JP2000315327A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform tracking control with a high degree of reliability by driving a moving part of an optical head and controlling it so that a light beam correctly scans on the track according to an output signal of a phase difference track deviation detecting part for converting the deviation into a signal corresponding to a positional relation between the optical beam and the track. SOLUTION: Reflected light from a disk 101 is made incident to 4-split photo- detector 114 via a condenser lens 113. A matrix computing element 116 calculates sums of various combinations of the detecting parts A-D of the 4-split photo-detector 114, and generates a phase difference tracking error signal (signal TE). An A/D 112 converts the signal TE, and inputs a signal phTE to a DSP 132, and the DSP 132 outputs a signal TRD and makes a current flow through a tracking actuator 103 via a synthesizing circuit 133 and a driving circuit 134. The converging lens 105 is driven in the tracking direction, and tracking control is performed so that a light beam pot 107 correctly scans the tracks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for optically recording a signal on an information carrier (including various information carriers such as a read-only type and a recording / reproducing type) by using a light source such as a laser. The present invention relates to an optical disk device for reproducing a signal, and more particularly to an optical disk device having tracking control for controlling a light beam spot to scan a track correctly.

[0002]

2. Description of the Related Art In a recording / reproducing optical disk apparatus, a signal is optically recorded on an information carrier by using a light source such as a laser of an optical head, and the recorded signal is reproduced. In a read-only optical disk device, information optically recorded in advance is reproduced using a light source such as a laser of an optical head. In an optical disc, a signal is formed in the form of a pit or the like along a track. In recording and reproduction, tracking control is performed, and the optical head is controlled to move along the track. Conventionally, CD-ROM drive, DVD-RO
As a tracking control device used in an M drive or the like, there is a tracking control device in which a phase difference tracking detection method and its control learning method are introduced (see IEICE technical report OPE96-150 (1997-02)).
This conventional tracking control device will be described with reference to FIGS.

FIG. 1 shows a principle of detecting a phase difference tracking error signal (hereinafter also referred to as a phase difference TE signal). When a beam spot generated by the optical head passes over a pit constituting a track on the optical disk, the intensity pattern of light reflected from the optical disk changes with time. The figure shows three situations in which the spot moves along the pit. As shown in the upper part of the figure, when the beam spot passes through the center of the pit, that is, the center of the track, the pattern changes symmetrically to the left and right. When the beam spot passes on the left side of the center of the pit, the pattern changes so as to rotate clockwise, and when it passes on the right side, the pattern changes so as to rotate counterclockwise. The change in the pattern rotation becomes sharper as the beam spot deviates from the center of the pit. The phase difference method is a method for detecting a tracking error signal by utilizing the change in the pattern, and uses a four-divided photodetector. As shown in the lower part of the figure, the phases of two signals obtained from the sum of the diagonals of the four detection areas of the photodetector are compared, and the positional deviation between the beam spot and the track is determined based on the amount of advance or delay of the phase. Is detected.

Next, the principle of occurrence of the offset of the phase difference tracking error and its correction method will be described.
When the objective lens is moved by the tracking control so that the beam spot follows the eccentricity of the track, the reflected light on the photodetector moves in accordance with the movement. When the pit depth is λ / 4 (λ is the wavelength of the light beam), the pattern of the reflected light is symmetric with respect to the center of the optical axis, and accurate tracking is performed even if the reflected light on the photodetector moves. An error signal can be detected. However, when the depth of the pit is different from λ / 4, the pattern of the reflected light is not symmetrical with respect to the center of the optical axis, and when the reflected light on the photodetector moves, an offset occurs in the tracking error signal. .

FIG. 2 is a diagram for explaining the principle of occurrence of this offset. The reflected light pattern on the photodetector when the beam spot is located at the end of the pit on the center of the track, and FIG. 4 shows the waveforms of each detection signal in the photodetector when the pit crosses the pit in the state. The photodetector includes four photodetection areas A to D. The optical head is equipped with an objective lens that focuses the beam on the disc,
As shown in (b), when the pit depth is λ / 4,
Even if the light beam pattern on the photodetector moves due to the lens shift of the lens, no phase difference occurs between the signals in the regions A and B and the signals in the regions C and D of the photodetector. If the pit depth is different from λ / 4, if there is no lens shift,
As shown in (c), there is no phase difference between the signals in the regions A and B of the photodetector and the signals in the regions C and D. However, when there is a lens shift, as shown in FIG. When the light beam pattern on the vessel moves, a phase difference occurs. At this time, since the signals in the regions A and B of the photodetector are different from the signal levels in the regions C and D of the photodetector, an offset occurs in the phase difference TE.

The offset of the tracking error signal due to the movement of the objective lens is, as shown in FIG. 3, two of the four photodetection areas before and after the division in the radial direction of the disk.
It can be removed by adjusting the phase (phase in the tangential direction) of the signal output from one of the light detection regions. That is, the phase of the signal output from the front or rear two areas is advanced or delayed by the phase adjuster, and the signals from the light detection areas at each diagonal are added, and (A + C)
And (B + D) are binarized into two signals.
The phase difference of the digitized signal is detected by a phase comparator, and a phase difference tracking error (TE) signal is obtained through a low-pass filter.

FIG. 4 shows an example of measuring the symmetry of the tracking error signal with respect to the movement of the lens by changing the amount of phase adjustment of the phase adjuster. As described above, in the conventional tracking control device, the offset caused when the lens is moved (shifted) due to the variation in the pit depth generated at the time of molding the disk is corrected by only the phase adjustment amount, and the Learning to be a tracking error signal with good symmetry.

Another tracking control device employed in a CD-ROM drive uses a three-beam system. A conventional tracking control device using the three beams will be briefly described with reference to FIGS. The three-beam method uses a diffraction grating to generate two sub-beams A and B of ± 1st-order diffracted light at positions as shown in FIG. 6 before and after a main beam for reproducing a central signal. Both two beams A and B are slightly tracked (pit area)
The light beam is reflected by the so-called mirror portion (where there is no pit) and reaches the photodetector. Each signal of this photodetector is input to the differential amplifier shown in FIG. 5, and a track shift signal can be obtained. When the main beam scans the center of the track as shown in FIG. 6B, the same amount of light is detected from the two sub-beams A and B, so that the track shift signal output becomes zero. When the main beam deviates from the track center, the diffraction due to the information pits of the two sub beams A and B becomes unbalanced as shown in FIGS. 6A and 6C. In the case of +, in the case of (c)-
Then, an error signal of both polarities can be obtained. That is, 1
It is possible to obtain information on which of the tracks (pit trains) the book is shifted, and information on the shift amount. This information is 3
It appears as the polarity and amplitude of the beam track shift signal.
Therefore, tracking control can be realized by controlling the objective lens based on the three-beam track shift signal.

The three-beam track shift signal is generally less susceptible to disc pit variations and disc tilt, but its amplitude varies with respect to the reflectivity of the disc, causing variations in the intensity of the sub-beams A and B and light detection. An offset occurs due to the imbalance of the vessel. In the conventional tracking control device, the offset is corrected by adding a differential gain balance circuit to the differential amplifier or by applying an offset voltage.

[0010]

The problem of a conventional tracking control device using a phase difference will be described. In an optical disk device, an optical head comprises an optical component such as an objective lens, a polarizing element, and a photodetector. In a normal state, the objective lens is located at the center of the photodetector, as shown in FIG. However, as shown in FIG. 7 (b), when the mounting error of the optical parts causes a shift of the center of the objective lens (tilt of the optical axis) in the initial state, or when the apparatus is set vertically, the weight of the objective lens is reduced. The objective lens may be in a sagging state, and the objective lens may largely move from the center in an initial state (this state is referred to as a lens shift). In this case, the image of the spot of the reflected beam is shifted from the photodetector.

This lens shift causes the following problem in a read-only disc or a reproduction area. 1) In the initial state, the output of each photodetector becomes small and cannot be binarized, so that a phase difference tracking error signal cannot be generated and control becomes impossible. 2) Since the tracking control operates at the lens-shifted position, off-track occurs and the control becomes unstable, the amplitude of the RF signal including the address signal and the data signal decreases, the offset of the reproduction signal, and the jitter. Deterioration, an increase in the error rate, and the like occur, and reproduction becomes impossible.

As described above, in the conventional tracking control device, the symmetry of the tracking error signal accompanying the shift of the objective lens is corrected by operating only the phase adjustment amount to make the symmetry of the tracking error signal almost optimal. (See FIG. 3). However, this correction is a correction of only the symmetry while the lens is shifted. Therefore, there is a problem that the tracking control becomes unstable or the reproduction performance is deteriorated due to the problems 1) and 2).

In the recording / reproducing area or the recordable disc, when the lens shift correction is performed in the reproduction-only area from the initial state shown in FIG. (B), and the center of the lens coincides with the center of the photodetector. However, the symmetry of the push-pull track shift signal in the recording / reproducing area is deteriorated, and the track center and the center of the light beam shift, that is, off-track occurs, and the tracking control becomes unstable. In addition, due to this track shift, the jitter of the information signal recorded on the track is deteriorated, and the read rate of the address signal on the boundary between the land and the groove of the track is deteriorated, which hinders stable signal reproduction. was there.

