JP2004111028A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To discriminate the kind of an optical disk being loaded in high precision by detecting the depth of an information surface of the optical disk. <P>SOLUTION: The optical disk device reads information from a plurality of kinds of optical disks having different depths of information surfaces from the optical disk surfaces. The device is provided with a light source (11), a lens (13), a photodetector (15) which detects reflected light beams from the information surface and outputs reflected light signals, a spherical aberration generating section (16) which generates minimum spherical aberration when focus is located at a reference depth determined by the depth of information surfaces of the plurality of kinds of optical disks, a focus driving section (22) which controls the location of a lens so as to move the focus along a normal direction to the information surface, a light quantity detecting section (40) which detects light quantity signals indicating the light quantity of the reflected light beams based on the reflected light signals outputted in accordance with the movement of the focus and a discrimination section (42) which discriminates the kind of an optical disk being loaded based on the symmetry of the waveforms of the light quantity signals. <P>COPYRIGHT: (C)2004,JPO

Description

{Circle around (2)} The present invention relates to a technique for discriminating the type of the loaded optical disc in an optical disc apparatus in which a plurality of kinds of optical discs such as a CD (Compact Disc), a DVD (Digital Versatile Disc), and a BD (Blu-Ray Disc) are loaded. The present invention also relates to a technique for focusing on a desired information surface and optimally adjusting spherical aberration in an optical disk having a plurality of information surfaces for recording information.

(4) When reproducing data recorded on an optical disk, the conventional optical disk device irradiates the optical disk with a relatively weak and constant light amount of light, and detects reflected light from the optical disk. For example, in an optical disk device disclosed in Patent Document 1, light is applied to an optical disk in which pits and spaces having physically different characteristics are formed. Since the intensity of the reflected light of the light applied to the optical disk is modulated by the pits and spaces, data on the optical disk can be reproduced based on the reflected light. On the other hand, when recording data on an optical disk, the optical disk device modulates the amount of light in accordance with the data to be recorded, and irradiates a material film (information surface) provided on the optical disk. Thereby, marks and spaces corresponding to the data are formed on the optical disc.

ピ ッ ト On a read-only optical disk, pits and spaces are recorded in a spiral shape. On the other hand, on an optical disc capable of both recording and reproducing data, an information surface is formed by a technique such as vapor deposition on the surface of a layer having a track formed of a spiral groove and an inter-groove region. Data is optically recorded on the information surface and optically reproduced from the information surface.

フ ォ ー カ ス Focus control and tracking control are required to record information on the optical disc or to reproduce the recorded information. Focus control is control of the focal position of the light beam in the direction normal to the surface of the optical disk (hereinafter referred to as the focus direction), and the light beam always keeps a predetermined convergence state on the recording material film. Hereinafter, controlling the focus position of the light beam on the predetermined information surface is referred to as “focus control on the predetermined information surface”. On the other hand, tracking control is control of the focus position of the light beam in the radial direction of the optical disc (hereinafter referred to as tracking direction), and always keeps the focus of the light beam on a predetermined track.

Hereinafter, a conventional optical disk device will be described with reference to FIG. FIG. 14 shows the configuration of functional blocks in a conventional optical disk device 510. The optical disk device 510 functions as a semiconductor laser 11 and a condenser lens 13 functioning as a converging irradiation unit, a focus actuator 14 functioning as a focus moving unit, an FE generator 20 functioning as a focus error detecting unit, and a focus driving unit. It has a focus drive generator 22.

The optical head 10 includes a semiconductor laser 11, a condenser lens 13, a beam splitter 12, a focus actuator 14, and a photodetector 15. The light beam output from the semiconductor laser 11 passes through the beam splitter 12 and is converged on the optical disc 1 by the condenser lens 13. The light beam reflected by the optical disc 1 passes through the condenser lens 13 again, is reflected by the beam splitter 12, and enters the photodetector 15. The condenser lens 13 is supported by an elastic body (not shown). When a predetermined amount of current flows through the focus actuator 14, the focusing lens 13 moves in the focusing direction due to electromagnetic force. Thereby, the focal position of the light beam can be changed. The light detector 15 detects the incident light beam, and sends a signal corresponding to the detected light to the FE generator 20.

The FE generator 20 responds to the signal indicating the convergence state of the light beam on the information surface of the optical disc 1 based on the signal of the photodetector 15, in other words, according to the displacement of the focal point of the light beam with respect to the information surface of the optical disc 1. The calculated error signal (focus error signal) is calculated, and the result is sent to the disk discriminator 43. The focus drive generator 22 generates a drive signal to the focus actuator 14 that moves the condenser lens 13 toward or away from the optical disc 1. This drive signal is also transmitted to the disk discriminator 43.

Next, a disc discriminating operation of the optical disc device 510 will be described with reference to FIGS. FIG. 15A shows a waveform of a signal output from the focus drive generator 22. FIG. 15B shows a waveform of a signal output from the FE generator 20. In the graphs of FIGS. 15A and 15B, the horizontal axis represents the time axis, and the vertical axis represents the signal level.

(4) The focus drive generator 22 moves the focal point of the light beam from a position that is far away from the optical disk 1 and makes the light beam approach the optical disk 1. When the position of the focal point of the light beam coincides with the position of the information surface of the optical disc 1, the level of the signal output from the FE generator 20 becomes 0, as shown as "information surface position" in FIG. This state is called "Zero Cross". When the output signal of the FE generator 20 crosses zero, the disc discriminator 43 detects the depth of the information surface of the optical disc 1 based on the level of the output signal of the focus drive generator 22. Since the distance from the natural position of the focus actuator 14 to the surface of the optical disc 1 is constant, and the amount of movement of the focus actuator 14 based on the signal from the focus drive generator 22 is also constant, the depth of the information surface of the optical disc 1 Can be detected. Since the depth from the optical disk surface to the information surface differs according to the type of the optical disk, the optical disk device 510 can determine the disk type of the optical disk 1 based on the detected depth.

Next, another conventional optical disk device will be described with reference to FIG. FIG. 16 shows a configuration of functional blocks in a conventional optical disk device 520. When the optical disk 1 having a plurality of information surfaces is loaded, the optical disk device 520 can perform focus control on a desired information surface of the optical disk 1 and position the focal point of the light beam on the desired information surface. Components common to those of the optical disk device 510 in FIG. 14 are denoted by common reference numerals, and description thereof is omitted.

In the optical disk device 520, the signal from the FE generator 20 is transmitted to the focus filter 21 and the pull-in selector 45. The focus filter 21 compensates a phase for focus control based on a signal from the FE generator 20. The focus filter 21 outputs the phase-compensated signal to the pull-in selector 45. The pull-in selector 45 selects a signal from the focus drive generator 22 or a signal from the focus filter 21 and sends it to the focus actuator 14.

Next, the focus control process of the optical disc device 520 will be described. When the focus control is not being performed (when the focus control is not operating), the pull-in selector 45 selects a signal output from the focus drive generator 22 and sends the signal to the focus actuator 14. Upon receiving the signal, the focus actuator 14 brings the focal point of the light beam closer to the optical disc 1 from a position that is far away from the optical disc 1. When the focus of the light beam coincides with the information surface of the optical disk 1, the level of the signal output from the FE generator 20 becomes 0, as shown as "information surface position" in FIG. The pull-in selector 45 switches the signal to be selectively output when the signal from the FE generator 20 crosses zero, and sends the signal from the focus filter 21 to the focus actuator 14. Thus, the position of the focal point of the light beam with respect to the information surface of the optical disc 1 is controlled. At this time, the information surface to be subjected to the focus control is the information surface at the position closest to the surface on which the light beam is irradiated. Contrary to the above operation, when the focus drive generator 22 moves the focus of the light beam away from a position sufficiently close to the optical disc 1, the information surface to be subjected to focus control is irradiated with the light beam. This is the information plane at the innermost position from the surface on the side where the user is. As described above, the focus control on the information surface is started.

Next, another conventional optical disk device will be described with reference to FIG. FIG. 17 shows a configuration of functional blocks in a conventional optical disk device 530. The optical disc device 530 can set the spherical aberration with respect to the information surface on which the light beam is focused. The optical disc device 530 has the aberration generator 16 and the aberration setting unit 30 as spherical aberration generating means, and has the aberration adjuster 32 as spherical aberration adjusting means. Note that, in FIG. 17, components common to those of the optical disk devices of FIGS. 14 and 16 are denoted by common reference numerals, and description thereof will be omitted.

In the optical disk device 530, the output signal of the photodetector 15 is sent to the FE generator 20 and the TE generator 24. The focus error signal output from the FE generator 20 is sent to the focus filter 21, where the focus error signal is subjected to predetermined processing, and sent to the focus actuator 14. Based on the signal from the photodetector 15, the TE generator 24 generates a tracking error (TE) signal indicating the positional relationship between the light beam and a track formed on the optical disc 1, and sends the signal to the amplitude detector 25. The amplitude detector 25 detects the magnitude of the amplitude of the tracking error signal from the TE generator 24 and sends the result to the aberration adjuster 32.

The aberration adjuster 32 stores the signal from the amplitude detector 25, generates a setting signal based on the signal, and sends the setting signal to the aberration setting device 30. Upon receiving the signal from the aberration adjuster 32, the aberration setter 30 sends an aberration setting signal for generating a spherical aberration at the focal point of the light beam to the aberration generator 16. The aberration generator 16 changes the spherical aberration of the light beam based on the aberration setting signal. As a result, the tracking error signal generated in the TE generator 24 changes and is output to the amplitude detector 25 again. The above-described processing (feedback processing) is performed by changing the spherical aberration in a predetermined range. The aberration adjuster 32 manages the signal from the amplitude detector 25 and the degree of spherical aberration for the signal in association with each other. Then, the aberration adjuster 32 specifies a setting signal for generating the spherical aberration at which the signal level from the amplitude detector 25 is maximized, and sends the setting signal to the aberration setting device 30.

