JP2002343023A - Optical disk drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reproducing device for optical disks which is capable of efficiently and rapidly inquiring an optimum waveform equalization quantity and reproducing diversified information carrier as well with high reliability in waveform equalization of the regenerative signals on the information carrier with a device equipped with a light source, such as a semiconductor laser. SOLUTION: Such a waveform equalization set quantity as to minimize jitters in the circumferential direction of the optical disk is set by changing over the same by using jitter measuring means and waveform equalization quantity saving means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for optically reproducing a signal on an information carrier using a light beam from a light source such as a semiconductor laser.

[0002]

2. Description of the Related Art A reproducing apparatus for an optical disk as an information carrier is provided with a light beam generated from a light source such as a semiconductor laser and the like convergently irradiated on a disk-shaped information carrier (optical disk) rotating at a predetermined rotation speed. And those that reproduce signals. On this information carrier, minute tracks are formed in a spiral shape as an information pit row. In general, an optical disk device includes a rotation control for rotating an optical disk at a predetermined number of rotations, a focus control so that a light beam irradiated on the optical disk is in a predetermined convergence state, and a light beam for a track on an information carrier. The tracking control is performed such that scanning is performed correctly. Also, the optical disc includes CD audio, CD-R
Read-only type in which information such as OM and DVD-ROM are recorded in a pit row, one-time recording type such as CD-R and DVD-R, and recording and reproduction in CD-RW, DVD-RAM and DVD-RW There are various types up to the type, and it is necessary to optimize a reproduction signal such as recording density and reflectivity of the disk by adapting it to the characteristics of each optical disk. Although the optical disk reproduction signal is a random signal, the amplitude of a high frequency signal component is extremely lower than that of a low frequency signal component due to intersymbol interference. For this reason, by boosting a predetermined frequency band by the waveform equalization characteristic as shown in FIG. 2, the signal amplitude of the high frequency component is improved, and the gain is rapidly reduced by a high-order equiripple filter or the like, and the signal bandwidth is reduced. External high-frequency noise is removed to improve reproduction signal quality. In FIG. 2, the horizontal axis represents frequency, and the vertical axis represents gain characteristics of the waveform equalizing means.

In general, when information is reproduced while scanning marks and pits with a light beam, if the size of the mark or pit is smaller than the spot size of the light beam, it is susceptible to intersymbol interference. . Further, when the light intensity distribution of the reflected light reflected from the optical disk is distorted, waveform distortion of the reproduced signal occurs. A waveform equalization method for correcting such reproduced waveform distortion has been proposed.

A method of performing waveform equalization for reducing intersymbol interference, focusing on the light intensity distribution distortion, will be described. First, FIG. 3 shows an example of light distribution distortion. In FIG. 3, the horizontal axis represents time, and the vertical axis represents light intensity. Also,
The scale on the horizontal axis is a reference clock time T which is a unit time for recording a mark or pit on the optical disk. The light intensity distribution A 300 is a case where the light intensity distribution is symmetric, and the light intensity distribution B 301 is a case where the light distribution is distorted. When such light intensity distribution distortion occurs, waveform distortion of a reproduced signal occurs. A method has been proposed in which a phase characteristic is varied when equalizing an asymmetric distortion of a reproduced signal waveform, that is, a delay characteristic is varied (Japanese Patent Laid-Open No. 7-1).
No. 76108).

Further, in the reproduction of an optical disk, if the optical axis of the light beam is inclined with respect to the reproduction surface of the optical disk, the light intensity distribution of the light beam on the optical disk is distorted, so that the reproduced waveform is distorted and the signal quality is reduced. , The error rate deteriorates. The inclination (skew) of the light beam with respect to the optical disk can be divided into a tangential direction perpendicular to the signal direction and a radial direction parallel to the signal direction. The optical disk is distorted in the disk radial direction (radial direction)
In contrast, the optical axis of the light beam is inclined. In this case, the light intensity distribution of the light beam reflected from the optical disk is distorted, causing a waveform distortion of the reproduced signal. This is because the light intensity distribution of the light beam has a certain spread,
This is because the optical path length changes between the left and right sides of the light beam. To cope with the deterioration of the reproduction signal in the radial direction, a configuration has been proposed in which the disk is divided into zones in the radial direction and the gain characteristic of the waveform equalizing circuit is varied for each zone (Japanese Patent Laid-Open No. 8-147882). Gazette).