An object of the present invention is to provide an optical disc apparatus which performs highly reliable tracking control even if an optical axis collapse (optical axis shift) due to an initial objective lens shift.

Another object of the present invention is that the center of the track on the optical disc and the center of the light beam spot on the optical disc are shifted in the recordable area after lens shift correction due to the initial shift of the objective lens (off-track occurs. The object of the present invention is to provide an optical disk device that performs highly reliable tracking control.

[0016]

According to a first optical disc apparatus of the present invention, an optical head includes a lens for converging a light beam generated by a light source toward an information carrier,
The moving section moves the optical head in a direction substantially perpendicular to the track on the information carrier. The photodetector includes a detection unit divided into a plurality of regions, and detects a light beam reflected from the information carrier by dividing the light beam into the plurality of regions. The phase difference detector detects a phase difference between signals detected in a plurality of regions of the photodetector, and the phase difference track deviation detector detects the phase difference detected by the phase difference detector between the position of the light beam and the track. The signal is converted into a signal corresponding to the relationship, and the phase difference tracking control unit drives the moving unit in accordance with the output signal of the phase difference track deviation detection unit, and controls the light beam to scan the track correctly. Further, the lens shift unit applies an offset signal to the moving unit to move the lens of the optical head by a predetermined amount in a direction substantially perpendicular to the track, and the lens shift correction unit includes a phase difference track shift detecting unit. An offset signal that minimizes the DC component appearing on the output signal is set in the lens shift unit. In this optical disc device, for example, the phase difference detection unit includes phase adjustment means for adjusting a phase error, and the lens shift correction means changes the phase adjustment means by a predetermined amount from a target value to provide the phase difference detection unit with a phase difference. Then, an offset signal which causes the DC component appearing on the signal converted by the track deviation detecting section to be substantially minimized is set in the lens shift section. Preferably, the phase difference detection unit is
A phase adjustment unit for adjusting a phase error, wherein the lens shift correction unit is configured to determine a relationship between a movement amount of the phase shift unit by the lens shift unit at the first set value and a DC component appearing in an output signal of the phase difference track deviation detection unit. And a second function indicating the relationship between the amount of movement of the lens shift unit at the second set value of the phase adjustment unit and the DC component appearing in the output signal of the phase difference track deviation detection unit, On the basis of the first and second functions, an offset signal that minimizes the DC component appearing on the output signal of the track deviation detecting section is determined.
Preferably, the lens shift correction means obtains an offset signal from an intersection of the first and second functions. Preferably, the optical disc device further obtains an offset signal to the lens shift unit by the lens shift correction unit, and converts a DC component so that an output signal of the phase difference track deviation detection unit is symmetric with respect to the reference potential. A track deviation offset correction unit for correcting the deviation is provided.

The second optical disk device according to the present invention has two types of areas: an embossed reproduction-only area in which information is recorded in advance, and a recordable area formed by guide tracks and on which information is recorded by marks on the tracks. Optical disc device for an information carrier having an area of In this optical disc device, the optical head includes a lens that converges the light beam generated by the light source toward the information carrier, and the moving unit moves the optical head in a direction substantially perpendicular to a track on the information carrier. I do. The photodetector includes a detection unit divided into a plurality of regions, detects the light reflected from the information carrier of the light beam by dividing the light into the plurality of regions, and the phase difference detection unit detects the reflected light in the divided region of the photodetector. Detecting a phase difference between the signals, a first track shift detecting unit detects a signal corresponding to a positional relationship between a light beam and a track in a reproduction-only area of the information carrier based on the phase difference detected by the phase difference detecting unit. Generate The push-pull detector detects the intensity of the light beam diffracted by the track, and the second track shift detector detects the light beam in the recordable area of the information carrier based on the detection signal of the push-pull detector. A signal corresponding to the positional relationship between the track and the track is generated. Further, the phase difference tracking control unit drives the moving unit in accordance with the output signal of the first track shift detection unit, and controls the light beam to scan the track on the information carrier correctly. Further, the push-pull tracking control section drives the moving section in accordance with the output signal of the second track shift detecting section, and controls the light beam to scan the track on the information carrier correctly. The lens shift unit applies an offset signal to the moving unit to move the optical head in a direction substantially perpendicular to the track on the information carrier. And the offset signal at which the DC component appearing on the output signal of the first track deviation detecting section is substantially minimized is set in the lens shift section. In this optical disc device, for example, the phase difference detection unit includes phase adjustment means for adjusting a phase error, and the lens shift correction means changes the phase adjustment means by a predetermined amount from a target value to provide the phase difference detection unit with a phase difference. Then, an offset signal that minimizes the DC component appearing on the detection signal of the track shift detecting section is set to the lens shift section. Preferably, the phase difference detection unit includes a phase adjustment unit that adjusts a phase error, and the lens shift correction unit detects a movement amount of the lens shift unit at a first set value of the phase adjustment unit and a first track shift. A first function indicating the relationship between the DC components appearing in the detection signal of the section, the amount of movement by the lens shift section at the second set value of the phase adjustment means, and the DC component appearing in the detection signal of the first track shift detecting section Is determined, and based on the first and second functions, an offset at which the DC component appearing on the detection signal of the first track deviation detecting unit is substantially minimized is determined.
Preferably, the lens shift correction means obtains an offset signal from an intersection of the first and second functions. In this optical disk device, preferably, a track shift offset correction unit is further provided, and at the time of activation of the optical disk device, the light beam is moved to a reproduction-only area of the information carrier, and the lens shift correction unit sets an offset signal. The light beam is moved to the recordable area of the information carrier to correct the DC component of the second track shift detection control unit.

In a third optical disk apparatus according to the present invention, the optical head includes a lens for converging the light beam generated by the light source toward the information carrier, the moving section includes m, and the optical head is connected to a track on the information carrier. And move in a direction substantially perpendicular to. The three beam generating means converts the light beam into a preceding sub beam
The beam is divided into a main beam and a succeeding sub-beam. Drives the moving unit in response to the output signal and controls the light beam to scan the track correctly. Also,
The lens shift unit applies an offset signal to the moving unit to move the lens of the optical head by a predetermined amount in a direction substantially perpendicular to the track, and the lens shift correction unit includes:
An offset signal at which the amplitude of the signal converted by the three-beam track deviation detecting unit becomes substantially maximum is set in the lens shift unit. Preferably, the optical disc device further comprises:
A track shift offset correcting means is provided. The lens shift correcting means sets an offset signal of the lens shift unit, and sets the remaining offset so that the converted signal of the three-beam track shift signal detecting unit is symmetric with respect to the reference potential. to correct.

A fourth optical disk device according to the present invention is formed by an emboss reproduction-only area in which information is recorded in advance, an uneven address portion and a guide track, and information is recorded on the guide track. Recordable area 2
An optical disc device for an information carrier having various types of information areas. In this optical disc device, the optical head includes a lens that converges the light beam generated by the light source toward the information carrier, and the moving unit moves the optical head in a direction substantially perpendicular to a track on the information carrier. . The light detector is
A detection unit divided into a plurality of regions is provided, and the reflected light of the light beam from the information carrier is divided and detected in the plurality of regions, and the phase difference detection unit detects a phase difference of each signal in the divided region of the photodetector. And the first track shift detecting section generates a signal corresponding to the positional relationship between the light beam and the track in the read-only area of the information carrier based on the phase difference detected by the phase difference detecting section. Further, the push-pull detector detects the intensity of the light beam diffracted by the track of the light beam, and the second track shift detector detects the intensity of the light beam in the recordable area of the information carrier based on the signal of the push-pull detector. A signal corresponding to the positional relationship between the light beam and the track is generated. The phase difference tracking control unit drives the moving unit in accordance with the output signal of the first track deviation detection unit, controls the light beam to scan the track correctly, and the push-pull tracking control unit The moving unit is driven in accordance with the output signal of the second track deviation detecting unit, and is controlled so that the light beam scans the track correctly. The reproducing means reproduces an address portion of the information carrier by a signal of the photodetector,
The information recorded in the recordable area of the information carrier is reproduced.
The lens shift unit moves the lens of the optical head in a direction substantially perpendicular to the track by applying an offset signal to the moving unit. The offset correction unit applies an offset signal to the push-pull tracking control unit. The lens shift correcting means sets an offset signal in which the DC component appearing on the signal of the first track shift detecting section is substantially minimized in the lens shifting section. The characteristic detecting section detects the initial lens shift based on the characteristic of the reproduced signal reproduced by the reproducing section, and the lens shift adjusting section detects the initial lens shift detected by the characteristic detecting section so that the reproduced signal characteristic becomes almost the best. Adjust as follows. In this optical disk device, for example, the characteristic detected by the characteristic detecting unit is a jitter component of a reproduction signal of information by the reproducing unit, and the lens shift adjusting unit sets the jitter component after the lens shift correcting unit applies the offset. Is adjusted so that is substantially minimized. In this optical disc device, for example, the characteristic detected by the characteristic detecting unit is an error rate of a reproduction signal of information reproduced by the information reproducing unit for each predetermined block. After applying the offset, the push-pull balance means is adjusted so that the error rate of the predetermined block is substantially minimized. In this optical disc device, for example, the characteristic detected by the characteristic detecting unit is a jitter component of an address signal reproduced by the reproducing unit, and the lens shift adjusting unit sets the jitter component after the lens shift correcting unit applies the offset. The push-pull balance means is adjusted so that is substantially minimized. In this optical disk device, for example, the characteristic detected by the characteristic detecting unit is an error rate of the address signal reproduced by the address reproducing means for each predetermined block,
The lens shift adjusting means adjusts the push-pull balance means so that the address error rate of the predetermined block becomes substantially minimum after the lens shift correcting means applies the offset. Preferably, in this optical disc device, the lens shift adjusting means includes a push-pull balance means for operating a gain balance of the second track deviation detecting unit to apply an offset. Preferably, in this optical disc apparatus, when the optical disc apparatus is started, the light beam is moved to the reproduction-only area of the information carrier, and the offset signal of the lens shift unit is detected by the lens shift correction unit, and then the light beam is moved to the recordable area of the information carrier. The beam is moved, and the lens shift adjusting means operates. Preferably, in this optical disk device, the offset signal set by the lens shift correction means is limited to a predetermined range. Preferably, in this optical disc device, the offset signal set by the lens shift correction means limits the symmetry of the second track shift signal in a recordable area of the information carrier to a predetermined range.