Next, the spherical aberration adjusting operation of the optical disk device 530 will be described with reference to FIGS. FIG. 18A shows a waveform of a setting signal output from the aberration adjuster 32. FIG. 18B shows a waveform of a signal output from the amplitude detector 25. 18A and 18B, the horizontal axis represents the time axis, and the vertical axis represents the signal level.

As shown in FIG. 18 (a), the aberration regulator 32 outputs a ramp signal of a predetermined width with respect to the aberration setter 30 at time t ₀ before shown in Fig. The tracking error signal obtained based on such a setting signal has the maximum amplitude when the spherical aberration at the focal point of the light beam is minimum. On the other hand, when the spherical aberration increases, the amplitude of the tracking error signal deteriorates. Therefore, it can be said that the setting signal when the level of the output signal waveform (FIG. 18B) of the amplitude detector 25 is maximized gives the optimum spherical aberration. The aberration adjuster 32 stores the level of the setting signal when the level of the output signal of the amplitude detector 25 becomes the maximum, and sends the stored setting signal to the aberration setting unit 30 after time t _0. . As a result, after time t _0, the amplitude of the tracking error signal becomes maximum, and the amplitude of the output signal of the amplitude detector 25 is maintained at the maximum value (FIG. 18B). In this way, the spherical aberration at the focal point of the light beam can be adjusted optimally.
JP-A-52-80802

(4) In the conventional optical disk device 510 (FIG. 14), an error occurs in the depth of the detected information surface due to variations in the sensitivity of the focus actuator 14, the sensitivity of the circuit system, and the like. In addition, the position of the information surface of the rotating optical disk 1 fluctuates up and down due to surface wobbling of the optical disk 1 and surface wobbling by a drive mechanism of the apparatus. This fluctuation also causes a detection error of the depth of the information surface. When the detection error becomes large, there is a problem that the type of the disc is erroneously determined.

In the conventional optical disk device 520 (FIG. 16), when the optical disk 1 has three or more information surfaces, focus control cannot be performed on an intermediate information surface. If focus control is to be performed on the innermost information surface counted from the surface of the optical disc 1, there is a possibility that the optical disc 1 and the condenser lens 13 collide. The reason is that at the start of the focus control, the focal point of the light beam needs to be located deeper than the information surface, so that the distance between the optical disc 1 and the condenser lens 13 during the focus control operation becomes smaller.

In the conventional optical disk device 530 (FIG. 17), the focus error signal from the FE generator 20 also deteriorates in amplitude in the same manner as the tracking error signal from the TE generator 24, so that the focus control becomes unstable. This is because the spherical aberration at the focal point of the light beam is not optimal at the beginning of the operation. In this case, it is difficult to measure the amplitude of the tracking error signal even when the focus control is activated to generate the tracking error signal. Therefore, it is difficult to optimally adjust the spherical aberration.

An object of the present invention is to detect the depth of an information surface in an optical disk device in which a plurality of types of optical disks are loaded, and to accurately determine the type of the loaded optical disk. Another object of the present invention is to enable highly accurate focus control to be started on a desired information surface of an optical disk having a plurality of information surfaces. Still another object of the present invention is to realize a stable adjustment operation of spherical aberration.

The optical disk device according to the present invention can write and / or read information on a plurality of types of optical disks having different information surface depths from the optical disk surface. The optical disc device includes a light source that emits light, a lens that focuses the light to form a focus, a light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal, and the focus. Controlling the position of the lens and a spherical aberration generating unit that generates a minimum spherical aberration when the optical disk is positioned at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs; A focus driving unit that moves the focal point in a direction perpendicular to the information surface of the optical disc, and a light amount of the reflected light based on the reflected light signal output from the detection unit according to the movement of the focal point. A light amount detection unit that detects a light amount signal; and a depth of the information surface from the surface based on symmetry of a waveform of the light amount signal, and a type of the loaded optical disk based on the specified depth. Determine And a determining unit for performing the determination. This achieves the above object.

The optical disc device further includes a symmetry detection unit that detects whether the waveform of the light quantity signal is symmetric or asymmetric within a predetermined period, and outputs a symmetry display signal indicating the symmetry of the waveform of the light quantity signal. The determination unit may determine a type of the loaded optical disc based on the symmetry display signal.

The optical disc apparatus further includes a focus signal generation unit that generates a focus signal indicating a positional relationship between the focus and the information surface, and the symmetry detection unit includes a first signal in which the level of the focus signal is maximum during the predetermined period. And the second time at which the light amount signal becomes the minimum, and whether the waveform of the light amount signal is symmetric or asymmetric based on the level of the light amount signal at the first time and the second time. It may be detected.

The symmetry detection unit is configured to change the waveform of the light quantity signal when the difference between the first level of the light quantity signal at the first time and the second level of the light quantity signal at the second time is 0. It may be detected that the waveform is symmetric, and when it is not 0, it may be detected that the waveform of the light amount signal is asymmetric.

The symmetry detection unit generates the symmetry display signal indicating whether the difference is 0, positive, or negative, and the discrimination unit determines the loaded optical disc based on the symmetry display signal. It may be specified whether the depth from the surface to the information surface is deeper or shallower than the reference depth.

The reference depth may be a value within a range defined by the information surface depth of the first type optical disk and the information surface depth of the second type optical disk.

The determination unit may specify the number of information surfaces of the loaded optical disc based on a waveform of the light amount signal.

The optical disc device further includes an aberration setting unit that generates an aberration setting signal that indicates a generation amount of the spherical aberration, the spherical aberration generating unit generates a spherical aberration based on the aberration setting signal, and the determination unit includes: Further, a depth of the information surface from the surface may be specified based on the aberration setting signal.

The optical disk device according to the present invention can write and / or read information on an optical disk having a plurality of information surfaces having different depths from the optical disk surface. The optical disc device includes a light source that emits light, a lens that focuses the light to form a focus, a light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal, and the focus is When located at a reference depth determined based on the depth of the plurality of information surfaces, a spherical aberration generating unit that generates a minimum spherical aberration, and controlling the position of the lens, the plurality of information surfaces A focus drive unit that moves the focal point in a direction perpendicular to the focus, and a light amount that detects a light amount signal indicating the light amount of the reflected light based on the reflected light signal output from the detection unit in response to the movement of the focus. A detection unit; and a number detection unit configured to detect a number of the information surface counted from the optical disk surface based on a waveform of the light amount signal. This achieves the above object.

The optical disc device selects a specific number of the information surface detected by the number detection unit, and drives the focus driving unit to move the focus to a position near a specific information surface corresponding to the specific number. And a focus signal generation unit that generates a focus signal indicating a positional relationship between the focus and the information surface. The focus signal generation unit may generate the focus signal for the specific information surface. Good.

The specific information surface may be changeable based on an instruction from the selection unit.

The optical disc device further includes a symmetry detection unit that detects whether the waveform of the light quantity signal is symmetric or asymmetric within a predetermined period, and outputs a symmetry display signal indicating the symmetry of the waveform of the light quantity signal. The number detection unit may further detect a number of the information surface counted from a surface of the loaded optical disc based on the symmetry display signal.

The symmetry detection unit specifies a first time at which the level of the focus signal is maximized and a second time at which the level of the focus signal is minimized in the predetermined period, and determines the light amount at the first time and the second time. Whether the waveform of the light amount signal is symmetric or asymmetric may be detected based on the signal level.

The optical disk device according to the present invention can write and / or read information on an optical disk having an information surface. The optical disc device includes a light source that emits light, a lens that focuses the light to form a focal point, a light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal, and a control signal. A spherical aberration generating unit that generates spherical aberration based on the focus driving unit that controls the position of the lens to move the focus in a direction perpendicular to the information surface, and one side of the information surface A focus driving unit that reciprocates the focal point between the other side and a light amount indicating the amount of the reflected light based on the reflected light signal output from the detection unit in response to the movement of the focal point A light quantity detection unit that detects a signal, a symmetry detection unit that detects whether the waveform of the light quantity signal is symmetric or asymmetric, and outputs a symmetry display signal indicating the symmetry of the waveform of the light quantity signal; , The symmetry indicating signal An aberration adjuster that generates the control signal in response to the control signal, and specifies the symmetry display signal indicating that the waveform of the light amount signal is symmetric, and outputs a control signal that provides the specified symmetry display signal. An aberration adjuster set in the spherical aberration generating section. This achieves the above object.

The optical disc device further includes a focus signal generation unit that generates a focus signal indicating a positional relationship between the focus and the information surface, and the symmetry detection unit includes a first signal in which a level of the focus signal is maximum during a predetermined period. And a second time at which the light amount signal becomes minimum, and based on the levels of the light amount signal at the first time and the second time, the waveform of the light amount signal is symmetric or asymmetric within a predetermined period. May be detected.

The optical disc device further includes a focus signal generation unit that generates a focus signal indicating a positional relationship between the focus and the information surface, wherein the symmetry detection unit is configured such that a level of the light amount signal is maximized within the predetermined period. A first time and a minimum second time are specified, and the waveform of the light amount signal is symmetric or asymmetric based on the level of the focus signal at the first time and the second time. May be detected.

