JP4476992B2 - Tracking error signal detection device and magnetic recording device - Google Patents

Description

The present invention relates to a tracking error signal detection apparatus and a magnetic recording apparatus for an optical information recording medium such as an optical disk, a magnetic information recording medium such as a fixed magnetic disk and a flexible disk, and capable of recording information at high density. .

In a magnetic disk system for recording information on a magnetic recording medium such as a flexible disk, the track pitch of a conventional magnetic recording medium is about 200 μm, which is very wide compared to about 1.6 μm of an optical disk. Therefore, mechanically rough track positioning by a stepping motor or the like can be sufficiently handled. However, in recent years, it has been required to narrow the track pitch to several μm to several tens of μm in order to increase the capacity of the magnetic recording medium. In that case, accurate track positioning is required.

  FIG. 1 shows a configuration of a conventional magnetic recording apparatus (Patent Document 1) that detects a tracking error signal using light. In FIG. 1, a linearly polarized divergent beam 70 emitted from the semiconductor laser light source 10 is converted into parallel light by the collimator lens 20, and the parallel light enters the polarization beam splitter 30. All the parallel beams 70 incident on the polarization beam splitter 30 pass through the polarization beam splitter 30 and enter the quarter-wave plate 31. The parallel beam 70 is converted into a circularly polarized beam when passing through the quarter-wave plate 31 and is focused on the magnetic recording medium 40 by the objective lens 21.

  FIG. 2 shows the relationship between the magnetic recording medium 40 and the focused beam 70. In the magnetic recording medium 40, tracks Tn-1, Tn, Tn + 1... That are areas where information is recorded or reproduced by the magnetic head 99 are set at a predetermined pitch pt (about 20 μm). In addition, in the middle of two adjacent tracks, discrete guide grooves Gn−1, Gn, Gn + 1,... Are detected so that a tracking error signal and a synchronization signal synchronized with the rotation of the magnetic recording medium 40 can be detected optically.・ ・ Is formed.

  The beam 70 reflected and diffracted by the magnetic recording medium 40 passes through the objective lens 21 again and then enters the quarter-wave plate 31. When the light passes through the quarter-wave plate 31 again, the transmitted beam 70 is converted into a linearly polarized beam having a direction different by 90 degrees from that emitted from the light source 10. The beam 70 transmitted through the quarter-wave plate 31 is totally reflected by the polarization beam splitter 30 and enters the photodetector 50. The photodetector 50 converts the incident light into an electrical signal and inputs it to the signal processing unit 80.

  As shown in FIG. 1, the photodetector 50 includes two light receiving units 501 and 502, and signals output from the light receiving units 501 and 502 are current-voltage (IV) conversion units 851 and 852, respectively. Is converted into a voltage signal and input to the differential operation unit 871. The differential operation unit 871 performs a differential operation on the two voltage signals from the IV conversion units 851 and 852.

The voltage signals v21 and v22 output from the IV converters 851 and 852 are approximated when the beam 70 from the optical system has a displacement x from the center of the guide groove (eg, Gn) on the magnetic recording medium 40, respectively. Are sine waves of opposite phases as represented by the following formulas (1) and (2). The signals v21 and v22 are shown in FIGS. 3A and 3B, respectively. In equations (1) and (2), A is the amplitude and B is the direct current component.
[Equation 1]
v21 = −A · sin (2πx / pt) + B (1)
v22 = A · sin (2πx / pt) + B (2)
The signal v23 output from the differential operation unit 871 is a signal represented by the following expression (3), and is output from the terminal 801 as a tracking error signal.
[Equation 2]
v23 = 2 · A · sin (2πx / pt) (3)
The signal v23 is illustrated as shown in FIG. The tracking error signal v23 output from the terminal 801 is a driving unit that adjusts the relative position between the magnetic recording medium 40 and the tracking error signal detection optical system and the base 95 including the magnetic head 99 that records and reproduces information. 90, the desired track on the magnetic recording medium 40 is tracked. This tracking error signal detection method is known as a push-pull method.
JP-A-6-96453

  In the case of a conventional magnetic recording apparatus that records and reproduces information using the magnetic head 99 and detects a tracking error signal using the optical system 95, the optical system and the point S1 where the magnetic head 99 contacts the magnetic recording medium 40 The distance d from the condensing point S2 of the beam 70 from at least several hundred μm to several mm is necessary. That is, the point S 1 where the magnetic head 99 is in contact with the magnetic recording medium 40 and the condensing point S 2 of the beam 70 scan different tracks on the magnetic recording medium 40.

  When the magnetic recording apparatus is assembled, when the point S1 is just on the track of the magnetic recording medium 40, the tracking servo operating point comes to S3 which is the midpoint of the signal amplitude of the tracking error signal v23 shown in FIG. The distance d is adjusted as described above. However, when the temperature and humidity change, the magnetic recording medium 40 expands or contracts, and the track pitch pt changes accordingly. Therefore, when the tracking operation is performed at the point S3 using the tracking error signal v23 obtained from the optical system 95, the point S1 is off-tracked, and the characteristic of reproducing information is extremely deteriorated.

  In this case, for example, if the output of the tracking error signal when the point S1 is just on the track is the point S4, a temporary tracking servo is possible by applying an offset voltage so that the tracking servo is performed at the point S4. It becomes. However, the dynamic range in the direction indicated by the arrow D1 decreases, and the followability when a disturbance occurs deteriorates. Further, the servo gain of the tracking operation decreases as the point S4 moves away from the point S3. When the point S4 finally reaches the point S5, the tracking servo gain becomes 0, and a new problem arises that the tracking servo is not applied at all.

  On the other hand, in an optical disc apparatus in which a beam for detecting a tracking error signal and a beam for recording information on the information recording medium are the same, tracks are provided on the guide grooves and between the guide grooves in order to record and reproduce information at a higher density. A configuration is proposed. However, in such a configuration, the wavelength λ of the beam emitted from the light source, the numerical aperture NA of the objective lens on the information recording medium side, the mark formed on the information recording medium to enable detection of the tracking error signal, or When the period of the guide groove is Pt and the relationship of Pt> λ / NA is established, if the beam focused by the objective lens and the information recording medium are tilted from a normal angle, the same as the magnetic recording medium described above Problems arise. Specifically, the case where the wavelength λ = 650 nm, the numerical aperture NA = 0.6, the mark or guide groove period Pt = 1.48 μm, and the thickness t = 0.6 mm of the substrate of the information recording medium is applicable. .

  Further, when dust adheres to or scratches the magnetic recording medium 40, the reflectance of the reflection on the magnetic recording medium 40 changes, and the intensity of the reflected beam 70 also changes. At this time, an offset occurs in the tracking error signal, which causes a problem that the magnetic head 99 cannot be controlled on a desired track of the magnetic recording medium 40.

  Further, as in the conventional example described above, a stepping motor is provided in the tracking drive unit 90 for a magnetic recording medium having a track pitch of several μm to several tens of μm on the assumption that a tracking error signal is detected using light. If used, off-track depending on the step width of the stepping motor occurs. If the step width is made fine to reduce the amount of off-track, there arises a problem that it takes a long time to search between different tracks. These two problems can be solved by using a DC motor instead of a stepping motor in the tracking drive system. However, since it is not possible to perform mechanical positioning by using a DC motor for the tracking drive unit 90, information cannot be recorded or read on a magnetic recording medium having a track pitch of 188 μm, which is currently widely used. New problems arise.

  For example, for a magnetic recording medium having a track pitch of 50 μm, the numerical aperture NA of the objective lens 21 is about 0.017, which is an optically optimal value. However, if there is an angle shift θ between the beam 70 condensed by the objective lens 21 and the magnetic recording medium 40, the beam 70 reflected by the magnetic recording medium 40 protrudes outside the opening of the objective lens 21. There has been a problem that the amount of the beam guided to the photodetector 50 is reduced and the tracking operation becomes unstable. When the evaluation function Ev with respect to the angle shift θ is 0.5 · tan (2 · θ) / NA, the relationship between the evaluation function Ev and the light quantity I of the beam 70 guided to the photodetector 50 is as shown in FIG. . When the numerical aperture NA of the objective lens 21 is 0.017, the angle deviation θ when the light quantity I of the beam 70 on the photodetector 50 is zero, that is, when the evaluation function Ev is 1, is 0.97 degrees. No tracking error signal can be obtained.

  A first object of the present invention is to provide a tracking error signal detection device capable of always realizing a stable tracking servo operation without reducing the dynamic range and gain of a tracking error signal. A second object is to provide a tracking error signal detection apparatus in which an offset is hardly generated in a tracking error signal even when a partial change in reflectance occurs in an information recording medium. A third object is to provide a magnetic recording apparatus capable of detecting a tracking error signal on a magnetic recording medium having a track pitch of several μm to several tens of μm and a magnetic recording medium having a track pitch of 188 μm.

The tracking error signal detection apparatus of the present invention includes a light source that emits a light beam, a diffraction unit that receives the beam emitted from the light source and generates three beams, and the three beams generated by the diffraction unit. a focusing optical system for converging a minute spot on the reflection member, is reflected by the reflector, a beam splitting means for splitting the diffracted said three beams, the three beams split by the beam splitting means A photodetector that receives light and outputs a signal in accordance with the amount of light; and a signal processing unit that calculates a signal obtained from the three beams output from the photodetector and generates a tracking error signal; A periodic physical change that gives a change in reflectance is formed on the reflector, and the focal length of the condensing optical system on the reflector side in a direction parallel to the direction of the physical change. But the physical longer than the focal length in the direction perpendicular to the direction of the change, the size of the light source side of the opening of the light converging optical system in the physical direction parallel to the direction of the change, the physical specific larger than a size in the direction perpendicular to the direction of the change, the magnitude of the beam focused on the reflector in the physical direction parallel to the direction of the change is, perpendicular to the direction of the physical change It is characterized in that it is larger than the size in the direction to do.

