JP4581825B2 - Optical disc apparatus, focus bias, and spherical aberration correction value adjustment method - Google Patents

Description

  The present invention relates to an optical disc apparatus that reproduces at least a signal on an optical disc recording medium, and a focus bias and spherical aberration correction value adjustment method.

JP 2002-352449 A JP-A-10-269611 JP 2000-285484 A JP-A-9-251645 JP2000-11388

  As a technique for recording / reproducing digital data, for example, data using optical disks (including magneto-optical disks) such as CD (Compact Disk), MD (Mini-Disk), and DVD (Digital Versatile Disk) as recording media There is a recording technology. An optical disk is a general term for recording media that read a signal by irradiating a laser beam to a disk in which a metal thin plate is protected with plastic, and changing the reflected light.

The optical disc includes, for example, a read-only type as known as CD, CD-ROM, DVD-ROM, MD, CD-R, CD-RW, DVD-R, DVD-RW, DVD + RW, DVD -There is a type in which user data can be recorded as known in RAM and the like. In the recordable type, data can be recorded by using a magneto-optical recording method, a phase change recording method, a dye film change recording method, or the like. The dye film change recording method is also called a write-once recording method, and can be recorded only once and cannot be rewritten. On the other hand, the magneto-optical recording method and the phase change recording method can rewrite data, and are used for various purposes including recording of various content data such as music, video, games, application programs and the like.
In recent years, a high-density optical disk called a Blu-ray Disc has been developed, and the capacity has been significantly increased.

For a high-density disc such as a Blu-ray disc, in a disc structure having a cover layer of about 0.1 mm in the disc thickness direction, a laser having a wavelength of 405 nm (so-called blue laser) and an objective lens having an NA (Numerical Aperture) of 0.85 The phase change mark (phase change mark) is recorded and reproduced under the condition of the combination of
As a storage capacity, about 23.3 GB (gigabytes) can be secured on a direct 12 cm disk. Further, when the recording layer has a two-layer structure, for example, a capacity of about 46.6 GB, which is about twice the above, can be obtained.

As already known, in an optical disc apparatus that performs recording / reproduction on an optical disc, a focus servo operation for controlling the focal position of a laser beam on a disc recording surface, or a track on a track (pit train or groove (groove) by a laser beam) Tracking servo operation is performed to control to trace).
Regarding the focus servo, it is known that it is necessary for an appropriate servo operation to apply an appropriate focus bias to the focus loop.

  In particular, in the case of a high-density disk, it is necessary to correct spherical aberration in order to cope with a cover layer thickness error or a multilayered recording layer. For example, an expander or a liquid crystal element is used in an optical pickup. A device having a spherical aberration correction mechanism has been developed, and is disclosed in, for example, Patent Documents 1 and 2 above.

In particular, in a writable optical disc apparatus (recording / reproducing apparatus) having a high NA lens such as the above-mentioned Blu-ray disc, since the margin of focus bias / spherical aberration is narrow, automatic adjustment of the focus bias and spherical aberration is essential. The
As a technique for adjusting the focus bias, for example, Patent Document 3 is known.
Also, for example, Japanese Patent Application Laid-Open No. 2004-133620 is known as a method for adjusting spherical aberration.
Further, a method for simultaneously adjusting the focus bias / spherical aberration is disclosed in Patent Document 5.

As shown in these Patent Documents 3 to 5, in the conventional method, the signal is read while sequentially changing the focus bias and the spherical aberration correction value, and the focus level at which the amplitude level of the RF signal obtained by this is maximized. The combination of the bias and the spherical aberration correction value is determined.
The focus bias and the spherical aberration correction value thus detected are set, and signal recording / reproduction is performed.

  According to such a method, the focus bias setting and the spherical aberration correction can be performed based on the actually measured RF signal. For example, when the focus error signal is offset due to a change over time, the cover thickness of the optical disc Even when spherical aberration occurs due to the difference between each solid or within the disk surface, it is possible to suppress deterioration in signal recording / reproduction quality.

By the way, it is assumed that the adjustment of the focus bias and the spherical aberration correction value is performed at the timing when the disc is loaded, or during the actual recording / reproducing operation such as the timing when the seek operation is performed.
In other words, by performing each time the disk is loaded, the focus bias and spherical aberration correction value can be adjusted to the optimum values according to the characteristics of each disk as described above. Also, by performing it at the required timing during operation, for example, it is possible to adjust the focus bias and spherical aberration correction value to appropriate values in response to changes in optical characteristics due to temperature changes and variations in cover thickness within the disk surface. Is possible.

In this case, the adjustment operation performed during an operation such as a seek operation requires a particularly quick adjustment, unlike the case where the adjustment operation is performed when there is a relatively long time, such as when a disc is loaded. .
Based on this, it is assumed that the conventional adjustment using the RF signal as described above is performed, for example, corresponding to a case where an unrecorded writable disc is loaded.
In this case, first, when a disc is loaded, trial writing is performed on a predetermined area, and an optimum value is obtained based on an RF signal obtained as a result of reproduction.
As an adjustment performed during an operation such as a seek operation, trial writing has already been performed at the time of loading as described above, so that a new trial writing operation is not necessary. At this time, an RF signal is obtained. In this case, it is necessary to seek to the area where test writing has been performed. That is, in the adjustment using only the conventional RF signal, the time required for the adjustment during the operation cannot be shortened in this way, and there is a problem in this respect.

Therefore, in the present invention, in view of the problems as described above, first, the optical disk apparatus is configured as follows.
That is, first, at least laser reading and reflected light detection for the optical disk recording medium for data reading, and a head means having a laser beam focus servo mechanism, tracking servo mechanism, and spherical aberration correction mechanism, and the head First evaluation signal generating means for generating a first evaluation signal that serves as an index of reproduction signal quality based on the reflected light obtained by the means.
Further, the focus servo means for driving the focus servo mechanism based on the focus error signal generated as a signal based on the reflected light obtained by the head means to execute the focus servo, and the reflected light obtained by the head means Tracking servo means for driving the tracking servo mechanism based on a tracking error signal generated as a signal based thereon to execute tracking servo.
In addition, a spherical aberration correction unit that performs spherical aberration correction by driving the spherical aberration correction mechanism based on a spherical aberration correction value, and a focus bias unit that adds a focus bias to a focus loop including the focus servo unit.
In addition, control means for executing the following processing is provided.
In other words, at least with the tracking servo by the tracking servo means turned on, the focus bias value set for the focus bias means and the spherical aberration correction value set for the spherical aberration correction means are changed while changing the first value. An indexing process for determining a focus bias value and a spherical aberration correction value at which the value of the first evaluation signal is optimal based on a result of detecting a value of the first evaluation signal obtained by one evaluation signal generating means; for the above focus bias value indexing by the indexing process, was obtained as representing the difference between the value of the focus bias is a focus bias value and optimal for the best values of the first evaluation signal the first difference value is subtracted or added, the resulting value, set to the focus bias means And it executes the setting control process for controlling the so that, a.

According to the first aspect of the present invention, the set of the focus bias value and the spherical aberration correction value that provides the best value of the first evaluation signal obtained at least with the tracking servo turned on is determined. For example, when the push-pull signal is generated as the first evaluation signal, the focus bias and the spherical aberration correction value that make the push-pull signal value the best (maximum) when the tracking servo is turned on are calculated. In other words, this is to determine the focus bias and the spherical aberration correction value that maximize the value of the amplitude signal (hereinafter also referred to as wobble signal) of the wobble of the track formed on the optical disc recording medium. .
Then, for at least a focus bias value thus is indexed is to set the displaced by the first difference value value.
At this time, for example, the value of the focus bias that maximizes the wobble signal amplitude as described above takes a value that deviates by a predetermined amount from the value of the focus bias when the optimum focus state is actually obtained. Therefore, if and requests reproduction signal value obtained by shifting the first difference value content from the focus bias value a first evaluation signal value and best as an index of quality as in the first invention, for example, such When a push-pull signal (wobble signal) is generated as the first evaluation signal, an optimum focus bias value can be obtained.
Further, not only the wobble signal but also the optimum focus when the focus bias value for which the value is the best is generated by a value deviated from the optimum focus bias value by a predetermined amount. A bias value can be obtained.

Furthermore, in the present invention, as a second example, the optical disk apparatus is configured as follows.
That is, first, at least laser reading and reflected light detection for the optical disk recording medium for data reading, and a head means having a laser beam focus servo mechanism, tracking servo mechanism, and spherical aberration correction mechanism, and the head First evaluation signal generating means for generating a first evaluation signal that serves as an index of reproduction signal quality based on the reflected light obtained by the means.
Further, the focus servo means for driving the focus servo mechanism based on the focus error signal generated as a signal based on the reflected light obtained by the head means to execute the focus servo, and the reflected light obtained by the head means Tracking servo means for driving the tracking servo mechanism based on a tracking error signal generated as a signal based thereon to execute tracking servo.
A spherical aberration correction unit configured to drive the spherical aberration correction mechanism based on the spherical aberration correction value to execute the spherical aberration correction; and a focus bias unit configured to add a focus bias to the focus loop including the focus servo unit. .
In addition, control means for executing the following processing is provided.
That is, at least with the tracking servo by the tracking servo means turned on, the focus bias value that makes the first evaluation signal value the best from the level of the focus bias value set in the focus bias means and the optimum Simultaneously, control is performed so that a focus bias that increases or decreases at the same level around the level shifted by the first difference value obtained so as to represent the difference from the focus bias value is added to the focus loop. Then, a first measurement process for measuring the value of the first evaluation signal obtained by the first evaluation signal generating means is executed in accordance with the addition of the focus bias that increases or decreases at the same level.
Further, a difference between the value of the first evaluation signal on the increase side of the focus bias and the value of the first evaluation signal on the decrease side of the focus bias, which is measured by the first measurement process, is obtained and the value is obtained. A predetermined step value is added to the focus bias value set in the focus bias means based on a first discrimination process for discriminating between positive and negative and a discrimination result of the first discrimination process Alternatively , a setting control process for performing control so that the subtracted focus bias value is set for the focus bias unit is executed.

Here, if the focus bias value already set in the focus bias means is adjusted to the optimum value at a certain point in time, the temperature rises as the operation time elapses. When the optical characteristics change, the actual optimum value also changes. As a result, the set focus bias value deviates from the actual optimum value.
In view of this, assuming that an optimum focus bias value has already been set at a certain point in time for the focus bias means, according to the second aspect of the present invention, it has already been set in this way. the focus bias value has the focus bias to increase or decrease at the same level around the level shifted the first difference value content from the level of that in the manner described above are added. Then, with respect to the value of the first evaluation signal obtained in accordance with the addition of the focus bias that increases and decreases at the same level, the value of the first evaluation signal on the increase side of the focus bias and the value on the decrease side of the focus bias. A difference from the value of the first evaluation signal is obtained, and a predetermined step value is added / subtracted to the set focus bias depending on whether the value is positive or negative.
Here, it is assumed that , for example, the actual optimum value is shifted so as to increase with respect to the set focus bias value due to the temperature rise.
Then, by adding the focus bias to the increasing side as described above with respect to the set focus bias, the actual evaluation value is approached, and accordingly, the first evaluation signal is correspondingly increased. As the value of, it comes closer to the maximum value. On the other hand, when the focus bias is added to the decreasing side, it is moved away from the actual optimum value, so that the value of the first evaluation signal measured at this time is further away from the maximum value side.
On the other hand, assuming that the actual optimum value is shifted so as to decrease with respect to the set focus bias value, the focus bias is added to the increase side with respect to the set focus bias. Depending on the situation, the value of the first evaluation signal is moved away from the maximum value side because it is moved away from the actual optimum value. In this case, when the focus bias is added to the decrease side, the value is closer to the actual optimum value, so that the value of the first evaluation signal approaches the maximum value side.
That is, when the optimum value is shifted so as to increase with respect to the set value, the value of the first evaluation signal value obtained by addition of the increase-side focus bias increases, and is obtained by addition of the decrease-side focus bias. The first evaluation signal has a smaller value.
In addition, when the optimum value is shifted so as to decrease with respect to the set value, the first evaluation signal value obtained by the addition of the increase-side focus bias is conversely reduced, and obtained according to the addition of the decrease-side focus bias. Conversely, the value of the first evaluation signal is increased.
Therefore, according to this, the difference between the value of the first evaluation signal on the increase side and the value of the first evaluation signal on the decrease side is reduced when the optimum value is shifted so as to increase with respect to the set value. It can be seen that positive / negative is reversed when the shift is performed.
From this, it is determined by determining whether the value of the difference between the value of the first evaluation signal on the increase side and the value of the first evaluation signal on the decrease side is positive or negative as described above. It can be determined whether the actual optimum value has shifted to the increasing side or the decreasing side with respect to the focus bias value in the middle.
In this case, if the actual optimum value is shifted to the increasing side, it can be brought closer to the actual optimum value by increasing the set focus bias value. For example, if the focus bias value being set is decreased, it can be made closer to the actual optimum value. Therefore, as in the second aspect of the present invention, the setting is performed by adding or subtracting a predetermined step value according to the positive / negative discrimination result of the difference between the first evaluation signal value on the increase side and the decrease side. Ru can be adjusted focus bias value according to the actual optimum value.

As described above, according to the first aspect of the present invention, the optimum focus bias and spherical aberration correction value can be obtained based on the information on the wobble signal amplitude. That is, when the optical disk recording medium is a writable disk, it is not necessary to obtain information on the RF signal amplitude when obtaining the optimum focus bias value, and accordingly, for example, adjustment during operation such as seeking is performed. However, the seek operation to the test writing area as in the prior art can be made unnecessary. In the case where adjustment during operation is performed in this way, the seek operation to the test writing area is not required, and thus the time required for adjustment during operation can be greatly shortened.
If a fixed value is used as the first difference value, an optimum focus bias value can be obtained based only on the wobble signal amplitude information. There is no need to obtain information, so that even when the optical disk recording medium is a writable disk, trial writing for adjustment can be completely eliminated, and the adjustment time can be shortened both when the disk is loaded and during operation. .

  Further, according to the second aspect of the present invention, assuming that an optimum focus bias value is set in the adjustment at the time of loading the disc, the adjustment performed during the operation includes the first evaluation signal. This can be done based on the result of measuring the values only at two points corresponding to the increase bias and decrease focus bias addition. As a result, the length of time required for adjustment during operation is greatly reduced compared to the conventional case where the signal amplitude must be measured while changing the focus bias value and spherical aberration correction value. Can do.

Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.

<First Embodiment>

FIG. 1 is a block diagram showing a configuration of an optical disc apparatus as a first embodiment of the present invention.
First, in the case of the first embodiment, it is assumed that the disk 1 is an optical disk (writeable disk) that records data by a phase change method, for example. Further, a wobbling (meandering) groove is formed on the disk, and this groove is used as a recording track. Depending on the wobbling of the groove, address information or the like is embedded as so-called ADIP information.

