a modified example of the signal processing circuit shown in FIG. 10;

13 is a light receiving area of a modified example of the photodetector used for detecting a track shift capable of detecting an offset component included in the reflected laser beam shown in FIG. 6 in the fixed optical system shown in FIG. 4; FIG.

14 (a) and (b) show a case where there is no lens shift with respect to the photodetector shown in FIG. 13;
FIG. 4 is a diagram illustrating a relative positional relationship between light beams when there is a lens shift.

FIG. 15 is a schematic block diagram illustrating an example of a signal processing unit and a control unit that can be used for the signal processing unit and the control unit of the optical disc device illustrated in FIG. 1;

FIG. 16 is a schematic block diagram illustrating a configuration of a signal processing circuit applied to the signal processing unit and the control unit illustrated in FIG. 15;

FIG. 17 is a schematic block diagram showing a configuration of a modified example of the signal processing circuit shown in FIG. 16;

FIGS. 18A and 18B are diagrams showing a relative positional relationship of a light beam when there is no lens shift with respect to the photodetector of the comparative example and when there is a lens shift;

FIG. 19 is a diagram illustrating a simulation result of a phase difference signal in a comparative example when a lens shift amount is used as a parameter.

FIG. 20 is a diagram illustrating a simulation result of a phase difference signal in the second embodiment illustrated in FIG. 11 when a lens shift amount is used as a parameter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk apparatus, 3 ... Optical head apparatus, 3a ... Fixed optical system, 3b ... Actuator, 5 ... Signal processing part, 7 ... Motor, 9 ... Control part, 10 ... Housing, 11 ... Semiconductor laser, 12 ... Collimator lens, 13: Elliptical correction prism, 14: Beam splitter (polarization), 15: λ / 4 plate (phase delay element), 16: Beam splitter (half mirror), 17: Convergent lens, 18: Concave lens, 19: Cylindrical lens, Reference Signs List 20 photodetector, 21 mirror, 22 convergent lens, 23 photodetector, 23 (a to d) light receiving area (track error detection), 23 (e to h) light receiving area (offset detection), 24 dead area Reference numeral 33: carriage, 34: radial drive coil, 35: rising mirror, 36: objective lens, 5 ... Main control circuit, 51 ... Information reproduction circuit, 61 ... Linear motor control circuit, 62 ... Focus error detection circuit, 63 ... Focus control circuit, 64 ... Track deviation detection circuit, 65 ... Track control circuit, 66 ... Laser drive circuit, 71 (a to d): current-voltage conversion circuit, 72: adder, 73 (a and b): differential amplifier, 74: adder, 81 (a to h): current-voltage conversion circuit, 82 (a) To d): an adder, 83 (a and b): an adder, 84 (a and b): an adder, 85 (a and b): a differential amplifier, 86: a differential amplifier, 87: a differential amplifier, 88: adder, 90 (a and b): gain controller, 91: gain controller, 92 (a and b): adder, 94: differential amplifier, 95: gain controller, 100: signal processing circuit, 200 ... Signal processing circuit, D: Optical disk, P: Pit row.

Claims (15)