In the above Quito tracking error signal detection apparatus, it is preferable focal length of the reflector side of the light converging optical system in the physical direction parallel to the direction of change is infinite.

In the tracking error signal detection device, the condensing optical system includes a collimating lens that converts divergent light emitted from the light source into parallel light, and a condensing light that converts parallel light converted by the collimating lens into convergent light. preferably includes a lens.

  Alternatively, the condensing optical system preferably includes a finite objective lens that converts divergent light emitted from the light source into convergent light.

  Moreover, it is preferable that the said condensing optical system is formed by resin molding.

  The beam branching means is preferably a diffraction element or a polarization beam splitter.

  Moreover, it is preferable that the period of the physical change formed in the reflector is smaller than the period of the track on the information recording medium.

  The reflector is preferably an information recording medium.

  As described above, according to the tracking error signal detection apparatus of the present invention, the light source that emits the light beam, the condensing optical system that converges the beam emitted from the light source as a minute spot on the reflector, and the reflection A beam branching means for branching the beam reflected and diffracted by the body, a photodetector for receiving the beam branched by the beam branching means and outputting a signal corresponding to the amount of light; and output from the photodetector A first computing means for computing the received signal, a variable gain amplifying means for changing the intensity of the signal outputted from the computing means and outputting at least two signals, and a signal outputted from the variable gain amplifying means And a second calculation means for adding or subtracting two signals.

  For this reason, the movement of the operating point in the tracking error signal is calculated as a change in the phase of the signal output from the second calculation means by calculating the two signals output from the variable gain amplification means by the second calculation means. Detected. At this time, by keeping the amplitude of the tracking error signal constant and performing the tracking servo operation at the midpoint of the amplitude of the tracking error signal, the magnetic head can be positioned just on the track.

  According to another tracking error signal detection device of the present invention, a light source that emits a light beam, a condensing optical system that converges the beam emitted from the light source as a minute spot on a reflector, and the reflector A beam branching unit for branching the beam reflected and diffracted by the light beam, a photodetector for receiving the beam branched by the beam branching unit and outputting a signal corresponding to the amount of light, and output from the photodetector A signal processing unit that calculates a signal to generate a tracking error signal, and a periodic physical change that gives a change in reflectance is formed in the reflector, and a beam on the reflector is the physical The magnitude in the direction parallel to the change is larger than the magnitude in the direction orthogonal to the physical change. Therefore, the change in beam intensity depending on the partial change in reflectivity in the reflector can be reduced by increasing the size of the beam focused on the reflector, and a tracking error signal with a small offset can be detected. Can do.

  According to the magnetic recording apparatus of the present invention, the light source that emits the light beam, the first condensing optical system that converges the beam emitted from the light source as a minute spot on the first reflector, A second condensing optical system for converging the beam emitted from the light source as a minute spot on the second reflector, and a beam branch for branching the diffracted beam reflected by the first and second reflectors Means, a photodetector for receiving the beam branched by the beam branching means and outputting a signal corresponding to the light quantity, and a magnetic head for recording information on the information recording medium or reproducing information on the information recording medium A signal processing unit for generating a tracking error signal from a plurality of signals output from the photodetector, and tracking of the magnetic head with respect to the information recording medium based on the tracking error signal And a physical change having a period is formed in the first and second reflectors, and the period of the physical change formed in the first reflector and the second reflection. The period of physical change formed in the body is different.

  Therefore, for a magnetic recording medium having a track pitch of several μm to several tens of μm, a tracking error signal is generated using the beam reflected by the first reflector, and for a magnetic recording medium having a track pitch of 188 μm. Thus, by generating a tracking error signal using the beam reflected by the second reflector, the tracking operation can be performed on any magnetic recording medium having a different track pitch.

Furthermore, according to another magnetic recording apparatus of the present invention, a light source that emits a light beam, a condensing optical system that converges the beam emitted from the light source as a minute spot on a reflector, and a reflection by the reflector A beam branching unit for branching the diffracted beam, a photodetector for receiving the beam branched by the beam branching unit and outputting a signal corresponding to the amount of light, and recording information on the magnetic recording medium or A magnetic head for reproducing information on a magnetic recording medium is provided, and the reflector is formed with a periodic physical change that gives a change in reflectivity, and any of the following (1) to (3) It has a component.
(1) Two mirrors integrally formed on a common support that changes the traveling direction of the beam in the optical path from the light source to the reflector,
(2) When the direction of the periodic physical change of the reflector is the first direction and the direction orthogonal to the first direction is the second direction, the opening in the second direction is the opening in the first direction. And (3) a condensing optical system in which a diffractive element is formed in the periphery.

  According to the method for adjusting a magnetic recording apparatus of the present invention, a light source that emits a light beam, a condensing optical system that converges the beam emitted from the light source as a minute spot on the reflector, and the reflector A beam branching unit for branching the reflected and diffracted beam, a photodetector for receiving the beam branched by the beam branching unit and outputting a signal corresponding to the amount of light, and recording information on the magnetic recording medium Or an adjustment method for assembling a magnetic recording apparatus having a magnetic head for reproducing information on a magnetic recording medium, wherein an angle formed between the beam condensed by the condensing optical system and the reflector is desired The position of the light source is moved in a direction perpendicular to the optical axis of the condensing optical system so that the angle becomes.

  By having the component of (1) above, the optical axis of the beam condensed by the condensing optical system and the magnetic recording medium caused by the mounting error of the mirror used when reducing the occupation area of the optical system, The angle deviation between the two mirrors cancels out the movement of one mirror by the movement of the other mirror, and no angular deviation occurs.

  By including the component (2) above, the numerical aperture NA in the second direction is increased, and due to the angular deviation between the optical axis of the beam condensed by the condensing optical system and the magnetic recording medium. It becomes difficult to be affected by beam vignetting in the optical optical system.

  In addition, since the component (3) is included, the beam in the condensing optical system that moves depending on the angular deviation between the optical axis of the beam condensed by the condensing optical system and the magnetic recording medium is Since the light is guided to the light receiving element by the diffractive element, the beam is not displaced in the condensing optical system.

  Accordingly, in any case, it is possible to provide a magnetic recording apparatus that can stably detect a tracking error signal.

  In addition, the above adjustment method corrects the angular deviation between the optical axis of the beam condensed by the condensing optical system and the magnetic recording medium due to the mounting error of the elements constituting the magnetic recording apparatus. The beam reflected by the body always returns into the aperture of the lens, and the tracking error signal can be detected stably.

  Hereinafter, embodiments of an information recording medium, a tracking error signal detection device, an information recording device, and an information recording device adjustment method according to the present invention will be described in detail with reference to FIGS. Components that can use the same components as those of the conventional magnetic recording apparatus are denoted by the same reference numerals. In addition, throughout this specification, “recording” includes not only information recording but also information reproduction and erasure.

Example 1
A first embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. FIG. 5 is a diagram illustrating the magnetic recording apparatus and the tracking error signal detection apparatus thereof according to the first embodiment. The tracking error signal detection apparatus of the magnetic recording apparatus of the first embodiment has the same configuration as that of the conventional example shown in FIG. 1, but the configuration of the signal processing unit 81 is different. FIG. 6 shows the configuration of the signal processing unit 81 of the first embodiment.

The photodetector 50 includes two light receiving units 501 and 502, and electric signals output from the light receiving units 501 and 502 are respectively input to the signal processing unit 81. Signals output from the light receiving units 501 and 502 are converted into voltage signals by the IV conversion units 851 and 852, respectively. The two voltage signals output from the IV conversion units 851 and 852 are input to the differential operation unit 872 and the addition unit 891, respectively. The differential operation unit 872 performs a differential operation on the two voltage signals output from the IV conversion units 851 and 852. When the beam 7 has a displacement x from the center of the guide groove (for example, Gn in FIG. 2), the signal v1 output from the differential calculation unit 872 becomes a sine wave as represented by Expression (4). In equation (4), A1 is the amplitude.
[Equation 3]
v1 = A1 · sin (2πx / pt) (4)
A signal output from the differential operation unit 872 is input to the variable gain amplification unit 832. The variable gain amplifying unit 832 is a variable gain amplifier that can arbitrarily change the amplitude A1 of the input signal. The signal output from the variable gain amplifying unit 832 is input to the arithmetic unit 892.