In a fifth optical disk apparatus according to the present invention, the optical head includes a lens for converging a light beam generated by the light source toward the information carrier, and the moving section moves the optical head to a track on the information carrier. Move in a substantially vertical direction. The photodetector includes a detection unit divided into a plurality of areas, detects the reflected light of the light beam from the information carrier by dividing the detection light into a plurality of areas, and the track shift detection unit detects the output of the photodetector. Converted to a track shift signal corresponding to the positional relationship between the beam and the track, the tracking control unit drives the moving unit according to the output signal of the track shift detection unit, so that the light beam scans the track correctly. Control. The lens shift unit applies an offset signal to the moving unit,
The optical head is moved by a predetermined amount in a direction substantially perpendicular to the track. The characteristic detecting section detects the characteristic of the reproduced signal reproduced by the reproducing section, and the lens shift adjusting section converts the offset signal whose reproduction signal characteristic becomes almost the best based on the characteristic detected by the characteristic detecting section. Set to. In this optical disc apparatus, for example, the characteristic detecting unit includes a reproduction signal processing unit for waveform-equalizing the sum signal of the photodetector, and a jitter between a reproduction clock for binarizing an output signal of the reproduction signal processing unit and taking synchronization. And the lens shift adjusting means sets an offset signal in which the jitter is substantially minimized to the lens shift unit. In this optical disk device, for example,
The characteristic detection unit detects the amplitude of the sum signal of the photodetector,
The lens shift adjusting means sets an offset signal at which the sum signal amplitude becomes substantially maximum to the lens shift unit. In this optical disk device, for example, the characteristic detecting unit includes a signal processing unit for waveform-equalizing a sum signal of a photodetector, a binarizing unit for binarizing an output of the signal processing unit, and the binarizing unit. Phase-locking means for synchronizing this signal with the reproduced clock, error correction means for decoding the output signal of the binarization means phase-locked by the phase-locking means and correcting the error, and error correction by the error correction means.
Error counting means for detecting and counting errors occurring during correction. Then, the lens shift adjusting means includes:
An offset signal is set in the lens shift unit such that the number of errors counted by the error counting unit is substantially minimized, or a range in which the number of errors is substantially minimized is substantially maximized. Preferably, the optical disc device is
The apparatus further includes offset correction means for setting the offset signal of the lens shift unit by the lens shift correction means and correcting the remaining offset of the track shift signal.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings,
The same reference symbols indicate the same or equivalent ones.

(Embodiment 1) FIG. 9 shows a configuration of an optical disk apparatus (optical recording / reproducing apparatus) according to a first embodiment of the present invention. In this optical disc device, tracking control is performed by detecting a phase difference. Even if an optical axis tilt (optical axis shift) due to an initial lens shift occurs, a signal corresponding to the amount of movement is detected and a lens shift is performed. Is corrected to 0, that is, the objective lens is properly positioned at the center, and a good tracking signal and RF signal are obtained in the state shown in FIG. 7A, and highly reliable tracking control is performed.

First, the basic operation will be described. FIG.
In the optical disk device shown in FIG. 1, a disk 101 as an information carrier is rotated at a predetermined rotation speed by a disk motor 102. Digital signal processor (DS
P) 132 connects the traverse motor 137 to the drive circuit 13
A traverse drive signal TRSD is output via the optical disk 6 to move the optical head in the radial direction of the optical disk 101 to the set track. An optical system for irradiating the disk 101 with the light beam spot 107 includes a light source 108 such as a semiconductor laser, a coupling lens 109, a polarization beam splitter 110, a polarization hologram element 106, and a converging lens 105. The light beam 140 emitted from the light source 108 is converted into parallel light by the coupling lens 109, and this parallel light is thereafter reflected by the polarization beam splitter 110, passes through the polarization hologram element 106, and is converged by the converging lens 105 After being converged, the light beam spot 107 is placed on the information track of the disk 101.
To form Disk 101 of light beam spot 107
Is transmitted through a converging lens 105, a polarization hologram element 106, and a polarizing beam splitter 110, and is incident on a photodetector 114 via a condenser lens 113.
The photodetector 114 includes a quadrant for detecting incident light,
The outputs of the four detectors A to D are input to preamplifiers 115a to 115d, respectively, where the current is converted to a voltage, and input to matrix calculator 116. The matrix calculator 116 calculates the sum of various combinations of the detection units A to D of the photodetector 114, and based on the calculated sum, as described later, a phase difference tracking error signal (hereinafter also referred to as a phase difference signal TE). , A tangential phase difference signal (hereinafter also referred to as a TG signal) and a focus error signal (not shown).

Next, generation of a phase difference tracking error (TE) signal and tracking control will be described. The matrix arithmetic unit 116 outputs an addition signal of A + C and B + D, which is a diagonal sum of the detection areas A to D of the photodetector 114, to the phase adjusters 117a and 117b. The phase adjusters 117a and 117b adjust the offset due to the phase difference in the tangential direction caused by the pit depth variation, for example, by changing the delay amount / lead amount of the filter. The phase adjusters 117a and 117b are
The signal can be delayed in the time axis direction by the output adjustment signal GBAL. The signals output from the phase adjusters 117a and 117b are output from the comparators 118a and 118, respectively.
The signal is binarized by 8b, converted into a pulse signal, and input to a phase comparator 120 via a phase difference balance circuit 119 for correcting an offset of a circuit or the like. Phase comparator 120
Detects the phase difference according to the track shift of the light beam spot 107 by comparing the input pulse signals, and the detected phase difference is smoothed by an LPF (low-pass filter) 121 to generate a phase difference TE. You. Next, the phase difference TE is converted by the AD converter 122, and D is obtained as phTE.
It is input to SP132. The DSP 132 executes a filter operation for performing phase compensation and low-frequency compensation on the input phase difference TE, and drives the drive signal TRD via the built-in DA converter.
Is output. The drive signal TRD is input to the drive circuit 134 via the synthesizing circuit 133, is current-amplified by the drive circuit 134, and causes a current to flow to the tracking element 103. As a result, the converging lens 105 is driven in the tracking direction. Thus, tracking control is performed so that the light beam on the disk 107 scans the track correctly. (The drive circuit 134 is also used when the lens shift is intentionally controlled by the tracking drive offset value LSD input to the synthesis circuit 133, as described later.)

Next, the tangential phase difference signal (TG
Signal) will be described. Matrix calculator 1
Reference numeral 16 denotes a phase for performing phase adjustment of the added signal of A + B and C + D divided in the tangential direction, in conjunction with phase adjusters 117a and 117b for adjusting an offset generated by the phase difference in the tangential direction with the phase difference TE. Output to the adjusters 123a and 123b, the phase adjuster 1
The outputs of 23a and 123b are output from comparators 124a and 1
The binary signal is converted into a pulse signal by 24b, and the tangential phase comparator 125 detects the phase difference between the converted pulse signals. Phase adjusters 123a, 123
b is the DSP1 similarly to the phase adjusters 117a and 117b.
The advance of the delay of the phase can be adjusted by the GBAL signal output from the output terminal 32. The tangential phase error detected by the tangential phase comparator 125 is LPF
(Low-pass filter) 126 to generate a tangential phase difference signal TG. This TG signal is AD
The signal is input to the DSP 132 via the converter 127. DS
P132 can detect the amount of phase difference in the tangential direction by the TG signal, and adjust the phase adjusters 123a, 123b, and 117a so that the TG signal becomes zero.
Adjust 117b. As a result, the phase difference in the tangential direction can be canceled, and the offset accompanying the phase difference can be removed.

Further, in the focus control, the difference between the signals of the diagonal sums A + C and B + D of the four-divided photodetector 114 is obtained to generate a focus error signal by the astigmatism method. To enter. The focus error signal is output as a drive signal FOD through a filter operation, is current-amplified by the drive circuit 135, and drives the focus element 104. This realizes focus control. However, since this focus control system is not directly related to the present invention, illustration and description are omitted.