[0006]

In the conventional optical disk apparatus having the above-described configuration, the quality against the optical intensity distribution distortion and the optical axis skew fluctuation in the radial direction due to the warp or the like of the optical disk itself has been ensured. However, since the optical disk is not necessarily flat, the optical axis also tilts in the disk circumferential direction (tangential direction), causing jitter fluctuation of the reproduction signal even within one round of the disk, which causes a problem of reducing the margin in the system design. did.

Another problem is that the jitter of a reproduced signal varies depending on the shape of recording marks or pits on an optical disk on which a CD-R or the like is recorded.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional technique, and has as its object to provide a highly reliable apparatus that reduces jitter fluctuation in the circumferential direction of a disk.

[0009]

SUMMARY OF THE INVENTION The present invention relates to an apparatus for optically recording or reproducing information recorded on an optical disk by means of a light beam emitted from a light source such as a semiconductor laser. Converging means, light detecting means for detecting reflected light reflected by the information carrier or transmitted light transmitted through the record carrier, a waveform equalizing means for changing a frequency characteristic of an output signal of the light detecting means, the waveform and the like. Jitter measuring means for measuring the jitter of the output signal of the converting means, minimum jitter searching means for searching for a waveform equalization amount which minimizes the jitter based on the output of the jitter measuring means, and a predetermined circle of the information carrier. A waveform equalization amount storing unit that stores a waveform equalization amount that is an output of the minimum jitter search unit and area information that specifies the circumferential division region, for the circumferential division area; It includes a waveform equalizing amount setting means for setting a reduction amount, a configuration such as to set the waveform equalization amount based on the stored values of the waveform equalization amount storage means.

[0010] The minimum jitter searching means may include a measurement condition storage memory for storing jitter, waveform equalization amount and area information corresponding to the circumferential divided area.

[0011] The minimum jitter searching means may use a storage timing signal for specifying a circumferential divided area on the information carrier.

The minimum jitter searching means may use a rotation synchronization signal output in synchronization with the rotation of the information carrier as a storage timing signal.

[0013] The minimum jitter searching means may use address information recorded on the information carrier as a storage timing signal.

The waveform equalization amount storage means may have a waveform equalization amount setting value memory for storing the waveform equalization amount corresponding to the circumferential divided area and the area information.

The waveform equalization amount storage means may include a waveform equalization amount setting value memory for storing the amount of waveform equalization that minimizes the jitter of each circumferentially divided area and area information.

The stored value of the waveform equalization amount storage means may include a cutoff frequency, a boost amount, and a group delay amount of the waveform equalization means.

The waveform equalization amount setting means may switch and set the waveform equalization amount, which is a value stored in the waveform equalization amount storage means, in the circumferential direction.

The waveform equalization amount setting means may set a value obtained by averaging the waveform equalization amount, which is a stored value of the waveform equalization amount storage means, as the waveform equalization amount.

The number of divisions in the circumferential direction of the information carrier may be from 4 to 6.

When the minimum jitter search is performed, the group delay characteristics of the waveform equalizing means may be flattened first.

The waveform equalization amount setting means may set the waveform equalization amount based on a preset waveform equalization amount setting pattern.

The area information for specifying the circumferential divided area on the information carrier includes radial position information for specifying a radial position on the information carrier and the circle on the information carrier with the center of the information carrier as a rotation center. The rotation phase information may be such that the circumferential position of the circumferential division area can be specified.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS. Members having similar functions are denoted by the same reference numerals. In the embodiment, the jitter is measured for a region divided in the circumferential direction of the disk, and the waveform equalizing means is optimally set.