The adder 891 adds the voltage signals output from the IV converters 851 and 852. The signal v2 output from the adder 891 is a sine wave as represented by the following equation (5). In equation (5), A2 is the amplitude and B1 is the direct current component.
[Equation 4]
v2 = A2 · cos (2πx / pt) + B1 (5)
The signal output from the adder 891 is input to the clock signal generator 895, and the clock signals CLK1 and CLK2 are generated. The clock signal generation unit 895 is a phase locked loop (PLL) circuit. The clock signals CLK1 and CLK2 are both synchronized with signals obtained when scanning the discrete guide grooves Gn-1, Gn... Formed on the magnetic recording medium 40 shown in FIG. FIG. 7 shows the timing relationship between the guide groove Gn and the clock signals CLK1 and CLK2. The clock signals CLK1 and CLK2 are input to the trigger signal generation unit 896, and timing signals Sa1 and Sa2 are generated. The signal from the adder 891 is output at the timing of the timing signals Sa1 and Sa2, and is sampled and held by the sample and hold units 811 and 812, respectively. The signal sampled and held by the sample and hold unit 812 is input to the differential operation unit 873 as it is. On the other hand, the signal sampled and held by the sample and hold unit 811 is adjusted to a desired intensity by the variable gain amplification unit 831 and then input to the differential operation unit 873. The gain of the variable gain amplifying unit 831 is set so that the DC component B1 of the signal v2 is subtracted by the differential operation unit 873. At this time, the signal v3 output from the differential operation unit 873 is a sine wave obtained by subtracting a DC component from the signal v2 as represented by the following equation (6).
[Equation 5]
v3 = A2 · cos (2πx / pt) (6)
The signal output from the differential operation unit 873 is adjusted to a desired amplitude by the variable gain amplification unit 833 and then input to the operation unit 892. The arithmetic unit 892 adds the input signals and outputs a tracking error signal v4 from the output terminal 802. The signal v4 has a waveform as represented by the following formula (7).
[Equation 6]
v4 = K1 · A1 · sin (2πx / pt)
+ K2 · A2 · cos (2πx / pt)
= K1 · A1 · sin (2πx / pt)
+ K2 · A2 · sin (2πx / pt + π / 2) (7)
In Expression (7), K1 and K2 are gains of the variable gain amplifying units 832 and 833, respectively. The signal v4 is a signal whose arbitrary phase and amplitude can be set by selecting appropriate K1 and K2. For example, when K1 · A1 = K2 · A2, the signal v4 is a signal whose phase is different from the signal v1 by π / 4. The signals v1, v3, and v4 are shown in FIGS. 8A to 8C, respectively.

  The tracking error signal v4 output from the terminal 802 is input to the drive unit 90. Based on the tracking error signal v4, the drive unit 90 adjusts the relative position between the tracking error signal detection optical system and the base 95 including the magnetic head 99 for recording and reproducing information and the magnetic recording medium 40, The magnetic head 99 is tracked to a desired track.

In the magnetic recording apparatus as shown in FIG. 1, a point S1 where the magnetic head 99 contacts the magnetic recording medium 40 and a condensing point S2 of the beam 70 from the optical system respectively scan different tracks on the magnetic recording medium 40. . On the other hand, when the magnetic recording medium 40 expands or contracts due to changes in temperature and humidity, the track pitch pt changes accordingly. However, according to the magnetic recording apparatus of the present invention, when tracking is performed using the tracking error signal obtained from the optical system 95, the gain of the variable gain amplifying units 832 and 833 is changed even when the point S1 is off-tracked. By doing so, as shown in FIG. 3C, the point S1 can be turned on-track at the midpoint of the amplitude of the tracking error signal, that is, the best point S3 where the gain and dynamic range of the tracking servo are maximized. . At this time, information can be recorded on and reproduced from the magnetic recording medium 40 in the best condition. Therefore, when the magnetic recording apparatus of the present invention is used, the tracking operation is very stable. Of course, not only changes due to temperature and humidity, but also in a magnetic recording apparatus in which a medium such as a flexible disk is exchanged, the tracking servo operation can always be performed at the best point. Also, compatibility between different magnetic recording media is improved.

  The gains K1 and K2 of the variable gain amplifying units 832 and 833 may be adjusted such that, for example, the signal read from the magnetic head 99 is the best. As a method of adjusting the gain of the variable gain amplifying means, a general method such as a method of changing a bias voltage applied to a semiconductor element such as a PIN diode, a bipolar transistor, or an FET can be used.

  In the magnetic recording apparatus shown in this embodiment, since a tracking error signal can be obtained with a simple optical system that focuses one beam on a magnetic recording medium, it is possible to provide an inexpensive magnetic recording apparatus with an optical system. it can.

(Example 2)
A second embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. FIG. 9 is a diagram illustrating the magnetic recording apparatus and the tracking error signal detection apparatus according to the second embodiment. In the first embodiment shown in FIG. 5, the diffraction grating 32 that generates three beams is provided between the light source 10 and the collimating lens 20, and the beam 70 reflected by the polarization beam splitter 30 is reflected on the condenser lens 22. And the configurations of the photodetector 51 and the signal processing unit 82 are different. Other components are the same as those in the first embodiment.

  The state of the beam 70 condensed on the magnetic recording medium 40 is shown in FIG. The beam 70 includes three beams 71 to 73. The beam 71 is the zero-order diffracted light of the diffraction grating 32, and the beams 72 and 73 are the first-order diffracted light of the diffraction grating 32, respectively. On the magnetic recording medium 40, the beams 71 and 72 and the beams 71 and 73 are arranged so as to irradiate different track positions by pt / 4 (pt: track pitch), and the beams 72 and 73 are different by pt / 2. .

The configuration of the photodetector 51 and the signal processing unit 82 is shown in FIG. The photodetector 51 includes three light receiving units 503 to 505, and receives the beams 71 to 73 one by one. The electrical signals output from the light receiving units 503 to 505 of the photodetector 51 are input to the signal processing unit 82 and converted into voltage signals by the IV conversion units 853 to 855, respectively. Signals v5 to v7 output from the IV conversion units 853 to 855 are signals as represented by the following equations (8) to (10), respectively. In the equations (8) to (10), A3 is an amplitude and B2 is a direct current component.
[Equation 7]
v5 = A3 · cos (2πx / pt) + B2 (8)
v6 = A3 · sin (2πx / pt) + B2 (9)
v7 = −A3 · sin (2πx / pt) + B2 (10)
The signals v5 and v6 are input to the differential operation unit 874, and the signals v5 and v7 are input to the differential operation unit 875, and are differentially calculated. The signals v8 and v9 output from the differential operation units 874 and 875 are signals as shown by the equations (11) and (12), respectively. In equations (11) and (12), A4 is the amplitude.
[Equation 8]
v8 = A4 · sin (2πx / pt + π / 4) (11)
v9 = A4 · sin (2πx / pt−π / 4) (12)
The signals v8 and v9 are sine waves having phases different by π / 2. The signals v8 and v9 output from the differential calculation units 874 and 875 are input to the variable gain amplification units 834 and 835, respectively, adjusted to a desired amplitude, and then input to the calculation unit 893. The arithmetic unit 893 adds the input signals and outputs a tracking error signal v10 from the output terminal 803. The signal v10 has a waveform represented by Expression (13).
[Equation 9]
v10 = K3 · A4 · sin (2πx / pt + π / 4)
+ K4 · A4 · sin (2πx / pt−π / 4)
= K4 ・ A4 ・ sin (2πx / pt + φ1)
+ K3 · A4 · sin (2πx / pt + π / 2 + φ1) (13)
The tracking error signal v10 output from the terminal 803 is input to the driving unit 91. The drive unit 91 adjusts the relative position between the base 96 including the tracking error signal detection optical system and the magnetic head 99 and the magnetic recording medium 40, and the magnetic head 99 is tracked to a desired track.

  In Expression (13), K3 and K4 are the gains of the variable gain amplifying units 874 and 875, respectively, and φ1 is −π / 4. The signal v10 is a signal whose arbitrary phase and amplitude can be set by selecting appropriate gains K3 and K4. This can be easily understood by comparing the equation (13) with the equation (7) shown in the first embodiment.

  In the magnetic recording apparatus according to the second embodiment, since the sample and hold operation is not performed, the guide grooves Gn−1, Gn... Formed on the magnetic recording medium 40 need not necessarily have a discrete configuration. In addition, the present invention can be applied to a magnetic recording medium having continuous guide grooves.

(Example 3)
A third embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIG. FIG. 12 shows the configuration of the signal processing unit 83 in the third embodiment. Since other configurations are the same as those of the second embodiment, description thereof is omitted. The difference between the signal processing unit 83 shown in FIG. 12 and the signal processing unit 82 shown in FIG. 11 is that the signals v5 to v7 are input to the differential operation units 874 and 875 via the variable gain amplification units 836 to 839. That is.

  Similarly to the second embodiment, the three beams 71 to 73 are generated by the diffraction grating 32 shown in FIG. 9, the beam 71 is the zero-order diffracted light of the diffraction grating 32, and the beams 72 and 73 are the first-order diffracted lights of the diffraction grating 32. . The first-order diffracted beams 72 and 73 can have the same intensity relatively easily even if variations occur in the width, depth, shape, etc. of the grating when the diffraction grating 32 is manufactured. On the other hand, in order to make the 0th-order diffracted light 71 and the first-order diffracted lights 72 and 73 have the same intensity, it is necessary to accurately manage the width, depth, shape, and the like of the diffraction grating.

  In the second embodiment, when the zero-order diffracted light 71 and the first-order diffracted lights 72 and 73 have different intensities, a direct current component remains in the signals output from the differential calculation units 874 and 875, and the tracking error signal v10 also includes a direct current component. Remains. In general, even if a slight DC component remains in the tracking error signal v10, the tracking servo operation is not hindered. However, if the level of the remaining DC component increases due to defects such as the width, depth, and shape of the diffraction grating 32, the tracking servo operation may become unstable.

  In the third embodiment, by providing the variable gain amplifiers 836 to 839 on the input side of the differential operation units 874 and 875, the signal amplitudes of the input signals v5 to v7 can be adjusted to a desired level. Therefore, even if the intensities of the zero-order diffracted light 71 and the first-order diffracted lights 72 and 73 generated by the diffraction grating 32 are different, the direct current component included in the signals output from the differential calculation units 874 and 875 is sufficiently reduced. be able to. The tracking error signal is output from the terminal 804.

  In the third embodiment, it is possible to realize a stable tracking servo operation even when variations occur in the width, depth, shape, etc. of the grating when producing the diffraction grating 32 that generates a plurality of diffracted lights. Become. Further, even when the intensity distribution of the beam 70 emitted from the light source 10 is not uniform, the intensity of the diffracted light 71 to 73 is different, but this case is acceptable without any problem. According to the configuration of the third embodiment, it is possible to greatly relax the requirements for the diffraction grating manufacturing accuracy and the light source mounting accuracy, and to reduce the diffraction grating and assembly cost.