[Claims] A light source for emitting a light beam; a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium; and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting a beam into an electric signal, the photoelectric conversion means, when the condensed spot obtained by converging by the condensing means is moved in the radial direction of the recording medium, The recording medium receives light beams positioned on both sides of a first division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. In the region not to be, the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is larger than the beam diameter of the reflected light beam. long A dead area formed in a rectangular shape, and a second dividing line located outside the dead area, the first dividing line, and substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam. And a first to a fourth light receiving area for receiving the reflected light beam protruding from the insensitive area, and photoelectrically converting the reflected light beam incident on the first to the fourth light receiving area. Generating first and second diagonal sum signals, which are two sets of sum signals of signals output from regions located diagonally to each other, among the obtained signals, And a phase difference signal generated by detecting a phase difference between the second diagonal sum signal and a center of a pit row formed in advance on a recording surface of the recording medium and a light beam having passed through the condensing means. For crossing the pit row with the light condensing means to match the center An optical head device which is characterized in that the track error signal used for tracking control for moving the. 2. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting a beam into an electric signal, the photoelectric conversion means, when the condensed spot obtained by converging by the condensing means is moved in the radial direction of the recording medium, The recording medium receives light beams positioned on both sides of a first division line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves. In the region not to be, the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is larger than the beam diameter of the reflected light beam. long A dead area formed in a rectangular shape, and a second dividing line located outside the dead area, the first dividing line, and substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam. And a first to a fourth light receiving area for receiving the reflected light beam protruding from the insensitive area, and photoelectrically converting the reflected light beam incident on the first to the fourth light receiving area. The first and second diagonal sum signals, which are two sets of sum signals of the signals output from the regions located diagonally to each other, are generated from the obtained signals, When the center of the previously formed pit row coincides with the center of the light beam that has passed through the condensing means, the phase difference between the first diagonal sum signal and the second diagonal sum signal matches. At least one of the first diagonal sum signal and the second diagonal sum signal The phase difference signal generated by detecting the phase difference between the first diagonal sum signal and the second diagonal sum signal whose gain has been adjusted is recorded on the recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction crossing the pit row so that the center of the pit row formed in advance and the center of the light beam passing through the light condensing means coincide with each other. An optical head device characterized by the above-mentioned. 3. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. A photoelectric conversion unit that converts a beam into an electric signal, wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, The recording medium is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensed spot is projected onto the photoelectric conversion means and moves; A region not receiving the light beam including the intensity center of the zero-order light component of the reflected light beam from the medium, wherein the length in the direction orthogonal to the first dividing line is shorter than the beam diameter of the reflected light beam. And the first
A dead area formed in a rectangular shape whose length in a direction parallel to the dividing line is longer than the beam diameter of the reflected light beam; and a light beam reflected from the recording medium positioned outside the dead area. Of the light beam mainly or partially reflected from the light beam in which only the zero-order light component and the first-order light component generated in the radial direction of the pit row overlap, and the light beam reflected and diffracted by the recording medium Among the light beams mainly composed of a part or all of the light beam in which only the 0th-order light component and the -1st-order light component generated in the radial direction of the pit row overlap, the reflected light beam protruding from the insensitive region is received. A first to fourth light-receiving areas divided substantially equally by the first dividing line and a second dividing line substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam.
A light receiving area, and among signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, two of signals output from areas located at diagonal positions to each other Generating first and second diagonal sum signals as a sum signal of a set, detecting a phase difference between the first diagonal sum signal and the second diagonal sum signal, generating a phase difference signal, It is used for tracking control in which the condensing means is moved in a direction crossing the pit row in order to make the center of the pit row formed in advance on the recording surface of the recording medium coincide with the center of the light beam passing through the condensing means. An optical head device characterized by using a track error signal. 4. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. A photoelectric conversion unit that converts a beam into an electric signal, wherein the photoelectric conversion unit is configured such that when a condensed spot obtained by being condensed by the condensing unit moves in a radial direction of the recording medium, The recording medium is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to a direction in which a reflected light beam reflected by the condensed spot is projected onto the photoelectric conversion means and moves; A region not receiving the light beam including the intensity center of the zero-order light component of the reflected light beam from the medium, wherein the length in the direction orthogonal to the first dividing line is shorter than the beam diameter of the reflected light beam. And the first