When the focus control is operated in the initial state at the time of starting (without operating the tracking control), the phase difference TE signal from the phase comparator 120 via the LPF 121 as shown in FIG. Is output. Even when the lens shift is zero, the symmetry is deteriorated as shown in FIG. 10B due to an initial photodetector and a circuit offset such as a variation in circuit gain of the preamplifier.
(In the case of FIG. 10 (b), a 50% symmetry shift occurs due to the offset.) Also, due to the variation of information pits on the disk (particularly, the pit depth variation), the beam on the four-divided detector 114 is changed. An unbalance occurs in the shape, and a phase difference in the tangential direction obtained by dividing the disk 101 in the radial direction occurs. As a result, FIG.
(A) or (c) as shown in (a) or (c)
When the lens is shifted by m lenses, an offset of the phase difference TE occurs, and the symmetry shifts as compared with the state without the lens shift. Furthermore, if there is an initial lens shift component due to the sagging of the lens or the deviation of the optical axis when installed vertically, the offset change of the phase difference TE with respect to the lens shift becomes unbalanced, and these are superimposed and the phase difference is superimposed. If the symmetry of the TE is significantly deteriorated, the control of the pull-in, access, and jumping of the tracking becomes unstable.

In the learning method of this embodiment, the symmetry of the phase difference tracking error (TE) (which is related to the difference between A + C and B + D, which is the diagonal sum of the quadrant photodetector 114) is determined. From the deteriorating factors, the offset due to the circuit variation and the lens shift offset due to the tangential phase difference peculiar to the phase difference tracking error detection are separated, and the initial lens shift amount is extracted and learned to achieve the almost optimal tracking position. adjust. As a result, even if there is an initial lens shift, an almost optimal reproduction signal and a lens shift margin are secured. FIG. 11 shows a change in the relationship between the lens shift and the symmetry of the phase difference tracking error (TE) in this series of learning operations.
2 shows a flowchart of the learning process. The learning is performed through four states shown in FIG. These four states are initial states, and the adjustment signal GBA is set so that TG = 0.
This is a state in which L is optimally adjusted, a state in which PHTBAL is further adjusted to adjust symmetry, and a state in which GBAL is intentionally shifted by a predetermined amount to detect a point having zero symmetry to search for a lens shift. The initial state is a state in which nothing is adjusted (GBAL = 0, PHTBAL = 0), and it is assumed that a tangential phase difference TG = a exists in this state. In the next state, the DSP 132
Phase adjustment circuits 123a and 123b so that TG = 0
, The tangential balance signal GBAL is adjusted optimally (S5 to S6). In this state, the offset due to the circuit variation is separated, and the phase difference tracking error (TE) maintains a certain asymmetry even if the lens shifts. In the next state, the DSP 132 obtains the remaining offset, and adjusts PHTBAL to the phase difference balance circuit 119 to adjust the symmetry so as to adjust the symmetry so that the phase difference TE has the same positive and negative amplitude (S7). ~ S
8). In this state, the characteristic of the phase difference TE with respect to the lens shift substantially coincides on the X axis. In the next state, the lens shift signal LSD is searched by intentionally shifting the GBAL by a predetermined amount and detecting a point having zero symmetry (S9 to S9).
12). By setting a tracking position corresponding to the correction amount of the lens shift as the tracking drive offset LSD, the lens shift amount is corrected, and then the GBAL is restored (S13). Thereby, the symmetry of the phase difference TE with respect to the lens shift substantially overlaps with the X axis. In addition, tracking control is performed with an optimum tracking position as a target, and a symmetrical phase difference TE that does not increase the offset even when the lens is shifted is obtained.

Hereinafter, a method of learning a lens shift according to the first embodiment of the present invention will be described in detail with reference to FIGS. First, referring to FIGS. 10 and 13, when the apparatus is powered on, the spindle motor 102 is driven, the light source (LD) 108 emits light, and the light beam spot on the disk 101 is brought into a predetermined convergent state. Focus control is performed (FIG. 1
2, S1 to S4). As described above, the output of the phase difference TE generated in this state becomes asymmetric with respect to the reference potential due to the offset even without the lens shift, as shown in FIG. Changes. FIG. 13 is a characteristic diagram showing the relationship between the lens shift amount and the symmetry of the phase difference TE. This initial state is a state in which nothing is adjusted, that is, GB.
AL = 0, TG = a, and the position represented by point 2B. -300 μm when lens shift occurs
In FIG. 13, 90% asymmetry is obtained at the point 2A in FIG.
At 0 μm, the asymmetry becomes −20% at the point 2C in FIG. It has been experimentally found that the relationship between the lens shift and the asymmetry is a linear relationship such as a straight line. FIGS. 10A and 10C show waveforms of the phase difference TE and the TG signal at points 2A and 2C shifted by ± 300 μm.

As shown in FIG. 9, the phase difference TE is taken into the DSP 132 via the AD converter 122, and its asymmetry can be detected as an offset. The tangential phase comparator 125 and the LPF 1
The tangential phase difference signal (TG signal) generated at 26 is generated as a DC signal as shown in FIG.
Similarly, the signal is taken into the DSP 132 via the D converter 127, and the tangential phase difference amount can be detected.

The DSP 132 captures the above-described TG signal via the AD converter 127, and converts the tangential balance signal GBAL into the phase adjusters 117a, 117b and 1b.
Output to 23a and 123b, search for an output value of GBAL at which the TG becomes almost 0, and set GBAL = a. FIG. 14 is a waveform diagram showing the phase difference TE signal and the TG signal at this time, and FIG. 15 is a characteristic diagram showing a change in the symmetry of the phase difference TE with respect to the lens shift. FIG.
As shown in FIG. 15, when the GBAL is adjusted and the TG signal becomes almost zero, the phase difference TE maintains a constant 20% asymmetry even if the lens is shifted. Therefore, in asymmetry, points 4A and 4C shifted by ± 300 μm are aligned on a straight line with a substantially constant amount to point 4B with zero lens shift (S5, S6).

Next, the remaining 20% offset is obtained by detecting the peak / bottom amplitude of the phase difference TE or calculating the positive / negative area by waveform integration. The DSP 132 adjusts the balance correction signal PH so as to correct the obtained offset.
The TBAL value is output to the phase difference balance circuit 119. As shown in FIG. 16, by calculating and setting the output c of PHTBAL such that the amplitude of the phase difference TE output on the sawtooth wave is symmetric with respect to the reference potential, the phase difference TE having the same positive and negative amplitudes is obtained. (S7, S
8). Even in this state, since the GBAL is adjusted to a, the characteristic of the phase difference TE with respect to the lens shift substantially coincides with the X axis as shown in FIG.

Next, the DSP 132 intentionally changes the tangential balance signal to a predetermined amount GBAL = b (S9). This makes it possible to again have the characteristic that the symmetry changes linearly with the lens shift as shown by the straight line in FIG. 19, and to appropriately adjust the sensitivity of the phase difference TE to the lens shift. At this time, the TE of the phase difference is again offset (asymmetry) as shown in FIG. Q occurs. As described above, since the symmetry (offset amount) of the lens shift and the phase difference TE has a linear characteristic, it is possible to easily detect a tracking drive offset LSD in which the phase difference TE is symmetric (offset is 0).

When the lens shift is 0, the amplitude of the phase difference TE becomes positive and negative as shown in FIG.
By setting a tracking drive offset LSD at a tracking position corresponding to this lens shift correction amount,
The lens shift amount can be corrected (S10, S11, S1
2). After the correction output of the lens shift, when the GBAL is returned to the original (S13), the symmetry of the phase difference TE with respect to the lens shift substantially overlaps with the X axis. The obtained phase difference TE is symmetric, tracking control is performed with an optimum tracking position as a target, and the offset does not increase even if the lens shifts. Even if the optical axis is initially tilted or the lens is shifted due to vertical deflection, it is possible to secure an optimal reproduction signal and a lens shift margin thereof.

In the above-described embodiment, first, the correction amount GBAL for correcting the tangential phase difference TG is optimally adjusted. However, even without seeking the optimal GBAL first,
An optimal lens shift correction amount (tracking drive offset value LSD) can be obtained. Hereinafter, this modified embodiment will be described. As shown in FIG. 20, the initial state is a state in which nothing is adjusted (GBAL = 0, PHT
BAL = 0), and it is assumed that a tangential phase difference TG = a exists in this state. First, the offset characteristic of the phase difference tracking error (TE) is approximated by a function with the first tangential phase difference correction amount GBAL = 0, and then G is obtained by shifting the tangential phase difference correction amount by a predetermined amount.
When BAL = d, the offset characteristic of the phase difference tracking error (TE) is approximated by a function. Then, the tracking drive offset value LSD at the intersection P, ie, the point P at which the offsets Dp of the two functions are equal, is determined. With this method, it is possible to more accurately and quickly obtain an almost optimum lens shift correction amount LSD.