Example 4
A fourth embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. The configuration of the fourth embodiment is almost the same as the configuration shown in the second embodiment, and the configurations of the photodetector and the signal processing unit are different. Therefore, description of common parts is omitted.

  FIG. 13 shows the state of the beam focused on the magnetic recording medium 40 in the fourth embodiment. The beam 71 is the zero-order diffracted light of the diffraction grating 32, the beams 72 and 73 are the first-order diffracted light of the diffraction grating 32, and the beams 74 and 75 are the second-order diffracted light of the diffraction grating 32. On the magnetic recording medium 40, the beams 71 and 72 and the beams 71 and 73 are pt / 4, the beams 71 and 74 and the beams 71 and 75 are pt / 2, the beams 72 and 73 are pt / 2, and the beams 74 and 75, respectively. Are arranged to irradiate different track positions by pt.

FIG. 14 shows the configuration of the photodetector 52 and the signal processing unit 84. The photodetector 52 has five light receiving portions 506 to 510 and receives the beams 71 to 75 one by one. The five electric signals output from the light receiving units 506 to 510 are respectively input to the signal processing unit 84 and converted into voltage signals by the IV conversion units 853 to 856. Signals output from the light receiving units 509 and 510 are added on the input side of the IV conversion unit 856. The signals v11 to v14 output from the IV conversion units 853 to 856 are signals as shown by the equations (14) to (17), respectively. In the equations (14) to (17), A5 to A7 are amplitudes, and B3 to B5 are direct current components.
[Equation 10]
v11 = −A5 · sin (2πx / pt) + B3 (14)
v12 = −A6 · cos (2πx / pt) + B4 (15)
v13 = A7 · sin (2πx / pt) + B5 (16)
v14 = A6 · cos (2πx / pt) + B4 (17)
The signals v11 to v14 are respectively input to the variable gain amplifying units 836 to 839, adjusted to a desired amplitude, and then input to the differential operation units 874 and 875, where they are differentially calculated. The reason why the variable gain amplifying units 836 to 839 are provided on the input side of the differential arithmetic units 874 and 875 is the same reason as that in which the variable gain amplifying units 836 to 839 are provided in the third embodiment.

The signals v15 and v16 output from the differential operation units 874 and 875 are signals as shown by the equations (18) and (19), respectively. In equations (18) and (19), A8 and A9 are amplitudes.
[Equation 11]
v15 = A8 · sin (2πx / pt) (18)
v16 = A9.cos (2πx / pt)
= A9 · sin (2πx / pt + π / 2) (19)
The signals v15 and v16 are sine waves having phases different by π / 2. The signals v15 and v16 output from the differential calculation units 874 and 875 are input to the variable gain amplification units 834 and 835, respectively, adjusted to a desired amplitude, and then input to the calculation unit 893. The arithmetic unit 893 adds the input signals and outputs a tracking error signal v17 from the terminal 805. The signal v17 is the same as in the first to third embodiments in that an arbitrary phase and amplitude can be set by adjusting the gains of the variable gain amplifying units 834 and 835.

The magnetic recording medium 40 has a spiral or concentric continuous track, as represented by a flexible disk, and is generally operated by a drive motor. In the fourth embodiment, the phases of the signals input to the differential operation units 874 and 875 are different from each other by π / 2 as shown in the equations (14) to (17). Therefore, when the magnetic recording medium 40 rotates, even if the rotation center of the drive motor and the rotation center of the magnetic recording medium 40 rotate and the track is decentered, the tracking error signal is deteriorated in the second to second embodiments. Less than the tracking error signal detector shown in Example 3. That is, according to the fourth embodiment, a stable tracking servo operation can be performed even when the eccentricity is large in the rotation of the magnetic recording medium.

  The signal processing unit can be realized by hardware using an analog device such as an operational amplifier, but after converting the analog signal to a digital signal, it can also be processed on software. There is no restriction on the configuration of the signal processing unit.

  In addition, the arithmetic units 432 to 434 that add two signals having different phase relations by π / 2 can be used as a differential arithmetic unit depending on the polarity of the signal. Further, when a certain degree of decrease in the dynamic range can be tolerated, the calculation unit may be a signal switcher, and an input signal may be selected and output. In this case, a stable operation without oscillation or the like can be realized by providing hysteresis characteristics at the switching timing.

(Example 5)
A fifth embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. FIG. 15 is a diagram illustrating the configuration of the magnetic recording apparatus and the tracking error signal detection apparatus according to the fifth embodiment.

  In FIG. 15, the linearly polarized divergent beam 70 emitted from the semiconductor laser light source 10 enters the region 60 </ b> A of the diffractive element 60, and becomes three beams that are zero-order and ± first-order diffracted light. In the region 60B, a plurality of beams are further generated from the three beams generated in the region 60A. Here, the grating pitch of the region 60B is designed so that only the 0th-order diffracted light is incident on the aperture of the objective lens 23 among the diffracted light generated in the region 60B in the optical path from the light source 10 to the objective lens 23. Yes. The objective lens 23 is a finite objective lens and condenses the beam 70 on the reflector 45.

  On the reflector 45, a lattice pattern with a period pt of 10 μm is formed. This period pt is the same period as the period of the track on the magnetic recording medium 41. The beam 70 reflected and diffracted by the reflector 45 passes through the objective lens 23 again and then enters the region 60B of the diffraction element 60. A plurality of diffracted lights are generated from the beam incident on the region 60B, and ± 1st order diffracted lights 76 and 77 among them are received by the photodetector 53 and converted into electric signals.

  16A shows the pattern of the region 60B of the diffractive element 60, FIG. 16B shows the pattern of the region 60A of the diffractive element 60, and FIG. 16C shows the beams 76 to 77 and the light on the photodetector 53. The states of the light receiving portions 511 to 516 formed in the detector 53 are shown. In the region 60A of the diffractive element 60, an equally spaced grating with a period of 10 μm is formed, and in the region 60B of the diffractive element 60, an equally spaced grating with a period of 3 μm is formed. The lattice directions formed in the region 60A and the lattice formed in the region 60B are orthogonal to each other.

  The light source 10 is disposed on a photodetector 53 obtained by etching a silicon substrate, and the beam 70 emitted from the light source 10 is reflected by a mirror 53A formed on the silicon substrate, and the optical path of the beam 70 is the photodetector 53. Are perpendicular to the surface on which the light receiving portions 511 to 516 are formed. The beams 76A and 77A are zero-order diffracted light generated when the beam 70 emitted from the light source 10 enters the region 60A of the diffractive element 60, and the beams 76B, 76C, 77B and 77C are diffracted by the beam 70. ± 1st order diffracted light generated by being incident on the region 60A. The beams 76A to 76C and 77A to 77C are received by the light receiving portions 511 to 516, respectively.

  A tracking error signal can be generated by inputting the electrical signal output from the photodetector 53 to, for example, the signal processing unit 82 shown in FIG. 11 of the second embodiment. Specifically, signals output from the light receiving units 511 and 514 are output to the IV conversion unit 854, signals output from the light receiving units 512 and 515 to the IV conversion unit 853, and output from the light receiving units 513 and 516. The signals to be processed may be input to the IV conversion unit 855, respectively.

  A tracking error signal v <b> 10 output from the terminal 803 of the signal processing unit 82 in FIG. 11 is input to the driving unit 92. The drive unit 92 adjusts the relative position between the base 97 including the tracking error signal detection optical system and the magnetic head 99 and the magnetic recording medium 41, and tracks the magnetic head 99 to a desired track.

  FIGS. 17A to 17C show the relationship between the size of the aperture of the objective lens 23 and the focal length. The sizes of the apertures of the objective lens 23 in the X direction and the Y direction are Wx and Wy, respectively, and the distances from the objective lens 23 on the reflector 45 side to the beam condensing point are fx and fy, respectively. Here, Wx = Wy = 2 mm, fx = 12 mm, fy = ∞, the size of the aperture of the objective lens 23 is the same in the X direction and the Y direction, and the focal length in the X direction is different from the focal length in the Y direction. It is This lens is a kind of cylindrical lens. The X, Y, and Z directions correspond to the X, Y, and Z directions in FIG. 15, respectively. The X direction is a direction orthogonal to the track, the Y direction is a direction parallel to the track, and the Z direction is a direction orthogonal to these. is there.

  FIG. 18 shows the relationship between the reflector 45 and the beam 70 condensed by the objective lens 23. The beam 70 includes three beams 76 to 78, which are zero-order and first-order diffracted light generated when the beam 70 emitted from the light source 10 enters the region 60 </ b> A of the diffractive element 60. The beam 70 condensed on the reflector 45 has a strip shape with a size in the X direction of about 5 μm and a size in the Y direction of about 2 mm. In the tracking error signal detection device according to the fifth embodiment, even if dust 49 adheres to the reflector 45 or is damaged, a partial change in reflectance occurs in the reflector 45, so that the beams 76 to 78 are in the Y direction. Is so large as 2 mm, the partial reflectivity change is averaged and the intensity variation of the three beams 76-78 is reduced. Accordingly, the offset generated in the tracking error signal is reduced.

  Further, since the distance between the centers of the beams 76 to 78 is set to about 100 μm, most of the beams overlap each other. For this reason, even if a partial change in reflectance occurs in the reflector 45, the three beams 76 to 78 receive the change, and the intensity variations of the three beams 76 to 78 reflected by the reflector 45. Becomes smaller. When the intensity of the three beams 76 to 78 varies, an offset occurs in the tracking error signal, causing off-track. On the other hand, if there is no variation even if the intensities of the three beams 76 to 78 are varied, the servo gain is reduced but no offset is generated, so that the magnetic head can be controlled on a desired track.