The method for determining the type of an optical disk according to the present invention determines the type of the loaded optical disk from among a plurality of types of optical disks having different information surfaces from the optical disk surface. The method of discriminating the type of the optical disc includes a step of emitting light, a step of forming a focal point by converging the light by a lens, and a step of detecting a reflected light of the light on the information surface to generate a reflected light signal. Generating the smallest spherical aberration when the focal point is located at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs, controlling the position of the lens, Moving the focal point in a direction perpendicular to the information surface of the loaded optical disc, and detecting a light quantity signal indicating the quantity of the reflected light based on the reflected light signal generated in accordance with the movement of the focus. And determining the depth of the information surface from the surface based on the symmetry of the waveform of the light amount signal, and determining the type of the loaded optical disk based on the specified depth. Along with a separate steps. This achieves the above object.

(4) The method for specifying an information surface of an optical disk according to the present invention specifies an information surface on which a focal point of light exists among a plurality of information surfaces having different depths from the optical disk surface. The method for identifying an information surface of an optical disc includes a step of emitting light, a step of focusing the light by a lens to form a focal point, and a step of detecting a reflected light of the light on the information surface to generate a reflected light signal. Setting the spherical aberration of the lens to a minimum when the focal point is located at a reference depth determined based on the depths of the plurality of information surfaces, controlling the position of the lens, Moving the focus in a direction perpendicular to a plurality of information surfaces, and detecting a light amount signal indicating the light amount of the reflected light, based on the reflected light signal generated in accordance with the movement of the focus, Detecting the number of the information surface counted from the optical disk surface based on the waveform of the light amount signal. This achieves the above object.

球面 The method for adjusting spherical aberration according to the present invention adjusts spherical aberration with respect to the information surface of an optical disc. The method of adjusting spherical aberration, emitting light, converging the light by a lens to form a focal point, detecting reflected light of the light on the information surface and generating a reflected light signal, Controlling the position of the lens to move the focal point in a direction perpendicular to the information surface, wherein the focal point reciprocates between one side and the other side of the information surface. Detecting a light amount signal indicating the light amount of the reflected light based on the reflected light signal generated in accordance with the movement of the focal point; and determining whether the waveform of the light amount signal is symmetric or asymmetric. Detecting and outputting a symmetry display signal indicating the symmetry of the waveform of the light quantity signal; and generating the control signal according to the symmetry display signal, wherein the waveform of the light quantity signal is Encompasses the Identify the symmetry indicating signal indicating that the step of setting the control signal to provide the symmetry indicating signal identified, a step of generating a spherical aberration based on the control signal. This achieves the above object.

The optical disk type determination program according to the present invention is a computer program that can be executed in an optical disk device and determines the type of an optical disk from a plurality of types of optical disks having different information surface depths from the optical disk surface. The optical disc type discriminating program includes the steps of: emitting light; converging the light by a lens to form a focal point; and detecting reflected light of the light on the information surface to generate a reflected light signal. Generating the smallest spherical aberration when the focal point is located at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs, controlling the position of the lens, Moving the focus in a direction perpendicular to the information surface of the optical disc loaded in the optical disc device; and a light quantity signal indicating the quantity of the reflected light based on the reflected light signal generated in accordance with the movement of the focus. Detecting the depth of the information surface from the surface based on the symmetry of the waveform of the light quantity signal, and loading the information surface based on the specified depth. Comprising the steps of determining a type of an optical disc has. This achieves the above object.

The optical disk information surface specifying program according to the present invention is a computer program that can be executed in an optical disk device and specifies an information surface on which a light focus exists among a plurality of information surfaces having different depths from the optical disk surface. The information surface identification program emits light, focuses the light by a lens to form a focal point, detects reflected light of the light on the information surface, and generates a reflected light signal. When the focus is located at a reference depth determined based on the depth of the plurality of information surfaces, setting the spherical aberration of the lens to a minimum, controlling the position of the lens, Moving the focal point in a direction perpendicular to the information surface; detecting a light quantity signal indicating the quantity of the reflected light based on the reflected light signal generated in accordance with the movement of the focus; Detecting the number of the information surface counted from the optical disk surface based on the signal waveform. This achieves the above object.

The spherical aberration adjustment program according to the present invention is a computer program that can be executed in an optical disk device and adjusts spherical aberration with respect to the information surface of an optical disk. A spherical aberration adjustment program emits light, focuses the light by a lens to form a focal point, and generates a reflected light signal by detecting reflected light of the light on the information surface. Controlling the position of the lens to move the focal point in a direction perpendicular to the information surface, wherein the focal point reciprocates between one side and the other side of the information surface. Detecting a light amount signal indicating the light amount of the reflected light based on the reflected light signal generated in accordance with the movement of the focal point; and determining whether the waveform of the light amount signal is symmetric or asymmetric. Detecting and outputting a symmetry display signal indicating the symmetry of the waveform of the light amount signal; and generating the control signal in accordance with the symmetry display signal, comprising: Specifying the symmetry display signal indicating that the symmetry is symmetric, and setting a control signal that gives the specified symmetry display signal; and generating spherical aberration based on the control signal. . This achieves the above object.

According to the present invention, the depth of the information surface from the optical disk surface is specified based on the symmetry of the waveform of the light amount signal of the light reflected on the optical disk, and the type of the loaded optical disk is determined based on the specified depth. Since the determination is made, the type of the optical disk can be determined without depending on the sensitivity variation of the circuit of the optical disk device or the like.

Further, according to the present invention, the number of the information surface counted from the optical disk surface is detected based on the waveform of the light amount signal of the light reflected on the optical disk. The position of the recording surface irradiated with the beam can be determined. As a result, it is possible to focus on a desired information surface. In particular, even if there are multiple information surfaces, it is possible to determine the information surface without depending on the position of the information surface. can do. When the amplitude or the symmetry of the focus error signal differs depending on the recording surface, the measurement for each recording surface can be performed. Further, even in the case of an optical disc apparatus in which the focal length of the light beam is short and the condensing lens and the optical disc are likely to collide at the time of starting the focus control, the focus control on an arbitrary recording surface can be started in a short time. The symmetry of the waveform of the light amount signal can be detected based on the direction of the disturbance of the sum signal. Thereby, for example, it is possible to confirm whether or not the optical disk satisfies a predetermined standard (a lower limit value, an upper limit value, and the like of a recording surface depth) defined by a physical standard.

Further, according to the present invention, when the waveform of the light amount signal of the light reflected on the optical disk is symmetric, the control signal for giving the symmetry is set in the spherical aberration generator, so that the optimum spherical aberration can be set to a desired value. Can be set to It is possible to set the optimum spherical aberration for a desired information surface without newly increasing the detection signal for detecting the spherical aberration and without performing focus control. The symmetry detection unit detects the symmetry based on a result of comparing the light amount signal level of the light amount detection unit when the focus signal is maximum and the light amount signal level of the light amount detection unit when the focus signal is minimum. Therefore, even when the change of the sum signal is small near the focal point, the disturbance of the sum signal can be accurately detected. Alternatively, even when there is little change near the maximum level and the minimum level of the focus signal, the disturbance of the sum signal can be accurately detected.

Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings, components denoted by the same reference numerals have similar functions and configurations, and perform similar operations. Prior to describing various embodiments of the present invention, first, an optical disc to which an optical disc apparatus records information and from which the recorded information is reproduced will be described.

FIG. 1 shows the appearance of the optical disc 1. The optical disk 1 is a disk-shaped recording medium such as a CD, a DVD, and a BD. The optical disk device records information by irradiating one side of the optical disk 1 with light such as a laser or reads out the recorded information. Information is recorded on a recording film formed of a phase change material or the like. Hereinafter, the recording film is referred to as an information surface. The information surface has a predetermined reflectance and reflects the received light. The information surface has a plurality of tracks (not shown) formed in a spiral shape, for example. Each track is defined as a groove or valley area on the information surface.

The depth from the surface to the information surface of the optical disc 1 varies depending on the type. 2A to 2C show cross sections of optical disks 1 of different types. 2A shows a CD, FIG. 2B shows a DVD, and FIG. 2C shows a BD. The cross-sectional direction is a direction perpendicular to the information surface of the optical disc 1. Light 110 entering from surface 2 and focusing on the information surface is shown for reference. In this specification, a surface of an optical disc on which light is irradiated to record information or read the recorded information is referred to as a “front surface”. As shown, the information surface La of the CD is 1200 μm from the surface 2, the information surface Lb of the DVD is 600 μm from the surface 2, and the information surface Lc of the BD is 100 μm from the surface 2. The depth of the information surface corresponds to, for example, the thickness of a protective film that protects the information surface.

Also, even for optical disks of the same type, the number of information surfaces may be different due to the required storage capacity. For example, in the case of a BD, one, two, or four layers of information surfaces can be provided. FIG. 3 shows a cross section of the optical disc 1 having a plurality of information surfaces L0, L1,..., Ln. Each information surface is provided at a different depth from the surface, for example, at an interval (I) of 25 μm.

Hereinafter, an embodiment of an optical disk device according to the present invention will be described.

(Embodiment 1)
FIG. 4 shows a configuration of functional blocks in the optical disc device 100 according to the present embodiment. The optical disk device 100 can record information on a plurality of types of optical disks and reproduce information recorded on the plurality of types of optical disks. However, the optical disk device 100 may not have both the recording function and the reproducing function. For example, only the information recorded on a plurality of types of optical disks may be reproduced.