A dead area formed in a rectangular shape whose length in a direction parallel to the dividing line is longer than the beam diameter of the reflected light beam; and a light beam reflected from the recording medium positioned outside the dead area. Of the light beam mainly or partially reflected from the light beam in which only the zero-order light component and the first-order light component generated in the radial direction of the pit row overlap, and the light beam reflected and diffracted by the recording medium Among the light beams mainly composed of a part or all of the light beam in which only the 0th-order light component and the -1st-order light component generated in the radial direction of the pit row overlap, the reflected light beam protruding from the insensitive region is received. A first to fourth light-receiving areas divided substantially equally by the first dividing line and a second dividing line substantially orthogonal to the first dividing line and substantially equally dividing the reflected light beam.
A light receiving area, and among signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas, two of signals output from areas located at diagonal positions to each other First and second diagonal sum signals, which are sum signals of a set, are generated, and the center of a pit row formed in advance on a recording surface of the recording medium and the center of a light beam passing through the light condensing means are equal to one another. And adjusting the gain of at least one of the first diagonal sum signal and the second diagonal sum signal so that the phase difference between the first diagonal sum signal and the second diagonal sum signal matches. A phase difference signal generated by detecting a phase difference between the first diagonal sum signal and the second diagonal sum signal whose gain has been adjusted, and a phase difference signal of a pit row previously formed on a recording surface of the recording medium. In order to make the center coincide with the center of the light beam passing through the focusing means, The optical head device is characterized in that the track error signal used for tracking control for moving in a direction transverse to the pit row. 5. A sum signal of the first diagonal sum signal and the second diagonal sum signal, and the sum signal is used as an information signal.
The optical head device according to any one of claims 1 to 4. 6. The optical head device is mounted on an optical disk system that records and reproduces information on and from a disk-shaped recording medium on which an information pit row is formed, and the track error signal is the first diagonal sum. The average time of the phase difference between the signal and the second diagonal sum signal is ΔT,
The channel clock interval of the optical disk system is Tw
When the center of the converging spot and the center of the information pit row are displaced in the radial direction by 0.1 μm, the minimum value of ΔT / Tw is 0.5, and Of the values of ΔT / Tw that change according to the shift between the center of the light spot and the center of the information pit row,
The maximum value of the absolute value | (T1−T2) / (T1 + T2) | is 0.2, where T1 is the maximum value on the negative side and T2 is the maximum value on the negative side. The optical head device according to any one of claims 1 to 4. 7. The radial pitch of the information pits is approximately 0.74 μm, the wavelength of a light beam emitted from a light source is 635 to 650 nm, and the condensing means has a numerical aperture. The shortest length of the pits in the information pit row is 0.4 to 0.44 μm.
m.
Item 6. The optical head device according to item 1. 8. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting a beam into an electric signal, the photoelectric conversion means, when the condensed spot obtained by converging by the condensing means is moved in the radial direction of the recording medium, The recording medium is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves, and the light beam is In the light receiving area, the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is the beam diameter of the reflected light beam. Yo A central light-receiving region formed in a long rectangular shape, the first light-receiving region being located outside the central light-receiving region,
A first dividing line that is substantially equally divided by a dividing line and a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and receives the reflected light beam protruding from the central light receiving region; A fourth light receiving area, and a position adjacent to the first to fourth light receiving areas in the central light receiving area, each of which is substantially equally divided by the first division line and the second division line. An eighth light receiving area is formed, and the first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other are formed. Generating a first and a second diagonal sum signal, which are two sets of sum signals of the sum signals output from regions located diagonally to each other among the first to fourth sum signals; The fifth to eighth light receiving regions Generating a third and a fourth diagonal sum signal, which are two sets of sum signals of signals output from regions located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam; The first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the second difference diagonal sum signal including the fourth diagonal sum signal. Generating a second difference signal obtained by subtracting a fourth diagonal sum signal; detecting a phase difference between the first difference signal and the second difference signal; and generating the phase difference signal on a recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction crossing the pit row in order to match the center of the pit row formed in advance with the center of the light beam passing through the light condensing means. An optical head device comprising: 9. A light source for emitting a light beam, a light condensing means for condensing the light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium Photoelectric conversion means for converting a beam into an electric signal, the photoelectric conversion means, when the condensed spot obtained by converging by the condensing means is moved in the radial direction of the recording medium, The recording medium is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected by the condensing spot is projected onto the photoelectric conversion means and moves, and the light beam is In the light receiving area, the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is the beam diameter of the reflected light beam. Yo A central light-receiving region formed in a long rectangular shape, the first light-receiving region being located outside the central light-receiving region,