(Example 6)
Example 6 relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIG. FIG. 19 shows the configuration of the objective lens 24 in the fifth embodiment. In the sixth embodiment, the objective lens 24 is used instead of the objective lens 23 in the fifth embodiment. Since other configurations are substantially the same, the description thereof is omitted.

  As shown in FIG. 19, the opening Wy in the Y direction of the objective lens 24 is larger than the opening Wx in the X direction. Here, Wx = 2 mm and Wy = 5 mm. The relationship between the track pitch pt on the reflector 45 and the aperture of the objective lens must be kept within a certain range in the X direction, and the Y direction can be arbitrarily set within a range in which a signal from the guide groove can be detected. It can be set. The focal length of the objective lens 24 is the same as that of the objective lens 23, and fx = 12 mm and fy = ∞. The size of the beam 70 on the reflector 45 when the objective lens 24 is used is 5 μm in the X direction and 5 mm in the Y direction, and the dimension in the Y direction is made larger than when the objective lens 23 is used. Can do.

  Further, the larger the opening of the objective lens 24 with respect to the angle shift between the reflector 45 and the beam 70, the smaller the ratio of the beam 70 reflected by the reflector 45 going to the outside of the opening of the objective lens 24. If the size of the opening is tripled, the angle deviation can be allowed to be tripled. In the sixth embodiment, by increasing the opening in the Y direction of the objective lens 24, the influence of the angular deviation between the reflector 45 and the beam 70 can be allowed without adjusting the Y direction. Therefore, in the assembly of the magnetic recording apparatus using the tracking error signal detection apparatus of the sixth embodiment, the angle deviation may be adjusted only in the X direction, and the adjustment work is completed in a short time. Therefore, the magnetic recording device according to the sixth embodiment is easy to produce and inexpensive.

  Further, in the magnetic recording apparatus of the sixth embodiment, the tracking error signal can be obtained even when the guide groove that makes it possible to detect the tracking error signal is not formed on the magnetic recording medium 41. Therefore, for example, a tracking operation can be performed even on a magnetic recording medium having a track pitch of 188 μm, which is called 2HD, which is widely used now.

(Example 7)
Embodiment 7 relating to a magnetic recording medium of the present invention, a magnetic recording apparatus using the same, and a tracking error signal detecting apparatus thereof will be described with reference to FIG. FIG. 20 shows the configuration of the magnetic recording apparatus of Example 7 and the tracking error signal detection apparatus thereof. The configuration of the optical system and the tracking error signal detection method of the magnetic recording device and the tracking error signal detection device of the seventh embodiment are the same as those of the fifth embodiment. The seventh embodiment is different from the fifth embodiment in that a guide groove capable of optically detecting a tracking error signal is formed on the magnetic recording medium 42.

  The magnetic recording medium 42 is equivalent to a composite of the magnetic recording medium 41 and the reflector 45 shown in FIG. An optical system and a magnetic head 99 for detecting a tracking error signal are attached to a base 98. The tracking operation is performed when a tracking error signal is input to the drive unit 93.

(Example 8)
An eighth embodiment relating to the magnetic recording apparatus and the adjustment method thereof according to the present invention will be described with reference to FIGS. FIG. 21 shows the relationship among the light source 10, the objective lens 23, and the magnetic recording medium 42. The configuration of the optical system for detecting the tracking error signal is the same as that shown in FIG.

  In FIG. 21, when the beam 70 condensed by the objective lens 23 is orthogonal to the magnetic recording medium 42, the beam reflected by the magnetic recording medium 42 enters the opening of the objective lens 23 as shown by a. Therefore, the light quantity of the beam guided to the photodetector 53 does not decrease. However, for example, when the magnetic recording medium 42 is fixed and the angle θ is set, the beam reflected by the magnetic recording medium 42 protrudes out of the opening of the objective lens 23 as shown by b. Generally, when assembling a magnetic recording apparatus, a mechanism for adjusting the angular deviation θ for fixing the magnetic recording medium 42 is complicated and expensive.

  In the adjustment method of the eighth embodiment, correction is performed by adjusting the position of the light source 10 in the X direction and the Y direction that are orthogonal to the optical axis of the objective lens 23 without adjusting the angular deviation of the magnetic recording medium 42. Do. When the distance from the light source 10 to the objective lens 23 is Z1, and the amount of movement of the position of the light source 10 is ΔX1 = Z1 · tan θ, the objective lens 23 has an angle deviation θ due to the magnetic recording medium 42 being fixed. Beam deflection is completely corrected. For example, when the numerical aperture NA of the objective lens 23 on the magnetic recording medium 42 side is 0.017 and the angular deviation θ = 0.97 degrees, the beam reflected by the magnetic recording medium 42 does not enter the opening of the objective lens 23 at all. . On the other hand, for example, when Z1 = 20 mm and ΔX1 = 340 μm, the beam reflected by the magnetic recording medium 42 is completely incident on the aperture of the objective lens 23. The position adjustment of the light source 10 can be performed, for example, in the same manner as the case where the photodetector of the optical pickup head device that reproduces information on the optical recording medium is fixed, and thus detailed description thereof is omitted. Therefore, the method of adjusting and fixing the light source 10 in the X direction and the Y direction can be realized at low cost and easily.

  As shown in FIG. 20, when the diffraction element 60 is used as a light branching means for guiding the beam 70 reflected by the magnetic recording medium 42 to the photodetector 53, the light source 10 and the diffraction element 60 are integrally configured. Thus, the tracking error signal can be detected stably.

  When the distance from the light source 10 to the region 60B of the diffraction element 60 is ZLH and the distance from the objective lens 23 to the magnetic recording medium 42 is Z2, the radius RLH = Z2 · ZLH of the object lens 23 projected onto the region 60B.・ It is given by NA / Z1. When Z1 = 20 mm, Z2 = 15 mm, ZLH = 3 mm, NA = 0.17, RLH = 38 μm. When the angle deviation θ is 0.97 degrees, the position ΔX1 of the light source 10 is moved by 340 μm. At this time, the distance ΔX2 = ΔX1 · ((between the position of the beam passing through the region 60B and the center of the regular diffraction element 60). Z1-ZLH) / Z1 and is 289 [mu] m. As apparent from comparing RLH and ΔX2, the region 60B requires a much larger area than the case where no adjustment is performed by adjusting the position of the light source 10 in the X direction and the Y direction.

  However, when the area of the region 60B is increased, the ± first-order diffracted light generated in the region 60B in the forward path from the light source 10 to the objective lens 23 enters the aperture of the objective lens 23, and causes noise and noise to the tracking error signal. Become. If the pitch of the grating pattern in the region 60B is reduced, it is possible to prevent ± first-order diffracted light from the region 60B from entering the aperture of the objective lens 23. However, in that case, it is necessary to increase the area of the photodetector 53, and the magnetic recording apparatus becomes expensive.

  When the light source 10 and the diffractive element 60 are integrally formed and the position of the diffractive element 60 is moved with the movement of the light source 10, the distance δ = ΔX1 between the position of the beam passing through the region 60B and the center of the regular diffractive element.・ It is given by ZLH / Z1, and is 51 μm under the same conditions as above. As can be seen by comparing δ and ΔX2, the area of the region 60B can be made smaller by integrating the light source 10 and the diffractive element 60 than when not integrally configured, and the ± first-order diffracted light generated in the region 60B can be reduced. It becomes difficult to enter the objective lens 23, and the angle deviation θ of the magnetic recording medium 42 can be allowed to a larger angle.

  FIG. 22 shows a configuration in which the light source 10 disposed on the photodetector 53 and the diffraction element 60 are integrated. The photodetector 53 is placed on the bottom of the package 33, and the diffraction element 60 is placed on the package 33 in a shape that also serves as a case for protecting the photodetector 53 placed on the package 33. The package 33 and the diffraction element 60 are fixed with an adhesive so as not to move. The position adjustment of the light source 10 in the X direction and the Y direction is performed by moving the package 33 in the X direction and the Y direction. At this time, since the diffraction element 60 is bonded and fixed to the package 33, the diffraction element 60 also moves with the movement of the package 33.

Example 9
A ninth embodiment relating to the magnetic recording apparatus and its adjustment method of the present invention will be described with reference to FIGS. FIGS. 23A and 23B show the relationship between the light source 10 and the magnetic recording medium 42 in Example 9, respectively. The basic configuration of the magnetic recording apparatus according to the ninth embodiment is the same as that illustrated in FIG. The difference from the magnetic recording apparatus shown in Example 7 is that two reflecting surfaces 34A and 34B are provided before and after the objective lens 23 and the optical path is bent in order to collect the optical system in a small volume.

  As shown in FIG. 23A, when the reflecting surfaces 34A and 34B are arranged at regular angles, the beam reflected by the magnetic recording medium 42 enters the aperture of the objective lens 23 as shown in c. To do. On the other hand, for example, when the reflecting surface 34A has an angular deviation θM1, the beam reflected by the magnetic recording medium 42 protrudes from the opening of the objective lens 23 as shown by d.

  When the reflecting surfaces 34A and 34B are attached to the base 98 as separate parts, the angular deviation of the reflecting surfaces 34A and 34B causes the beam reflected by the magnetic recording medium 42 to protrude beyond the opening of the objective lens 23. Cause. When the reflecting surfaces 34A and 34B are attached to the base 98 as separate parts, due to various factors such as uneven thickness of the adhesive when fixed and processing accuracy of the base 98, the reflecting surfaces 34A and 34B Angular misalignment exists as a non-negligible amount.