Such a disk 1 is loaded on a turntable (not shown) and is rotationally driven by a spindle motor 52 at a constant linear velocity (CLV) during a recording / reproducing operation.
Then, ADIP information embedded as wobbling of the groove track on the disk 1 is read by the optical pickup (optical head) 51.
At the time of recording, the user data is recorded on the track as a phase change mark by the optical pickup 51, and at the time of reproduction, the phase change mark recorded by the optical pickup is read out.

  In the pickup 51, a laser diode serving as a laser light source, a photodetector for detecting reflected light, an objective lens serving as an output end of the laser light, and a laser recording light are irradiated onto the disk recording surface via the objective lens. An optical system (described later) for guiding the reflected light to the photodetector is formed.

In the pickup 51, the objective lens is held so as to be movable in the tracking direction and the focus direction by a biaxial mechanism.
The entire pickup 51 can be moved in the radial direction of the disk by a thread mechanism 53.
The laser diode in the pickup 51 is driven to emit laser light by a drive signal (drive current) from the laser driver 63.

  As will be described later, the pickup 51 is provided with a mechanism for correcting the spherical aberration of the laser light, and the spherical aberration is corrected under the control of the system controller 60 and the servo circuit 61.

Reflected light information from the disk 1 is detected by a photo detector, converted into an electric signal corresponding to the amount of received light, and supplied to the matrix circuit 54.
The matrix circuit 54 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements serving as photodetectors, and generates necessary signals by matrix calculation processing.
For example, a high-frequency signal (also referred to as a reproduction data signal or an RF signal) corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, and the like are generated.
Further, a push-pull signal is generated as a signal related to groove wobbling, that is, a signal for detecting wobbling (wobble amplitude).

The reproduction data signal output from the matrix circuit 54 is supplied to the reader / writer (RW) circuit 55, the focus error signal and tracking error signal are supplied to the servo circuit 61, and the push-pull signal is supplied to the wobble circuit 58.
In particular, in the case of the embodiment, the push-pull signal is also supplied to the system controller 60 described later.

The reader / writer circuit 55 performs binarization processing, reproduction clock generation processing by PLL, and the like on the reproduction data signal, reproduces the data read as the phase change mark, and supplies it to the modulation / demodulation circuit 56.
The modem circuit 56 includes a functional part as a decoder at the time of reproduction and a functional part as an encoder at the time of recording.
At the time of reproduction, as a decoding process, a run-length limited code is demodulated based on the reproduction clock.
The ECC encoder / decoder 57 performs an ECC encoding process for adding an error correction code at the time of recording and an ECC decoding process for correcting an error at the time of reproduction.
At the time of reproduction, the data demodulated by the modulation / demodulation circuit 56 is taken into an internal memory, and error detection / correction processing and deinterleaving processing are performed to obtain reproduction data.
Data decoded up to reproduction data by the ECC encoder / decoder 57 is read out and transferred to an AV (Audio-Visual) system 120 based on an instruction from the system controller 60.

The push-pull signal output from the matrix circuit 54 as a signal related to groove wobbling is processed in the wobble circuit 58. The push-pull signal as ADIP information is demodulated into a data stream constituting an ADIP address in the wobble circuit 58 and supplied to the address decoder 59.
The address decoder 59 decodes the supplied data, obtains an address value, and supplies it to the system controller 60.
The address decoder 59 generates a clock by PLL processing using the wobble signal supplied from the wobble circuit 58, and supplies it to each unit as an encode clock at the time of recording, for example.

At the time of recording, recording data is transferred from the AV system 120. The recording data is sent to a memory in the ECC encoder / decoder 57 and buffered.
In this case, the ECC encoder / decoder 57 performs error correction code addition, interleaving, subcode addition, and the like as encoding processing of the buffered recording data.
The ECC-encoded data is subjected to RLL (1-7) PP modulation in the modulation / demodulation circuit 56 and supplied to the reader / writer circuit 55.
As described above, a clock generated from a wobble signal is used as an encoding clock serving as a reference clock for these encoding processes during recording.

The recording data generated by the encoding process is subjected to recording compensation processing by the reader / writer circuit 55, and fine adjustment of the optimum recording power and adjustment of the laser drive pulse waveform with respect to the recording layer characteristics, laser beam spot shape, recording linear velocity, etc. Etc. are sent to the laser driver 63 as a laser drive pulse.
The laser driver 63 applies the supplied laser drive pulse to the laser diode in the pickup 51 to perform laser emission driving. As a result, pits (phase change marks) corresponding to the recording data are formed on the disc 1.

The laser driver 63 includes a so-called APC (Auto Power Control) circuit, and the laser output is independent of temperature or the like while the laser output power is monitored by the output of the laser power monitoring detector provided in the pickup 51. Control to be constant.
The target value (recording laser power / reproducing laser power) of the laser output at the time of recording and reproduction is given from the system controller 60, and the laser output level is controlled to be the target value at the time of recording and reproduction.

The servo circuit 61 generates various servo drive signals for focus, tracking, and thread from the focus error signal and tracking error signal from the matrix circuit 54, and executes the servo operation.
That is, a focus drive signal and a tracking drive signal are generated according to the focus error signal and the tracking error signal, and the focus coil and tracking coil of the biaxial mechanism in the pickup 51 are driven. As a result, a pickup 51, a matrix circuit 54, a servo circuit 61, a tracking servo loop and a focus servo loop by a biaxial mechanism are formed.

  The servo circuit 61 turns off the tracking servo loop and outputs a jump drive signal in response to a track jump command from the system controller 60, thereby executing a track jump operation.

  The servo circuit 61 generates a thread drive signal based on a thread error signal obtained as a low frequency component of the tracking error signal, access execution control from the system controller 60, and the like, and drives the thread mechanism 53. Although not shown, the sled mechanism 53 has a mechanism including a main shaft that holds the pickup 51, a sled motor, a transmission gear, and the like, and by driving the sled motor according to a sled drive signal, a required slide of the pick-up 51 Movement is performed.

The spindle servo circuit 62 performs control to rotate the spindle motor 2 at CLV.
The spindle servo circuit 62 obtains the clock generated by the PLL processing for the wobble signal as the current rotational speed information of the spindle motor 52 and compares it with predetermined CLV reference speed information to generate a spindle error signal. .
At the time of data reproduction, the reproduction clock (clock serving as a reference for decoding processing) generated by the PLL in the reader / writer circuit 55 becomes the current rotational speed information of the spindle motor 52, and this is used as a predetermined CLV. A spindle error signal can also be generated by comparing with the reference speed information.
The spindle servo circuit 62 outputs a spindle drive signal generated according to the spindle error signal, and causes the spindle motor 62 to perform CLV rotation.
The spindle servo circuit 62 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 60, and executes operations such as starting, stopping, acceleration, and deceleration of the spindle motor 2.

Various operations of the servo system and the recording / reproducing system as described above are controlled by a system controller 60 formed by a microcomputer.
The system controller 60 executes various processes according to commands from the AV system 120.

  For example, when a write command (write command) is issued from the AV system 120, the system controller 60 first moves the pickup 51 to the address to be written. Then, the ECC encoder / decoder 57 and the modulation / demodulation circuit 56 execute the encoding process as described above on the data transferred from the AV system 120 (for example, video data of various systems such as MPEG2 or audio data). Then, recording is executed by supplying the laser drive pulse from the reader / writer circuit 55 to the laser driver 63 as described above.

For example, when a read command for requesting transfer of certain data (eg, MPEG2 video data) recorded on the disc 1 is supplied from the AV system 120, seek operation control is first performed for the designated address. Do. That is, a command is issued to the servo circuit 61 to cause the pickup 51 to access the address specified by the seek command.
Thereafter, operation control necessary for transferring the data in the designated data section to the AV system 120 is performed. That is, data reading from the disk 1 is performed, decoding / buffering and the like in the reader / writer circuit 55, the modem circuit 56, and the ECC encoder / decoder 57 are executed, and the requested data is transferred.

  When recording / reproducing data using these phase change marks, the system controller 60 uses the ADIP addresses detected by the wobble circuit 58 and the address decoder 59 to control access and recording / reproducing operations.

In the example of FIG. 1, the optical disk device connected to the AV system 120 is used. However, the optical disk device of the present invention may be connected to, for example, a personal computer.
Furthermore, there may be a form that is not connected to other devices. In this case, an operation unit and a display unit are provided, and the configuration of the interface part for data input / output is different from that in FIG. That is, it is only necessary that recording and reproduction are performed in accordance with a user operation and a terminal unit for inputting / outputting various data is formed.

Next, FIG. 2 shows an example of a spherical aberration correction mechanism provided in the pickup 51.
In FIG. 2, the configuration of the optical system in the pickup 51 is shown.
In FIG. 2, laser light output from a semiconductor laser (laser diode) 81 is converted into parallel light by a collimator lens 82, passes through a beam splitter 83, a movable lens 87 as a spherical aberration correction lens group, and a fixed lens 88. , And the disc 1 is irradiated from the objective lens 84. The spherical aberration correction lens groups 87 and 88 are called expanders. Since spherical aberration correction is performed by driving the movable lens 87, hereinafter, it may be expressed in particular as an expander 87.

  The reflected light from the disk 1 passes through the objective lens 84, the fixed lens 88, and the movable lens 87, is reflected by the beam splitter 83, and enters the detector 86 through the collimator lens (condensing lens 85).

In such an optical system, the objective lens 84 is supported by the biaxial mechanism 91 so as to be movable in the focus direction and the tracking direction, and focus servo and tracking servo operations are performed.
The spherical aberration correction lenses 87 and 88 have a function of defocusing the wavefront of the laser light. That is, the movable lens 87 can be moved in the J direction, which is the optical axis direction, by the actuator 90, and the object point of the objective lens 84 is adjusted by this movement.
In other words, spherical aberration correction can be performed by performing control for causing the actuator 90 to move back and forth.

In FIG. 2, the configuration corresponding to the case where spherical aberration correction is performed by a so-called expander is illustrated, but a configuration in which spherical aberration correction is performed using a liquid crystal panel can also be adopted.
In other words, in the liquid crystal panel inserted in the optical path from the semiconductor laser 81 to the objective lens 84, the diameter of the laser beam is varied to variably adjust the boundary between the laser beam transmitting region and the shielding region, thereby correcting spherical aberration. Is to do.
In this case, the liquid crystal driver that drives the liquid crystal panel is controlled to change the transmission region.

3 shows the internal configuration of the servo circuit 61 shown in FIG.
In FIG. 3, the focus error signal FE and the tracking error signal TE from the matrix circuit 54 shown in FIG. 1 are converted into digital data by the A / D converters 11 and 21, respectively, and input to the DSP 10 in the servo circuit 61. Is done.
The DSP 10 has functions as a focus servo calculation unit 12 and a tracking servo calculation unit 22.

The focus error signal FE from the A / D converter 11 is input to the focus servo calculation unit 12 via the adder 15.
The focus servo calculation unit 12 generates and outputs a focus servo signal by performing predetermined calculations such as filtering for phase compensation and loop gain processing on the focus error signal FE input as digital data. . The focus servo signal is converted into an analog signal by the D / A converter 13 (including PWM and PDM) and then input to the focus driver 14 to drive the focus actuator. That is, a current is applied to the focus coil of the biaxial mechanism 91 that holds the objective lens 84 in the optical pickup 51, and the focus servo operation is executed.

  The tracking servo calculation unit 22 performs predetermined calculations such as filtering for phase compensation and loop gain processing on the tracking error signal TE input as digital data, and generates and outputs a tracking servo signal. . The tracking servo signal is converted into an analog signal by the D / A converter 23 (including PWM and PDM), and then input to the tracking driver 24 to drive the tracking actuator. That is, a current is applied to the tracking coil of the biaxial mechanism 91 that holds the objective lens 84 in the optical pickup 51 to execute a tracking servo operation.

The DSP 10 is provided with functional parts for focus bias addition, spherical aberration correction value setting, and adjustment of the focus bias and spherical aberration correction value.
The adder 15 adds a focus bias to the focus error signal FE. The focus bias value to be added is set in the focus bias setting unit 16. When the focus bias setting unit 16 outputs a focus bias value set in an adjustment process described later, an appropriate focus bias is added to the focus servo loop.

The spherical aberration correction value setting unit 20 sets a spherical aberration correction value by a spherical aberration correction mechanism. The set spherical aberration correction value is converted into an analog signal by the D / A converter 25 and supplied to the spherical aberration correction driver 26.
For example, in the case of a spherical aberration correction mechanism as shown in FIG. 2, the spherical aberration correction driver 26 is a circuit that supplies a drive signal Sd to an actuator 90 that moves the expander 87. Alternatively, in the case of a spherical aberration correction mechanism using a liquid crystal panel, the circuit supplies a signal Sd for instructing the liquid crystal driver to apply a voltage to a required cell of the liquid crystal panel.
Accordingly, the spherical aberration correction driver 26 is configured to drive the spherical aberration correction mechanism in the pickup 51 based on the spherical aberration correction value supplied from the spherical aberration correction value setting unit 20.

The nonvolatile memory 18 stores an initial value as a focus bias value and a spherical aberration correction value, and further, an adjustment value obtained by adjusting a focus bias / spherical aberration correction value described later, that is, an optimum focus bias. Value and spherical aberration correction value are stored.
The setting unit 17 sets the setting value in the focus bias setting unit 16 and the setting value in the spherical aberration correction value setting unit 20. For example, the setting value is set to a value stored in the nonvolatile memory 18 or each setting value is changed according to an instruction from the system controller 60.

  As described above, the operation related to the adjustment of the focus servo / spherical aberration correction value formed by the DSP 10 and the focus servo calculation unit 22 and the tracking servo calculation unit 22 is controlled by the system controller 60.

Here, in the embodiment, the focus bias and the spherical aberration correction value are to be adjusted to optimum values by the configuration of the optical disc apparatus described so far.
However, as described above, when adjusting the focus bias to the optimum value, for example, when the RF signal amplitude is maximized as in the conventional case, the adjustment time can be shortened. There may not be.
That is, particularly when the disc 1 is a writable disc as in this example, trial writing may be required to obtain an RF signal in the adjustment at the time of loading the disc. Further, it is assumed that the adjustment operation is performed at a required timing during the operation of the apparatus, for example, during the seek operation, in addition to when the disk is loaded. Even if trial writing has already been performed as described above, it is necessary to perform an adjustment operation by seeking to this trial writing area, and accordingly, adjustment takes time accordingly.

  In this case, the adjustment operation performed during an operation such as a seek operation is particularly required to shorten the adjustment time, unlike the case where the adjustment operation is performed when there is a relatively long time, such as when a disk is loaded. That is, it takes a long time for the adjustment operation to be executed during the operation as described above.