A first dividing line that is substantially equally divided by a dividing line and a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and receives the reflected light beam protruding from the central light receiving region; A fourth light receiving area, and a position adjacent to the first to fourth light receiving areas in the central light receiving area, each of which is substantially equally divided by the first division line and the second division line. An eighth light receiving area is formed, and the first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other are formed. Generating a first and a second diagonal sum signal, which are two sets of sum signals of the sum signals output from regions located diagonally to each other among the first to fourth sum signals; The fifth to eighth light receiving regions Generating a third and a fourth diagonal sum signal, which are two sets of sum signals of signals output from regions located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam; When the center of the pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the light condensing means, the phase difference between the third and fourth diagonal sum signals coincides. The gain of at least one of the third and fourth diagonal sum signals is adjusted as described above, and the third diagonal sum is obtained from the first diagonal sum signal including the gain-adjusted third diagonal sum signal. Generating a first difference signal obtained by subtracting the signal and a second difference signal obtained by subtracting the fourth diagonal sum signal from the second diagonal sum signal including the gain-adjusted fourth diagonal sum signal; A phase difference signal generated by detecting a phase difference between the first difference signal and the second difference signal, Used for tracking control in which the condensing means is moved in a direction crossing the pit row so that the center of the pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the condensing means. An optical head device for generating a track error signal. 10. A light source for emitting a light beam, a condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting the beam into an electric signal;
In the optical head device having the above, when the condensed spot obtained by being converged by the condensing unit moves in the radial direction of the recording medium, the photoelectric conversion unit reflects the light reflected by the recording medium on the condensed spot. An area which is located on both sides of a first dividing line defined in a direction substantially orthogonal to a direction in which a light beam is projected onto the photoelectric conversion means and moves, and which receives the light beam; A central light-receiving area formed in a rectangular shape whose length in a direction perpendicular to the direction of the reflected light beam is shorter than the beam diameter of the reflected light beam, and whose length in the direction parallel to the first dividing line is longer than the beam diameter of the reflected light beam. The first light receiving area is located outside the central light receiving area;
A first dividing line that is substantially equally divided by a dividing line and a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and receives the reflected light beam protruding from the central light receiving region; A fourth light receiving area, and a position adjacent to the first to fourth light receiving areas in the central light receiving area, each of which is substantially equally divided by the first division line and the second division line. An eighth light receiving area is formed, and the first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other are formed. Generating a first and a second diagonal sum signal, which are two sets of sum signals of the sum signals output from regions located diagonally to each other among the first to fourth sum signals; The fifth to eighth light receiving regions Generating a third and a fourth diagonal sum signal, which are two sets of sum signals of signals output from regions located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam; The first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the second difference diagonal sum signal including the fourth diagonal sum signal. A second difference signal obtained by subtracting the fourth diagonal sum signal is generated, and the center of the pit row formed in advance on the recording surface of the recording medium coincides with the center of the light beam passing through the light condensing means. And adjusting the gain of at least one of the first difference signal and the second difference signal so that the phase difference between the first difference signal and the second difference signal coincides with each other. A phase difference signal generated by detecting a phase difference between the signal and the second difference signal, A track error signal used for tracking control for moving the light condensing means in a direction crossing the pit row so that the center of the pit row formed in advance on the recording surface and the center of the light beam passing through the light condensing means coincide An optical head device comprising: 11. The optical head device according to claim 8, wherein a sum signal of the first diagonal sum signal and the second diagonal sum signal is generated, and the sum signal is used as an information signal. . 12. The optical head device is mounted on an optical disk system for recording and reproducing information on and from a disk-shaped recording medium on which an information pit row is formed, wherein the track error signal is different from the first difference signal. The second