  FIG. 23B shows a case where the mirror 34 in which the reflecting surfaces 34A and 34B are integrally formed has an angular deviation θM. The mirror 34 is a block formed by resin molding into a predetermined shape such as a triangle in cross section, for example, and the reflecting surfaces 34A and 34B are formed by plating metal on the surface. The relative angular accuracy of the reflecting surfaces 34A and 34B reflects the accuracy of the mold used when the mirror 34 is formed. Therefore, by increasing the accuracy of the mold, it is possible to produce a large number of mirrors 34 with less relative angular deviation between the two reflecting surfaces 34A and 34B.

  When the mirror 34 is used, the angle deviation of the reflecting surface 34A is corrected by the angle deviation of the reflecting surface 34B, and does not depend on the angle deviation θM when the mirror 34 is attached, and the angle formed between the magnetic recording medium 42 and the beam is constant. It is. Accordingly, the beam reflected by the magnetic recording medium 42 enters the opening of the objective lens 23. As a result, according to the ninth embodiment, the magnetic recording apparatus can be reduced in size and can be easily assembled.

  Further, when the objective lens 23 is mounted on the mirror 34, the allowable range of the mounting angle error of the mirror 23 becomes wider and the assembly becomes easier than when the objective lens 23 is not mounted on the mirror 34.

(Example 10)
Example 10 relating to the magnetic recording medium of the present invention and the magnetic recording apparatus using the same will be described with reference to FIGS. 24 (a) and 24 (b). 24A and 24B show configurations of the magnetic recording medium 43 and the reflector 46 in Example 10, respectively. The basic configuration of the optical system of the magnetic recording apparatus of the tenth embodiment is the same as that shown in FIG. 15 of the fifth embodiment. In the magnetic recording apparatus shown in FIG. 15, the magnetic recording apparatus of Example 10 can be configured by using the magnetic recording medium 43 and the reflector 46 instead of the magnetic recording medium 41 and the reflector 45.

  As shown in FIGS. 24A and 24B, in Example 10, the pitch of the guide groove of the reflector 46 is set to pt / 2 with respect to the track pitch pt on the magnetic recording medium 43. The numerical aperture NA of the objective lens 23 can be increased in inverse proportion to the pitch of the guide groove. When the track pitch pt is 50 μm, the optimum numerical aperture NA of the objective lens 23 in Example 5 is 0.017. However, when the reflector 46 shown in Example 10 is used, the pitch of the guide groove is pt / Since the numerical aperture NA of the objective lens is 2, 0.034 is the optimum value.

  When assembling the magnetic recording apparatus, the angular deviation when fixing the reflector 46 causes the beam reflected by the reflector 46 to protrude beyond the opening of the objective lens 23. However, in the magnetic recording apparatus according to the tenth embodiment, the numerical aperture of the objective lens 23 can be arbitrarily set by changing the pitch of the guide groove on the reflector 46, so that the numerical aperture NA of the objective lens 23 is increased. In addition, it is possible to make it less susceptible to the effects of angular deviation when the reflector 46 is fixed. That is, adjustment at the time of assembling can be eliminated, and an inexpensive magnetic recording apparatus can be provided.

(Example 11)
An eleventh embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. 25 (a) and 25 (b) and FIG. FIG. 25A is a front view showing the configuration of the objective lens 25 of the magnetic recording apparatus and its tracking error signal detection apparatus of Example 11, and FIG. 25B is a side sectional view thereof. FIG. 26 shows the relationship between the photodetector 54 and the beams 78 and 79. The basic configuration of the optical system of the magnetic recording apparatus and its tracking error signal detection apparatus in the eleventh embodiment is the same as that shown in FIG. In the magnetic recording apparatus and its tracking error signal detection apparatus shown in FIG. 15, the objective lens 25 and the photodetector 54 are used in place of the objective lens 23 and the photodetector 53, whereby the magnetic recording apparatus of Example 11 and its tracking are used. An error signal detection apparatus can be configured.

  As shown in FIGS. 25A and 25B, the objective lens 25 has a region 25A which is a simple lens and a region 25B where a diffraction grating is formed on the lens. Here, the numerical aperture NA of the region 25A is 0.017, and the numerical aperture of the region 25B is 0.034. As shown in FIG. 25 (b), the cross-sectional shape of the diffraction grating in the region 25B is a sawtooth shape, and the generation of unnecessary diffracted light that becomes noise with respect to the tracking error signal is suppressed. The depth of the grating is designed so that the 0th-order diffracted light from the region 25B becomes zero. Further, the objective lens 25 is designed so that the numerical aperture of the objective lens 25 does not become larger than necessary for the beam 70 condensed on the reflector 45.

  Assuming that the objective lens 23 is replaced with 25 in FIG. 15, if there is no angular deviation when fixing the reflector 45, the beam reflected by the reflector 45 returns to the region 25A. When there is an angle shift when fixing the reflector 45, the beam reflected by the reflector 45 according to the angle enters the region 25B. The beam incident on the region 25B becomes + 1st order diffracted light and enters the region 60B of the diffraction element 60.

  As shown in FIG. 26, the photodetector 54 has three light receiving portions 517 to 519 and receives the diffracted lights 78 and 79 from the region 60 </ b> B of the diffractive element 60. The beam 78 is diffracted light generated from the beam transmitted through the objective lens region 22A, and the beam 79 is diffracted light generated from the beam transmitted through the objective lens region 25B. The beams 78 and 79 include three beams 78A to 78C and 79A to 79C, respectively. These are 0th-order diffracted light and ± 1st-order diffracted light generated in the region 60A of the diffractive element 60 in the optical path from the light source 10 to the reflector 45. Similar to the photodetector 53, the light source 10 is arranged on the photodetector 54, the beam 70 emitted from the light source 10 is reflected by the mirror 54 </ b> A, and the surface including the light receiving portions 517 to 519 of the photodetector 54. Bent in the vertical direction.

  According to the eleventh embodiment, even when the beam reflected by the reflector 45 protrudes from the opening of the region 25A of the objective lens 25 due to the angular deviation when the reflector 45 is fixed, it enters the region 25B. After that, it is diffracted and guided to the photodetector 54. Therefore, the beam of the objective lens 25 is not distorted. Therefore, it can be made difficult to be affected by the angle shift when the reflector 45 is fixed. That is, adjustment at the time of assembly can be made unnecessary, and an inexpensive magnetic recording apparatus can be provided.

(Example 12)
A twelfth embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. FIG. 27 shows the configuration of the magnetic recording apparatus of Example 12 and its tracking error signal detection apparatus.

  In FIG. 27, a linearly polarized divergent beam 70 emitted from the semiconductor laser light source 10 enters the diffraction grating 32. The incident light is diffracted by the diffraction grating 32 and becomes three beams. The three beams generated by the diffraction grating 32 are converted into parallel light by the collimator lens 20 and then enter the polarization beam splitter 35. The beam incident on the region 35A of the polarization beam splitter 35 is further branched into two beams 70A and 70B. The beam 70A is a beam reflected by the region 35A, and the beam 70B is a beam reflected by the region 35B after passing through the region 35A. The beams 70A and 70B are transmitted through the quarter-wave plate 36 and converted into circularly polarized beams, and are focused by the regions 26A and 26B of the objective lens 26, respectively. The focused beams 70A and 70B are reflected by the mirrors 37 and 38, respectively, are bent on the optical path, and then focus on the magnetic recording medium 44 and the reflector 47. The optical paths of the beams 70A and 70B can be bent by the mirrors 37 and 38, respectively, and the beams can be guided onto different magnetic recording media 44 and reflectors 47.

FIG. 28A shows the reflecting surface of the reflector 47, and FIG. 28B shows the reflecting surface of the magnetic recording medium 44. On the reflection surface of the reflector 47, a lattice pattern 7AR having a period pt1 of 188 μm is formed. In addition, a lattice pattern 7BR having a period pt2 of 50 μm is formed on the magnetic recording medium 44. The period 188 μm of the lattice pattern is the same as the track pitch of a flexible disk called 2DD or 2HD having a diameter of 3.5 inches or 5 inches, and the lattice patterns 7AR and 7BR are the roles of the tracks. Fulfill.

  The reflector 47 is made of a glass substrate, and the lattice pattern 7AR is formed by evaporating a metal such as aluminum or chromium. The magnetic recording medium 44 is a polyester substrate coated with a magnetic material, and the lattice pattern 7BR on the magnetic recording medium 44 is formed by pressing. The beams 70A and 70B applied to the magnetic recording medium 44 and the reflector 47 are respectively composed of three beams 70AA to 70AC and 70BA to 70BC generated by the diffraction grating 32. The beams 70BA to 70BC irradiate different areas by pt1 / 4 with respect to the period pt1. Further, the beams 70AA to 70AC irradiate different areas by pt2 / 4 with respect to the period pt2.

  The beams 70A and 70B reflected and diffracted by the magnetic recording medium 44 and the reflector 47 are transmitted through the objective lens 26 again, then transmitted through the quarter-wave plate 36, and the polarization direction when emitted from the light source 10. Are converted into linearly polarized beams that differ by 90 degrees. The beams 70 </ b> A and 70 </ b> B that have passed through the quarter-wave plate 36 pass through the polarization beam splitter 35 and then enter the condenser lens 27. The beams 70A and 70B are condensed by the regions 27A and 27B of the condenser lens 27, respectively, and then received by the photodetector 55 and converted into electrical signals.

  FIG. 29 shows the states of the beams 70AA to 70AC and 70BA to 70BC on the photodetector 55 and the light receiving portions 520 to 525 formed in the photodetector 55. The beam 70AA is received by the light receiving unit 524. Similarly, the beam 70AB is received by the light receiving unit 523, the beam 70AC is received by the light receiving unit 525, the beam 70BA is received by the light receiving unit 521, the beam 70BB is received by the light receiving unit 520, and the beam 70BC is received by the light receiving unit 522.