(4) When the optical disk 1 is loaded, the optical disk device 100 first performs a process of determining the type of the optical disk 1. The reason for this is that the wavelength of laser light for reproducing information from the optical disc 1 and the reproduction processing are different depending on the type of the optical disc 1. Further, the structure of the optical disc 1 is different depending on the type of the optical disc 1. As shown in FIGS. 2A to 2C, the depth of the information surface from the surface of the optical disc 1 differs depending on the type of the optical disc 1.

In the present embodiment, the type determination process of the optical disk by the optical disk device 100 will be described. For convenience, the following description will be made on the assumption that the information surface of the loaded optical disk 1 is one. However, in the case of an optical disk having a plurality of information surfaces, it can be replaced with the selected specific information surface.

The optical disk device 100 includes an optical head 10, a focus error (FE) generator 20, a focus drive generator 22, an aberration setting unit 30, a reflected light amount detector 40, an asymmetry detector 41, a disk discriminator. And a vessel 42.

The optical head 10 irradiates the optical disc 1 with laser light based on the aberration setting signal from the focus drive generator 22 and the aberration setting device 30, detects the reflected light, and outputs the light. The optical head 10 includes a light source 11, a beam splitter 12, a lens 13, a focus actuator 14, a photodetector 15, and an aberration generator 16.

光源 The light source 11 of the optical head 10 emits a laser having a wavelength corresponding to the optical disk 1 that can be handled. For example, assuming that the optical disk device 100 can reproduce a CD, a DVD-ROM, and a BD, the light source 11 includes a red laser for a CD (wavelength: 750 nm), a red laser for a DVD-ROM (wavelength: 650 nm), and a BD. For emission of blue-violet laser (405 nm). The beam splitter 12 transmits the light from the light source 11 and reflects the reflected light from the optical disc 1 to direct the light to the photodetector 15. The lens 13 collects light from the light source 11 to form a focal point. The lens 13 is supported by an elastic body (not shown).

The focus actuator 14 controls the position of the lens 13 based on a drive signal from the focus drive generator 22, and a direction perpendicular to the information surface of the optical disk loaded in the optical disk device 100 (hereinafter, referred to as "focus direction"). Move the focus to. For example, when a drive signal is given to the focus actuator 14, a current according to the level (signal voltage value) of the drive signal flows inside the focus actuator 14, and an electromagnetic force is generated. As a result, the focus actuator 14 can change the position of the lens in the focus direction according to the magnitude of the electromagnetic force.

The photodetector 15 outputs a signal obtained by converting the received light (reflected light from the optical disk 1 in this case) into a signal capable of specifying the light in accordance with the position and the light amount. The aberration generator 16 generates spherical aberration based on the aberration setting signal. “Spherical aberration” refers to the amount of deviation between the focal position of light passing inside the lens 13 and the focal position of light passing outside. The aberration generator 16 can adjust the amount of spherical aberration generated by adjusting the path of the light 110 incident on the lens 13 according to the level (signal voltage value) of the aberration setting signal. FIG. 5 shows a convergence state when no spherical aberration occurs. As can be understood from the figure, since the focal position of the light passing through the inside of the lens 13 and the focal position of the light passing outside the lens 13 coincide, the shift amount is zero.

(4) The configuration of the optical disk device 100 will be described with reference to FIG. 4 again. The FE generator 20 generates a focus error signal (FE signal) indicating the positional relationship between the focal point of light on the optical disc 1 and the information surface based on the signal output from the photodetector 15. The positional relationship is a positional relationship of the optical disc 1 with respect to the focus direction. That is, the focus error signal indicates a state of convergence of light on the information surface of the optical disc 1. This is synonymous with the shift of the focal position. According to the focus error signal, it is possible to specify whether the focal point of the light is located on the information surface, on the surface side of the information surface, or on the opposite side (back side) from the surface side.

The focus drive generator 22 generates a drive signal to the focus actuator 14 that moves the condenser lens 13 toward or away from the optical disc 1. For example, when the level (voltage) of the drive signal is large, the lens 13 can be moved in a direction approaching the optical disc 1, and when the level (voltage) is small, the lens 13 can be moved in a direction separating the lens 13. The aberration setting device 30 outputs an aberration setting signal for generating spherical aberration.

The reflected light amount detector 40 generates and outputs a light amount signal indicating the amount of reflected light based on the signal output from the photodetector 15. For example, the reflected light amount detector 40 calculates the sum of the signals output from the light detector 15 and outputs the result as a light amount signal.

As described above, the signal output from the photodetector 15 is generated based on the light reflected from the optical disc 1. Therefore, the manner in which light strikes the optical disc 1 (specifically, the amount of occurrence of spherical aberration) and the light amount signal output from the reflected light amount detector 40 are closely related. Hereinafter, the relationship will be described in more detail with reference to FIGS. 4 and 6A to 6J.

FIGS. 6A to 6J show the relationship between the generation amount of spherical aberration and the light amount signal. First, as shown in FIG. 6 (e), together with the in focus on the information recording surface at the position of the depth D ₃ from the surface of the optical disc 1, the state (i.e., the spherical aberration of the spherical aberration is zero is generated Is not adjusted). Placing the reference depth D and the depth D ₃ of the time. Now, the aberration setting unit 30 fixes the level (signal voltage value) of the aberration setting signal given to the aberration generator 16 (FIG. 4), and further fixes the path of the light 110 incident on the lens 13. When the focus actuator 14 is driven to gradually move the focus position from a position shallower than the reference depth D to a position deeper than the reference depth D, the reflected light amount detector 40 returns to the state shown in FIG. ) Is output (the horizontal axis is the time axis). As is apparent from the figure, the waveform has symmetry, and the focus is located on the recording surface having a depth D at time P at which the maximum amplitude of the light amount signal is given.

Next, with the aberration setting device 30 fixing the level (signal voltage value) of the aberration setting signal, an optical disc having an information recording surface at a depth different from the reference depth D is loaded, and the information recording surface is focused. Consider the case of matching. FIG. 6A shows a state in which an information recording surface located at a depth D ₁ (D ₁ <D) from the surface is focused. The focal position of light passing through the inside of the lens 13 is deeper than the information recording surface, and the focal position of light passing outside of the lens 13 is closer to the information recording surface. Since the two focal positions do not coincide, spherical aberration occurs at this time. Similar to the above-described process, the position of the focal point, when is gradually moved to the deeper position beyond the depth D ₁ from a position shallower than the depth D _1, the reflected light quantity detector 40 in FIG. 6 (b) The light amount signal having the waveform shown is output. At time P, the position of the focal point matches the position of the information recording surface. Then, as shown in FIG. 6C, when another optical disk having an information recording surface is loaded at a position of depth D ₂ (D ₁ <D ₂ <D) and the information recording surface is focused. Generates the light amount signal shown in FIG. 6 (g) and 6 (h), and FIG. 6 (i) and FIG. 6 (j). However, the information recording surface of the optical disk shown in FIG. 6 (g) is located at a depth D ₄ (D <D ₄ ), and the information recording surface of the optical disk shown in FIG. 6 (i) is a depth D ₅ (D <D _4). <D ₅ ). In any case, the focal position of the light passing through the inside of the lens 13 is located before the information recording surface, and the focal position of the light passing through the outside of the lens 13 is located behind the information recording surface.

As apparent from FIGS. 6B, 6D, 6F, 6H, and 6J, no spherical aberration occurs when the waveform of the light amount signal is symmetric, and when the waveform of the light amount signal is asymmetric, Has spherical aberration. In the case of asymmetry, it means that the position of the information recording surface is shallower or deeper than the reference depth D. When the position of the information recording surface is shallower than the reference depth D (FIGS. 6B and 6D), the maximum level of the reflected light amount signal is such that the focal point is located at a position deeper than the information recording surface. You get when you do. Conversely, when the position of the information recording surface is deeper than the reference depth D (FIGS. 6H and 6J), the maximum level of the reflected light amount signal is such that the focal point is at a position shallower than the information recording surface. Obtained when present.

From these facts, when the time when the level of the reflected light amount signal becomes maximum is earlier than the time P, it can be said that the information recording surface of the optical disk is deeper than the reference depth D. When the time when the level of the reflected light amount signal becomes maximum is later than the time P, it can be said that the depth of the information recording surface of the optical disk is smaller than the reference depth D. Further, it is possible to specify how shallow or deep the information recording surface of the optical disk is with respect to the reference depth D according to the degree of the delay and the degree of the speed. The processing described below is performed based on the above principle. As another example, the difference in the waveform of the reflected light signal is determined based on the difference between the level of the reflected light signal when the focus error signal is the maximum and the level of the reflected light signal when the focus error signal is the minimum. However, it is also possible to specify how shallow or deep the information recording surface is with respect to the reference depth D.

(4) The asymmetry detector 41 shown in FIG. 4 detects whether the waveform of the light quantity signal is symmetric or asymmetric, and outputs a symmetry display signal indicating the symmetry of the waveform of the light quantity signal. In the following embodiments, the asymmetry detector 41 further specifies the symmetry using a focus error signal. Specifically, the asymmetry detector 41 minimizes the output signal of the reflected light amount detector 40 when the level of the signal from the FE generator 20 becomes maximum and the level of the signal from the FE generator 20 becomes minimum. Then, the difference from the output signal of the reflected light amount detector 40 at the time of the calculation is calculated. Then, the asymmetry detector 41 specifies the symmetry according to the magnitude of the difference, and generates a symmetry display signal indicating the sign of the difference.

Hereinafter, the processing of the asymmetry detector 41 will be described with reference to FIGS. In the description, the information surface that matches the position of the focal point is referred to as “target information surface”.