Therefore, in the embodiment, when adjusting the focus bias and the spherical aberration correction value to be optimum values, the wobble signal amplitude is used as a reference instead of using the RF signal amplitude as a reference.
This will be described with reference to the characteristic diagram of FIG.
For confirmation, the wobble signal described above refers to a push-pull signal obtained when the tracking servo is turned on. In this case, wobbling on the disk 1 is performed. This is a signal for detecting address information recorded by the groove.
It can be said that such a wobble signal has a better reproduction signal quality if its amplitude value is large. That is, it can be said that the maximum value of the evaluation signal indicating the reproduction signal quality is the best signal.

In FIG. 4, the characteristics of the wobble signal amplitude when the focus bias is on the vertical axis and the spherical aberration correction value is on the horizontal axis are indicated by contour lines.
In the contour line shown in this figure, it is shown that the smaller the value of the number given in the figure, the higher the level of wobble amplitude is obtained.

Here, Y in the figure indicates the value of the focus bias that maximizes the wobble signal amplitude.
In the figure, X indicates a spherical aberration correction value that maximizes the wobble signal amplitude.
A line indicated by a broken line indicates a focus bias value at which an optimum focus state is actually obtained.
As shown by these relationships, the value of the focus bias at which the wobble signal amplitude is maximum and the value of the focus bias (optimal focus bias value, optimum value) at which an actually optimum focus state is obtained are as follows: This is a characteristic in which a predetermined amount of deviation occurs.

  Based on this characteristic, in the first embodiment of the present invention, first, a focus bias value that maximizes the wobble signal amplitude is obtained, and then the optimum value derived from the above characteristic in advance from this focus bias value. A value obtained by subtracting a difference value from the focus bias value is obtained. The focus bias value thus obtained is set as the focus bias value during actual recording / reproduction.

The adjustment operation as the first embodiment will be specifically described.
First, when the focus bias and the spherical aberration correction value are adjusted in the first embodiment, the focus bias value and the spherical aberration correction value are obtained in respective steps while being changed stepwise. An operation for detecting the amplitude level of the wobble signal is performed.
In performing such an operation, the optical disk apparatus stores, for example, five levels of setting values for each of the focus bias value and the spherical aberration correction value in the nonvolatile memory 18 shown in FIG. 3, for example. It has been made to keep.
Then, under the setting of the first stage value of the focus bias stored in this manner, the spherical aberration correction value is changed in five stages, and the amplitude level of the wobble signal obtained in each stage is detected. To be. Further, the information on the amplitude level of each wobble signal is stored in association with the focus bias value and the spherical aberration correction value set at that time.
By performing this operation in the same manner for the remaining four stages of the focus bias, a total of 25 kinds of amplitude levels of the wobble signal are detected in which the focus bias value and the spherical aberration correction value are changed in five stages, and are set similarly. Each value is stored in association with each value.

Based on the information stored by the above operation, a set of the focus bias value and the spherical aberration correction value when the highest wobble signal amplitude is obtained is determined.
Hereinafter, the focus bias value calculated based on the wobble signal amplitude in this way is referred to as a focus bias value FBa. Similarly, the spherical aberration correction value is referred to as a spherical aberration correction value SAa.

After that, a focus bias value FBb is calculated by subtracting a difference value sfb prepared in advance from the focus bias value FBa calculated as described above.
Here, in the first embodiment, as the difference value sfb, a difference value between a focus bias value at which the wobble signal amplitude is maximum and a focus bias value at which an optimum focus state is actually obtained is obtained in advance. This is determined from the characteristics shown in FIG.
That is, the difference value sfb indicating the difference from the focus bias value when the optimum focus state is actually obtained in this way is subtracted from the focus bias value that maximizes the wobble signal amplitude as described above. Thus, the optimum focus bias value (FBb) can be obtained.

Here, the difference value sfb is subtracted as described above, but the difference value sfb is added according to the positive / negative value of the difference value sfb.
That is, in this case, when obtaining the optimum focus bias value using the difference value sfb as described above, the difference value sfb obtained from the characteristics as described above is either positive or negative. Accordingly, it is only necessary to perform subtraction or addition so that the focus bias value that maximizes the wobble amplitude can be set to the optimum focus bias value.
In other words, a value obtained by shifting the difference value sfb from the focus bias value that maximizes the wobble amplitude is obtained so that the focus bias value that maximizes the wobble amplitude can be set as the optimum focus bias value. You can do it.

In the first embodiment, a fixed value common to all sets of the optical disc apparatus is set as the difference value sfb.
Alternatively, a fixed value may be set individually for each set based on the result of inspection of the characteristics shown in FIG.
If the difference value sfb common to all the optical disk devices is set as described above, there is an advantage that an inspection process at the time of factory shipment as in the case of setting individual values for each set can be eliminated.
On the other hand, when an individual value is set for each set, the difference value sfb suitable for each set can be set, and the detection accuracy of the optimum value can be improved.

When the optimum focus bias value FBb and the spherical aberration correction value SAa are obtained as described above, the setting unit 17 shown in FIG. 3 uses the focus bias value FBb and the spherical aberration correction value setting unit, respectively. 20 is set.
Thus, an actual recording / reproducing operation can be performed under the setting of the optimum focus bias FBb and the spherical aberration correction value SAa.

Next, processing operations to be executed to realize the adjustment operation as the first embodiment according to the above description will be described with reference to the flowchart of FIG.
The processing operation shown in FIG. 5 is performed by the system controller 60 shown in FIG.

First, in step S101 shown in the figure, the wobble signal amplitude is detected while changing the focus bias value and the spherical aberration correction value, and processing for storing the information of the detected wobble signal amplitude is performed.
As the processing of step S101, first, the tracking servo calculation unit 22 is controlled to turn on the tracking servo, and the setting unit 17 sets the first-stage focus bias value and spherical surface stored in the nonvolatile memory 18. The aberration correction value is set in the focus bias setting unit 16 and the spherical aberration correction value setting unit 20, respectively. At this time, the amplitude level of the push-pull signal supplied from the matrix circuit 54 is detected. Further, the information of the push-pull signal amplitude level detected in this way is stored in association with the set focus bias value and spherical aberration correction value.
The processing operation from the setting of the focus bias and the spherical aberration correction value to the storage is similarly performed for all combinations of the remaining four stages of the focus bias value and the remaining four stages of the spherical aberration correction value. In this case, information on the wobble signal amplitude level obtained by a total of 25 settings of focus bias value × 5 and spherical aberration correction value × 5 is stored.

  In step S102, the focus bias value (FBa) and the spherical aberration correction value (SAa) at which the wobble signal amplitude level is maximized are determined based on the information stored in step S101.

  In the subsequent step S103, a process of calculating a focus bias value FBb by subtracting a prepared difference value sfb from the determined focus bias value FBa is executed. Thereby, the optimum focus bias value FBb is obtained.

In step S104, processing for setting the focus bias value FBb and the spherical aberration correction value SAa is executed. That is, the setting unit 17 causes the focus bias setting unit 16 and the spherical aberration correction value setting unit 20 to set the focus bias value FBb and the spherical aberration correction value SAa, respectively.
As a result, the actual recording / reproducing operation can be performed under the setting of the focus bias FBb and the spherical aberration correction value SAa which are optimum thereafter.

As described above, according to the first embodiment, by using the difference value sfb based on the fixed value, the reference signal for adjusting the focus bias and the spherical aberration correction value can be only the wobble signal. It becomes possible. That is, this makes it possible to effectively adjust the focus bias and the spherical aberration correction value to the optimum values even when the RF signal cannot be obtained from the disk 1.
According to this, for example, even when the disc 1 is a writable disc and no signal is recorded, it is not necessary to perform a trial writing operation, and the adjustment operation performed when the disc is loaded is also based on the conventional RF signal. In comparison with the case of adjustment, the adjustment time can be shortened.
In addition, by using the fixed difference value sfb as described above, the evaluation signal necessary for the adjustment can be made only the wobble signal, so that the RF signal can be adjusted even during the adjustment executed during the operation such as a seek operation. Therefore, it is not necessary to perform a seek operation to the test writing area, and in this case, adjustment time can be shortened both when the disk is loaded and during adjustment.

Further, such wobble signal amplitude information can be obtained even during a recording operation, for example. That is, the adjustment operation in this case can be performed even during the recording operation.
According to this, for example, even when the recording operation on the disc 1 is continued for a relatively long time, the temperature of the pickup is significantly increased, and the adjusted focus bias is likely to deviate from the optimum value. It becomes possible to readjust the focus bias / spherical aberration correction value to the optimum value.
That is, in the prior art in which adjustment is performed based only on the RF signal amplitude, it is impossible to effectively prevent the deterioration in signal recording quality during the recording operation for a long time as described above. According to the embodiment, this can be effectively prevented.
In particular, when the recording operation is continued for a long time immediately after the start of the optical disk device, the set temperature rises considerably during that time. Therefore, readjustment can be performed in such a case to reduce the recording quality. It is advantageous for suppression.

Here, various timings for executing the series of adjustment processing as the first embodiment shown in FIG. 5 can be considered as follows.
First, it is possible to adjust the focus bias value and the spherical aberration correction value according to the characteristics of each disk 1 by executing the process when the disk is loaded.
It is also conceivable to execute during playback, before and after seek, or after a predetermined time has elapsed, or according to the trace position (inner and outer periphery) on the disk. For example, during playback, the data read from the disk 1 may be performed with sufficient timing for buffering. By being executed at the required timing during operation in this way, even if the set value deviates from the optimum value due to changes in the optical characteristics due to temperature changes (particularly temperature rise) of the set, the focus is set to follow this. The bias and spherical aberration correction values can be reset.

From the viewpoint of such temperature characteristics, it is also conceivable to perform the adjustment operation based on the result of actually measuring the temperature of the device. Alternatively, it may be possible to perform adjustment processing using, as a trigger, an error rate / jitter deterioration of the reproduction data. Furthermore, by adjusting according to the secular change, the trace position (radius position) on the disk, etc., it is possible to obtain an adjustment state corresponding to these circumstances.
In general, even during the operation period for the disk 1, the adjustment process is executed regularly or irregularly, which is appropriate for stabilizing the operation of the apparatus.

In the first embodiment, the wobble signal amplitude detection process shown as step S101 in FIG. 5 is preferably performed in the following area on the disk 1.
First, when the wobble wavelength is wl and the track pitch is tp,
The wobble signal amplitude is detected over an area longer than the length of wl / (2π · tp).

Here, it is known that the wobble signal amplitude periodically repeats the magnitude due to the influence of the wobble of the adjacent track. Actually, the magnitude is repeated in the form of a sine wave every wl / (2π · tp).
Therefore, the detection of the wobble signal amplitude for each combination of the focus bias value and the spherical aberration correction value is performed over a region that becomes wl / (2π · tp) or more as described above. A value obtained by averaging the wobble signal amplitude values detected over the length including the fluctuation for one cycle is stored as information on the wobble signal amplitude for each set of the focus bias value and the spherical aberration correction value. By doing so, errors due to fluctuations are absorbed.
In this case, it is also possible to absorb an error in fluctuation of the wobble signal amplitude by storing the maximum value among the amplitude values detected over the length including the fluctuation for one cycle.

Second, similarly, when wobble wavelength is wl and track pitch is tp,
wl / (2π · tp) × 1/4 lap
This is performed in an area that is less than or equal to the length of. That is, the detection process is performed in a region that is 1/4 or less of the length of one cycle of the wobble signal amplitude variation as described above.
This also makes it less susceptible to errors due to periodic fluctuations in the wobble signal amplitude.

The third is performed in the area of the minimum unit of recording and reproduction.
Here, as for the wobble signal, the signal amplitude obtained is naturally different between the recorded portion and the unrecorded portion. For example, in the case of phase change recording exemplified in the first embodiment, the recording unit tends to have a smaller amplitude level.
For this reason, if the area where the detection process is performed straddles the recorded / unrecorded area, the focus bias and spherical aberration correction are maximized based on the information of each amplitude value obtained under different conditions of the amplitude level. Since a pair with a value is determined, accuracy is lost accordingly.

Therefore, if it is performed within the area of the minimum unit of recording / reproduction as described above, the focus bias value and spherical aberration correction that maximize the wobble signal amplitude more accurately without straddling the recorded / unrecorded part A set of values can be determined.
At this time, the minimum unit of recording / reproduction is sufficiently shorter than the length of one cycle of the fluctuation of the wobble signal amplitude as described above. Therefore, the third detection processing method is used. Accordingly, at the same time, it is possible to make the influence of the wobble signal amplitude fluctuation error less susceptible.
In the embodiment, the third method is adopted.

As can be understood from the above description, in the first and second methods, there is a possibility of straddling recorded / unrecorded portions, and therefore wobble amplitude detection based on each set value is performed under different wobble amplitude conditions. It may be broken.
Therefore, as the first and second methods, in fact, whether each wobble amplitude value is detected is a recorded portion or an unrecorded portion in association with each other, and according to the information. The focus bias and the spherical aberration correction value with the maximum wobble amplitude value may be determined.

<Second Embodiment>

Next, the optical disc apparatus according to the second embodiment will be described.
Note that the internal configuration of the optical disc apparatus according to the second embodiment is the same as that shown in FIGS.
The optical disc apparatus according to the second embodiment has an optimum focus bias value obtained by calculating the difference value sfb, which is a fixed value in the first embodiment, with reference to an evaluation value other than the wobble signal amplitude. The difference between the focus bias value and the maximum wobble signal amplitude is obtained.

Here, as shown in FIG. 4 above, the deviation between the focus bias value at which the optimum focus state is actually obtained and the focus bias value at which the wobble signal amplitude becomes maximum is, for example, the characteristic of the loaded disc 1. In addition, it is expected that it may change due to changes over time from the time of manufacture of the device.
Accordingly, when the difference value sfb is a fixed value as in the first embodiment, the focus at which the wobble signal amplitude is maximized due to such characteristics as the characteristics of each disk 1 and changes over time on the apparatus side. It cannot be asserted that the focus bias value obtained by subtracting the difference value sfb from the bias value may not be the optimum focus bias value.

In view of this, the second embodiment deals with this point, and specifically, the following operation is performed.
First, in the second embodiment, when the focus bias and the spherical aberration correction value are adjusted, the signal is reproduced while the focus bias and the spherical aberration correction value are changed step by step as in the prior art. The operation of determining the set of the focus bias and spherical aberration correction value having the maximum RF signal amplitude thus obtained is performed.
That is, as an evaluation signal other than the wobble signal, in this case, an optimum focus bias / spherical aberration correction value is determined based on the amplitude value of the RF signal.
The focus bias value obtained with reference to the RF signal amplitude in this way is referred to as a focus bias value FBc. The spherical aberration correction value is referred to as a spherical aberration correction value SAb.
The focus bias value FBc and the spherical aberration correction value SAb are held in, for example, the nonvolatile memory 18 or the like.