When the average time of the phase difference with the difference signal is ΔT, and the channel clock interval of the optical disk system is Tw, the center of the condensed spot and the center of the information pit row are shifted in the radial direction by 0.1 μm. ΔT /
The minimum value of Tw is 0.5, and among the values of ΔT / Tw that change according to the shift between the center of the converging spot and the center of the information pit row, +
The maximum value of the absolute value | (T1−T2) / (T1 + T2) | is 0.2, where T1 is the maximum value on the negative side and T2 is the maximum value on the negative side. 8 to 11
The optical head device according to any one of the above. 13. A radial pitch of the information pits is:
The light beam emitted from the light source has a wavelength of about 635 to 650 nm, and the condensing means includes a lens having a numerical aperture of about 0.6. The minimum length of the pit is 0.4 to 0.44
The optical head device according to claim 8, wherein the optical head device has a thickness of μm. 14. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting the beam into an electric signal;
In the signal processing method for generating a tracking error signal applied to an optical head device having: the photoelectric conversion unit, wherein a condensed spot obtained by being converged by the condensing unit has moved in a radial direction of the recording medium. A light beam positioned on both sides of a first division line defined in a direction substantially perpendicular to a direction in which the reflected light beam reflected by the recording medium is projected on the photoelectric conversion means and moved by the recording medium; Where the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is the beam of the reflected light beam. A dead area formed in a rectangular shape longer than the diameter, and located outside the dead area, the first dividing line, and substantially equally dividing the reflected light beam substantially orthogonal to the first dividing line. A first to a fourth light receiving area for receiving the reflected light beam that is substantially equally divided by the two dividing lines and that protrudes from the insensitive area, wherein the reflection incident on the first to the fourth light receiving area is provided. Generating first and second diagonal sum signals, which are sum signals of two sets of signals output from regions located at diagonal positions among signals obtained by photoelectrically converting the light beam; A phase difference signal generated by detecting a phase difference between the first diagonal sum signal and the second diagonal sum signal is transmitted to a center of a pit row formed in advance on a recording surface of the recording medium and the focusing means. A signal processing method comprising: using a tracking error signal used for tracking control in which the light condensing means is moved in a direction crossing a pit row in order to match the center of a light beam that has passed through. 15. A light source for emitting a light beam, a light condensing means for converging a light beam emitted from the light source on a recording surface of a recording medium, and reflected light reflected and diffracted on the recording surface of the recording medium. Photoelectric conversion means for converting the beam into an electric signal;
In the signal processing method for generating a tracking error signal applied to an optical head device having: the photoelectric conversion unit, when a condensed spot obtained by being converged by the condensing unit moves in a radial direction of the recording medium The recording medium is positioned on both sides of a first dividing line defined in a direction substantially orthogonal to the direction in which the reflected light beam reflected by the condensed spot is projected onto the photoelectric conversion means and moves; Where the length in the direction orthogonal to the first division line is shorter than the beam diameter of the reflected light beam, and the length in the direction parallel to the first division line is the beam of the reflected light beam. A central light-receiving region formed in a rectangular shape longer than a diameter, and
A first dividing line that is substantially equally divided by a dividing line and a second dividing line that is substantially orthogonal to the first dividing line and substantially divides the reflected light beam, and receives the reflected light beam protruding from the central light receiving region; A fourth light receiving area, and a position adjacent to the first to fourth light receiving areas in the central light receiving area, each of which is substantially equally divided by the first division line and the second division line. An eighth light receiving area is formed, and the first to fourth sum signals obtained by photoelectrically converting the reflected light beams incident on the first to fourth light receiving areas and the fifth to eighth light receiving areas adjacent to each other are formed. Generating a first and a second diagonal sum signal, which are two sets of sum signals of the sum signals output from regions located diagonally to each other among the first to fourth sum signals; The fifth to eighth light receiving regions Generating a third and a fourth diagonal sum signal, which are two sets of sum signals of signals output from regions located at diagonal positions among signals obtained by photoelectrically converting the reflected light beam; The first difference signal obtained by subtracting the third diagonal sum signal from the first diagonal sum signal including the third diagonal sum signal, and the second difference diagonal sum signal including the fourth diagonal sum signal. Generating a second difference signal obtained by subtracting a fourth diagonal sum signal; detecting a phase difference between the first difference signal and the second difference signal; and generating the phase difference signal on a recording surface of the recording medium. A track error signal used for tracking control for moving the light condensing means in a direction crossing the pit row in order to match the center of the pit row formed in advance with the center of the light beam passing through the light condensing means. A signal processing method characterized by the above-mentioned.