FIGS. 7A to 7C show signal waveforms obtained when the reference depth at which the optimal spherical aberration is obtained matches the position of the target information surface. 7A shows the waveform of the focus error signal, FIG. 7B shows the waveform of the reflected light amount signal, and FIG. 7C shows the symmetry display signal. 7A to 7C, the horizontal axis is the time axis, and the vertical axis is the signal level. When the spherical aberration is optimal with respect to the target information surface, the focus is located on the target information surface when the level of the focus error signal becomes 0 in the period R in FIG. At this time, since the spherical aberration also becomes 0, the level of the reflected light amount signal shown in FIG.

The procedure in which the asymmetry detector 41 detects the symmetry of the reflected light amount signal is as follows. First, in the period R, the asymmetry detector 41 defines times t ₁ , t ₂ , and t ₃ . These are the time at which the focus error signal reaches the maximum level, the time of the zero cross, and the time at which the focus error signal reaches the minimum level, respectively. The waveform of the focus error signal is substantially symmetric with respect to the target information surface. Then, the asymmetry detector 41 obtains the levels T (t ₁ ) and T (t ₃ ) of the reflected light amount signals at the times t ₁ and t ₃ , and calculates the difference (T (t ₁ ) −T (t ₃ )). Is calculated. As can be understood from the figure, in this case, T (t ₁ ) = T (t ₃ ), so that T (t ₁ ) −T (t ₃ ) = 0. Asymmetry detector 41 the reflected light quantity signal is determined to be symmetrical time t ₂ as a reference, value and generates and outputs a symmetry indicating signal of 0. Although in the figure is generated and end at the same time symmetry indicating signal period R, which is an example, it may be determined prior to the expiration of the period R as long as it is after the elapse of e.g., time t _3.

FIGS. 8A to 8C show signal waveforms obtained when the position of the target information surface is deeper than the reference depth at which the optimum spherical aberration is obtained. FIG. 8A shows the waveform of the FE signal, FIG. 8B shows the waveform of the reflected light amount signal, and FIG. 8C shows the symmetry display signal. The asymmetry detector 41 defines the times t ₁ , t ₂ , and t ₃ according to the above-described procedure, and based on the levels T (t ₁ ) and T (t ₃ ) of the reflected light amount signals at the times t ₁ and t ₃ . The symmetry of the reflected light amount signal can be detected. In the case of this example, T (t ₁ )> T (t ₃ ), that is, T (t ₁ ) −T (t ₃ )> 0. The asymmetry detector 41 determines that the amount of reflected light is not symmetric, and generates and outputs a positive symmetry display signal (FIG. 8C) corresponding to the difference. For example, the value of the symmetry display signal can be given as {T (t ₁ ) −T (t ₃ )} (> 0) which is the same as the difference.

When the position of the target information surface is deeper than the reference depth at which the optimum spherical aberration is obtained, the amplitude of the focus error signal deteriorates from the waveform of FIG. And the waveform of the reflected light quantity signal, not with respect to the zero-crossing time t ₂ of the focus error signal and the line symmetry, the level of the reflected light quantity signal, the position of the focal point is maximized at a position shallower than the target information plane.

FIGS. 9A to 9C show signal waveforms obtained when the position of the target information surface is shallower than the reference depth at which the optimum spherical aberration is obtained. 9A shows the waveform of the FE signal, FIG. 9B shows the waveform of the reflected light amount signal, and FIG. 9C shows the symmetry display signal. The asymmetry detector 41 defines the times t ₁ , t ₂ , and t ₃ according to the above-described procedure, and based on the levels T (t ₁ ) and T (t ₃ ) of the reflected light amount signals at the times t ₁ and t ₃ . The symmetry of the reflected light amount signal can be detected. In the case of this example, T (t ₁ ) <T (t ₃ ), that is, T (t ₁ ) −T (t ₃ ) <0. The asymmetry detector 41 determines that the amount of reflected light is not symmetric, and generates and outputs a negative symmetry display signal (FIG. 9C) corresponding to the difference. For example, the value of the symmetry display signal can be given as {T (t ₁ ) −T (t ₃ )} (<0) which is the same as the difference.

As shown in FIG. 9A, when the position of the target information surface is shallower than the reference depth at which the optimum spherical aberration is obtained, the amplitude of the focus error signal deteriorates compared to the waveform of FIG. And the waveform of the reflected light quantity signal, not with respect to the zero-crossing time t ₂ of the focus error signal and the line symmetry, the level of the reflected light quantity signal position of the focal point is maximized at a position deeper than the target information plane.

(4) The configuration of the optical disk device 100 will be described with reference to FIG. 4 again. The disc discriminator 42 specifies the depth of the information surface from the surface of the optical disc 1 based on the symmetry display signal output from the asymmetry detector 41, and based on the result, the type of the loaded optical disc. Is determined. The disc discriminator 42 can discriminate the type of the optical disc by further utilizing the aberration setting signal output from the aberration setting device 30. Specifically, the position, magnitude, and the like of the spherical aberration for which the aberration setting signal currently indicates the setting.

Next, the operation of the optical disc device 100 will be described with reference to FIGS. First, there are a plurality of optical disks on which the optical disk device 100 can record and / or reproduce information, and each of them has a unique depth from the surface to the information surface and is different from each other. Therefore, if the depth at which the information surface exists can be specified, the type of the optical disc can be determined. However, the depth does not have to be specified as a specific numerical value.

Hereinafter, a process of determining which of the two types of optical disks (optical disks A and B) the loaded optical disk is will be described. In this process, the type of the optical disk 1 is determined depending on whether the position of the information surface from the disk surface is deeper or shallower than a certain reference depth. Here, it is assumed that the information surface of the optical disk A is provided at a shallower position with respect to the information surface of the optical disk B. For example, the optical disc A is a BD in FIG. 2C, and the optical disc B is a DVD in FIG. 2B.

FIG. 10 is a flowchart showing the operation of the optical disk device 100. First, in step 121, the aberration setting unit 30 or the central processing unit (not shown) calculates an average value of the information surface depths of the optical discs A and B that can be determined. This average value is defined as a reference depth D. The depth of each information surface of the optical disks A and B is a depth determined by design. The reference depth D does not need to be calculated every time the optical disc device 100 operates, and may be held as a preset value.

Next, in step 122, the aberration setting device 30 outputs an aberration setting signal for minimizing spherical aberration when the focus is located at the reference depth D. Here, “minimum” means that the spherical aberration is 0 or the amount of the spherical aberration is the smallest. The aberration generator 16 performs setting according to the aberration setting signal.

Steps 121 and 122 can also be performed before the optical disc 1 whose type is to be determined is loaded. That is, by storing the set values in advance, the above-described processing may be performed simultaneously with, for example, turning on the power of the optical disc apparatus 100.

In step 123, when the optical disk is loaded, the light source 11 emits light. The focus drive generator 22 moves the focal point of the light from a position that is far away from the optical disc 1. Accordingly, the FE generator 20 generates a focus error signal, and the reflected light amount detector 40 generates a reflected light amount signal. In step 124, the asymmetry detector 41 identifies the time t ₁ and time t ₃ when a minimum level of the focus error signal in a predetermined time period is maximized. Thereafter, in step 125, the asymmetry detector 41 calculates the difference between the level of the reflected light quantity signal at the level and time t ₃ of the reflected light quantity signal at time t _1, generates a symmetry indicating signal.

In step 126, the disk discriminator 42 determines whether the symmetry indicating signal is negative. If negative, the process proceeds to step 127. On the other hand, if it is not negative, the process proceeds to step 128.

In step 127, the disc discriminator 42 discriminates that the loaded optical disc is the optical disc A having the information surface at a position shallower than the reference depth D. This is the case corresponding to FIGS. 6A to 6D and FIGS. 9A to 9C. Thereafter, the process ends.

In step 128, the disk discriminator 42 determines whether the symmetry indication signal is positive. If positive, the process proceeds to step 129. On the other hand, if it is not positive, the process ends.

In step 129, the disc discriminator 42 discriminates that the loaded optical disc is the optical disc B having an information surface at a position deeper than the reference depth D. This is the case corresponding to FIGS. 6 (g) to (j) and FIGS. 8 (a) to (c). Thereafter, the process ends.

If the symmetry display signal is neither positive nor negative, that is, if it is 0, it may be determined that an error has occurred and the process may be executed again. The above processing is performed on two information planes, and the average value of the depths of the information planes is set as the reference depth D. Therefore, the symmetry display signal becomes 0 (that is, the depth of the information plane is the reference depth). This is because it is considered that they do not coincide with the depth D).

The operation of the optical disk device 100 has been described above.

The above processing can also be used when discriminating three types of optical discs. Specifically, the depth of the second information surface when the depth of the information surface from the surface is arranged in order may be adopted as the reference depth D. If the symmetry display signal is neither positive nor negative and is 0, it may be determined that the loaded optical disk is the optical disk having the second information surface depth.

By repeatedly applying the above processing, three or more types of optical disks can be determined. For example, it is assumed that there are four types of optical disks (optical disks A to D) on which the optical disk device 100 can record and / or reproduce information. The depth from the optical disc A~D each surface to the information plane is denoted by _{d 1, d 2, d 3} , d 4 (d 1 <d 2 <d 3 <d 4). First, it obtains the reference depth D ₁ on the basis of the depth of each information surface of the optical disk A and B, performs the processing of FIG. 10. If it is determined that the type of the optical disc is the optical disc A, the type of the loaded optical disc is the optical disc A, and the process is terminated. On the other hand, if it is determined that the optical disk B, then obtains the reference depth D ₂ on the basis of the depth of each information surface of the optical disk B and C, and again performs the process of FIG. 10. As a result, if it is determined that the type of the optical disk is the optical disk B, the process is terminated, assuming that the type of the loaded optical disk is the optical disk B. On the other hand, if it is determined that the optical disk C, then obtains the reference depth D ₃ based on the depth of each information surface of the optical disc C and D, again performs the process of FIG. 10. As a result, it is determined whether the type of the loaded optical disk is the optical disk C or D. Through the above processing, it is possible to determine which of the optical discs A to D has been loaded.