After that, the optimum value is determined based on the wobble signal amplitude similar to that described in the first embodiment.
That is, in the state where the tracking servo is on, the push-pull signal amplitude is detected while changing the focus bias and the spherical aberration correction value in stages, and the push-pull signal ( (Wobble signal) amplitude level information is stored. Then, the focus bias and the spherical aberration correction value with the maximum wobble signal amplitude are determined.
The focus bias value thus determined is referred to as a focus bias value FBd.

As described above, when the optimum focus bias value FBc that maximizes the RF signal amplitude and the focus bias value FBd that maximizes the wobble signal amplitude are determined,
“Focus bias value FBd−Focus bias value FBc”
The difference value is held as a difference value sfb.

When the difference value sfb is obtained, first, the focus bias value FBc and the spherical aberration correction value SAb held as described above are set in the focus bias setting unit 16 and the spherical aberration correction value setting unit 20, respectively. To do.
That is, first, a signal recording / reproducing operation is started under the setting of the optimum focus bias and spherical aberration correction value obtained with reference to the RF signal amplitude.

Then, at a predetermined timing thereafter, an operation for adjusting the focus bias and the spherical aberration correction value is performed again.
As such a re-adjustment operation, the same adjustment operation as in the first embodiment is performed. That is, first, the wobble signal amplitude is detected while changing the focus bias and the spherical aberration correction value in stages, and the amplitude information obtained in each stage is stored.
Further, the focus bias and the spherical aberration correction value with the maximum wobble signal amplitude are determined.
The focus bias value and the spherical aberration correction value obtained here are referred to as a focus bias value FBe and a spherical aberration correction value SAc, respectively.

For the focus bias value FBe determined in this way,
“Focus bias value FBe−difference value sfb”
To calculate the focus bias FBf obtained by subtracting the difference value sfb obtained as described above from the focus bias value FBe.
The focus bias FBf is set as an optimum value in the focus bias setting unit 16, and the spherical aberration correction value SAc determined as described above is also set as an optimum value for the spherical aberration correction value setting unit 20. To do.

  In this case as well, the difference value sfb is subtracted, but subtraction or addition may be performed according to the positive / negative value of the difference value sfb.

As described above, according to the second embodiment, first, the optimum focus bias value (FBc) is obtained based on the actually measured evaluation signal value (RF signal amplitude value). Similarly, a focus bias value (FBd) based on the actually measured value of the wobble signal amplitude is obtained. Then, a difference value between these focus bias values is obtained as a difference value sfb.
According to this, it is possible to obtain the difference value sfb corresponding to the characteristics of each disk 1 and changes with time. If such a difference value sfb is used, the focus bias value set based on the subsequent wobble signal amplitude can be more surely optimized according to the characteristics of each disk 1 and changes over time. Value can be obtained.

According to the operation of the second embodiment, after the adjustment based on the RF signal amplitude is performed once at the initial adjustment timing such as when a disc is loaded, for example, the adjustment is performed during the subsequent operation. Since the adjustment based only on the wobble signal amplitude is possible, also in the second embodiment, the time required for the adjustment during the operation can be shortened compared to the case where the conventional method is adopted.
Further, once the adjustment based on the RF signal amplitude is performed in this way, the adjustment based only on the wobble signal amplitude can be performed. Even in this case, after the adjustment based on the RF signal amplitude is performed once, Even during the recording operation, readjustment to the optimum value can be performed. That is, even in this case, it is possible to prevent the recording quality of the signal from being deteriorated during the recording operation.

The processing operation to be executed to realize the adjustment operation as the second embodiment according to the above description will be described with reference to the flowcharts of FIGS.
The processing operations shown in FIGS. 6 and 7 are also performed by the system controller 60 shown in FIG.
Further, in this case, for convenience of explanation, it is assumed that an operation when a recorded rewritable disc is loaded as the disc 1 is shown.

First, in step S201 shown in the figure, signal reproduction is performed while changing the focus bias value and the spherical aberration correction value, and processing for storing information on the amplitude level of the RF signal obtained thereby is executed. .
That is, first, the setting unit 17 is controlled to cause the focus bias setting unit 16 to set the focus bias value as the first stage stored in the nonvolatile memory 18. Then, under the setting of the focus bias, the setting unit 17 is controlled so that each spherical aberration correction value stored in the nonvolatile memory 18 is changed stepwise by the spherical aberration correction value setting unit 20. Execute the signal playback operation while setting. Then, the amplitude level of the RF signal obtained under the setting of each spherical aberration correction value is detected as described above, and information on the amplitude level of these RF signals is set to the set focus bias value and spherical aberration correction value. And store them in correspondence.
By performing this operation in the same manner for the remaining four levels of the focus bias value, information on the RF signal amplitude level obtained with a total of 25 settings of the focus bias value × 5 and the spherical aberration correction value × 5. Remember.
As a matter of course, at least the tracking servo is controlled to be turned on when performing the signal reproduction in step S201.

In the subsequent step S202, a set of the focus bias value (FBc) and the spherical aberration correction value (SAb) when the RF signal amplitude is maximized is determined from the information stored in step S201.
In step S203, a process for holding the focus bias value FBc and the spherical aberration correction value SAb thus determined is executed. For example, information on the focus bias value FBc and the spherical aberration correction value SAb is stored in the nonvolatile memory 18.

In step S204, the wobble signal amplitude is detected while changing the focus bias value and the spherical aberration correction value, and processing for storing the detected wobble signal amplitude information is performed.
That is, similar to the process of step S101 described above with reference to FIG. 5, first, the tracking servo calculation unit 22 is controlled to turn on the tracking servo. In this state, the setting unit 17 causes the focus bias setting unit 16 and the spherical aberration correction value setting unit 20 to set the first-stage focus bias value and the spherical aberration correction value stored in the nonvolatile memory 18, respectively. At this time, the amplitude level of the push-pull signal supplied from the matrix circuit 54 is detected. At the same time, the information of the push-pull signal amplitude level detected in this way is stored in association with the set focus bias value and spherical aberration correction value.
The focus bias / spherical aberration correction value setting / storing operation is similarly executed for all combinations of the remaining four stages of the focus bias value and the remaining four stages of the spherical aberration correction value. Information on wobble signal amplitude levels obtained by a total of 25 settings of value × 5 and spherical aberration correction value × 5 is stored.

In subsequent step S205, based on the information stored in step S204, the focus bias value (FBd) at which the wobble signal amplitude level is maximized is determined.
In step S206, the optimum focus bias value FBc obtained in step S202 is subtracted from the focus bias value FB obtained in step S205 to obtain a difference value sfb. Further, in step S207, information on the difference value sfb is held. Information on the difference value sfb is also stored in the nonvolatile memory 18, for example.

In step S208, processing for setting the focus bias value FBc and spherical aberration correction value SAb held in step S203 is executed.
Thereby, first, the focus bias value FBc and the spherical aberration correction value SAb are set for the focus bias setting unit 16 and the spherical aberration correction value setting unit 20, respectively, and the recording / reproducing operation is performed under the optimum conditions. It can be carried out.

Subsequently, referring to FIG. 7, processing to be executed in accordance with the adjustment operation based on the wobble signal amplitude to be executed after the focus bias / spherical aberration correction value adjustment based on the RF signal amplitude is performed as described above. The operation will be described.
The processing operation shown in FIG. 7 is performed at a predetermined timing during the operation after the adjustment operation based on the RF signal amplitude shown in FIG. 6 is performed.

First, in step S301 shown in the figure, the wobble signal amplitude is detected while changing the focus bias value and the spherical aberration correction value, and processing for storing the information of the detected wobble signal amplitude is performed.
That is, also in this step S301, the same processing as in the previous steps S101 and S204 is executed.

  In step S302, based on the information stored in step S301, the focus bias value (FBe) and the spherical aberration correction value (SAc) at which the wobble signal amplitude level is maximized are determined.

  In the subsequent step S303, a process of calculating the focus bias value FBf by subtracting the difference value sfb held in step S207 shown in FIG. 6 from the calculated focus bias value FBe is executed. Thereby, the optimum focus bias value FBf is obtained.

After that, in step S304, processing for setting the focus bias value FBf and the spherical aberration correction value SAc is executed.
Thereby, thereafter, the recording / reproducing operation can be performed under the optimum condition by the focus bias FBf and the spherical aberration correction value SAc.

As the processing operation of FIG. 6 described above, the operation has been described by taking the case where the disc 1 is a recorded writable disc as an example. However, for an unrecorded writable disc, the processing before the illustrated processing is performed. First, processing for performing a test writing operation is added. Then, the amplitude level of the RF signal may be detected for the signal written in this way.
It should be noted that the laser power set for performing the trial writing may be based on a rough setting using an initial value or the like, for example.

As a timing for executing the series of adjustment processes based on the RF signal amplitude shown in FIG.
As described above, when the disc is loaded, the difference value sfb corresponding to each characteristic of the disc 1 can be obtained, and the focus bias value obtained by the adjustment operation based on the wobble signal amplitude performed thereafter is also used. A more appropriate value corresponding to each characteristic of the disk 1 can be set.
In addition to this, it is possible to update to a more appropriate difference value sfb by executing, as a trigger, a condition in which the difference value sfb is expected to change, such as in response to a secular change.

  Further, the execution timing of the adjustment processing based on the wobble signal amplitude shown in FIG. 7 performed after the processing shown in FIG. 6 is the same as that in the first embodiment except that it is performed at the disc loading timing. Same as the case.

Also, the setting of the area for performing the detection process for the wobble signal amplitude may be the same as in the case of the first embodiment.

<Third Embodiment>

Here, according to the first and second embodiments described so far, the focus bias value can be adjusted to the optimum value based on the information of the wobble signal amplitude. In particular, the seek operation to the test writing area can be omitted during adjustment during operation, thereby shortening the time required for the adjustment operation performed during the operation.
However, in the operations of the first and second embodiments, in the adjustment, the signal amplitude value is sequentially measured while changing the focus bias value and the spherical aberration correction value as in the conventional case. Considering this point, it is difficult to say that the adjustment time has been greatly shortened.

Therefore, in the next third embodiment, the signal amplitude value is sequentially measured while changing the focus bias value and the spherical aberration correction value as in the first and second embodiments. Therefore, the adjustment time is further shortened.
The operation as the third embodiment will be described with reference to FIGS.
In the third embodiment, the internal configuration of the optical disc apparatus is the same as that shown in FIGS. 1 to 3, and a description thereof will not be repeated. Also in the third embodiment, it is assumed that the disk 1 is a writable disk, and the adjustment operation is performed based on the measurement result of the wobble signal amplitude.

  For the sake of confirmation, the adjustment operation of the third embodiment is an adjustment operation to be performed during the operation, and is already optimized by the adjustment performed when the disc 1 is loaded. This is an operation to be performed under the condition where the focus bias value is set. In this case, as the focus bias value already set prior to the adjustment during the operation, the adjustment operation (FIG. 5) of the first embodiment or the disc loading described in the second embodiment is used. The following description will be continued on the assumption that it is set by the adjustment operation (FIG. 6).

First, FIG. 8 shows the jitter characteristics and wobble signal amplitude characteristics of the reproduction data when the focus bias is taken on the horizontal axis.
In this case, the jitter characteristic of the reproduction data indicates that the focus bias value that minimizes the value is the optimum focus bias value. That is, the focus bias value that minimizes the jitter shown in FIG. 8A corresponds to the optimum focus bias value shown in FIG. 4 in the first embodiment, and the second embodiment. In terms of form, this corresponds to a focus bias value that maximizes the RF signal amplitude value.
According to this, the optimum focus bias value that minimizes the jitter is set as the optimum focus bias in the adjustment in the first embodiment or the second embodiment when the disc is loaded. It can be regarded as the bias value FBb or the focus bias value FBc. Thus, for example, the focus bias value set as optimum by past adjustments such as when a disc is loaded is referred to as a focus bias value FBbef.
In FIG. 8A, the difference between the focus bias value FBbef, which is the optimum value, and the focus bias value that maximizes the wobble signal amplitude is equal to the required difference value sfb as described above. This will cause deviation.

Here, it is assumed that the optical characteristics change from the state of the characteristics shown in FIG. 8A as the temperature of the set increases, for example.
Depending on the change in the optical characteristics accompanying such a temperature rise, as shown in FIG. 8B, the optimum focus bias value indicated by the minimum jitter value is shown in FIG. 8A. The value changes from the value FBbef to the value FBaft that is increased. That is, depending on the temperature rise, the optimum focus bias value changes so as to shift in the increasing direction.
It can also be seen that the value of the focus bias that maximizes the wobble signal amplitude shown in FIG. 8B also shifts from the value shown in FIG.

  8A and 8B, the focus bias value FBsp obtained by adding the difference value sfb to the set focus bias value FBbef is the wobble signal in FIG. 8A. Although the focus bias value maximizes the amplitude, in the case of FIG. 8B, the focus bias value that maximizes the wobble signal amplitude as described above is different from the value shown in FIG. By shifting so as to increase, it can be seen that the focus bias value FBsp is positioned at a value lower than the focus bias value that maximizes the wobble signal amplitude.

From this, it can be understood that when the optimum focus bias value is shifted so as to increase due to the temperature rise, the focus bias value FBsp becomes a low value in view of the focus bias value that maximizes the wobble signal amplitude.
In this case, when the temperature tends to decrease, the focus bias value FBsp is set to a high value in view of the focus bias value that maximizes the wobble signal amplitude.

Based on this, the focus bias value FBsp obtained by adding the difference value sfb to the set focus bias value FBbef is lower than or higher than the focus bias value that maximizes the wobble signal amplitude. If it is known whether the value is the value, it can be determined whether the optimum value FBaft is shifted so as to increase from the optimum value FBbef or shifted so as to decrease.
If the optimum value FBaft is shifted so as to increase from the optimum value FBbef, as shown in FIG. 8C, a predetermined step value (with respect to the focus bias value FBbef that has already been set) is set. If a focus bias value obtained by adding (FBstep) is set, adjustment can be performed so as to approach the optimum focus bias value according to the actual deviation. Although not shown in the figure, when the optimum value FBaft is shifted so as to decrease from the optimum value FBbef, the focus bias value obtained by subtracting a predetermined step value (FBstep) is set in the same manner. In addition, adjustment can be performed so as to approach the optimum focus bias value according to the actual deviation.

  Even in this case, it is assumed that the optimum focus bias value is a value obtained by subtracting the difference value sfb from the focus bias value that maximizes the wobble signal amplitude value, based on the characteristics shown in FIG. Therefore, as described above, the focus bias value FBbef + the difference value sfb is shown as the focus bias value that maximizes the wobble signal amplitude. However, the optimum value is changed to the focus bias value that maximizes the wobble signal amplitude value. When the value becomes a value obtained by adding the focus bias value FBbef−the difference value sfb, the focus bias value at which the wobble signal amplitude is maximum is obtained.