  The electric signal output from the photodetector 55 is input to the signal processing unit. As the signal processing unit, for example, the signal processing unit 83 of Example 3 shown in FIG. 12 is used. The signals output from the light receiving units 520 to 522, 523 to 525 are the same as the signals output from the light receiving units 503 to 505 of the second embodiment shown in FIG. 11, and the light receiving units 520 to 520 according to the magnetic recording medium to be used. What is necessary is just to input the suitable one of the signal output from 522,523-525 to a signal processing part.

  The tracking error signal output from the signal processing unit is input to the driving unit 94. The drive unit 94 adjusts the relative positions of the base 89 including the tracking error signal detection optical system and the magnetic heads 99 and 100 and the magnetic recording media 44 and 48, and tracks the magnetic heads 99 and 100 to desired tracks. To do. In the twelfth embodiment, since tracking is performed by optically detecting a tracking error signal, even if an inexpensive DC motor is used for the drive unit, tracking can be performed with high accuracy.

  In the magnetic recording apparatus of the twelfth embodiment, a tracking operation is performed on the magnetic recording medium 48 with a track pitch of 188 μm using signals output from the light receiving units 70BA to 70BC, and the magnetic recording medium 44 with a track pitch of 50 μm. On the other hand, since the tracking operation is performed using signals output from the light receiving units 70AA to 70AC, information can be recorded and reproduced on a plurality of types of magnetic recording media having different track pitches.

  Note that the pitch of the lattice pattern formed on the magnetic recording medium 44 and the reflector 47 shown in FIGS. 28A and 28B is an example, and the optical system should be designed appropriately for an arbitrary track pitch. Thus, it goes without saying that the magnetic recording apparatus of Example 12 can be applied.

  In the twelfth embodiment, the mirrors 37 and 38 are used to bend the optical paths of the beams 70A and 70B. However, it goes without saying that the same effect can be obtained by using other optical elements such as a prism and a diffraction grating. When there is a sufficient amount of light of the beams 70A and 70B received by the photodetector 55, a half mirror can be used instead of the polarization beam splitter 35. In this case, the quarter wavelength plate 36 is not necessary, and an inexpensive magnetic recording apparatus can be provided.

(Example 13)
A thirteenth embodiment relating to the magnetic recording apparatus and the tracking error signal detection apparatus of the present invention will be described with reference to FIGS. 30 and 31 (a) to 31 (c). FIG. 30 shows the configuration of the magnetic recording apparatus of Example 13 and its tracking error signal detection apparatus.

  In FIG. 30, a linearly polarized divergent beam 70 emitted from the semiconductor laser light source 10 enters the region 61A of the diffractive element 61, and becomes three beams, which are zero-order diffracted light and ± first-order diffracted light. Among the three beams generated in the region 61A, a plurality of beams are further generated in the regions 61BA and 61BB. The grating pitches of the regions 61BA and 61BB are designed such that only the 0th-order diffracted light is incident on the aperture of the lens 28 among the diffracted light generated in the regions 61BA and 61BB in the optical path from the light source 10 to the objective lens 28. Yes. The lens 28 is a finite objective lens, and different portions of the beam 70 are incident on the regions 28A and 28B to form two beams 70C and 70D. The objective lens 28 is formed by resin molding, for example.

  The beams 70C and 70D are reflected by the regions 39A and 39B of the mirror 39, respectively, and then condensed on the reflector 47 and the magnetic recording medium 44. As in the case of the twelfth embodiment, a grating pattern 7AR having a period pt1 of 188 μm is formed on the reflector 47. When the track pitch of the magnetic recording medium 44 has a narrow track pitch different from 188 μm, a pattern corresponding to the track pitch is formed on the magnetic recording medium 44. The beams 70C and 70D reflected and diffracted by the reflector 47 and the magnetic recording medium 44 pass through the objective lens 28 again and then enter the regions 61BA and 61BB of the diffraction element 61, respectively. A plurality of diffracted lights are generated from the beams incident on the regions 61BA and 61BB, and ± first-order diffracted lights are received by the photodetector 56.

  FIG. 31A shows the state of the regions 61BA and 61BB of the diffraction element 16. FIG. 31B shows the state of the region 61 </ b> A of the diffraction element 61. FIG. 31C shows the states of the beams 70CA to 70CF and 70DA to 70DF on the photodetector 56 and the light receiving portions 526 to 537 formed on the photodetector 56. Beams 70CA, 70CB, and 70CC are + 1st order diffracted lights generated when the beam 70C is incident on the region 16BA. Beams 70CD, 70CE, and 70CF are -1st order diffracted light generated when the beam 70C is incident on the region 16BA. Beams 70DA, 70DB, and 70DC are + 1st-order diffracted lights generated when the beam 70D is incident on the region 16BB. Beams 70DD, 70DE, and 70DF are −1st-order diffracted light generated when the beam 70D is incident on the region 16BB.

  The beam 70CA is received by the light receiving unit 527. Similarly, the beam 70CB is received by the light receiving unit 526, the beam 70CC is received by the light receiving unit 528, the beam 70CD is received by the light receiving unit 536, the beam 70CE is received by the light receiving unit 535, the beam 70CF is received by the light receiving unit 537, and the beam 70DA is received by the light receiving unit 530. The beam 70DB is received by the light receiving unit 529, the beam 70DC is received by the light receiving unit 531, the beam 70DD is received by the light receiving unit 533, the beam 70DE is received by the light receiving unit 532, and the beam 70DF is received by the light receiving unit 534.

  The signals obtained by adding the signals output from the light receiving units 527, 536, 526, 535, 528, 537, 530, 533, 529, 532, 531 and 534 are signals output from the light receiving units 520 to 525 in the first embodiment. For example, a tracking error signal can be obtained by inputting the signal into the signal processing unit 83 shown in FIG. The generated tracking error signal is supplied to the drive unit 101 so that the magnetic heads 99 and 100 are positioned on a desired track.

  In the thirteenth embodiment, the light source 10 is disposed on the photodetector 56 obtained by etching a silicon substrate. The beam 70 emitted from the light source 10 is reflected by the mirror 56A formed on the silicon substrate so that the optical path of the beam 70 is perpendicular to the surface on which the light receiving portions 526 to 537 of the photodetector 56 are formed. Emitted.

  The beams 70 </ b> C and 70 </ b> D reflected by the reflector 47 and the magnetic recording medium 44 are configured to be received by one photodetector 56 in which the light source 10 is disposed. Furthermore, since the finite objective lens 28 is used, the magnetic recording apparatus can be downsized. Further, by equalizing the distances from the light source 10 to the regions 28A and 28B, the lens 28 can be constituted by one part, and the regions 28A and 28B can be formed by one molding. As a result, cost reduction of the magnetic recording apparatus can be realized.

  In the thirteenth embodiment, the focus servo is not described, but it can be used if necessary. Further, the magnetic recording apparatus of the thirteenth embodiment is not limited by any focus error signal detection method, and any of the astigmatism method, Foucault method, spot size detection method and the like generally used in optical disk devices. A scheme can also be used. In addition, although a semiconductor laser is used as the light source, other light sources such as an inexpensive light-emitting diode can be used depending on the track pitch and the numerical aperture of the lens.

(Example 14)
A fourteenth embodiment relating to the information recording medium, information recording apparatus and tracking error detection apparatus of the present invention will be described with reference to FIGS. 32 and 33. FIG. FIG. 32 shows the structure of the information recording medium of Example 14. Examples 1 to 13 above mainly relate to a magnetic recording medium and a magnetic recording apparatus, but an information recording medium of Example 14 relates to an optical disk. That is, the tracking error signal detection apparatus of the present invention can be applied not only to a magnetic recording medium such as a flexible disk but also to an optical disk. The optical system of the information recording apparatus and tracking error detection apparatus of the fourteenth embodiment can be the same as the optical system of the first embodiment shown in FIG. 5, for example.

  32, Gn-1, Gn, Gn + 1,... Are guide grooves as patterns that enable detection of tracking error signals, and Pt is the period of adjacent guide grooves. Tn−1, Tn, Tn + 1... Indicate tracks on which information is recorded / reproduced. Tracks Tn−1, Tn, Tn + 1... Are provided on the guide grooves Gn−1, Gn, Gn + 1. tp is the period of the adjacent track. Therefore, there is a relationship of pt = 2 · tp.

  The guide grooves Gn-1, Gn, Gn + 1,... Have two patterns R1, R2 periodically. The patterns R1 and R2 are formed at different positions by ± Δpt in the direction orthogonal to the track. Here, pt = 1.48 μm, tp = 0.74 μm, and Δpt = 0.04 μm.

  FIG. 33 shows the configuration of the signal processing unit 85 in the information recording apparatus and its tracking error signal detection apparatus in the fourteenth embodiment. Signals output from the light receiving units 501 and 502 of the photodetector 50 are subjected to current-voltage conversion by current-voltage conversion units 851 and 852, respectively. The signals output from the current-voltage converters 851 and 852 are differentially calculated by the differential calculator 872. A signal output from the differential operation unit 872 is input to the clock signal generation unit 897, and a clock signal CLK synchronized with the period of the patterns R1 and R2 is generated. The clock signal generation unit 897 is a phase locked loop (PLL) circuit. The clock signal CLK is input to the trigger signal generation unit 898, and timing signals Sa3 and Sa4 are generated.