In the above description, the wavelength of the light (laser) emitted from the light source 11 is not particularly limited. However, the shorter the wavelength, the higher the detection sensitivity of various signals. For example, assuming that the optical disk device 100 can reproduce a CD, a DVD-ROM, and a BD, it is better to perform the above processing using a BD laser (405 nm) shorter than a CD laser (wavelength: 750 nm). The detection sensitivity increases.

In the present embodiment, in order to detect the asymmetry of the reflected light amount signal of the reflected light amount detector 40, the level of the reflected light amount signal when the focus error signal output from the FE generator 20 becomes maximum and minimum is obtained. The difference was calculated. However, this is merely an example, and it can also be obtained by using the level of the focus error signal when the signal level of the reflected light amount detector 40 is maximized.

In the present embodiment, the spherical aberration is set to be minimum when the focal point of the light is at the position of the average depth of the information surface of the optical disc where the light can be determined. However, any setting may be made as long as the deterioration of the focus error signal and the reflected light amount signal does not increase and the detection becomes impossible.

In the present embodiment, the symmetry indicating signal from the asymmetry detector 41 is used for discriminating the disc type of the optical disc 1. However, in order to detect the number of layers on the information face of the optical disc 1, the information face of the optical disc 1 is used. May be used to confirm whether or not is within a specified range.

(Embodiment 2)
The optical disk device of the present embodiment performs processing on an optical disk having a plurality of information surfaces. Specifically, the optical disk device obtains a depth to a desired information surface of the optical disk, and performs focus control on the desired information surface based on the depth.

FIG. 11 shows the configuration of functional blocks in the optical disc device 200 according to the present embodiment. The difference between the optical disk device 200 and the optical disk device 100 (FIG. 4) according to the first embodiment is that the focus filter 21, the asymmetry detector 41, and the layer-by-layer pull-in selector 46 are used instead of the disk discriminator 42 of the optical disk device 100. It is in the point provided. The configuration and operation mainly related to this difference will be described below. The functions and operations of components not particularly described are the same as those of the optical disc device 100 of FIG. Further, the optical disk 1 loaded in the optical disk device 200 has a plurality of information surfaces, for example, as shown in FIG. The optical disk device 200 holds in advance information on the number of information surfaces of the loaded optical disk 1, the depth of each information surface from the surface of the optical disk 1, and the like.

The optical disc device 200 is designated from among a plurality of information surfaces, an information surface on which information is to be recorded and / or reproduced (hereinafter, referred to as a “desired information surface”). Perform focus control. The designation of the desired information surface is performed by, for example, a central processing unit (not shown) that has specified the position where the information is recorded. As a result, it is possible to record and / or reproduce information on a desired information surface. The desired information surface is not limited to the information surface whose depth from the surface of the optical disc 1 is the shallowest or the deepest, and may be an information surface existing between these information surfaces.

First, the focus error signal output from the FE generator 20 is sent to the focus filter 21, the asymmetry detector 41, and the layer-by-layer pull-in selector 46. The symmetry indicating signal output from the asymmetry detector 41 is sent to the layer number detector 44.

Based on the symmetry indicating signal output from the asymmetry detector 41 and the aberration setting signal output from the aberration setting device 30, the layer number detector 44 determines whether the information surface where the focal point of the light beam is located The number of the information surface located from the surface is specified. Hereinafter, the case where there are three information surfaces will be described in more detail. First, the spherical aberration is set to be minimum on the intermediate (second layer) information surface, and the focal position is continuously moved in the depth direction from the surface side of the optical disc 1 having the three-layer information surface. Let it. Then, the waveforms of FIG. 9 (a), FIG. 7 (a) and FIG. 8 (a) appear in sequence as the waveform of the focus error signal. As described in connection with the optical disc device 100 of the first embodiment, the symmetry display signal output from the asymmetry detector 41 outputs one discrete value in a predetermined period R shown in FIG. 7A, for example. . Therefore, when the focus error signal waveforms shown in FIGS. 9A, 7A, and 8A are obtained, the symmetrical waveforms shown in FIGS. 9C, 7C, and 8C are obtained. Thus, a sex indication signal is obtained.

レ ベ ル The level of the discrete value of the obtained symmetry indication signal corresponds to the position of the information surface. The layer number detector 44 specifies, based on the level of the discrete value of the symmetry indication signal, the information surface where the focal point of the light beam is located, as counted from the surface of the optical disc 1. be able to. More specifically, if the discrete value of the symmetry display signal is negative, the layer number detector 44 determines that the information surface where the focal point of the light beam is located is the closest first layer counted from the surface, If it is present, it is determined that it exists in the second layer, and if it is positive, it is determined that it is present in the innermost third layer counted from the surface. The layer number detector 44 outputs a number display signal indicating information (number information) specifying the order of the information surface.

The layer-by-layer pull-in selector 46 selects and outputs one of the signal output from the focus filter 21 and the signal output from the focus drive generator 22 based on the number display signal and the focus error signal. The selected and output signal is sent to the focus actuator 14 as a drive signal. The focus actuator 14 moves the focus based on the drive signal. Thereafter, when the number display signal indicates a desired layer number and the focus error signal crosses zero, the layer-by-layer pull-in selector 46 switches the signal to be selectively output at that time. For example, at the start of the operation, the stratified pull-in selector 46 selects the signal from the focus drive generator 22, and the normal focus operation is performed. Then, when the number display signal indicates a desired layer number and the focus error signal crosses zero, the layer-by-layer pull-in selector 46 selects and outputs the signal output from the focus filter 21.

Hereinafter, the operation of the optical disk device 200 will be described. In the present embodiment, the average value of the depth of each information surface from the optical disk surface is determined. This average value is defined as a reference depth D. The aberration setting unit 30 generates an aberration setting signal so as to generate an optimal spherical aberration when the focal point is located at the reference depth D. Here, the depth from the optical disk surface to the intermediate information surface is defined as the reference depth D, and the spherical aberration is set to be minimum at the reference depth D. The aberration generator 16 performs setting according to the aberration setting signal of the aberration setting device 30. Since the depth of each information surface from the optical disk surface is obtained in advance as a design value, the reference depth D may be calculated in advance and held as a preset value.

(4) At the beginning of the operation, the optical disc device 200 has the focus control in a non-operating state. At this time, the stratified pull-in selector 46 selects a drive signal from the focus drive generator 22 and sends it to the focus actuator 14. The focus actuator 14 receives the drive signal, moves the focal point of the light beam from a position that is far away from the optical disk 1, and moves the optical beam closer to the optical disk 1.

As the focus of the light beam continues to move in the focus direction, the focus passes through the information surface of the optical disc 1. At this time, for example, a focus error signal having a waveform shown in FIG. 9A is obtained from the FE generator 20. When the focus of the light beam passes through the information surface, the focus error signal crosses zero (time t _{2 in} FIG. 9A). When the focal point moves to a deeper position and sequentially passes through the next information plane and the next information plane, the focus error signals shown in FIGS. 7A and 8A are obtained. On the other hand, the reflected light amount signal output from the reflected light amount detector 40 when the above-described focal point shift is performed changes in order to the shapes shown in FIGS. 9B, 7B, and 8B. . The reason why the reflected light amount signals do not match is that the reflected light amount signal is affected by spherical aberration according to the difference between the depth to the information surface and the reference depth D, as in the first embodiment.

The asymmetry detector 41 detects such asymmetry of the signal from the reflected light amount detector 40 based on the level of the signal from the FE generator 20 when the reflected light amount detector 40 is maximized. The layer number detector 44 specifies the depth of the information surface based on the asymmetry information from the asymmetry detector 41 and the spherical aberration generation amount specified by the aberration setting unit 30 to the aberration generator 16. That is, it is determined whether the position of the information surface is deeper or shallower than the reference depth D. Then, based on the detected depth, it is determined on which information surface of the optical disc 1 the focus of the light beam is located. When the desired layer number is output from the layer number detector 44 and the signal from the FE generator 20 crosses zero, the layer-by-layer pull-in selector 46 selects the signal from the focus filter 21 and sends it to the focus actuator 14. Switch to send. Thereby, the focal position of the light beam with respect to the information surface of the optical disc 1 is controlled. As a result, focus control is performed on a desired information surface.

As described above, the position of each information surface is specified by detecting the depth of the information surface where the focal point of the light beam is located and the symmetry change of the signal from the reflected light amount detector 40 according to the spherical aberration. The focus control for a desired information surface of the optical disc 1 can be started based on the specified position. In particular, even when a jump operation is performed on a recording surface other than the adjacent recording surface, since the jump is performed after the information surface of the jump destination is specified, it is possible to move in a short time with one jump.

In the present embodiment, the asymmetry of the reflected light amount signal of the reflected light amount detector 40 is detected based on the level of the focus error signal when the signal level of the reflected light amount detector 40 is maximized. However, this is only an example, and the asymmetry of the reflected light amount signal is detected based on the difference between the levels of the reflected light amount signals at the time when the focus error signal output from the FE generator 20 becomes maximum and minimum. You can also. This is the same as in the first embodiment. In the present embodiment, the spherical aberration is set to be minimum when the focal point of the light is at the position of the average depth of the information surface of the optical disk where the focus can be determined. However, any setting may be made as long as the deterioration of the focus error signal and the reflected light amount signal does not increase and the detection becomes impossible.