FIG. 21 shows a flowchart of this learning. Operation until focus control is performed (S101 to S101)
S104) is the same as steps S1 to S4 in the flow of FIG. Next, the tangential phase difference correction amount GB
AL = 0 is set (S105). Then, the lens shift is increased by one step, and the offset of the phase difference TE is measured and stored. This is continued until a predetermined number of samplings can be performed (S106 to S108). And GBAL
The characteristic of = 0 is approximated by a function (S109). Next, the tangential phase difference correction amount GBAL = d is set (S11).
0). Then, the lens shift is increased by one step, and the offset of the phase difference TE is measured and stored. This is continued until a predetermined number of samplings can be performed (S111 to S1).
13). Then, the characteristic of GBAL = d is approximated by a function (S114). Next, the intersection P of the two obtained functions is obtained, and the tracking drive offset value LSD is determined (S115).

(Embodiment 2) FIG. 22 shows an optical disc apparatus according to a second embodiment of the present invention for a recordable optical disc (hereinafter referred to as RW disc) 101. This optical disk device is obtained by adding circuits 150 to 153 for push-pull balance to the device of FIG. 9, and the same parts as those of the optical disk device of the first embodiment shown in FIG. Write the number. In this optical disc apparatus, since there is an initial lens shift, when the track center on the optical disc and the center of the light beam spot on the optical disc are shifted (off-track occurs) in the recordable area after the lens shift correction, the off-track Is 0, that is, the center of the light beam spot is positioned at the track center in a state where the lens shift has been corrected (the state of FIG.
That is, 1) the push-pull track deviation signal becomes symmetrical with respect to the reference potential, 2) the jitter of the reproduction signal is minimized or the error is minimized, and 3) the address signal between tracks is learned and adjusted so that it can be read most. As a result, the control center is moved to a position where the characteristics of the reproduced signal are good, and a highly reliable device is provided.

The RW disk 101 will be described.
As shown in FIG. 23A, the information of the innermost lead-in section (ROM area: area A) is formed as an emboss, and the user data section (RW area: area B to
In C), the tracks of the concave and convex guide grooves for recording information by phase change or the like are formed in a spiral shape. The tracking control in the RW area of the disk 101 is performed by using a push-pull tracking error signal (push-pull TE) which is the difference between the reflection intensities of the ± 1st-order diffracted light of the light beam on the uneven track.

The generation of the push-pull TE will be described. The matrix calculator 116 outputs an addition signal of A + D and B + C divided in the tracking direction. Each output corresponds to the light intensity of + 1st-order light and -1st-order light at the light beam spot on the disk having the uneven guide tracks. Push-pull balance circuit 150
Adjusts the balance of symmetry by adjusting the gain of each input signal. Thereafter, the differential amplifier 151 generates a push-pull TE (PPTE) from the difference between the two. The push-pull balance circuit 150 includes a DSP 132
The push-pull TE adjusted and balanced by the output signal PPTBAL is input to the DSP 132 via the LPF 152 and the AD converter 153.
The DSP 132 executes a filter operation for performing phase compensation and low-frequency compensation on the input push-pull TE,
The drive signal TRD is output via the built-in DA. The output TRD is input to the drive circuit 134 via the synthesizing circuit 133, and the current is amplified by the drive circuit 134 so that a current flows to the tracking element 103. Thereby, the converging lens 105 is driven, and tracking control is performed such that the light beam on the disk 107 scans the uneven track correctly.

FIG. 25 shows the RW in the second embodiment.
4 shows a flowchart of learning on a disc. When the power is turned on (S201), the spindle motor is operated (S202). Next, the DSP 132 outputs a traverse drive signal TRSD to the traverse motor 137 via the drive circuit 136, moves the converging lens 105 and the like to the innermost circumference, and the light beam 107 is moved to the area A of the innermost embossed portion of the disk 101. (Lead-in section) (S203). Thereafter, in the same manner as in steps S4 to S13 in FIG. 11 of the first embodiment, the G
The lens shift is adjusted based on BAL, PHTBAL, and drive offset LSD (S206 to S214). Thereby, the push-pull tracking error (TE) is corrected by the lens shift due to the drive offset.

Thereafter, the focus control is stopped (S2).
15), the traverse motor 13 via the drive circuit 136
7 is provided with a drive signal directed toward the outer periphery, and the light beam 107 is positioned on a predetermined track outside the embossed portion A, for example, an uneven track in the area B (S216). When the focus control is performed again in the RW area B (S217), the push-pull tracking shift signal (push-pull TE) as shown in FIG. 24 is output from the differential amplifier 125. The offset PPOFS of this output push-pull TE
Since the lens shift is optimally adjusted in the embossed portion, all factors of the offset are due to variations in the optical system and the circuit system. Therefore, after calculating the PPTE offset (S218), the ppTBAL value for correcting the push-pull balance is output from the DSP 132 to the push-pull balance circuit 150, and the offset POFS of the push-pull TE is corrected (S21).
9). Thereafter, tracking control is performed, a hold track operation (retrace operation) is performed on a predetermined track, and a command waiting state is set.

(Embodiment 3) FIG. 26 shows an optical disk apparatus according to a third embodiment of the present invention. Here, especially C
A description will be given of an example of a tracking error signal of three beams used in D and the like. The same parts as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. In this apparatus, a method of three-beam tracking detection and tracking control and lens shift learning in that case is realized.

This optical disk device uses a photodetector 160 composed of two divided detection areas E and F. The light beam
The polarization hologram element 106 diffracts the light onto the disk 101 into a main beam 107M and sub-beams 107S1 and 107S2 for three-beam tracking detection, which are split and converged. The reflected light from the sub-beams 107S1 and S2 is applied to the two-divided photodetector 160, respectively. The signals in the detection areas F and E are
The current-voltage conversion is performed by 1a and 161b, and the voltage value passes through the matrix operation circuit 116 and is input to the differential amplifier 152 via the balance adjustment circuit 162. The output of the differential amplifier 163 is connected to the LPF 164 and the A / D
The sub-beam S1 is supplied to the DSP 132 via the converter 165.
It is output as a light amount difference signal of S2, that is, a three-beam tracking error signal (TE3B).

Here, if the center of the light beam is largely shifted from the center of the lens or the center of the photodetector due to the lens shift in the initial state, the spot of the reflected beam is shifted from the photodetector to form an image. Therefore, an asymmetric three-beam tracking error having an offset as shown in FIG.
(TE). The amplitude and offset of the three beams TE are further changed by the lens shift, and the characteristics are as shown in FIGS. 28 (a) and (b). As shown in FIG. 28, the lens shift amount at which the amplitude of the three beams TE becomes almost maximum, that is, the tracking drive offset value 3BL
The offset can be corrected by searching for and setting SD as the optimum adjustment value. At this time, if the offset of the three beams TE does not become 0, the remaining offset 3BOF
Since S is an offset other than lens shift, DSP
By outputting 3BTBAL for correcting this offset from 132 to the balance adjustment circuit 162 and correcting it, a good three-beam TE can be obtained. The above three beam TE
There are various methods for searching for the lens shift amount at which is approximately the maximum. For example, 1) Measure the relationship between the lens shift and the amplitude at several points,
A method of approximating the relationship to a predetermined function and obtaining a lens shift amount at which the approximation function is maximized; 2) moving the lens shift amount by a predetermined amount of positive / negative; And 3) increasing or decreasing the lens shift amount by a predetermined amount to find an extreme point at which the amplitude decreases from the increase. The present embodiment is not limited by the method of obtaining the maximum value of the tracking error amplitude.

The push-pull tracking error (TE) in the second embodiment is also shown in FIGS.
Since the characteristics are almost the same as shown in (1), the third embodiment can also be applied by adjusting the push-pull TE of the RW disc in the second embodiment so as to be almost maximum.

FIG. 30 shows a flow of learning in the third embodiment. The flow (S1 to S1) in FIG.
As in S4), when the apparatus is powered on, the spindle motor 102 is driven, the light source (LD) 108 emits light, and focus control for controlling the light beam spot on the disk 101 to a predetermined convergence state is performed. (S30
1 to S304). Next, a drive offset 3BLSD that maximizes the three beams TE is searched (S305), and a corresponding drive offset 3BLSD is set (S30).
6). Next, the three beam offset is measured (S30).
7) The obtained 3BTBAL is transferred to the balance adjustment circuit 162.
To adjust the offset (S308).

(Embodiment 4) FIG. 31 shows the configuration of an optical disk device according to a fourth embodiment. In FIG. 31, the same portions as those of the optical disc device of the first embodiment (FIG. 9) are denoted by the same reference numerals, and description thereof will be omitted. The tracking control is realized by performing a filter operation process on the phase difference tracking error (TE) or the push-pull TE by the DSP 132. Matrix operation unit 116
Also outputs the full addition signal of A + B + C + D of the four-divided photodetector 114 to the analog signal processing circuit 170 and the envelope detection circuit 181 as an RF signal. The analog signal processing circuit 170 reproduces a signal recorded on the disk 101 as information.

FIG. 32 shows the internal structure of the analog signal processing circuit 170. The input RF signal is input to the data slice circuit 1703 via the waveform equalizing circuit 1702 which emphasizes the frequency of the signal band after the amplitude is made constant by the AGC circuit 1701. Data slice circuit 17
03 slices the data and converts it into a binary signal. 2
The digitized signal is input to the PLL circuit 1704, and the synchronous clock for data extraction is subjected to frequency control and phase control. The binarized signal is supplied to the decoder / ECC circuit 170
5 for decoding and error correction, and the host I /
The host 1709 as reproduction information via the F circuit 1706
Is output to Since a phase error of a phase comparator (not shown) of the PLL circuit 1704 corresponds to data and clock jitter, the jitter detection circuit 1707 converts the phase data into a voltage, and converts the phase data into a voltage as a jitter signal JIT.
3 to the DSP 132. The DSP 132 can detect the level of this jitter signal.