FIG. 1 is a block diagram showing the configuration of the embodiment. As shown in FIG. 1, an optical disc apparatus according to the present invention includes an optical disc 1, which is an information carrier, an optical head 2, which emits light from a light source such as a semiconductor laser, and converges and irradiates a light beam onto the optical disc. A preamplifier 3 for amplifying a signal corresponding to the reflected light from the optical disk 1, a waveform equalizing means 4 for waveform equalizing the output signal of the preamplifier 3, a disk motor 17 for rotating the optical disk 1, and a disk motor for driving the disk motor 17 Drive circuit 1
6, a disk motor control unit 15 for controlling the disk motor drive circuit 16 is provided. Further, the amplitude of the output signal of the preamplifier 3 is detected in order to set a target position, that is, a focus position of the focus control unit 10 such that the light beam emitted from the optical head 2 is in an optimum convergence state on the optical disc 1. An amplitude detecting section 8 and a maximum amplitude searching means 9 for searching for a focus position at which the amplitude of the reproduction signal detected by the amplitude detecting section 8 becomes maximum are provided.

The control device 7 outputs a drive signal to the optical head 2 via a synthesizing circuit 11 for synthesizing the signal of the maximum amplitude search section 9 with the control signal of the focus control section 10, so that the light beam is optimized. It is controlled so as to be in a convergence state. In the control device 7, a control signal for causing the light beam to scan a track on the optical disk 1 correctly is provided to the optical head 2.
The tracking control unit 12 which outputs the data to the tracking control unit is also provided. However, since the tracking control is not directly related to the present invention, the detailed description is omitted.

The reproduced signal whose waveform has been equalized by the waveform equalizing means 4 is pulsed by the binarizing circuit 13 and its jitter is detected by the jitter detecting section 5. The actual detection of jitter is controlled by P to control the binarized pulse to match.
The phase error from the LL clock is detected by performing voltage conversion or the like.

The output of the jitter detector 5 is input to the controller 7 and sent to the minimum jitter detector 6 for searching for the minimum value of jitter. The minimum jitter exploring unit 6 controls the cut-off frequency Fc and the boost amount B of the waveform equalizing means 4 so that the jitter is minimized.
Search for a combination of ST and group delay GD. The result of searching for the minimum jitter is sent to the waveform equalization amount storage means 14.
The waveform equalization amount storage means 14 has a waveform equalization amount setting value memory (not shown), and each set value when the minimum jitter is searched is stored in the waveform equalization amount setting value memory. Further, the information stored on the optical disk is reproduced through the filter of the frequency characteristic set by the waveform equalization amount setting unit 19 using the stored value of the waveform equalization amount storage unit 14.

The address information on the optical disk 1 is
It is extracted from the reproduced signal by the address information obtaining means 18.

Hereinafter, a method of setting the waveform equalization amount in the present embodiment will be described in detail. First, the waveform equalizing means will be described. The waveform equalizing means 4 in FIG. 1 has a configuration in which a cutoff frequency for removing noise components higher than a signal component and a boost for relatively increasing a high frequency component of a reproduced signal can be changed. Further, the configuration is such that a group delay characteristic (unit of the group delay characteristic is time) defined by a change in phase with respect to frequency can also be changed. FIG. 5 shows a configuration example of the waveform equalizing means 4. FIG. 4 shows a seventh-order equiripple filter, in which three second-order low-pass filters (LP
F1 400, LPF2 401, LPF3 40
2) It is composed of a first-order low-pass filter LPF4 403, a second-order high-pass filter HPF1 404, an amplifier 405, and a coefficient setting circuit 406. The group delay characteristic can be varied by arbitrarily setting any one of these components.