In the present embodiment, based on the number display signal output from the layer number detector 44, focus control on a desired information surface is started. However, the number display signal can also be used to measure information such as the signal amplitude from the FE generator 20 for each information surface of the optical disc 1, or to another information surface while the focus control is operating. May be used to move.

(Embodiment 3)
The optical disc device of the present embodiment generates the optimum spherical aberration when the focus of the light beam is located on the information surface of the optical disc without performing focus control.

FIG. 12 shows a configuration of functional blocks in the optical disc device 300 according to the present embodiment. The optical disc apparatus 300 differs from the optical disc apparatus 100 (FIG. 4) according to the first embodiment in that an aberration adjuster 31 is provided instead of the disc discriminator 42 of the optical disc apparatus 100. The configuration and operation mainly related to this difference will be described below. The functions and operations of components not particularly described are the same as those of the optical disc device 100 of FIG.

Aberration adjuster 31 receives a symmetry indication signal from asymmetry detector 41. The aberration adjuster 31 sends a step-like setting signal to the aberration setting device 30 to change the amount of generation of spherical aberration. The aberration adjuster 31 sends a high-level signal to the focus drive generator 23 while holding the signal from the asymmetry detector 41. Thereafter, the aberration adjuster 31 specifies the amount of spherical aberration when the symmetry display signal from the asymmetry detector 41 indicates that the symmetry is symmetric, and sends the aberration to the aberration setter 30 so as to generate the spherical aberration. Send setting signal. At the same time, the aberration adjuster 31 sends a low-level signal to the focus drive generator 23.

The spherical aberration adjusting operation of the optical disk device 300 will be described with reference to FIGS. 12 and 13A to 13C. 13A shows an output signal of the focus drive generator 23, FIG. 13B shows a setting signal from the aberration adjuster 31 to the aberration setter 30, and FIG. 13C shows an asymmetry detector. 4 shows the symmetry indication signal received from 41. In each figure, the horizontal axis is the time axis.

First, before reaching time t ₁ , the aberration adjuster 31 outputs a continuous step signal of a predetermined cycle to the aberration setter 30 as shown in FIG. In synchronization with the step cycle, as shown in FIG.
The focus actuator 14 is driven so that the focal point of the light beam reciprocates in the focusing direction around the information surface of the optical disc 1 in the vicinity thereof. As a result, the focal point of the light beam repeatedly passes through the information surface in the focus direction. The cycle in which the focal point of the light beam makes one round trip in the focus direction near the information surface of the optical disc 1 is synchronized with the cycle in which the step-like signal from the aberration adjuster 31 to the aberration setter 30 changes. When the signal from the aberration adjuster 31 goes low, the focus drive generator 23 stops driving the focus actuator 14.

Each time the focal point of the light beam passes through each information surface of the optical disc 1, the focus error signal output from the FE generator 20 shows one of the waveforms shown in FIGS. Corresponding to the waveform, the light amount signal output from the reflected light amount detector 40 shows the waveforms shown in FIGS. 7B to 9B. That is, as a result of driving in the focus direction, the symmetry of the signal from the reflected light amount detector 40 changes according to the difference between the depth from the surface of the optical disc 1 to the information surface and the reference depth where spherical aberration does not occur. When the depth to the information surface is shallower than the reference depth D, the waveforms of FIGS. 9A and 9B are obtained. When the depth to the information surface is deeper than the reference depth D, FIG. The waveforms (a) and (b) are obtained.

The asymmetry detector 41 detects such asymmetry of the signal from the reflected light amount detector 40 based on the level of the signal from the FE generator 20 when the reflected light amount detector 40 is maximized. As shown in FIG. 13C, the asymmetry detector 41 sends a signal to the aberration adjuster 31 each time the focus drive generator 23 makes one round trip. The aberration adjuster 31 sequentially updates the level of the setting signal to the aberration setter 30 when the absolute value of the symmetry display signal from the asymmetry detector 41 is minimized. Here, the level of the setting signal for the aberration setting device 30 at the time when the symmetry display signal becomes 0 is stored as the minimum value. The aberration regulator 31, after time t ₁ in FIG. 13 sends a setting signal stored as a minimum value to the aberration setter 30. Thereby, an optimum spherical aberration can be generated at the position of the information surface.

In this manner, focus control is performed by detecting a change in the symmetry of the signal from the reflected light amount detector 40 according to the depth of the information surface where the focal point of the light beam is located and the spherical aberration generated by the aberration generator 16. The spherical aberration adjustment operation can be performed so as to generate spherical aberration at the focal point of the light beam that is optimal for the information surface of the optical disc 1 without performing the above operation.

In the present embodiment, the asymmetry of the reflected light amount signal of the reflected light amount detector 40 is detected based on the level of the focus error signal when the signal level of the reflected light amount detector 40 is maximized. However, this is only an example, and the asymmetry of the reflected light amount signal is detected based on the difference between the levels of the reflected light amount signals at the time when the focus error signal output from the FE generator 20 becomes maximum and minimum. You can also. This is the same as in the first embodiment. In the present embodiment, the spherical aberration is set to be minimum when the focal point of the light is at the position of the average depth of the information surface of the optical disk where the focus can be determined. However, any setting may be made as long as the deterioration of the focus error signal and the reflected light amount signal does not increase and the detection becomes impossible.

The embodiments of the optical disk device according to the present invention have been described above. The optical disk device in each of the above-described embodiments executes each operation based on a computer program. The computer program is executed by a central processing unit (not shown) that controls the operation of the entire optical disc device. The computer program can be recorded on a recording medium such as an optical recording medium represented by an optical disk, an SD memory card, a semiconductor recording medium represented by an EEPROM, and a magnetic recording medium represented by a flexible disk. The optical disc device 100 can acquire a computer program not only through a recording medium but also through an electric communication line such as the Internet. A DSP (Digital Signal Processor) that incorporates such a computer program and instructs an operation based on the computer program is a component excluding physically essential components such as a light source 11, a lens 13, and a photodetector 15 of an optical disk device. Can be replaced by For example, the DSP can implement the processing of the aberration setting unit 30, the asymmetry detector 41, the disc discriminator 42, the layer-by-layer pull-in selector 46, the layer number detector 44, and the aberration adjuster 31.

According to the present invention, the type of the optical disk loaded in the apparatus can be determined, the number of the information surface counted from the optical disk surface can be detected, or the optimal spherical aberration can be set. This method is effective in applications such as a computer program for operating an optical disk.

FIG. 2 is a diagram illustrating an appearance of the optical disc 1. It is sectional drawing of the optical disc 1 of a different kind. (A) shows a CD, (b) shows a DVD, and (c) shows a BD. FIG. 3 is a cross-sectional view of an optical disc 1 having a plurality of information surfaces L0, L1,..., Ln. FIG. 2 is a diagram illustrating a configuration of a functional block in the optical disc device 100 according to the first embodiment. FIG. 7 is a diagram illustrating a convergence state when spherical aberration does not occur. (A)-(j) is a figure which shows the relationship between the generation amount of spherical aberration and the light quantity signal according to the depth from the surface of an optical disk. FIG. 7 is a diagram illustrating a signal waveform obtained when a reference depth at which an optimum spherical aberration is obtained matches a position of a target information surface. FIG. 9 is a diagram illustrating a signal waveform when the position of the target information surface is deeper than a reference depth at which an optimum spherical aberration is obtained. FIG. 9 is a diagram illustrating a signal waveform obtained when the position of the target information surface is shallower than the reference depth at which an optimum spherical aberration is obtained. 4 is a flowchart illustrating an operation of the optical disc device 100. FIG. 3 is a diagram illustrating a configuration of functional blocks in the optical disc device according to the present embodiment. FIG. 3 is a diagram illustrating a configuration of functional blocks in the optical disc device according to the present embodiment. (A) shows an output signal of the focus drive generator 23, (b) shows a setting signal from the aberration adjuster 31 to the aberration setting unit 30, and (c) shows a symmetry display received from the asymmetry detector 41. It is a figure showing a signal. FIG. 9 is a diagram showing a configuration of a functional block in a conventional optical disc device 510. (A) is a waveform diagram of a signal output from the focus drive generator 22, and (b) is a waveform diagram of a signal output from the FE generator 20. FIG. 11 is a diagram illustrating a configuration of a functional block in a second conventional optical disc device. FIG. 11 is a diagram illustrating a configuration of a functional block in a third conventional optical disc device. (A) shows the waveform of the setting signal output from the aberration adjuster 32, and (b) shows the waveform of the signal output from the amplitude detector 25.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Optical disk 10 Optical head 11 Semiconductor laser 12 Beam splitter 13 Focusing lens 14 Focus actuator 15 Photodetector 16 Aberration generator 20 FE generator 21 Focus filter 22 Focus drive generator 23 Focus drive generator 24 TE generator 25 Amplitude detection Device 30 Aberration setting device 31 Aberration adjuster 32 Aberration adjuster 40 Reflection light amount detector 41 Asymmetry detector 42 Disk discriminator 43 Disk discriminator 44 Layer number detector 45 Retraction selector 46 Layer retraction selector

Claims (22)