Here, in determining the shift direction of the optimum value as described above, whether the focus bias value FBsp is a low value or a high value as viewed from the focus bias value that maximizes the wobble signal amplitude. It is necessary to determine. The specific method will be described with reference to FIG.
In FIG. 9, FIG. 9A shows an example of the actual state of the wobble signal and the wobble signal amplitude corresponding thereto. As described above, one cycle of the wobble signal is obtained by wl / (2π · tp) where wobble wavelength is wl and track pitch is tp. For example, in the case of 1 × speed defined in the Blu-ray Disc format, the specific value is about 80.2 ms.
FIGS. 9B and 9C are enlarged views of a wobble signal within a certain period within one wobble cycle, and FIG. 9D is a focus bias to be applied within the same period. It shows the voltage waveform of (focus error signal FE).

First, in determining the relationship between the focus bias value FBsp and the focus bias value that maximizes the wobble signal amplitude as described above, as shown in FIG. 9D, it is sufficiently shorter than one wobble period. In a cycle, a focus bias that increases or decreases by level FB-h / level FB-l with the focus bias value FBsp as the center is added. In this case, the level FB-h and the level FB-l have the same absolute value level. In this case, the period during which the focus bias that increases or decreases at the same level is added is called a focus bias oscillation period TFB as shown in the figure.
By setting the focus bias oscillation period TFB to a time sufficiently shorter than one wobble period, the reliability of the values of wobh and wobl measured as described later decreases due to the periodic fluctuation of the wobble signal amplitude level. Can be effectively suppressed.

  Here, as can be seen with reference to the characteristic of FIG. 8B, when the increasing level FB-h is added to the focus bias value FBsp, the wobble signal amplitude tends to increase. I understand that. Therefore, as shown in the transition from FIG. 8A to FIG. 8B, when the optimum value is increased due to the temperature rise, in FIG. 9B according to the addition of the level FB-h. As shown, the wobble signal amplitude will increase. On the other hand, according to the addition of the decreasing side level FB-l, the wobble signal amplitude tends to decrease as shown in FIG. 8B. Therefore, according to the addition of the level FB-l, the wobble signal amplitude is decreased as shown in FIG. 9B.

  On the other hand, when the temperature is lowered, the shift of the optimum value and the wobble signal amplitude characteristic are opposite to the transition shown in FIGS. 8A to 8B. Therefore, depending on the addition of the level FB-h, As shown in FIG. 9C, the wobble signal amplitude decreases. On the other hand, according to the addition of the level FB-l, the wobble signal amplitude changes so as to increase.

From these characteristics, in order to determine whether the optimum value of the focus bias has shifted in the increasing direction or in the decreasing direction, for example, the wobble signal amplitude at the time of level FB-h addition is It is only necessary to determine whether or not the amplitude is greater than the wobble signal amplitude at the time of level FB-l addition.
That is, for example, when the wobble signal amplitude value at the time of level FB-h addition is wobh and the wobble signal amplitude value at the time of level FB-l addition is wobl, wobh−wobl = Δwob is calculated, and Δwob is a positive value. If so, it can be determined that the shift is an upward shift shown in FIG.
If Δwob is a negative value, it can be determined that the shift is in the decreasing direction shown in FIG.

  As described above, when the optimum value is shifted upward (Δwob> 0), a predetermined step value FBstep is set with respect to the set focus bias value FBbef (FBb, FBc). Control to add. Further, when the optimum value is shifted in the decreasing direction (Δwob <0), control is performed so as to subtract a predetermined step value FBstep from the set focus bias value FBbef.

  In this example, since it is determined whether or not the wobble amplitude at the time of addition of the level FB-h is larger, Δwob = wobh−wobl, and Δwob> 0, an upward shift, Δwob <0 However, it is also possible to check whether the amplitude at the time of addition of FB-l is larger. In this case, Δwob = wobl−wobh and Δwob> 0. It may be determined that the shift is on the decrease side, and the shift is on the increase side when Δwob <0.

  In the example of FIG. 9, a case where a rectangular wave voltage is applied for focus bias addition that increases or decreases at the levels FB-h and FB-l is illustrated. However, for example, as shown in FIG. A similar determination operation can be performed even when voltage application is performed using a sine wave.

FIG. 11 is a flowchart for explaining the processing operation to be performed in order to realize the operation as the third embodiment described above.
The processing operation shown in this figure is also executed by the system controller 60 shown in FIG.
As described above, the adjustment operation of the third embodiment is an adjustment operation to be performed during the operation. Therefore, prior to the adjustment operation shown in FIG. Depending on the timing of loading, etc., the adjusting operation of the first embodiment (FIG. 5) or the adjusting operation at the time of loading the disc described in the second embodiment (FIG. 6) is performed. It is a prerequisite.
Here, assuming that the adjustment operation (FIG. 6) at the time of loading the disc already described in the second embodiment has been performed, the first adjustment after the adjustment at the loading is performed as the focus bias value FBbef described above. At this time, it is assumed that the focus bias value FBc is set.

First, in step S401, calculation is performed using the focus bias value FBc being set + the difference value sfb = the focus bias value FBsp.
In step S402, control is performed so that a focus bias of level FB-h and level FB-l is added around the level of the focus bias value FBsp, and at the same time, the wobble signal amplitude at the level FB-h. A process of measuring the wobble signal amplitude value wobl when the value is wobh and the level FB-l is executed.
In other words, the setting unit 17 shown in FIG. 3 is instructed with focus bias values of level FB-h and level FB-l with the focus bias value FBsp as the center, and the focus bias corresponding to this is finally set. Control is performed by the adder 15 so as to be added to the focus servo loop. At the same time, the level of the push-pull signal supplied from the matrix circuit 54 shown in FIG. 1 is measured while the tracking servo calculation unit 22 shown in FIG. 3 is controlled to turn on the tracking servo. Thus, the wobble signal amplitude value wobh when the level FB-h is added and the wobble signal amplitude value wobl when the level FB-l is added are measured.

  Here, for convenience of explanation, it is assumed that the focus bias value being set is the focus bias value FBc adjusted at the time of loading the disc. However, in actuality, as the adjustment operation during the operation shown in FIG. After the first adjustment after the time adjustment, it is performed at the timing of each seek operation, in which case the focus bias value adjusted by the processing operation shown in this figure becomes the focus bias value being set above. . Therefore, strictly speaking, the focus bias value being set in step S401 is set to be optimum before the adjustment operation shown in this figure is performed, and represents the focus bias value FBbef currently set. It is.

In subsequent step S403, calculation is performed using Δwob = wobble signal amplitude value wobh−wobble signal amplitude value wobl. In step S404, it is determined whether or not the value of Δwob is positive.
If a positive value is determined by Δwob> 0, in step S405, control is performed to set the focus bias value based on the focus bias value FBbef + step value FBstep being set.
In this case, the system controller 60 stores the step value FBstep with a predetermined value in advance in the internal storage means. By instructing the setting unit 17 with the step value FBstep, control is performed so that the step value FBstep is finally added to the focus servo loop by the adder 15.

On the other hand, if a negative value is determined by Δwob <0 in step S404, control for setting the focus bias value based on the currently set focus bias value FBbef−step value FBstep is performed in step S406.
That is, the system controller 60 instructs the setting unit 17 to provide the step value FBstep, and in this case, the control is performed so that the step value FBstep is finally subtracted from the focus servo loop by the adder 15.

  As the step value FBstep, a predetermined value is stored in advance in the nonvolatile memory 18 shown in FIG. 3, and the system controller 60 instructs the setting unit 17 to read out the value, so that the final value is obtained. Further, the adder 15 may be configured to add / subtract to the focus servo loop.

  According to the third embodiment as described above, in the adjustment during the operation, the wobble signal amplitude at two points at the time of adding the focus bias by the levels FB-h and FB-l is measured, and the calculation based on the result is performed. The focus bias can be set by performing. According to this, the signal amplitude value is sequentially changed while changing the focus bias value and the spherical aberration correction value as in the conventional adjustment operation using the RF signal and the adjustment operation in the first and second embodiments. An operation such as measurement can be omitted, which can greatly reduce the time required for the adjustment operation to be performed during the operation.

Here, the step value FBstep is a fixed value, but the numerical value is how often the adjustment is performed, that is, how much the temperature changes between the adjustment operations and how much the optimum value is associated with it. Should be set in consideration of whether or not to shift.
For example, the adjustment operation during the operation may be executed at the timing of each seek operation. However, in the case of the optical disk device connected to the AV system 120 as in the present embodiment, the drive device of the personal computer As a result, the seek frequency is different from the case of being connected as. In the former case, recording data may be intermittently transferred from the AV system 120, and a seek operation is also performed relatively frequently. In the latter case, since the recording data is continuously transferred from the personal computer side at a constant transfer rate and the data is continuously written to the disk 1, the seek frequency is low.
Therefore, in the former case, the step value FBstep may be set to a relatively small value, and in the latter case, it may be set to a relatively large value.

Alternatively, the step value FBstep can be variably set.
For example, as can be understood from the above description, when the seek operation is not frequent, the change in the optimum value accompanying the temperature change between the adjustment operations also increases. On the contrary, when seek frequently enters, the temperature change is small and the deviation of the optimum value is small.
The frequency of the seek operation can be estimated by, for example, the transfer rate of recording / playback data. That is, if the transfer rate is low, a command with a small amount of data is intermittently transferred to the AV system 120 correspondingly, so that the frequency of the seek operation is increased. Conversely, when the transfer rate is high, commands with a large amount of data are transferred continuously, so the seek frequency is reduced accordingly. Therefore, a small step value FBstep is set when the rate is low, and a large step value FBstep is set when the rate is high, according to the transfer rate of the recording / playback data, so that the actual optimum value shift amount is set. It is possible to make appropriate adjustments.

In the third embodiment, the case where the adjustment is performed based on the result of measuring the wobble signal is exemplified. Instead, the step value FBstep is added / subtracted based on the result of measuring the RF signal amplitude. You can also
However, the following points need to be taken into consideration when adjusting based on the step value FBstep using the RF signal as described above and when adjusting based on the wobble signal described above.
First, since the maximum value of the wobble signal is set to a value that is offset by a predetermined difference value sfb from the focus bias value that is optimum, as shown in FIG. A focus bias of FB-h · FB-l is added around a value shifted by the difference value sfb with respect to the bias value FBbef.
However, as the RF signal, according to the description so far, the set focus bias value FBbef (FBc) itself is the optimum value. In other words, in the case of an RF signal, the transition of the RF signal amplitude characteristic due to the temperature change can be regarded as the transition of the jitter characteristic itself in the case of FIGS. 8A to 8B.
Accordingly, in this case, the difference value sfb is not necessary in determining the shift direction of the optimum value, and a focus bias that becomes FB-h · FB-l is added around the level of the focus bias value FBbef (FBc) itself. Then, it may be performed based on the result of measuring the RF signal amplitude value obtained accordingly.
This also makes it possible to appropriately determine the shift direction of the optimum value, and the same effect as when the wobble signal is used can be obtained.

<Fourth embodiment>

Subsequently, a fourth embodiment will be described.
In the first to third embodiments so far, the focus bias value (and spherical aberration correction value) that maximizes the RF signal amplitude is the optimum focus bias value (and spherical aberration correction value). The explanation has been given on the assumption.
This is particularly effective when the signal recording density has a sufficient margin with respect to the reproduction limit of the optical head, such as a CD (Compact Disc).
However, with the recent increase in recording density, optical disc recording media having a recording density close to the reproduction limit of the optical head have been proposed. In such a high recording density disc, the amplitude level of a component having a particularly short mark length in the reproduction signal is reduced or intersymbol interference occurs, so that accurate binary data using a comparator is accurate. Therefore, binarization processing using a PRML (Pertial Response Maximum Likelihood) technique is performed as an optical disc apparatus.
Since PRML assumes intersymbol interference, it is considered that detection accuracy (that is, reproduced signal quality) at the decoder cannot be accurately represented by TI jitter, which is fluctuation in the time axis direction. The detection accuracy in PRML is such that the path metric value for the maximum likelihood path and the path metric for the second path for the two paths (the maximum likelihood path and the second path) that are finally compared with each other are compared. This can be expressed by calculating the difference from the value. That is, if the value of the path metric for the maximum likelihood path is sufficiently small and the value of the path metric for the second path is sufficiently large, the possibility of erroneous detection is low. An index representing quality can be obtained.
Specifically, the standard deviation of the difference metric is obtained as the evaluation value of the reproduction signal quality when the PRML method is adopted. The difference metric is a difference value between the path metric value for the maximum likelihood path and the path metric value for the second path, and the standard deviation value is obtained.
As the difference metric, the larger the value, the lower the possibility of erroneous detection, and the better the reproduced signal quality. As the standard deviation value, the minimum value indicates the best reproduction signal quality.

Here, with respect to a high recording density disc adopting such a PRML technique, evaluation based on the RF signal amplitude is performed because of intersymbol interference or the like in the reproduction signal (RF signal) as described above. Rather, the evaluation based on the standard deviation of the difference metric as described above can perform the reproduction signal quality evaluation with higher reliability.
That is, according to this, it can be understood that the focus bias value that minimizes the value of the standard deviation of the difference metric is a more appropriate focus bias value than the focus bias value that maximizes the RF signal amplitude.

  In the fourth embodiment, when the disc 1 is a high recording density disc and PRML decoding is performed as described above, the standard deviation of the difference metric can be adjusted to a more appropriate focus bias value. The adjustment operation is performed with the focus bias value that minimizes the value of the focus bias value as the optimum focus bias value.

  For confirmation, the RF signal amplitude described in the first and second embodiments is maximized even in the case of a high recording density disc employing the PRML method. By adjusting the focus bias value to be the optimum focus bias value, the optimum value is surely approached as compared with the case where the adjustment is not performed. That is, regardless of which adjustment method is adopted, the adjustment is made so that the optimum value is obtained. Especially, the method of the fourth embodiment is adopted so that the PRML method is adopted. Can be adjusted to a more optimal value when the disc is a high recording density disc.

  In the fourth embodiment, a read-only ROM disk is taken as an example of the disk 1. Specifically, the disc 1 in this case is assumed to be a ROM disc conforming to the Blu-ray Disc format.