FIG. 5 shows an example of the frequency characteristics of the filter shown in FIG. The horizontal axis shows frequency, the vertical axis (right) shows delay characteristics, and the vertical axis (left) shows gain characteristics. The graph shows the characteristics when the delay amount is varied by ΔGD with respect to the group delay amount characteristic flat condition (GDF). Arrows indicate the width of the bandwidth of the frequency component of the reproduced signal. In general, the reproduction signal on the optical disk 1 has a shortest recording mark or pit and a longest recording mark or pit. Therefore, when the reproduction signal is reproduced at a desired rotation speed, the signal has a frequency component within a certain range. . As described above, the filter shown in FIG. 4 has a configuration capable of changing the group delay characteristic with respect to the signal band.

Next, the relationship between the jitter, the cutoff frequency, the amount of boost, and the amount of group delay, which are characteristic elements of waveform equalization, will be described.

If these three variables are not optimally set, they are factors that can cause waveform distortion of the reproduced signal and affect the jitter of the reproduced signal. Since the jitter of the optical disc reproduction signal is affected by the high-frequency noise component, the jitter characteristic of the reproduction signal is as shown in FIG. 6A shows the jitter characteristic 601 with respect to the cutoff frequency and the boost amount, FIG. 6B shows the jitter characteristic 602 with respect to the group delay and the boost amount, and FIG. 6C shows the jitter characteristic 603 with respect to the group delay and the cutoff frequency. I have. FIG. 6 is all shown in a rectangular coordinate system. The cutoff frequency, boost amount, and group delay are not independent variables for jitter,
The jitter characteristic becomes a contour line. Optimal settings are made for such jitter characteristics. Since there are three waveform equalization setting variables, first, the group delay characteristics are made flat, the cutoff frequency and the boost amount are varied, and a two-dimensional search is performed. this is,
This is because the transmission characteristic of the electric information transmission path is a necessary condition that the group delay characteristic flat does not cause waveform distortion.

Here, an example of searching for the cutoff frequency and the boost amount of the waveform equalizing means 4 will be described. FIG. 7 shows a flowchart for performing the minimum jitter value search.

First, in step S700, the group delay of the waveform equalizing means 4 is set to be flat. Next, in step S701, an initial cutoff frequency and an initial boost amount are set. The two variables in this case are such that the reproduced signal can pass through the waveform equalizing means without distortion, and can be set to any values as long as they are within the range in which the signal can be reproduced. Next, in step S702, jitter measurement is performed on the optical disc 1 at a predetermined radial position or address. Next, in step S703, it is determined whether it is the first measurement. If it is the first time, step S704
Save as the measurement initial value with.

Again, in the resetting 1 of step S705, the cutoff frequency and the boost amount of the waveform equalizing means 4 are reset, and
Perform jitter measurement. Next is the second and subsequent jitter measurements, and thus a jitter comparison is performed in step S706. if,
If the jitter is equal to or less than a predetermined value (for example, the jitter is 0.2%), the cutoff frequency and the boost amount are the set values that minimize the jitter, and thus the jitter search is completed. However, if the jitter exceeds the predetermined value, in step S707, a comparison is made between the jitter minimum storage value at the first measurement and the jitter measured this time. If the jitter measured this time is large, the process proceeds to step S708, where it is determined whether or not the waveform equalization variable parameter search range remains. If so, the process proceeds to step S710; otherwise, the process proceeds to step S711. Proceed to.

In step S709, the minimum setting of the measured jitter is always stored. In step S711, the setting that minimizes the jitter is set in the waveform equalizing means 4.

In the method of setting the waveform equalizing means and the boost amount in step S710, all combinations may be performed, or the cutoff frequency may be reduced by comparing the previous and current waveform equalization setting values to reduce the jitter. A vector composed of the set value and the boost set value may be calculated and set. By repeating the jitter measurement until the jitter comparison in step S706 becomes equal to or less than the predetermined value or the search range in step S708 disappears, the minimum jitter search is completed. In this way, it is possible to obtain the setting of the cutoff frequency and the boost amount of the waveform equalizing means that minimize the jitter.