The jitter signal JIT is in a proportional relationship with the actual jitter, and the level decreases when the jitter is small, and increases when the jitter is large. FIG. 33 shows the relationship between the jitter signal JIT and the lens shift. The characteristics of the waveform equivalent circuit 1702 can be varied programmably. In FIG. 33, the solid line shows the characteristics of the lens shift and the jitter signal according to the characteristics set at the time of actual signal reproduction, and the broken line shows the lens shift and the jitter when the degree of emphasis on the signal band of the waveform equivalent circuit 1702 is set slightly lower. It is a characteristic of a signal. In the case of the solid line in FIG.
132 detects the inflection points a and b of the jitter signal, and detects the midpoint c between the two, so that the optimum lens shift position can be obtained. Further, in order to further increase the accuracy, a method of intentionally switching the setting of the waveform equivalent circuit 1702 so as to have the characteristics indicated by the broken line, and finding the minimum point P as a function approximation or the midpoint of two points where the jitter signal amplitude is equal. And sets a lens shift correction amount corresponding to the adjustment position, that is, a tracking drive offset value LSD.

The RF signal input to the analog signal processing circuit 170 is also input to the envelope detection circuit 181, and the DSP 132 can detect the amplitude of the RF signal via the AD converter 182. The relationship between the lens shift and the RF amplitude, that is, the RF envelope detection circuit output RFENV is
As shown in FIG. 34, the DSP 132 searches for a point where RFENV becomes almost maximum, thereby detecting an optimum lens shift position, and similarly to the case of the jitter, a lens shift correction amount corresponding to this lens shift position. That is, the tracking drive offset value LSD is set.

A decoder / error correction circuit 1705
Is input to an error number counting circuit 1700 that counts errors (ERR) that have occurred. The error number counting circuit 1700 inputs the number of generated errors to the DSP 132. The relationship between the lens shift and the number of errors is as shown in the characteristic of FIG. 35. by doing,
It can be adjusted to the optimal lens shift position. As in the second and third embodiments, after adjusting the lens shift with the jitter JIT, the envelope RFENV, or the number of errors ERR, the remaining offset of the phase difference TE is measured. Output a correction signal. Thereby, a good phase difference tracking error signal is obtained.

FIGS. 36 (a), (b) and (c) show flowcharts of learning of these three types of lens shifts in the fourth embodiment. Here, the phase difference tracking error (TE) will be described, but the same can be applied to the case where the tracking control is performed by the push-pull TE or the three-beam TE. In the flow of FIG. 36A, when the apparatus is powered on, the spindle motor 102 is driven, and the light source (LD) 108 emits light (S401 to S403). Next, focus control for controlling the light beam spot on the disk 101 to a predetermined convergence state is performed, and the tracking control is activated (S4).
04), a tracking drive offset that minimizes the jitter JIT is searched (S405A), and a drive offset LSD is set accordingly (S406). Next, the tracking control is stopped (S407), and the phase difference T
The E offset is measured (S408). Next, PHTB
AL is set (S409), and tracking control is activated (S410). The flow of (b) and (c) of FIG.
Only the content of step S405A is different from (a). In (b), a tracking drive offset in which the RF amplitude, that is, the RF envelope detection circuit output RFEMV is almost maximized is searched (S405B), and in (c), a tracking drive offset in which the error number ERR is almost minimized and the margin is almost maximized. Search (S4
05C).

(Embodiment 5) FIG. 37 shows a configuration of an optical disk apparatus according to a fifth embodiment of the present invention. FIG.
In FIG. 28, the same parts as those in FIG. 31 showing the configuration of the optical disk device of the fourth embodiment and FIG. 22 showing the configuration of the optical disk device of the second embodiment are denoted by the same reference numerals.
Description is omitted. In FIG. 37, the analog signal processing circuit 170 is the same as that shown in FIG.

When the apparatus is powered on, the DSP 132
Outputs a traverse drive signal TRSD to the traverse motor 137 via the drive circuit 136, and outputs the convergent lens 105
Etc. to the innermost circumference, and the light beam 107
In the region A (lead-in portion) of the innermost embossed portion. Thereafter, in the same manner as in the first and second embodiments, the lens shift is adjusted by GBAL, PHTBAL, and drive offset LSD in the embossed portion, thereby making it possible to optimize the phase difference tracking error (TE). Set. Next, the focus control is stopped again, and the traverse motor 1 is
A drive signal directed to the outer periphery is given to 37, and the light beam 107 is positioned on a predetermined track outside the embossed portion A, for example, an uneven track in the area B. When the focus control is operated again in the RW area B, the differential amplifier 125 outputs the signal shown in FIG.
4, a push-pull tracking signal (push-pull TE) is output. The configuration and processing up to this point are the same as those in the second embodiment, but in the second embodiment, after the lens shift is optimally adjusted in the embossed portion,
P to correct the push-pull balance from DSP132
The PTBAL value was output to the push-pull balance circuit 150, and the offset PPOFS of the push-pull TE was corrected to stabilize the tracking control. In this embodiment, a configuration for improving signal reproduction performance will be described.

The jitter signal output from the jitter detection circuit 1707 in the analog signal processing circuit 170
2 is input via an AD converter 183. DSP
132 can detect the level of this jitter signal. The jitter signal JIT is in a proportional relationship with the actual jitter. The level decreases when the jitter is small, and increases when the jitter is large. FIG. 38 shows the PPTB from the DSP 132.
5 shows the relationship between the tracking offset that changes with the AL output and the jitter signal JIT. The characteristics of the waveform equivalent circuit can be varied programmably. In FIG. 38, the solid line shows the tracking and jitter signal characteristics based on the characteristics set during the actual signal reproduction, and the broken line shows the lens shift and the jitter when the degree of emphasis on the signal band of the waveform equivalent circuit is set slightly lower. It is a characteristic of a signal. FIG.
In the case of the solid line, the DSP 132 detects the inflection points a and b of the jitter signal and detects the midpoint c between the two points,
An optimal tracking control position can be obtained.
In order to further increase the accuracy, the setting of the waveform equivalent circuit is intentionally switched so as to have the characteristics indicated by the broken line, and the minimum point P is approximated by a function or the amplitude of the jitter signal becomes equal.
The tracking offset correction value PPTBAL corresponding to the adjustment position is set by detecting the midpoint of the point.

The RF signal input to the analog signal processing circuit 170 is also input to the envelope detection circuit 181, and the DSP 132 can detect the amplitude of the RF signal via the AD converter 182. PPTBA from DSP132
FIG. 39 shows the relationship between the tracking offset that changes with the L output and the RF amplitude, that is, the RF envelope detection circuit output RFENV. The DSP 132 searches for a point at which RFENV becomes substantially maximum, thereby detecting an optimum lens shift position, and setting a tracking offset correction value PPTBAL corresponding to the tracking control position as in the case of the jitter.

The decode / error correction circuit 1705 inputs the error (ERR) to an error number counting circuit 1700 for counting the generated errors (ERR). Error count circuit 1
Numeral 700 is used to input the number of occurrence errors to the DSP 132.
The relationship between the tracking offset that changes with the PPTBAL output and the number of errors is as shown in the characteristic of FIG. 40. By doing so, it is possible to adjust to the optimal control position. As in the second embodiment, after adjusting the lens shift in the emboss region using the phase difference TE, the jitter or the number of errors is substantially minimized or the data (RF) signal is substantially maximized. Determine the tracking control position. That is, the push-pull balance circuit is operated and adjusted to a position where the reproduction performance of the recorded signal is almost the best. In the recordable area, an address signal is always recorded in advance. Therefore, the recording position of the address signal is detected, and the control position is determined such that the reproduction jitter or the number of errors of the address signal is substantially minimized, or the amplitude of the address signal is substantially maximized. That is, the push-pull balance circuit is operated and adjusted to a position where the reproduction performance of the address signal is almost the best. This makes it possible to improve the quality of a reproduced signal in a state where the lens shift has been corrected, and to ensure the reliability of the apparatus.

At this time, ideally, a signal in which the offset of the push-pull TE is 0, that is, a signal which is symmetric with respect to the reference potential and which is controllable, should be obtained. However, in practice, there are variations in the detection efficiencies of A to D of the photodetectors 114 and variations in circuit offsets of the preamplifiers 115a to 115d and the matrix calculator.
When the control position is adjusted to a position where the reproduction signal is good, the push-pull track shift signal becomes asymmetric, and the control target is shifted. For this reason, tracking control may become unstable. In such a case, PPTBA
A predetermined clip level (limiter) may be added to the set amount of L so that the symmetry does not extremely deteriorate. As a result, it is possible to improve the signal quality while ensuring the required stability of tracking control.

[0059]

According to the present invention, even if a shift of the center of the objective lens (tilt of the optical axis) occurs due to the mounting error of the optical parts or the initial movement of the objective lens due to the vertical installation, it corresponds to the movement amount. Signals are detected and corrected so that the movement amount is 0, that is, the objective lens is properly positioned, so that good tracking signals and RF signals can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a detection principle of phase difference tracking according to a conventional technique.