An optical disc device capable of writing and / or reading information from / to a plurality of types of optical discs having different information surface depths from an optical disc surface,
A light source that emits light,
A lens that focuses the light to form a focal point;
A light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal;
When the focus is located at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs, a spherical aberration generating unit that generates a minimum spherical aberration,
A focus drive unit that controls the position of the lens and moves the focal point in a direction perpendicular to the information surface of the loaded optical disc;
A light amount detection unit that detects a light amount signal indicating a light amount of the reflected light based on the reflected light signal output from the detection unit in accordance with the movement of the focus;
A discriminating unit that specifies a depth of the information surface from the surface based on the symmetry of the waveform of the light amount signal, and that determines a type of the loaded optical disk based on the specified depth. apparatus. A symmetry detection unit that detects whether the waveform of the light amount signal is symmetric or asymmetric within a predetermined period, and outputs a symmetry display signal indicating the symmetry of the waveform of the light amount signal,
The optical disc device according to claim 1, wherein the discriminating unit discriminates a type of the loaded optical disc based on the symmetry display signal. A focus signal generator configured to generate a focus signal indicating a positional relationship between the focus and the information surface,
The symmetry detection unit specifies a first time at which the level of the focus signal is maximum and a second time at which the level of the focus signal is minimum during the predetermined period, and determines the light amount signal at the first time and the second time. 3. The optical disk device according to claim 2, wherein whether the waveform of the light amount signal is symmetric or asymmetric is detected based on the level of the optical signal. The symmetry detection unit is configured to change the waveform of the light quantity signal when the difference between the first level of the light quantity signal at the first time and the second level of the light quantity signal at the second time is 0. 4. The optical disk device according to claim 3, wherein the optical disk device detects that the waveform is symmetric, and detects that the waveform of the light amount signal is asymmetric when the waveform is not 0. The symmetry detection unit generates the symmetry display signal indicating whether the difference is 0, positive or negative,
The method according to claim 4, wherein the determination unit specifies whether a depth from the surface of the loaded optical disc to the information surface is deeper or shallower than the reference depth based on the symmetry display signal. Optical disk device. 2. The optical disc device according to claim 1, wherein the reference depth is a value within a range defined by a depth of an information surface of a first type optical disc and a depth of an information surface of a second type optical disc. . The optical disk device according to claim 1, wherein the determination unit specifies the number of information surfaces of the loaded optical disk based on a waveform of the light amount signal. An aberration setting unit that generates an aberration setting signal that indicates the amount of spherical aberration to be generated is further provided.
The spherical aberration generating section generates a spherical aberration based on the aberration setting signal,
The optical disc device according to claim 1, wherein the determination unit further specifies a depth of the information surface from the surface based on the aberration setting signal. An optical disk device capable of writing and / or reading information on an optical disk having a plurality of information surfaces having different depths from the optical disk surface,
A light source that emits light,
A lens that focuses the light to form a focal point;
A light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal;
When the focal point is located at a reference depth determined based on the depth of the plurality of information surfaces, a spherical aberration generating unit that generates a minimum spherical aberration,
A focus drive unit that controls the position of the lens and moves the focal point in a direction perpendicular to the plurality of information surfaces;
A light amount detection unit that detects a light amount signal indicating a light amount of the reflected light based on the reflected light signal output from the detection unit in accordance with the movement of the focus;
An optical disc device comprising: a number detection unit that detects the number of the information surface counted from the optical disc surface based on the waveform of the light quantity signal. A selection unit that selects a specific number of the information surface detected by the number detection unit and drives the focus driving unit to move the focus to a position near a specific information surface corresponding to the specific number;
The focus signal generator further comprising: a focus signal generator configured to generate a focus signal indicating a positional relationship between the focus and the information surface, wherein the focus signal generator generates the focus signal for the specific information surface. An optical disk device according to claim 1. 11. The optical disk device according to claim 10, wherein the specific information surface can be changed based on an instruction from the selection unit. A symmetry detection unit that detects whether the waveform of the light amount signal is symmetric or asymmetric within a predetermined period, and outputs a symmetry display signal indicating the symmetry of the waveform of the light amount signal,
10. The optical disk device according to claim 9, wherein the number detection unit further detects a number of the information surface counted from a surface of the loaded optical disk based on the symmetry display signal. The symmetry detection unit specifies a first time at which the level of the focus signal is maximized and a second time at which the level of the focus signal is minimized in the predetermined period, and determines the light amount at the first time and the second time. 13. The optical disk device according to claim 12, wherein whether the waveform of the light amount signal is symmetric or asymmetric is detected based on a signal level. An optical disc device capable of writing and / or reading information on an optical disc having an information surface,
A light source that emits light,
A lens that focuses the light to form a focal point;
A light detection unit that detects reflected light of the light on the information surface and outputs a reflected light signal;
A spherical aberration generator that generates spherical aberration based on the control signal,
A focus drive unit that controls the position of the lens to move the focus in a direction perpendicular to the information surface, and reciprocates the focus between one side and the other side of the information surface. A focus drive unit for
A light amount detection unit that detects a light amount signal indicating a light amount of the reflected light based on the reflected light signal output from the detection unit in accordance with the movement of the focus;
A symmetry detection unit that detects whether the waveform of the light quantity signal is symmetric or asymmetric, and outputs a symmetry display signal indicating the symmetry of the waveform of the light quantity signal,
An aberration adjuster that generates the control signal in accordance with the symmetry display signal, wherein the symmetry display signal indicating that the waveform of the light amount signal is symmetric is specified, and the specified symmetry display is specified. An optical disc device comprising: an aberration adjuster that sets a control signal for giving a signal to the spherical aberration generation unit. A focus signal generator configured to generate a focus signal indicating a positional relationship between the focus and the information surface,
The symmetry detection unit specifies a first time at which the level of the focus signal is maximum and a second time at which the level of the focus signal is minimum during a predetermined period, and determines the light amount signal at the first time and the second time. 15. The optical disk device according to claim 14, wherein whether the waveform of the light amount signal is symmetric or asymmetric within a predetermined period is detected based on the level of the optical signal. A focus signal generator configured to generate a focus signal indicating a positional relationship between the focus and the information surface,
The symmetry detection unit specifies a first time at which the level of the light amount signal is maximized and a second time at which the level of the light amount signal is minimized within the predetermined period, and determines the first time and the second time at the second time. 15. The optical disk device according to claim 14, wherein whether the waveform of the light amount signal is symmetric or asymmetric is detected based on a level of the focus signal. A method of determining the type of an optical disc from among a plurality of types of optical discs having different information surface depths from the optical disc surface,
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Generating the smallest spherical aberration when the focus is located at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs;
Controlling the position of the lens to move the focal point in a direction perpendicular to the information surface of the loaded optical disc;
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Identifying the depth of the information surface from the surface based on the symmetry of the waveform of the light amount signal, and determining the type of the loaded optical disk based on the identified depth. Type determination method. A method for identifying an information surface on which a focal point of light exists, among a plurality of information surfaces having different depths from an optical disk surface,
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Setting the spherical aberration of the lens to a minimum when the focal point is located at a reference depth determined based on the depths of the plurality of information surfaces;
Controlling the position of the lens to move the focal point in a direction perpendicular to the plurality of information surfaces;
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Detecting the number of the information surface counted from the surface of the optical disk based on the waveform of the light amount signal. A method for adjusting spherical aberration with respect to an information surface of an optical disc, comprising:
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Controlling the position of the lens to move the focal point in a direction perpendicular to the information surface, wherein the focal point reciprocates between one side and the other side of the information surface. When,
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Detecting whether the waveform of the light quantity signal is symmetric or asymmetric, and outputting a symmetry display signal indicating the symmetry of the waveform of the light quantity signal;
Generating the control signal in accordance with the symmetry display signal, identifying the symmetry display signal indicating that the waveform of the light quantity signal is symmetric, and identifying the identified symmetry display signal. Setting a control signal to be applied;
Generating spherical aberration based on a control signal. A computer program that can be executed in an optical disk device and that determines a type of an optical disk from among a plurality of types of optical disks having different information surface depths from the optical disk surface,
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Generating the smallest spherical aberration when the focus is located at a reference depth determined based on the depth of the information surface of the plurality of types of optical discs;
Controlling the position of the lens, moving the focal point in a direction perpendicular to the information surface of the optical disk loaded in the optical disk device,
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Identifying the depth of the information surface from the surface based on the symmetry of the waveform of the light amount signal, and determining the type of the loaded optical disk based on the identified depth. Type determination program. A computer program that can be executed in an optical disk device and specifies an information surface on which a focal point of light exists, among a plurality of information surfaces having different depths from an optical disk surface,
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Setting the spherical aberration of the lens to a minimum when the focal point is located at a reference depth determined based on the depths of the plurality of information surfaces;
Controlling the position of the lens to move the focal point in a direction perpendicular to the plurality of information surfaces;
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Detecting the number of the information surface counted from the surface of the optical disk based on the waveform of the light amount signal. A computer program that can be executed in an optical disk device and adjusts spherical aberration with respect to an information surface of an optical disk,
Emitting light;
Focusing the light by a lens to form a focal point;
Detecting reflected light of the light on the information surface to generate a reflected light signal;
Controlling the position of the lens to move the focal point in a direction perpendicular to the information surface, wherein the focal point reciprocates between one side and the other side of the information surface. When,
Based on the reflected light signal generated according to the movement of the focal point, detecting a light amount signal indicating the light amount of the reflected light,
Detecting whether the waveform of the light quantity signal is symmetric or asymmetric, and outputting a symmetry display signal indicating the symmetry of the waveform of the light quantity signal;
Generating the control signal in accordance with the symmetry display signal, identifying the symmetry display signal indicating that the waveform of the light quantity signal is symmetric, and identifying the identified symmetry display signal. Setting a control signal to be applied;
Generating spherical aberration based on a control signal.

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