There are various methods for searching for the minimum jitter value, but the method for searching for the minimum jitter value itself is not limited to the present invention.

Next, a method for specifying an area on an optical disk for switching and setting the amount of waveform equalization in the disk circumferential direction for each area on the disk according to the present embodiment will be described with reference to FIGS.
This will be described with reference to FIG. In the present embodiment, the description will be made by dividing the optical disk into six radially. The radial direction will be described by dividing into four for simplicity.

FIG. 8 shows an example of a circumferentially divided area on the optical disc 1. In this example, one rotation is divided into six radially from the center of the optical disc 1 and divided into four in the radial direction. On the optical disk 1, a position at a certain rotation phase of 0 ° is determined, and the zone
805 is set. In addition, the disk radius is also divided in the radial direction, and a division region R3 823 is set from a division region R0 820 of a circumferential band shape. In FIG. 9, the information surface of the optical disc 1 is divided into 24 areas. The number of divisions of the optical disc 1 in the radial direction is not limited at all. Since it is necessary to set the optimum amount of waveform equalization for each divided region, it is necessary to specify the position where the light beam is scanning. This position can be specified from the radial position information and the circumferential rotation phase information that are the area information.

If a mechanism such as a stepping motor can mechanically specify the position of the optical head, the radius position can be specified by the mechanism. Further, based on the address information acquiring means 18 in FIG. 1, the radius position can be specified by the system control software (not shown) from the format information of the optical disc.

Next, a method using a rotation synchronizing signal (FG) output from a disk motor as the rotation phase information will be described.

FIG. 9A shows the rotation synchronizing signal FG.
(B) shows the disk area. Rotation synchronization signal FG
The initial phase at an output position with 0
° are shown at intervals. In this case, the configuration is such that six pulses of the rotation synchronization signal FG are output per rotation of the optical disk. The number of pulses per rotation of the rotation synchronization signal FG does not necessarily have to be 6 pulses, and is always output at the same position at least once per rotation.
It suffices if the phase with respect to the optical disk at the position where the light beam scans can be specified. Further, the rotation phase may be specified using a pulse obtained by multiplying or dividing the rotation synchronization signal FG.

By using such a rotation synchronizing signal FG, the rotation phase information of each divided area can be specified. The rotation phase information is stored in the address information acquisition unit 18.
, It is also possible to specify the rotation phase information.

Further, the rotation phase is specified by using an output of a sector clock (not shown) which counts a PLL clock synchronized with a sector which is an information unit on the optical disk or a clock obtained by dividing or multiplying the PLL clock. Is also possible.

Next, the behavior of the jitter of the reproduced signal on the optical disk will be described with reference to FIGS. 10, 11 and 12. FIG.

As described above, the jitter of the reproduction signal of the optical disk 1 is deteriorated by the skew of the optical beam and the optical disk, and the jitter characteristic is shown in FIG. FIG.
In FIG. 1, the horizontal axis is tangential skew, and the vertical axis is jitter.

The solid line indicates that the group delay characteristic is flat (the set value is G
DF). This is a characteristic when the group delay setting amount shown in FIG. 5 is a GDF. The jitter is deteriorated regardless of whether the tangential skew is positive or negative. However, when the tangential skew occurs in the positive direction, the waveform amount is corrected by adding the group delay characteristic to ΔGD, thereby correcting the waveform distortion and deteriorating the jitter amount with respect to the group delay characteristic flat (GDF) condition. From point A 1010 to point B1
011. Conversely, when the tangential tilt occurs in the negative direction, the point C 1 is obtained by changing the group delay characteristic to ΔGD-subtracted characteristic.
From 012 to point D 1002, jitter can be improved. However, the variable amount ΔGD of the delay characteristic is an amount that varies depending on the tangential skew amount. As described above, by varying the group delay characteristics according to the tangential skew amount, it is possible to correct waveform distortion and improve signal quality.