The optical disk apparatus in this case is configured to perform reproduction corresponding to such a ROM disk.
As the configuration, the following changes are made to the configuration shown in FIG.
First, address information is not recorded on the disc 1 in this case by track wobbling, but is recorded by a signal based on a combination of pits and lands. Therefore, the wobble circuit 58 is omitted in the optical disc apparatus in this case, and the address decoder 59 detects the address information based on the reproduction signal of the signal recorded on the disc 1 by a combination of pits and lands, and supplies this to the system controller 60. Configured to do.
The reader / writer circuit 55, the modem circuit 56, and the ECC encoder / decoder 57 are each configured to execute only the reproduction operation described with reference to FIG.
In the description of FIG. 1, the reader (writer) circuit 55 performs the binarization process. As the binarization process, a decoding process using the above-described PRML method is performed. That is, the reader circuit 55 includes a PRML decoder.
Furthermore, a signal evaluator for calculating the standard deviation of the above-described difference metric is added to the reader circuit 55 in this case. That is, the signal evaluator is based on the RF signal from the matrix circuit 54 and the binarization result of the PRML decoder, and the difference value between the path metric for the maximum likelihood path and the path metric for the second path. A difference metric is obtained, and the standard deviation is calculated.
Note that the configuration of the signal evaluator for calculating the standard deviation of such a difference metric is well known and is not particularly limited here.
The value of the standard deviation of the difference metric calculated by the signal evaluator is supplied to the system controller 60.

Here, as described above, the focus bias value can be adjusted to a more appropriate focus bias value by adjusting the standard deviation value of the difference metric to the minimum value.
However, in obtaining the standard deviation of the difference metric, it takes a corresponding sampling time for obtaining the standard deviation through the PRML decoding process, and therefore a relatively long time is required. For this reason, the adjustment operation based on the standard deviation of the difference metric is good when it is performed when the disc is loaded, but it is not preferable to perform the adjustment operation during the operation such as seeking from the viewpoint of shortening the adjustment time.

Therefore, as a fourth embodiment, when the disc is loaded, a focus bias value and a spherical aberration correction value that minimize the standard deviation of the difference metric are obtained and set as optimum values.
At this time, a focus bias value that optimizes the value of another evaluation signal different from the standard deviation of the difference metric is obtained, and the focus bias value that minimizes the value of the focus bias value and the standard deviation of the difference metric By obtaining the difference value, it is possible to adjust to the optimum focus bias value using the other evaluation signal at the time of adjustment during operation.

However, since the disc 1 in this case does not record address information by wobbling the track as described above, a wobble signal can be obtained as before as an evaluation signal other than the standard deviation of the difference metric. Can not.
For this reason, in the adjustment during operation, adjustment using the RF signal is performed.
In the case of a ROM disk, an RF signal can be obtained without performing trial writing. Therefore, there is no problem in using the RF signal in this respect as in the case of the writable disc. Further, the time length for measuring the RF signal amplitude is shorter than the time length required for obtaining the standard deviation value of the difference metric. From these points, in this case, since the adjustment based on the RF signal is performed as described above, the time required for the adjustment during the operation can be shortened.

12 and 13 show the standard deviation value characteristic of the difference metric and the RF signal amplitude characteristic when the vertical axis represents the focus bias and the horizontal axis represents the spherical aberration correction value. In this case as well, each characteristic is indicated by a contour line, and the smaller the value of the number given in the figure, the better the value is obtained.
First, in FIG. 12, the focus bias value (and the spherical aberration correction value) that makes the standard deviation value of the difference metric the best (minimum) is the value indicated by the point pMD in the figure. On the other hand, the focus bias value (and the spherical aberration correction value) that makes the RF signal amplitude the best (maximum) in FIG. 13 is the value indicated by the point pRF in the figure.
In FIG. 13, the point pMD in FIG. 12 is also shown. As described above, the focus bias value (the optimum value in this case) that makes the standard deviation value of the difference metric the best (minimum) and the RF signal amplitude are shown. The relationship with the best (maximum) focus bias value is also a relationship having a predetermined difference value between each value.

  From these characteristic diagrams of FIG. 12 and FIG. 13, even in this case, a focus bias value that makes the best standard deviation value of the difference metric and a focus bias value that makes the RF signal amplitude the best are obtained in advance, and the difference value between them. Thus, it can be understood that the adjustment can be made to the optimum focus bias value by using the focus bias value that makes the RF signal amplitude the best and the difference value at the time of adjustment during the operation.

FIG. 14 and FIG. 15 are flowcharts showing the processing operation to be performed to realize the operation as the fourth embodiment. Note that the system controller 60 also executes the processing operations shown in these drawings.
The adjustment operation as the fourth embodiment shown in FIG. 14 and FIG. 15 is the same as the adjustment operation of the second embodiment shown in FIG. 6 and FIG. The wobble signal can be regarded as an RF signal. That is, as a basic operation, an operation similar to that in the case of the second embodiment is performed.

First, FIG. 14 shows an adjustment operation to be performed when a disc is loaded.
In step S501, signal reproduction is performed while changing the focus bias value and the spherical aberration correction value, and processing for storing the standard deviation value of the difference metric obtained thereby is executed.
That is, first, the setting unit 17 is controlled to cause the focus bias setting unit 16 to set the focus bias value as the first stage stored in the nonvolatile memory 18. Then, under the setting of the focus bias, the setting unit 17 is controlled so that each spherical aberration correction value stored in the nonvolatile memory 18 is changed stepwise by the spherical aberration correction value setting unit 20. Execute the signal playback operation while setting. Then, under the setting of each spherical aberration correction value, the standard deviation value of the difference metric input from the signal evaluator in the reader circuit 55 is changed to the set focus bias value and spherical aberration correction value. And memorize it.
By performing this operation in the same manner for the remaining four steps of the focus bias value, the standard deviation of the difference metric obtained by a total of 25 settings of the focus bias value × 5 and the spherical aberration correction value × 5 is set. Remember the value.

In the subsequent step S502, a set of the focus bias value (FBg) and the spherical aberration correction value (SAd) when the standard deviation value of the difference metric is minimized is determined from the information stored in step S501.
In step S503, a process for holding the focus bias value FBg and the spherical aberration correction value SAd determined in this way is executed. For example, information on the focus bias value FBg and the spherical aberration correction value SAd is stored in the nonvolatile memory 18.

In step S504, signal reproduction is performed while changing the focus bias value and the spherical aberration correction value, and processing for storing information on the RF signal amplitude obtained thereby is performed.
That is, also in this case, first, the setting unit 17 is controlled to cause the focus bias setting unit 16 to set the focus bias value as the first step stored in the nonvolatile memory 18. Then, under the setting of the focus bias, the setting unit 17 is controlled so that each spherical aberration correction value stored in the nonvolatile memory 18 is changed stepwise by the spherical aberration correction value setting unit 20. Execute the signal playback operation while setting. In addition, the amplitude value of the RF signal obtained under the setting of each spherical aberration correction value is detected as described above, and the information is stored in association with the set focus bias value and the spherical aberration correction value.
By performing this operation in the same manner for the remaining four steps of the focus bias value, information on the RF signal amplitude obtained by a total of 25 settings of the focus bias value × 5 and the spherical aberration correction value × 5 is obtained. Remember.

In subsequent step S505, based on the information stored in step S504, the focus bias value (FB) having the maximum RF signal amplitude value is determined.
In step S506, the optimum focus bias value FBg obtained in step S502 is subtracted from the focus bias value FBh obtained in step S505 to obtain a difference value sfb. Further, in step S507, information on the difference value sfb is held. Information on the difference value sfb is also stored in the nonvolatile memory 18, for example.

Then, in step S508, processing for setting the focus bias value FBg and spherical aberration correction value SAd held in the previous step S503 is executed.
Thus, first, the focus bias value FBg and the spherical aberration correction value SAd are set for the focus bias setting unit 16 and the spherical aberration correction value setting unit 20, respectively, and the recording / reproducing operation is performed under the optimum conditions. It can be carried out.

Next, the flowchart of FIG. 15 shows processing corresponding to the adjustment operation based on the RF signal amplitude to be executed after the adjustment of the focus bias / spherical aberration correction value based on the standard deviation of the difference metric as described above. The operation is shown.
The processing operation shown in FIG. 15 is also performed at a predetermined timing set in advance during the operation after the adjustment operation based on the standard deviation of the difference metric shown in FIG.

First, in step S601 shown in the figure, signal reproduction is performed while changing the focus bias value and the spherical aberration correction value, and processing for storing information on the RF signal amplitude obtained thereby is performed.
That is, also as this step S601, the same processing as the previous step S504 is executed.

  In step S602, based on the information stored in step S601, the focus bias value (FBi) and the spherical aberration correction value (SAe) at which the RF signal amplitude level is maximized are determined.

  In the subsequent step S603, a process of calculating the focus bias value FBj by subtracting the difference value sfb held in step S507 shown in FIG. 6 from the determined focus bias value FBi is executed. Thereby, the optimum focus bias value FBj is obtained.

Then, in step S604, processing for setting the focus bias value FBj and the spherical aberration correction value SAe is executed.
Thereby, the recording / reproducing operation can be performed under the optimum condition by the focus bias FBj and the spherical aberration correction value SAe.

Here, as an adjustment operation when the focus bias value that minimizes the standard deviation value of the difference metric is the optimum value, the case where the disk 1 is a ROM disk is illustrated, and the adjustment during operation is based on the RF signal. it is assumed to be adjusted in the case of a recordable disc, and the focus bias value for the standard deviation value of the difference metric and the minimum, the adjustment method using a difference value between the focus bias value to maximize the wobble signal amplitude It is also possible to do.
Even in this case, the effect of the adjustment using the wobble signal amplitude during operation with the writable disc is the same as in the case of the first and second embodiments.

Here, the adjustment operation during the operation when the focus bias value that minimizes the standard deviation of the difference metric is the optimum value is the same as in the case of the third embodiment. By adjusting using the value FBstep, the adjustment time can be further shortened.
In other words, the operation in this case is performed after setting the optimum condition by setting the focus bias value FBg (and the spherical aberration correction value SAd) that minimizes the standard deviation of the difference metric when the disc is loaded, and then seek. In adjustment during operation such as time, a focus bias based on levels FB-h and FB-l is added, and the shift direction of the optimum value is determined based on the RF signal amplitude value obtained at this time.

Here, as in the fourth embodiment, the focus bias value that minimizes the standard deviation of the difference metric is the optimum value, and the focus bias value that maximizes the RF signal amplitude is determined from the optimum value by a predetermined value. The fact that the relationship is shifted by the difference value means that in the characteristic diagram of FIG. 8 described in the third embodiment, the jitter characteristic can be regarded as a characteristic of the standard deviation value of the difference metric. The wobble signal amplitude characteristic can be considered in terms of the RF signal amplitude characteristic.
That is, according to this, with respect to the focus bias value obtained by adding the difference value sfb to the set focus bias value FBbef, the focus bias based on the levels FB-h and FB-l is added, and the RF signal amplitude obtained thereby It can be understood that the shift direction of the optimum value can be determined based on the result of measuring the value.

FIG. 16 shows the state of the RF signal obtained when the focus bias values based on the levels FB-h and FB-l are added.
First, as shown in FIG. 16D, also in this case, the addition of the focus bias by the level FB-h and the level FB-l is performed in a relatively short period as the illustrated focus bias oscillation period TFB. To be. In this case, FBsp, which is the center level between the levels FB-h and FB-l, is a level obtained by adding the difference value sfb to the set focus bias value FBbef as understood from the above description. .
As shown in FIG. 16B, when the actual optimum value FBaft is shifted to the increasing side with respect to the set focus bias value FBbef, the level FB-h is added. Thus, the RF signal amplitude value increases, and the RF signal amplitude value at the time of level FB-l addition decreases.
Further, as shown in FIG. 16C, when the actual optimum value FBaft is shifted to the decreasing side with respect to the focus bias value FBbef set in reverse, the RF signal is added at the time of level FB-h addition. The amplitude level decreases, and the amplitude value increases when level FB-l is added.
Accordingly, even in this case, for example, when the RF signal amplitude value at the time of level FB-h addition is RFh and the RF signal amplitude value at the time of level FB-l addition is RF1, RFh−RFl = ΔRF is calculated, and this ΔRF If is a positive value, it can be determined that the shift is in the upward direction of FIG.
If ΔRF is a negative value, it can be determined that the shift is in the decreasing direction of FIG.

Even in this case, when the optimum value is shifted upward (ΔRF> 0), the predetermined step value FBstep is added to the set focus bias value FBbef (FBg). To control. Further, when the optimum value is shifted in the decreasing direction (ΔRF <0), control is performed so that a predetermined step value FBstep is subtracted from the set focus bias value FBbef.
Thus, in setting the optimum focus bias value, the focus bias value can be set based on the result of measuring the RF signal amplitude value only at the two points obtained by adding the level FB-h and the level FB-l. The time can be greatly shortened.

FIG. 17 shows a processing operation for realizing an operation as a modification of the fourth embodiment.
Note that the processing operation shown in this figure is performed as an adjustment operation during operation, and here, it is assumed that the adjustment operation at the time of loading the disk in FIG. 14 has already been performed.

First, in step S701, calculation is performed using the focus bias value FBg being set + the difference value sfb = the focus bias value FBsp.
In step S702, control is performed so that a focus bias of level FB-h and level FB-l is added around the level of the focus bias value FBsp, and at the same time, the RF signal amplitude at the level FB-h. Processing for measuring the RF signal amplitude value RFl at the value RFh and the level FB-l is executed.
The processing in step S702 is the same as the processing in step S402 shown in FIG. 11 except that the RF signal amplitude value is measured at the time of level FB-h addition and at the time of level FB-l addition. .

  Even in this case, for convenience of explanation, it is assumed that the focus bias value being set is the focus bias value FBg adjusted at the time of loading the disc. Strictly speaking, the focus bias value being set in step S701 is This represents the focus bias value FBbef that is set as optimum before the adjustment operation shown in FIG.

In subsequent step S703, calculation is performed using ΔRF = RF signal amplitude value RFh−RF signal amplitude value RFl. In step S704, it is determined whether or not the value of ΔRF is positive.
If a positive value is determined by ΔRF> 0, in step S705, control is performed to set the focus bias value based on the focus bias value FBbef + step value FBstep being set.
The processing in this case is the same processing as step S405 shown in FIG.

  On the other hand, if a negative value is determined by ΔRF <0 in step S704, control for setting the focus bias value based on the focus bias value FBbef−step value FBstep being set is performed in step S706. This process is also the same as the previous step S406.

In this case as well, the step value FBstep is a fixed value, but the numerical value indicates how often the adjustment is performed, that is, how much the temperature changes between the adjustment operations and how much is optimal accordingly. It may be set in consideration of whether the value shifts. Alternatively, in this case as well, the value of the step value FBstep can be variably set according to, for example, the transfer rate of recording / playback data.

<Fifth embodiment>

In the first to fourth embodiments described so far, only the focus bias value is adjusted to be closer to the optimum value using the difference value sfb or the step value FBstep. The aberration correction value can also be adjusted to be closer to the optimal spherical aberration correction value.