FIG. 2 is a schematic diagram for explaining the principle of generation of an offset in phase difference tracking according to the related art.

FIG. 3 is a block diagram showing the configuration of a conventional technique for detecting phase difference tracking and its offset correction circuit.

FIG. 4 is a characteristic diagram showing a change in TE symmetry due to an offset of phase difference tracking with respect to a lens shift according to a conventional technique.

FIG. 5 is a circuit diagram for explaining a conventional three-beam tracking detection method.

FIG. 6 is a schematic diagram showing a positional relationship between a light beam and a track for explaining a conventional three-beam tracking detection method.

FIG. 7 is a schematic diagram illustrating a positional relationship between a lens center and a photodetector center for describing a problem to be solved by the present invention.

FIG. 8 is a schematic diagram illustrating a positional relationship among a lens center, a photodetector center, and a track center for describing a problem to be solved by the present invention.

FIG. 9 is a block diagram showing a configuration of an optical disc device according to the first embodiment of the invention;

FIG. 10 is a waveform chart of a phase difference tracking error signal for explaining the first embodiment of the present invention;

FIG. 11 is a characteristic diagram showing changes in characteristics of lens shift and phase difference TE offset in each process in the learning method according to the first embodiment of the invention;

FIG. 12 is a flowchart of a learning method according to the first embodiment of the invention;

FIG. 13 is a characteristic diagram of a lens shift and a phase difference TE offset according to the first embodiment of the present invention.

FIG. 14 is a waveform chart of a phase difference tracking error signal for explaining the first embodiment of the present invention;

FIG. 15 is a characteristic diagram of a lens shift and a phase difference TE offset according to the first embodiment of the present invention.

FIG. 16 is a waveform chart of a phase difference tracking error signal for explaining the first embodiment of the present invention;

FIG. 17 is a characteristic diagram of a lens shift and a phase difference TE offset according to the first embodiment of the present invention.

FIG. 18 is a waveform chart of a phase difference tracking error signal for describing the first embodiment of the present invention.

FIG. 19 is a characteristic diagram of a lens shift and a phase difference TE offset according to the first embodiment of the present invention.

FIG. 20 is a characteristic diagram of a lens shift and a phase difference TE offset for describing another learning method according to the first embodiment of the present invention.

FIG. 21 is a flowchart of another learning method according to the first embodiment of the invention;

FIG. 22 is a block diagram illustrating a configuration of an optical disc device according to a second embodiment of the invention;

FIG. 23 is a schematic view of a disk used in the second embodiment of the invention.

FIG. 24 is a waveform diagram of a push-pull tracking error signal for describing a second embodiment of the present invention.

FIG. 25 is a flowchart of learning according to the second embodiment of the present invention;

FIG. 26 is a block diagram showing a configuration of an optical disc device according to a third embodiment of the invention;

FIG. 27 is a waveform diagram of a three-beam tracking error signal for describing a third embodiment of the present invention.

FIG. 28 is a characteristic diagram of amplitude and symmetry of a three-beam tracking error signal with respect to a lens shift for explaining a third embodiment of the present invention;

FIG. 29 is a characteristic diagram of the amplitude and symmetry of a push-pull tracking error signal with respect to a lens shift for explaining another configuration and effect of the third embodiment of the invention.

FIG. 30 is a flowchart of learning according to the third embodiment of the present invention.

FIG. 31 is a block diagram showing a configuration of an optical disc device according to a fourth embodiment of the present invention.

FIG. 32 is a block diagram showing a configuration of a signal processing circuit in an optical disk device according to a fourth embodiment of the invention;

FIG. 33 is a characteristic diagram of a jitter signal with respect to a lens shift for explaining a fourth embodiment of the present invention;

FIG. 34 is an amplitude characteristic diagram of an RF signal with respect to a lens shift for explaining a fourth embodiment of the present invention;

FIG. 35 is a characteristic diagram of the number of errors with respect to a lens shift for explaining a fourth embodiment of the present invention;

FIG. 36 is a flowchart of learning according to the fourth embodiment of the present invention;

FIG. 37 is a block diagram showing the configuration of the fifth embodiment of the present invention.

FIG. 38 is a characteristic diagram of a jitter signal with respect to a lens shift for explaining a fifth embodiment of the present invention;

FIG. 39 is an amplitude characteristic diagram of an RF signal with respect to a lens shift for explaining a fifth embodiment of the present invention;

FIG. 40 is a characteristic diagram of an error number with respect to a lens shift for describing a fifth embodiment of the invention

[Explanation of symbols]

 101 Disc 102 Motor 103 Tracking Actuator 104 Focus Actuator 105 Converging Lens 106 Polarization Hologram Element 107 Light Beam Spot 108 Laser 114 Quadrant Photodetector 115 Preamplifier 116 Matrix Operation Unit 117 Phase Adjuster 118 Comparator 119 Phase Difference Balance Circuit 120 Phase Comparator 123 phase adjuster 124 comparator 125 tangential phase comparator 132 digital signal processor 133 synthesis circuit 134, 135, 136 drive circuit 137 traverse motor 150 push-pull balance circuit 151 differential amplifier 152 low-pass filter 160 two-segment photodetector 161 preamplifier 170 Analog signal processing circuit 181 Envelope detection circuit 1700 d Over the counter 1701 AGC 1702 waveform equalization circuit 1703 data slice circuit 1704 PLL circuit 1705 Decoder · ECC circuit

Continuing from the front page (72) Inventor Hirodori Ishibashi 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (26)