FIG. 11A shows each region with respect to the rotational phase.
FIG. 11B shows the tangential skew fluctuation amount corresponding to the disk rotation phase, and FIG. 11C shows the jitter value according to the tangential skew fluctuation. FIG.
In 1, the condition in which the group delay characteristic is flat and tangential skew is not generated will be described as a condition for obtaining the best signal quality. FIG. 11 shows, for simplicity, a case where the tangential skew amount changes from + TG to −TG corresponding to the rotation phase. For example, if the tangential skew is 0, the rotation phase is 90 ° and 2
70 ° point. Further, when the angle is most inclined in the positive direction, the rotation phase is 180 °, and when the angle is most inclined in the negative direction, the rotation phase is 0 ° (360 °).

FIG. 12 shows a case where the group delay characteristic is flat.
In (c), the jitter according to the rotation phase is plotted. Thus, the jitter also varies according to the tangential skew.

Next, the behavior of jitter at each rotation phase when the group delay characteristic is varied will be described with reference to FIG.

FIG. 12A shows the tangential skew fluctuation amount corresponding to the disk rotation phase, and FIG.
Jitter for tangential skew and group delay setting amount, FIG. 12C shows jitter for group delay setting when tangential skew amount is -TG, and FIG. 12D shows group delay setting when there is no tangential skew amount. FIG. 12E shows the jitter with respect to the group delay setting when the tangential skew amount is + TG. In FIG. 12C, when the group delay characteristic is flat, G
DF is indicated by a circle, a case where the group delay characteristic is changed in the positive direction of ΔGD is indicated by Δ, and a case where the group delay characteristic is changed in the negative direction is indicated by square. In FIG. 12D, the jitter is minimized when the tangential skew amount is 0 with respect to the case where the group delay characteristic is flat. However, if the tangential skew fluctuation increases, the jitter deteriorates. Further, focusing on the tangential skew fluctuation amount, the jitter increases regardless of the positive or negative direction of the tangential skew amount. In FIG. 12 (c) in which the tangential skew is -TG, the amount of group delay correction is larger than that in the case where the group delay characteristic is flat, in order to correct the waveform distortion.
The jitter is improved by changing the ΔGD. Conversely, + ΔG
When D is varied, the jitter is worse than when the group delay characteristic is flat. When the rotation phase is 90 ° and 270 °, the tangential skew fluctuation is 0 °, so that the jitter is smallest when the group delay characteristic is flat. When the rotation phase is 180 °, tangential skew +
Since the TG exists, the value of the jitter becomes smallest when the group delay characteristic is changed by -ΔGD. Here, the code of the tangential skew and the code of the group delay set value for correcting the waveform distortion are in the same composite order, and are uniquely determined by the configuration of the optical disk.

Table 1 shows each group delay setting amount which minimizes the jitter for each region obtained from FIG.

[0054]

[Table 1]

As described above, the amount of waveform equalization that minimizes the jitter can be determined for each region.

Next, the search for the amount of waveform equalization that minimizes the jitter in each circumferential area will be described with reference to the jitter storage timing chart of FIG. 13 and the waveform equalization amount setting flowchart of FIG.

The jitter storage timing in FIG.
The example using the rising edge of the pulse signal synchronized with the rotation synchronization signal FG is generated. FIG. 13B shows each area for the rotational phase, but the storage timings correspond to each of these areas. FIG. 13 (c) uses the group delay set value as a parameter.
It shows a jitter value with respect to the rotation phase. The solid line shows the case where the group delay characteristic is flat, and the dotted line and the chain line show the group delay setting value reduced and increased by ΔGD, respectively. FIG.
(D) shows the tangential skew fluctuation amount during one rotation of the disk.

By such a storage timing signal,
It is possible to acquire a jitter measurement value and a measurement condition at the time of jitter measurement according to each area and each group delay setting value.