FIG. 18 shows the wobble signal amplitude characteristics (contour lines) when the focus bias is on the vertical axis and the spherical aberration correction value is on the horizontal axis, similar to that shown in FIG.
As can be seen from this figure, the spherical aberration correction value that maximizes the wobble signal amplitude (the value indicated by the solid line in the vertical direction in the figure) is the spherical aberration that is actually optimal. A value deviated from the correction value (value indicated by the vertical broken line) by the required difference value ssa is taken.
Therefore, according to this, it can be understood that the adjustment operation of the focus bias value described in each of the embodiments so far can be applied to the adjustment of the spherical aberration correction value.

In the adjustment during the operation of the first embodiment and the second embodiment, the spherical aberration correction value is adjusted to a value that maximizes the wobble signal amplitude.
According to this, the spherical aberration correction value is not adjusted to the optimum value with respect to the focus bias value, but the spherical aberration correction value is set to a value that maximizes the wobble signal amplitude as described above. If the adjustment is made, the adjustment is closer to the optimum value than in the case where the adjustment is not performed. Therefore, the adjustment operation to a more appropriate value is still performed.
The same applies to the case of the fourth embodiment. In other words, the relationship between the standard deviation of the difference metric and the RF signal ensures that even if the spherical aberration correction value that maximizes the RF signal amplitude is adjusted, compared to the case where no adjustment is made, the optimum value is surely obtained. There is no change in being adjusted so that it may approach.

In the fifth embodiment, as an example in which the adjustment operation similar to the adjustment operation of the focus bias value in the previous embodiments is also performed for the spherical aberration correction value, the spherical surface with the best value of the required evaluation signal is used. The aberration correction value is adjusted to a value shifted by the difference value ssa.
As a specific example, in this case, an operation of adjusting the spherical aberration correction value using such a difference value ssa is added to the operation of the second embodiment (FIGS. 6 and 7). The operation in this case will be described.

19 and 20 are flowcharts showing the processing operation for realizing the operation as the fifth embodiment. The processing operation shown in this figure is also executed by the system controller 60.
First, FIG. 19 shows processing operations to be performed in response to loading of a disc.
In steps S801 to S804 in this case, processing similar to the processing operation at the time of loading the disc shown in FIG. 6 is executed. That is, in each process of steps S801 to S804, the focus bias value (FBc) and the spherical aberration correction value (maximum RF signal amplitude value are changed while changing the focus bias value and the spherical aberration correction value, similarly to steps S201 to S204. SAb) is determined and held, and then the wobble signal amplitude is detected and held while changing the focus bias value and the spherical aberration correction value.

In step S805 in this case, the focus bias value FBd that maximizes the wobble signal amplitude and the spherical aberration correction value SAd are determined from the information held in step S804.
Also in this case, in the subsequent step values S806 and S807, similarly to the previous steps S206 and S207, the calculation is performed by the focus bias value FBd−the focus bias value FBc = the difference value sfb, and the difference value sfb is held. Execute.

In this case, in the next step S808, the spherical aberration correction value SAb determined in the previous step S802 and the spherical aberration correction value SAd calculated in step S805 are expressed by SAb−SAd. A difference value ssa is obtained by performing an operation.
That is, similarly to the focus bias value, a difference value between the spherical aberration correction value that maximizes the RF signal amplitude (the optimum value in this case) and the spherical aberration correction value that maximizes the wobble signal amplitude is obtained. .

  In the subsequent step S810, similarly to step S208 in FIG. 6, a process for setting the focus bias value FBc and the spherical aberration correction value SAb determined in step S802 is performed. That is, even in this case, the adjustment at the time of loading the disc sets the focus bias value FBc and the spherical aberration correction value SAb that maximize the RF signal amplitude.

FIG. 20 shows a processing operation to be performed corresponding to the adjustment in the operation after the processing operation shown in FIG. 19 is performed.
Also in this case, as the adjustment operation during the operation, processing substantially similar to the adjustment operation during the operation in the second embodiment shown in FIG. 7 is executed.
That is, as the processing in steps S901 to S903, the focus in which the wobble signal amplitude is maximized while changing the focus bias value and the spherical aberration correction value is the same as the processing in steps S301 to S303 shown in FIG. The bias value (FBe) and the spherical aberration correction value (SAc) are determined, and the focus bias value FBe is set to a value shifted by the previously held difference value sfb.

In this case, in the subsequent step S904, a process for setting a value shifted by the difference value is similarly added to the spherical aberration correction value. That is, in step S904, the spherical aberration correction value SAf is obtained by subtracting the difference value ssa held in step S809 in FIG. 19 from the spherical aberration correction value SAc determined in step S903. To be done.
In step S905, processing for setting the focus bias value FBf obtained in the previous step S903 and the spherical aberration correction value SAf obtained in step S904 is executed.
As a result, the spherical aberration correction value can also be adjusted so as to be closer to the actual optimum value, similarly to the focus bias.

Note that, here, as in the second embodiment, the case where the adjustment is performed using the RF signal and the wobble signal is illustrated as an example. However, as in the previous fourth embodiment, the recording density is particularly high. The present invention can also be applied to an adjustment using a standard deviation of a difference metric and an RF signal as an adjustment corresponding to a disk.
As the processing operation in this case, with respect to the processing operation (FIGS. 14 and 15) as the fourth embodiment described above, the RF signal amplitude is changed in step S505 in FIG. The spherical aberration correction value is determined together with the maximum focus bias value. Further, after the processing, a difference value ssa between the spherical aberration correction value that minimizes the standard deviation of the difference metric held in step S503 and the spherical aberration correction value that maximizes the RF signal amplitude is obtained and held. Add processing to be performed.
Then, the processing operation of FIG. 15 as the adjustment processing during the operation is held from the spherical aberration correction value that maximizes the RF signal amplitude obtained by the indexing process after the indexing process in step S502. A process for subtracting the difference value ssa to obtain an optimum spherical aberration correction value is added. In addition, a process of controlling so that the spherical aberration correction value that is finally optimized may be added.
As a result, even when the adjustment using the standard deviation of the difference metric and the RF signal is performed as in the fourth embodiment, the spherical aberration correction value is adjusted to be an optimum value as in the case of the focus bias. It can be performed.

Furthermore, the present invention can also be applied to a case where a fixed difference value is used as in the case of the first embodiment. That is, in this case, the difference value ssa between the optimum spherical aberration correction value and the spherical aberration correction value that maximizes the wobble signal amplitude is examined from the characteristics shown in FIG. Based on the above, a difference value ssa with a fixed value is set for each set. The spherical aberration correction value is also set by shifting the spherical aberration correction value that maximizes the wobble signal amplitude by the fixed difference value ssa.
The spherical aberration correction value can also be adjusted to an optimum value based only on the wobble signal amplitude by using the fixed difference value ssa as described above. The effect obtained by using the fixed difference value ssa is the same as that described for the focus bias in the first embodiment.

<Sixth Embodiment>

In the sixth embodiment, as an example in which the spherical aberration correction value is adjusted in the same manner as the focus bias adjustment so far, the adjustment operation during the operation is performed in a predetermined manner as in the third embodiment. Adjustment using the step value is performed.
As the spherical aberration correction value, the wobble signal amplitude value is changed by changing the value from the characteristic diagram of FIG. 18 (and FIG. 4). Therefore, in this case as well, as in the case of the third embodiment, the spherical aberration correction value that increases or decreases at the same level is added to the spherical aberration correction value, and the wobble signal amplitude at that time is measured. Thus, the shift direction of the optimum value can be determined. Then, by adding / subtracting a predetermined step value to / from the spherical aberration correction value being set according to the determined shift direction, the spherical aberration is brought closer to the optimum value shifted in accordance with the temperature change in this case as well. The correction value can be adjusted.

Here, the adjustment operation (FIG. 19) in the case of the previous fifth embodiment was executed when the disc was loaded as the case where the spherical aberration correction value is adjusted using a predetermined step value. A case where the adjustment operation is executed later as an example will be described.
Processing operations to be executed in this case will be described with reference to FIG. It should be noted that the processing operation shown in this figure is also executed by the system controller 60.
First, in step S1001, calculation is performed using the currently set spherical aberration correction value + difference value ssa = spherical aberration correction value SAsp.
In this case, as described above, since the adjustment operation is performed when the adjustment operation shown in FIG. 19 is performed as the adjustment at the time of loading the disc, the spherical aberration correction value being set is the spherical aberration correction value SAb. However, even in this case, the adjustment operation during the operation shown in this figure is actually performed at the timing of each seek operation after the first time after the adjustment at the time of loading the disk, In that case, the spherical aberration correction value adjusted by the processing operation shown in FIG. In other words, the spherical aberration correction value being set in step S1001 is set to be optimal before the adjustment operation shown in this figure is performed, and becomes the spherical aberration correction value SAbef set at the present time.

In step S1002, a spherical aberration correction value that indicates level SA-h / level SA-l is instructed centering on the level of the spherical aberration correction value SAsp, and at the same time, the wobble signal amplitude value wobh and level SA at level SA-h are indicated. A process of measuring the wobble signal amplitude value wobl when -l is executed.
In other words, the setting unit 17 shown in FIG. 3 is instructed with a spherical aberration correction value that is increased or decreased by the level SA-h and the level SA-l around the level of the spherical aberration correction value SAsp, and the spherical aberration correction corresponding to this. Control is performed so that the value is set in the spherical aberration correction driver 26 by the spherical aberration correction value setting unit 20. At the same time, the level of the push-pull signal supplied from the matrix circuit 54 shown in FIG. 1 is measured while the tracking servo calculation unit 22 shown in FIG. 3 is controlled to turn on the tracking servo. Thus, the wobble signal amplitude value wobh when the level SA-h is added and the wobble signal amplitude value wobl when the level SA-l is added are measured.
In this case as well, the level SA-h and the level SA-l have the same absolute value level.

In subsequent step S1003, calculation is performed using Δwob = wobble signal amplitude value wobh−wobble signal amplitude value wobl. In step S1004, it is determined whether or not the value of Δwob is positive.
If a positive value is determined by Δwob> 0, in step S1005, control is performed to set a spherical aberration correction value by the spherical aberration correction value SAbef + step value SAstep being set.
On the other hand, if a negative value is determined by Δwob <0 in step S1004, in step S1006, control is performed to set a spherical aberration correction value based on the spherical aberration correction value SAbef-step value SAstep being set.

  In this case, the values of the level SA-h, the level SA-l, and the step value SAstep need only be stored in the system controller 60. Alternatively, a predetermined value is stored in advance in the nonvolatile memory 18 side shown in FIG. 3, and the system controller 60 finally instructs the setting unit 17 to read the value, so that the spherical aberration correction driver is finally obtained. It can also be configured to be set to 26.

  Further, although the step value SAstep is a fixed value, as for the numerical value, how often the adjustment is performed also in this case, that is, how much the temperature changes during each adjustment operation, and how much is optimal accordingly. It may be set in consideration of whether the value shifts. Alternatively, the step value SAstep can also be variably set according to, for example, the transfer rate of recording / playback data.

  The spherical aberration correction value is also adjusted based on the result of measuring the wobble signal amplitude only at two points when level SA-h and level SA-l are added, by using the predetermined step value SAstep as described above. Since the spherical aberration correction value can be set, the time required for adjustment during operation is significantly reduced in this case as compared with the result of measuring the signal amplitude while changing the focus bias and the spherical aberration correction value. be able to.

  In FIG. 19, only the adjustment for the spherical aberration correction value is shown as the adjustment using the step value. At the same time, by performing the processing operation shown in FIG. The adjustment using the step value can be performed for both the focus bias value and the spherical aberration correction value. In other words, both the focus bias value and the spherical aberration correction value can greatly reduce the time required for adjustment during operation.

In the above example, the shift direction of the optimum value is determined based on the result of measuring the wobble signal amplitude value when level SA-h and level SA-l are added. However, level SA-h and level SA-l are determined. The shift direction of the optimum value may be determined based on the result of measuring the RF signal amplitude value at the time of addition.
In this case, however, the shift direction of the optimum value cannot be properly determined simply by using the wobble signal as the RF signal in the processing shown in FIG.
That is, in the case of the fifth embodiment as in the above example, the relationship between the wobble signal and the RF signal is such that the focus bias / spherical aberration correction value that maximizes the RF signal amplitude is the optimum value, and the wobble signal It is assumed that the focus bias / spherical aberration correction value that maximizes the amplitude takes a value that deviates from this optimum value. For this reason, in the above example, spherical aberration correction values of level SA-h and level SA-l are added around the level (SAsp) obtained by adding the difference value ssa to the spherical aberration correction value SAbef being set. In addition, based on the measurement result of the wobble signal amplitude value at the level SA-h and level SA-l, the shift direction of the optimum value can be properly determined.
However, when determining the shift direction as described above, based on the measurement result of the RF signal amplitude value when level SA-h and level SA-l are added, the spherical aberration correction value SAbef being set is the RF signal amplitude. Since the spherical aberration correction value with the maximum value can be considered as such, the spherical aberration correction values of level SA-h and level SA-l are added around the level of the spherical aberration correction value SAb itself. The shift direction of the optimum value can be appropriately determined based on the result of measuring the RF signal amplitude at that time.

Even when the adjustment operation using the standard deviation of the difference metric and the RF signal is performed as in the fourth embodiment, the step value SAstep of this example is used for the adjustment operation during the operation. Adjustments can be made.
In the case of the fourth embodiment, the focus bias / spherical aberration correction value that maximizes the standard deviation value of the difference metric is the optimal value, and the focus bias / spherical aberration correction value that maximizes the RF signal amplitude is the optimal value. It is assumed that the value deviates from the value.
Therefore, in this case, the spherical aberration correction values of level SA-h and level SA-l are added around the level obtained by adding the difference value ssa to the spherical aberration correction value being set, and the RF signal at that time is added. Based on the result of measuring the amplitude, it is possible to appropriately determine the shift direction of the optimum value.
When the adjustment using the step value SAstep is performed when the adjustment operation using the standard deviation of the difference metric and the RF signal is performed as described above, in the process when loading the disc shown in FIG. A process for calculating the spherical aberration correction value with the maximum signal amplitude and a process for calculating and holding the difference value ssa between the spherical aberration correction value and the spherical aberration correction value with the maximum standard deviation of the difference metric are added. There is a need.
As an adjustment operation during the operation in this case, the wobble signal amplitude (wobh · wobl) at the level SA-h / level SA-l is measured as the processing of step S1002 shown in FIG. What has been changed is changed to measure the RF signal amplitude (RFh · RF1) at the level SA-h · level SA-l. Then, in step S1003, the calculation may be performed by ΔRF = RFh−RF1, and in step S1004, the determination may be made so that ΔRF> 0 is determined.

Further, since the adjustment operation shown in FIG. 21 is based on the premise that the operation in the fifth embodiment is executed as the adjustment operation at the time of loading the disc, the difference value ssa is actually the RF signal amplitude. Although the value calculated from the spherical aberration correction value having the maximum and the spherical aberration correction value having the maximum wobble signal amplitude is used, the difference value ssa is a fixed value based on the first embodiment. It may be used.
Note that the effect of the adjustment using the fixed difference value sfb as the adjustment operation when the disc is loaded is the same as that described in the first embodiment.