The signals output from the differential operation unit 872 are sampled and held by the sample and hold units 811 and 812 at timings of the timing signals Sa3 and Sa4, respectively. Signals v18 and v19 output from the sample-and-hold units 811 and 812 are signals as shown by equations (20) and (21), respectively. In equations (20) and (21), A10 is the amplitude.
[Equation 12]
v18 = A10 · sin (2π (x−Δpt) / pt) (20)
v19 = A10 · sin (2π (x + Δpt) / pt) (21)
The signals sampled and held by the sample and hold units 811 and 812 are adjusted to a desired intensity by the variable gain amplification units 832 and 833 and then input to the arithmetic unit 892. The arithmetic unit 892 adds the input signals and outputs a tracking error signal v20 from the output terminal 806. The signal v20 has a waveform as expressed by the equation (22). In Expression (22), K1 and K2 are gains of the variable gain amplifying units 832 and 833, respectively.
[Equation 13]
v20 = K1 · A10 · sin (2π (x−Δpt) / pt)
+ K2 · A10 · sin (2π (x + Δpt) / pt) (22)
As in the case of the first embodiment, the signal v20 can be set to an arbitrary phase and amplitude by selecting appropriate K1 and K2. However, in order to allow the phase shift in the entire range when Δpt is small, K1 and K2 must be changed greatly, which is not practical. The tracking error signal detection apparatus according to the fourteenth embodiment is suitable for an optical disk apparatus in which the phase error of the tracking error signal is smaller than pt / 2.

  In the tracking error signal detection apparatus of the fourteenth embodiment, since a plurality of signals having different phases are obtained from one beam, even if the information recording medium is eccentric, it is hardly affected. Therefore, the information recording apparatus using the tracking error signal detection apparatus according to the fourteenth embodiment has high reliability when recording / reproducing is performed on an information recording medium having eccentricity.

  In addition, since information is recorded on and reproduced from the patterns R1 and R2 for detecting the tracking error signal and between the patterns R1 and R2, the capacity that can be recorded on the information recording medium is not reduced, so that the capacity is high. Thus, an optical information recording apparatus with high reliability can be provided.

The figure which shows the structure of the tracking error signal detection apparatus of the conventional magnetic-recording apparatus. The figure which shows the relationship between the magnetic recording medium and the beam in the conventional magnetic recording apparatus The figure which shows the signal waveform of the signal processing part in the conventional magnetic recording device The figure which shows the relationship between the inclination of the magnetic recording medium in the conventional magnetic recording apparatus, and the light quantity which injects into an objective lens 1 is a diagram illustrating the configuration of a magnetic recording apparatus and a tracking error signal detection apparatus according to a first embodiment of the invention. The figure which shows the structure of the signal processing part in Example 1. FIG. The figure which shows the relationship between the guide groove of a magnetic-recording medium in Example 1, and a timing signal. The figure which shows the signal waveform of the signal processing part in Example 1. The figure which shows the structure of the magnetic-recording apparatus of Example 2 of this invention, and its tracking error signal detection apparatus. The figure which shows the relationship between the guide groove of a magnetic recording medium in Example 2, and a timing signal. The figure which shows the structure of the signal processing part in Example 2. The figure which shows the structure of the signal processing part of the magnetic-recording apparatus of Example 3 of this invention, and its tracking error signal detection apparatus. The figure which shows the relationship between the guide groove of a magnetic recording medium used for the magnetic recording apparatus of Example 4 of this invention, and its tracking error signal detection apparatus, and a timing signal. The figure which shows the structure of the signal processing part in Example 4. The figure which shows the structure of the magnetic-recording apparatus of Example 5 of this invention, and its tracking error signal detection apparatus. (A) And (b) is a figure which shows the pattern of the diffraction element in Example 5, (c) is a figure which shows the mode of the beam on a photodetector, and a light-receiving part. (A)-(c) is a figure which shows the structure of the lens in Example 5, respectively. The figure which shows the relationship between the reflector in Example 5, and a beam. The figure which shows the structure of the objective lens of the magnetic recording apparatus of Example 6 of this invention, and its tracking error signal detection apparatus. The figure which shows the structure of the magnetic-recording apparatus of Example 7 of this invention, and its tracking error signal detection apparatus. The figure which shows the principle of the adjustment method of the magnetic recording device of Example 8 of this invention, the relationship between the light source in the adjustment method, an objective lens, and a magnetic recording medium. The figure which shows the structure of the light source and diffraction element which were arrange | positioned on the photodetector in Example 8. FIG. It is a figure which shows the relationship between the light source, magnetic recording medium, and optical system in the magnetic recording apparatus of Example 9 of this invention, and its adjustment method, (a) is when a reflective surface is arrange | positioned at a regular angle, (B) shows the case where the mirror which integrally formed the reflective surface has an angle shift. (A) is a figure which shows the structure of the magnetic recording medium of Example 10 of this invention, (b) is a figure which shows the structure of the reflector of Example 10. FIG. (A) is a front view which shows the structure of the objective lens of the magnetic recording apparatus of Example 11 of this invention, and its tracking error signal detection apparatus, (b) is the side sectional drawing. The figure which shows the relationship between the light-receiving part of the photodetector in Example 11, and diffracted light The figure which shows the structure of the magnetic-recording apparatus of Example 12 of this invention, and its tracking error signal detection apparatus. (A) is a figure which shows the reflective surface of the reflector in Example 12, (b) is a figure which shows the reflective surface of the magnetic recording medium in Example 12. The figure which shows the relationship between the beam on the photodetector in Example 12, and a light-receiving part. The figure which shows the structure of the magnetic-recording apparatus of Example 13 of this invention, and its tracking error signal detection apparatus. (A) And (b) is a figure which shows the mode of the area | region of the diffraction element in Example 13, (c) is a figure which shows the relationship between the beam on a photodetector, and a light-receiving part. The figure which shows the structure of the information recording medium in Example 14 of this invention. The figure which shows the structure of the signal processing part of the tracking error signal detection apparatus in Example 14.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor laser light source 20 Collimating lens 21 Objective lens 22 Condensing lens 23-26 Objective lens 25A-25B Area | region 26A-26B Lens 27 Condensing lens 27A-27B Area | region 28 Condensing lens 28A-28B area | region 30 Polarizing beam splitter 31 1 / Four-wave plate 32 Diffraction grating 33 Package 34 Mirrors 34A-34B Reflective surfaces 35A-35B Reflective surface 35 Beam splitter 36 1/4 wave plates 37-39 Mirrors 39A-39B Reflective surfaces 40-44 Magnetic recording media 45-47 Reflector 48 Magnetic recording medium 49 Dust 50 to 56 Photo detector 53A Mirror 54A Mirror 60 Diffraction element 60A to 60B Area 61 Diffraction element 61A Area 61BA to 61BB Area 7AR to 7BR Lattice pattern 70 Beam 70A to 70D Beam 70AA to 70AC Beam 70B ˜70BC beam 71-79 diffracted light 76A-76C diffracted light 77A-77C diffracted light 78A-78C diffracted light 79A-79C diffracted light 80-85 signal processing unit 88-89 base 90-94 drive unit 95-98 base 99 -100 Magnetic head 101 Driving unit 501 to 537 Light receiving unit 801 to 805 Terminal 811 to 812 Sample and hold unit 831 to 839 Variable gain amplifying unit 851 to 856 Current-voltage (IV) conversion unit 871 to 875 Differential operation unit 891 Adder 892-893 Operation unit 895 Clock signal generator 896 Trigger signal generator 897 Clock signal generator 898 Trigger signal generator d Distance interval D1 Direction Gn Guide groove S1 Magnetic head position S2 Condensing beam position S3 to S5 Operating point Tn track pt track pitch

Claims (9)

A light source that emits a light beam, a diffractive unit that receives the beam emitted from the light source and generates three beams, and a collection that converges the three beams generated by the diffractive unit as a minute spot on a reflector. a light optical system, is reflected by the reflector, a beam splitting means for splitting the diffracted said three beams, said beam receiving the branched the three beams by the branching unit, outputting a signal corresponding to the light amount And a signal processing unit that calculates a signal obtained from the three beams output from the photodetector and generates a tracking error signal, and the reflector has a change in reflectance. A periodic physical change is applied, and a focal length on the reflector side of the condensing optical system in a direction parallel to the direction of the physical change is orthogonal to the direction of the physical change Longer than the focal length in the size of the light source side of the opening of the light converging optical system in the direction parallel to the direction of the physical changes, than a size in the direction perpendicular to the direction of the physical change A tracking error signal detection device that is large and has a larger beam size converged on the reflector in a direction parallel to the direction of the physical change than in a direction orthogonal to the direction of the physical change.   The tracking error signal detection apparatus according to claim 1, wherein a focal length on the reflector side of the condensing optical system in a direction parallel to the direction of the physical change is infinite. The light converging optical system includes a collimating lens for converting a divergent light emitted from the light source into parallel light, according to claim 1 comprising a condensing lens for converting a parallel light converted by the collimating lens into a convergent light or 3. The tracking error signal detection device according to 2. The tracking error signal detection device according to claim 1, wherein the condensing optical system includes a finite objective lens that converts divergent light emitted from the light source into convergent light. The light converging optical system, the tracking error signal detection apparatus according to any one of claims 1 to 4, which has been formed by resin molding. It said beam splitting means is a tracking error signal detection apparatus according to any one of claims 1 to 5 which is a diffraction element. It said beam splitting means is a tracking error signal detection apparatus according to any one of claims 1 to 5 which is a polarization beam splitter. The period of the physical change formed on the reflecting body is an information tracking error signal detection apparatus according to any one of recording claims rather smaller than the period of the tracks on the medium term 1-7. The reflector tracking error signal detection apparatus according to any one of claims 1 to 7, which is the information recording medium.

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