The tangential skew fluctuation in one rotation of the optical disc 1 may be a behavior other than that shown in the figure. However, by performing search by changing the group delay set value, regardless of the area division method, It is possible to obtain a condition for minimizing jitter as a group delay characteristic of the waveform equalizing means in each of the regions.

The waveform equalization amount setting flowchart of FIG. 14 will be described sequentially. First, in step S1401, a seek operation is performed to a target address where the optimum waveform is to be equalized.
Next, initial setting for waveform equalization is performed in step S1402.
Do with. Here, the cutoff frequency, boost, and group delay characteristics are also set. Next, jitter measurement is performed in step S1403, and the measurement is sequentially stored in a measurement condition storage memory (not shown) in the minimum jitter search unit 6 in FIG. The measurement condition storage memory is configured to simultaneously store a rotation phase, which is a parameter for specifying an area, or address information, and a group delay setting value as a waveform equalization setting parameter. In the waveform equalization means, when the group delay set value is changed, the gain characteristic of the waveform equalization means changes.
The cutoff frequency set value and the boost set value that do not change the gain characteristics may be stored. Step S14
At 05, it is determined whether the predetermined group delay setting pattern has been completed. This setting pattern is for obtaining the minimum jitter setting, and a plurality of settings may be made. For example, if at least three group delay setting patterns are provided, a more reliable search can be performed. However, if two group delay setting patterns are provided to shorten the search time, switching can be performed at the time of retry. Is also possible.

If the group delay setting pattern has not been completed in step S1405, the group delay characteristics are reset, and the jitter measurement is performed again in step S1403. If the group delay setting pattern has been completed in step S1405, in step S1407, the jitter, which is the value stored in the measurement condition storage memory, is compared for each region, and the waveform or the like that minimizes the jitter in each region. Exploration of set amount Next, in step S1408, the search result in S1407 is stored in the waveform equalization amount setting value memory for each area. Further, in step S1409, the waveform equalization amount set value stored in step S1408 is sequentially switched according to the rotation phase and set in the waveform equalization means 4.

Here, as the waveform equalization amount, an averaged value may be used without using the stored value of the waveform equalization amount as it is and when the number of divided regions for performing the jitter measurement is increased. For example, the group delay set value of the area 3 is changed to the area 2 and the area 3
And the area 4 may be added and divided by 3. Further, the waveform equalization amount setting means sets a waveform equalization amount setting amount for each predetermined area on the optical disc 1 or an average of all the areas in order to reduce a waveform equalization amount setting value memory. The fluctuation jitter may be reduced.

In this way, it is possible to realize the waveform equalization setting for reducing the jitter during reproduction in each region.

[0064]

As described above, according to the present invention, the optimum waveform equalization amount is searched for each area divided with respect to the rotation phase in one rotation of the optical disk, and the rotation is set for each area. It is possible to reduce jitter fluctuation in the circumferential direction and to provide a highly reliable optical disk device having a wider system margin.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a frequency characteristic of a waveform equalizing unit;

FIG. 3 is a diagram showing light intensity distribution characteristics of a light beam;

FIG. 4 is a block diagram showing a configuration of a waveform equalizing unit according to the embodiment;

FIG. 5 is a diagram illustrating frequency characteristics of a waveform equalizing unit according to the embodiment;

FIG. 6 is a diagram showing a jitter characteristic showing a cutoff frequency, a boost, a group delay, and a jitter contour.

FIG. 7 is a flowchart for explaining the search for the minimum value jitter when the group delay characteristic is flat;

FIG. 8 is a diagram for explaining a divided area on an optical disc;

FIG. 9 is a timing chart for explaining a divided area and a rotation synchronization signal.

FIG. 10 is a diagram showing a relationship between tangential skew and jitter.

FIG. 11 is a timing chart for explaining jitter fluctuation during one rotation of the optical disk.

FIG. 12 is a diagram illustrating jitter with respect to a group delay setting at a specific rotation phase.