[Claims] An optical head including a lens for converging a light beam generated by a light source toward an information carrier; a moving unit configured to move the optical head in a direction substantially perpendicular to a track on the information carrier; With a detection unit divided into a plurality of regions, a photodetector that detects the reflected light of the light beam from the information carrier by dividing into a plurality of regions, and a signal detected in the plurality of regions of the photodetector. A phase difference detection unit that detects a phase difference; a phase difference track shift detection unit that converts the phase difference detected by the phase difference detection unit into a signal corresponding to a positional relationship between a light beam and a track; A phase difference tracking control unit that drives the moving unit in accordance with an output signal of the detecting unit and controls the light beam to scan the track correctly, and applies an offset signal to the moving unit to control the optical head. Les A lens shift unit that moves the lens in a direction substantially perpendicular to the track by a predetermined amount; and an offset signal that minimizes a DC component appearing on an output signal of the phase difference track deviation detection unit to the lens shift unit. An optical disk device comprising a lens shift correction unit to be set. 2. The phase difference detecting section includes a phase adjusting section for adjusting a phase error, and the lens shift correcting section changes the phase adjusting section by a predetermined amount from a target value to cause the phase difference detecting section to detect the phase difference. 2. The optical disk device according to claim 1, wherein an offset signal that minimizes a DC component appearing on the signal converted by the track shift detecting unit is set in the lens shift unit. 3. A lens shift correction unit comprising: a first function indicating a relationship between a movement amount of the lens shift unit at a first set value of the phase adjustment unit and a DC component appearing in an output signal of the phase difference track deviation detection unit. And a second function indicating the relationship between the amount of movement of the lens shift unit at the second set value of the phase adjustment unit and the DC component appearing in the output signal of the phase difference track deviation detection unit, and calculating the first and second functions. 3. The optical disk apparatus according to claim 2, wherein an offset signal that minimizes a DC component appearing on an output signal of the track deviation detecting unit is determined based on the function. 4. The optical disk device according to claim 3, wherein the lens shift correction means obtains an offset signal based on an intersection of the first and second functions. 5. A track that corrects a DC component so that a lens shift correction unit obtains an offset signal to a lens shift unit and an output signal of a phase difference track shift detection unit is symmetric with respect to a reference potential. 3. The optical disk device according to claim 2, further comprising a shift offset correcting unit. 6. An information carrier having two types of areas: an embossed read-only area in which information is recorded in advance, and a recordable area formed by a guide track and on which information is recorded by a mark on the track. An optical head comprising: a lens for converging a light beam generated by a light source toward an information carrier; and a moving unit for moving the optical head in a direction substantially perpendicular to a track on the information carrier. A detection unit divided into a plurality of regions, and a light detector that divides and detects the reflected light of the light beam from the information carrier in the plurality of regions; and a position of each signal in the divided regions of the photodetector. A phase difference detection unit for detecting a phase difference, and a signal corresponding to a positional relationship between a light beam and a track in a read-only area of the information carrier based on the phase difference detected by the phase difference detection unit. A push-pull detector for detecting the intensity of the light beam diffracted by the track, and a light-beam and a track in the recordable area of the information carrier based on the detection signal of the push-pull detector. A second track shift detecting unit that generates a signal corresponding to a positional relationship; and a driving unit that drives the moving unit according to an output signal of the first track shift detecting unit, so that a light beam travels on a track on the information carrier. A phase-difference tracking control unit for controlling the scanning to be performed correctly; and a driving unit for driving the moving unit in accordance with an output signal of the second track deviation detecting unit, so that the light beam scans correctly on the track on the information carrier. A push-pull tracking control unit for controlling the optical head; and applying an offset signal to the moving unit to move the optical head in a direction substantially perpendicular to a track on the information carrier. And a lens shift unit that, when the apparatus is started, first positions the light beam in a reproduction-only area of the information carrier, and outputs an offset signal that minimizes a DC component appearing on an output signal of the first track deviation detecting unit. An optical disc device comprising: a lens shift correcting unit set in a lens shift unit. 7. The phase difference detecting section includes a phase adjusting section for adjusting a phase error, and the lens shift correcting section causes the phase difference detecting section to detect a phase difference by changing the phase adjusting section by a predetermined amount from a target value. 7. The optical disk apparatus according to claim 6, wherein an offset signal that minimizes a DC component appearing on a detection signal of the track deviation detecting section is set to the lens shift section. 8. The phase difference detection section, wherein the lens shift correction section includes a shift amount of the lens shift section at the first set value of the phase adjustment section and a DC component appearing in a detection signal of the first track shift detection section. A first function indicating the relationship, a movement amount by the lens shift unit at a second set value of the phase adjustment unit, and a first function.
A second function indicating the relationship between the DC components appearing in the detection signal of the track shift detecting section is obtained, and based on the first and second functions, the DC component appearing on the detection signal of the first track shift detecting section is calculated. 8. The optical disk device according to claim 7, wherein an offset which is substantially minimized is determined. 9. The optical disk device according to claim 8, wherein the lens shift correction means obtains an offset signal based on an intersection of the first and second functions. 10. When the optical disc apparatus is started, the light beam is moved to a reproduction-only area of the information carrier, and the lens shift correction means sets an offset signal and moves the light beam to a recordable area of the information carrier. 7. The apparatus according to claim 6, further comprising a track deviation offset correcting means for correcting a DC component of the second track deviation detection control unit.
An optical disk device as described in the above. 11. An optical head comprising a lens for converging a light beam generated by a light source toward an information carrier; a moving unit for moving the optical head in a direction substantially perpendicular to a track on the information carrier; Three beam generating means for splitting the light beam into a preceding sub beam, a main beam, and a following sub beam; And a three-beam track shift detecting unit that generates a signal corresponding to the following.
A three-beam tracking control unit that drives the moving unit to control the light beam to scan the track correctly; and applies an offset signal to the moving unit to make the lens of the optical head substantially perpendicular to the track. An optical disk apparatus comprising: a lens shift unit for moving a predetermined amount in a predetermined direction; and a lens shift correcting unit for setting an offset signal in which the amplitude of the signal converted by the three-beam track shift detecting unit becomes substantially maximum to the lens shift unit. . 12. An offset signal of a lens shift unit is set by a lens shift correction unit, and the remaining offset is corrected so that a signal converted by a three-beam track shift signal detection unit is symmetric with respect to a reference potential. 12. The optical disk device according to claim 11, further comprising: a track deviation offset correction unit that performs the correction. 13. Two types of information areas, an emboss reproduction-only area in which information is recorded in advance, and a recordable area formed by an uneven address portion and a guide track, and information is recorded on the guide track. An optical disc device for an information carrier having: an optical head having a lens for converging a light beam generated by a light source toward the information carrier; and an optical head substantially perpendicular to a track on the information carrier. A moving unit that moves in the direction, a detector that is divided into a plurality of regions, a light detector that detects the reflected light of the light beam from the information carrier by dividing the light into the plurality of regions, and a division of the light detector. A phase difference detection unit that detects a phase difference between the signals in the region, and a positional relationship between the light beam and the track in the read-only region of the information carrier based on the phase difference detected by the phase difference detection unit. A first track deviation detecting section for generating a signal, a push-pull detecting section for detecting the intensity of the light beam diffracted by the light beam track, and a recordable area of the information carrier based on the signal of the push-pull detecting section. A second track shift detecting unit for generating a signal corresponding to the positional relationship between the light beam and the track in the step, and driving the moving unit in accordance with an output signal of the first track shift detecting unit. A phase difference tracking control unit for controlling to scan the track correctly; and controlling the moving unit in accordance with an output signal of the second track shift detecting unit to control the light beam to scan the track correctly. A push-pull tracking control unit that reproduces an address part of the information carrier by a signal of the photodetector and reproduces information recorded in a recordable area of the information carrier. A reproducing unit; a lens shift unit that applies an offset signal to the moving unit to move the lens of the optical head in a direction substantially perpendicular to the track; and an offset that applies an offset signal to the push-pull tracking control unit. Correction means; lens shift correction means for setting an offset signal in which the DC component appearing on the signal of the first track deviation detection section is substantially minimized in the lens shift section; characteristics of the reproduction signal reproduced by the reproduction means An optical disc apparatus comprising: a characteristic detecting unit that detects an initial lens shift based on the characteristic detection unit; and a lens shift adjusting unit that adjusts the initial lens shift detected by the characteristic detecting unit so that reproduction signal characteristics become almost the best. 14. The characteristic detected by the characteristic detecting unit is a jitter component of a reproduced signal of information by a reproducing unit. 14. The optical disk device according to claim 13, wherein the offset correction unit is adjusted so that the value of the offset correction unit is substantially minimized. 15. The characteristic detected by the characteristic detecting unit is an error rate of a reproduction signal of information reproduced by an information reproducing unit for each predetermined block. 14. The optical disk device according to claim 13, wherein after applying the offset, the push-pull balance unit is adjusted so that an error rate of a predetermined block is substantially minimized. 16. The characteristic detected by the characteristic detecting unit is a jitter component of an address signal reproduced by a reproducing unit. The lens shift adjusting unit is configured to perform a jitter component after the lens shift correcting unit applies an offset. 14. The optical disk device according to claim 13, wherein the push-pull balance means is adjusted so that the value of the push-pull balance is substantially minimized. 17. The characteristic detected by the characteristic detecting unit is an error rate of an address signal reproduced by a reproducing unit for each predetermined block, wherein the lens shift adjusting unit applies an offset by the lens shift correcting unit. 14. The optical disk device according to claim 13, wherein the push-pull balance unit is adjusted so that an address error rate of a predetermined block is substantially minimized. 18. The optical disk apparatus according to claim 13, wherein the lens shift adjusting means includes a push-pull balance means for operating a gain balance of the second track deviation detecting unit to apply an offset. 19. A light beam is moved to a reproduction-only area of an information carrier when an optical disc apparatus is started, an offset signal of a lens shift unit is detected by a lens shift correction unit, and the light beam is moved to a recordable area of the information carrier. 14. The optical disk device according to claim 13, wherein the lens shift adjusting means operates. 20. The optical disk device according to claim 19, wherein the offset signal set by the lens shift correction means is limited to a predetermined range. 21. The offset signal set by the lens shift correction means is limited so that the symmetry of the second track shift signal in a recordable area of the information carrier is within a predetermined range. 20. The optical disk device according to 20. 22. An optical head comprising a lens for converging a light beam generated by a light source toward an information carrier; a moving unit for moving the optical head in a direction substantially perpendicular to a track on the information carrier; A photodetector comprising a detection unit divided into a plurality of regions, and detecting the reflected light of the light beam from the information carrier by dividing the light into a plurality of regions; and outputting the output of the photodetector to the positions of the light beam and the track. A track shift detecting unit that converts the track shift signal into a track shift signal corresponding to the relationship; a tracking control unit that drives the moving unit according to an output signal of the track shift detecting unit and controls the light beam to scan the track correctly. A lens shift unit that applies an offset signal to the moving unit to move the optical head by a predetermined amount in a direction substantially perpendicular to the track; An optical disc comprising: a characteristic detecting unit for detecting characteristics of the reproduced signal; and a lens shift adjusting unit for setting, in the lens shift unit, an offset signal having almost the best reproduction signal characteristics based on the characteristic detected by the characteristic detecting unit. apparatus. 23. The characteristic detecting section, wherein a reproduction signal processing means for waveform-equalizing the sum signal of the photodetector, and a jitter between a reproduction clock for binarizing an output signal of the reproduction signal processing means and synchronizing the output signal with the reproduction signal. 23. The optical disk apparatus according to claim 22, further comprising a jitter detection unit for detecting, wherein the lens shift adjustment unit sets an offset signal that minimizes jitter to the lens shift unit. 24. The characteristic detecting section detects an amplitude of a sum signal of the photodetector, and the lens shift adjusting section sets an offset signal at which the sum signal amplitude becomes substantially maximum to the lens shift section. 23. The optical disk device according to claim 22, wherein: 25. A signal processing unit for waveform-equalizing a sum signal of the photodetector, a binarizing unit for binarizing an output of the signal processing unit, Phase lock means for synchronizing a signal with a reproduced clock, error correction means for decoding an output signal of the binarization means phase-locked by the phase lock means and performing error correction, and error correction by the error correction means Error counting means for detecting and counting errors occurring in the lens shift adjusting means, wherein the number of errors counted by the error counting means is substantially minimized, or a range in which the number of errors is substantially minimized. 23. The optical disk device according to claim 22, wherein an offset signal that maximizes a maximum value is set in the lens shift unit. 26. The apparatus according to claim 22, further comprising offset correction means for setting an offset signal of the lens shift section by the lens shift correction means and correcting the remaining offset of the track shift signal.
An optical disk device as described in the above.