FIG. 13 is a flowchart illustrating a method for setting a waveform equalization amount according to an embodiment;

FIG. 14 is a timing chart illustrating a jitter measurement timing according to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Optical head 3 Preamplifier 4 Waveform equalization means 5 Jitter detector part 6 Minimum value jitter search part 7 Controller 8 Amplitude detection 9 Maximum amplitude search means 10 Focus control part 11 Adder 12 Tracking control part 13 Binarization circuit 14 waveform equalization amount storage means 15 disk motor control unit 16 disk motor drive circuit 17 disk motor 18 address information acquisition means 19 waveform equalization amount setting means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D044 BC02 CC04 FG02 FG10 FG12 5D090 AA01 CC04 CC16 CC18 EE17 FF30 FF41 HH01

Claims (14)

[Claims] An apparatus for optically recording or reproducing information recorded on an optical disk by a light beam emitted from a light source such as a semiconductor laser, comprising: converging means for converging and irradiating a light beam; A light detecting means for detecting reflected reflected light or transmitted light transmitted through the record carrier; a waveform equalizing means for changing a frequency characteristic of an output signal of the light detecting means; and a jitter of an output signal of the waveform equalizing means. For the jitter measuring means to measure, the minimum jitter searching means for searching for the amount of waveform equalization such that the jitter is minimized based on the output of the jitter measuring means, and for a predetermined circumferential divided area of the information carrier, Waveform equalization amount storage means for storing the waveform equalization amount output from the minimum jitter search means and area information for specifying the circumferential divided area; and a waveform equalization amount for setting the waveform equalization amount With a constant section, the optical disk apparatus characterized by setting the waveform equalization amount based on the stored values of the waveform equalization amount storage means. 2. The optical disk according to claim 1, wherein the minimum jitter searching means has a measurement condition storage memory for storing jitter, waveform equalization amount and area information corresponding to the circumferential divided area. apparatus. 3. The optical disk apparatus according to claim 1, wherein the minimum jitter searching means uses a storage timing signal for specifying a circumferential divided area on the information carrier. 4. The optical disk apparatus according to claim 3, wherein said minimum jitter searching means uses a rotation synchronization signal output in synchronization with the rotation of the information carrier as a storage timing signal. 5. The optical disk apparatus according to claim 3, wherein the minimum jitter searching means uses address information recorded on the information carrier as a storage timing signal. 6. The waveform equalization amount storage means includes a waveform equalization amount setting value memory for storing a waveform equalization amount corresponding to a circumferential divided area and area information. An optical disk device according to the above. 7. The waveform equalization amount storing means includes a waveform equalization setting value memory for storing a waveform equalization amount and a region information for minimizing a jitter of each circumferentially divided region. Item 2. The optical disk device according to item 1. 8. The optical disk apparatus according to claim 1, wherein the stored values of the waveform equalization amount storage means include a cutoff frequency, a boost amount, and a group delay amount of the waveform equalization means. 9. The optical disk apparatus according to claim 1, wherein the waveform equalization amount setting means switches the waveform equalization amount, which is a value stored in the waveform equalization amount storage means, in a circumferential direction. 10. The waveform equalization amount setting means sets an average value of the waveform equalization amount, which is a stored value of the waveform equalization amount storage means, as a waveform equalization amount. Optical disk device. 11. The optical disc device according to claim 1, wherein the number of divisions in the circumferential direction of the information carrier is from 4 to 6. 12. The optical disk apparatus according to claim 1, wherein the group delay characteristic of the waveform equalizing means is first flattened when the minimum jitter search is performed. 13. The apparatus according to claim 1, wherein the waveform equalization amount setting means is configured to be able to set the waveform equalization amount based on a preset waveform equalization amount setting pattern. An optical disk device as described in the above. 14. Area information for specifying a circumferentially divided area on an information carrier includes radial position information for specifying a radial position on the information carrier and information about the center of rotation of the information carrier on the information carrier. 2. The optical disk device according to claim 1, wherein the rotation phase information is such that the circumferential position of the circumferential division area can be specified.