Here, it should not be limited to the embodiment described so far.
For example, in each embodiment, the setting value for calculating the focus bias / spherical aberration correction value that provides the best signal evaluation value is prepared for each of the five stages, but this is merely an example. The number is not particularly limited.

  Further, as the spherical aberration correction mechanism, in addition to the beam expander and the liquid crystal element exemplified in the embodiment, it is possible to configure a mechanism by another method such as a mechanism using a deforming mirror.

In each embodiment, as a variation of the disc 1, a writable disc with a track wobbled and a read-only disc with no track wobbled are assumed. However, as the disc 1, the pit row is wobbled. A disk can also be considered.
In such a case, even a read-only disk can be adjusted based on the result of measuring the wobble signal (push-pull signal) amplitude during adjustment during operation.

  In addition, as an evaluation signal used as an index for obtaining an optimum value, a wobble signal, an RF signal, and a standard deviation of a difference metric are exemplified. For example, a push-pull signal (in a traverse state) obtained when a laser spot crosses a track. Other evaluation signals can be used as long as they are obtained based on the reflected light from the disk, such as a push-pull signal), and can be used as an index of the reproduction signal quality.

It is the block diagram shown about the internal structure of the optical disk apparatus as embodiment in this invention. It is the figure illustrated about the structure of the spherical aberration correction mechanism with which the optical disk apparatus of embodiment is provided. It is the block diagram shown about the internal structure of the servo circuit with which the optical disk apparatus of embodiment is provided. FIG. 10 is a characteristic diagram showing wobble signal amplitude characteristics with respect to focus bias and spherical aberration correction values by contour lines. 3 is a flowchart showing processing operations to be executed to realize a focus bias and spherical aberration correction value adjustment operation as the first embodiment. It is the flowchart shown about the processing operation which should be performed in order to implement | achieve the focus bias and spherical aberration correction value adjustment operation | movement as 2nd Embodiment. Similarly, it is a flowchart showing a processing operation to be executed in order to realize a focus bias and spherical aberration correction value adjustment operation as the second embodiment. FIG. 10 is a diagram illustrating a jitter characteristic and wobble signal amplitude characteristic of reproduction data with respect to a change in focus bias as a diagram for explaining an adjustment operation as a third embodiment. FIG. 10 is a diagram illustrating a relationship between a focus bias addition / subtraction and a wobble signal waveform obtained according to the addition / subtraction of a focus bias as a diagram for explaining an adjustment operation according to the third embodiment. It is the figure which illustrated the waveform of the focus drive signal applied in the adjustment operation of 3rd Embodiment. It is the flowchart shown about the processing operation for implement | achieving the adjustment operation | movement as 3rd Embodiment. FIG. 5 is a characteristic diagram showing standard deviation value characteristics of a difference metric with respect to a focus bias and a spherical aberration correction value by contour lines. FIG. 5 is a characteristic diagram showing RF signal amplitude characteristics with respect to a focus bias and a spherical aberration correction value by contour lines. It is the flowchart shown about the processing operation for implement | achieving the adjustment operation | movement as 4th Embodiment. Similarly, it is the flowchart shown about the process operation | movement for implement | achieving the adjustment operation | movement as 4th Embodiment. As a diagram for explaining an adjustment operation as a modification of the fourth embodiment, it is a diagram showing a relationship between addition / subtraction of a focus bias and an RF signal waveform obtained accordingly. FIG. It is the flowchart shown about the processing operation for implement | achieving the adjustment operation as a modification of 4th Embodiment. FIG. 10 is a characteristic diagram showing wobble signal amplitude characteristics with respect to focus bias and spherical aberration correction values by contour lines. It is the flowchart shown about the processing operation for implement | achieving the adjustment operation | movement as 5th Embodiment. Similarly, it is the flowchart shown about the processing operation for implement | achieving the adjustment operation | movement as 5th Embodiment. It is the flowchart shown about the processing operation for implement | achieving the adjustment operation | movement as 6th Embodiment.

Explanation of symbols

  1 disk, 10 DSP, 11, 21 A / D converter, 12 focus servo calculation unit, 13, 23, 25 D / A converter, 14 focus driver, 15 adder, 16 focus bias setting unit, 17 setting unit, 18 non-volatile memory, 20 spherical aberration correction value setting unit, 22 tracking servo calculation unit, 24 tracking driver, 26 spherical aberration correction driver, 51 pickup, 52 spindle motor, 53 thread mechanism, 54 matrix circuit, 55 reader / writer circuit, 56 modulation / demodulation circuit, 57 ECC encoder / decoder, 58 wobble circuit, 59 address decoder, 60 system controller, 61 servo circuit, 62 spindle servo circuit, 63 laser driver, 87 expander, 120 AV system

Claims (17)

A head means for performing laser irradiation and reflected light detection on an optical disk recording medium, and having a laser beam focus servo mechanism, tracking servo mechanism, and spherical aberration correction mechanism;
First evaluation signal generating means for generating a first evaluation signal that serves as an index of reproduction signal quality based on the reflected light obtained by the head means;
Focus servo means for driving the focus servo mechanism based on a focus error signal generated as a signal based on reflected light obtained by the head means to execute focus servo;
Tracking servo means for driving the tracking servo mechanism and executing tracking servo based on a tracking error signal generated as a signal based on reflected light obtained by the head means;
Spherical aberration correction means for performing spherical aberration correction by driving the spherical aberration correction mechanism based on the spherical aberration correction value;
A focus bias means for adding a focus bias to a focus loop including the focus servo means, and
The first evaluation is performed while changing both the focus bias value set in the focus bias means and the spherical aberration correction value set in the spherical aberration correction means at least with the tracking servo by the tracking servo means turned on. An indexing process for determining a focus bias value and a spherical aberration correction value at which the value of the first evaluation signal is the best based on the result of detecting the value of the first evaluation signal obtained by the signal generating means;
For the above focus bias value indexing by the indexing process, was obtained as representing the difference between the value of the focus bias is a focus bias value and optimal for the best values of the first evaluation signal A setting control process for performing control to subtract or add the first difference value and set the resulting value to the focus bias unit;
An optical disc device comprising control means configured to execute The first difference value is
The optical disk apparatus according to claim 1 which is a fixed value which is pre-Me set. Further, an evaluation signal that is an index of reproduction signal quality different from the first evaluation signal based on the reflected light obtained by the head means, and has the best value compared to the first evaluation signal. A second evaluation signal generating means for generating a second evaluation signal that is closer to the focus bias value and the spherical aberration correction value at which the focus bias value and the spherical aberration correction value are respectively optimized .
The control means includes
At least the second evaluation signal obtained by the second evaluation signal generation means and the first evaluation signal obtained by the first evaluation signal generation means at least according to the timing at which the optical disc recording medium is loaded. The result of detecting the value while changing both the focus bias value set for the focus bias means and the spherical aberration correction value set for the spherical aberration correction means with the tracking servo by the tracking servo means turned on. Based on the above, the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best are calculated. Indexing process during loading,
The value of the second evaluation signal indexed by said loading during indexing process and the value of the focus bias became most good, the difference between the value of the focus bias value of the first evaluation signal is the best A first difference value calculation process for calculating a value as the first difference value;
The focus bias value and the spherical aberration correction value at which the value of the second evaluation signal determined by the loading index process is the best are set in the focus bias unit and the spherical aberration correction unit, respectively. And a loading setting control process for performing control so as to
In the above setting control process,
Wherein the focus bias value obtained by subtracting or adding the first difference value calculated by the first difference value calculation processing for the values indexed by the indexing process to claim 1 to set to the focus bias means Optical disk device. The optical disc recording medium is a recordable disc in which a recording track is wobbled,
The first evaluation signal generation means generates a push-pull signal as the first evaluation signal,
In the indexing process by the control means,
As the focus bias value and spherical aberration correction value the value of the first evaluation signal becomes the best, the claims to leave dividing the focus bias value and spherical aberration correction value amplitude value is maximized for the push-pull signal 1. An optical disc device according to 1. The optical disc recording medium is a recordable disc in which a recording track is wobbled,
The first evaluation signal generation means generates a push-pull signal as the first evaluation signal,
The second evaluation signal generating means generates an RF signal as the second evaluation signal,
In the loading indexing process by the control means,
As the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best, respectively, value and spherical aberration correction value of the focus bias amplitude is maximized, the optical disc according to the focus bias value and claim 3 to exit dividing the spherical aberration correction value amplitude value is maximized in the RF signal apparatus. In the indexing process and the loading indexing process,
The detection of the amplitude value of the push-pull signal, intends row in the region of the minimum unit of recording and / or reproducing
The optical disk apparatus according to 請 Motomeko 5. The optical disc recording medium is a read-only disc in which the recording track is not wobbled,
The first evaluation signal generating means generates an RF signal as the first evaluation signal,
The second evaluation signal generation means generates an evaluation signal based on a standard deviation of a difference metric as the second evaluation signal,
In the above loading indexing process,
As the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best, the amplitude of the RF signal, respectively. value and spherical aberration correction value of the focus bias value is maximized, according to claim 3, to leave dividing the value of the focus bias and spherical aberration correction value the value of the standard deviation is minimized in the difference metric Optical disk device. The control means as the setting control process,
The first difference value is subtracted or added to the focus bias value determined by the indexing process , and the resulting value is controlled to be set in the focus bias means. for the above spherical aberration correction value indexing, the second difference value that has been determined as representing the difference between the spherical aberration correction value and the spherical aberration correction value and best to the best values of the first evaluation signal The optical disk apparatus according to claim 1, wherein control is performed such that the value obtained as a result is subtracted or added to the spherical aberration correction unit. The second difference value is
The optical disk apparatus according to claim 8 which is a fixed value which is pre-Me set. Further, an evaluation signal that is an index of reproduction signal quality different from the first evaluation signal based on the reflected light obtained by the head means, and has the best value compared to the first evaluation signal. A second evaluation signal generating means for generating a second evaluation signal that is closer to the focus bias value and the spherical aberration correction value at which the focus bias value and the spherical aberration correction value are respectively optimized .
The control means includes
At least the second evaluation signal obtained by the second evaluation signal generation means and the first evaluation signal obtained by the first evaluation signal generation means at least according to the timing at which the optical disc recording medium is loaded. The result of detecting the value while changing both the focus bias value set for the focus bias means and the spherical aberration correction value set for the spherical aberration correction means with the tracking servo by the tracking servo means turned on. Based on the above, the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best are calculated. Indexing process during loading,
A value of a difference between the spherical aberration correction value with the best value of the second evaluation signal calculated by the loading indexing process and the spherical aberration correction value with the best value of the first evaluation signal Second difference value calculation processing for calculating as the second difference value,
The focus bias value and the spherical aberration correction value at which the value of the second evaluation signal determined by the loading index process is the best are set in the focus bias unit and the spherical aberration correction unit, respectively. And a loading setting control process for performing control so as to
In the above setting control process,
With respect to the spherical aberration correction value indexing by the indexing process, claim a value obtained by subtracting or adding the calculated said second difference value by the second difference value calculation processing to set on the spherical aberration correction means 9. The optical disc device according to 8. For the first evaluation signal that is generated based on the reflected light of the laser beam irradiated to the optical disk recording medium and serves as an index of the reproduction signal quality, at least both the focus bias value and the spherical aberration correction value with the tracking servo turned on An indexing procedure for determining a focus bias value and a spherical aberration correction value at which the value of the first evaluation signal is the best based on the result of detecting the value of the first evaluation signal while changing
In setting the focus bias and the spherical aberration correction value according to the focus bias value and the spherical aberration correction value determined from the index procedure, at least the focus bias value calculated from the index procedure, Subtracting or adding the first difference value obtained so as to represent the difference between the focus bias value that optimizes the value of the first evaluation signal and the optimum focus bias value to the value ; A focus bias and spherical aberration correction value adjustment method, comprising: a setting control procedure for controlling to set a value obtained as a result . A head means for performing laser irradiation and reflected light detection on an optical disk recording medium, and having a laser beam focus servo mechanism, tracking servo mechanism, and spherical aberration correction mechanism;
First evaluation signal generating means for generating a first evaluation signal that serves as an index of reproduction signal quality based on the reflected light obtained by the head means;
Focus servo means for driving the focus servo mechanism based on a focus error signal generated as a signal based on reflected light obtained by the head means to execute focus servo;
Tracking servo means for driving the tracking servo mechanism and executing tracking servo based on a tracking error signal generated as a signal based on reflected light obtained by the head means;
Spherical aberration correction means for performing spherical aberration correction by driving the spherical aberration correction mechanism based on the spherical aberration correction value;
A focus bias means for adding a focus bias to a focus loop including the focus servo means, and
At least with the tracking servo by the tracking servo means turned on , the focus bias value that optimizes the value of the first evaluation signal is optimized from the level of the focus bias value set in the focus bias means. At the same time, control is performed so that a focus bias that increases or decreases at the same level around the level shifted by the first difference value obtained so as to represent the difference from the focus bias value is added to the focus loop. A first measurement process for measuring the value of the first evaluation signal obtained by the first evaluation signal generation means in accordance with the addition of the focus bias that increases or decreases at the same level;
A difference between the value of the first evaluation signal on the increase side of the focus bias and the value of the first evaluation signal on the decrease side of the focus bias measured by the first measurement process is obtained, and the value is positive. First discrimination processing for discriminating between negative and negative,
Based on the discrimination result of the first discrimination process, a focus bias value obtained by adding or subtracting a predetermined step value to the focus bias value set in the focus bias unit is set for the focus bias unit. Setting control processing to control
An optical disc device comprising control means configured to execute Further, the control means includes
The focus bias value set in the focus bias means and the spherical aberration correction means are set at least in a state where the tracking servo by the tracking servo means is turned on at least according to the timing when the optical disc recording medium is loaded. Based on the result of detecting the value of the first evaluation signal obtained by the first evaluation signal generation means while changing both the spherical aberration correction values, the focus bias value and the spherical surface where the value of the first evaluation signal is the best A loading indexing process for determining an aberration correction value;
For at least a focus bias value indexed by the loader during indexing process, the first difference value is subtracted or added, the loading time of setting the resulting value performs control so as to set to the focus bias means the optical disk apparatus according to claim 12 to run a control process, the. Further, an evaluation signal that is an index of reproduction signal quality different from the first evaluation signal based on the reflected light obtained by the head means, and has the best value compared to the first evaluation signal. A second evaluation signal generating means for generating a second evaluation signal that is closer to the focus bias value and the spherical aberration correction value at which the focus bias value and the spherical aberration correction value are respectively optimized .
The control means includes
At least the second evaluation signal obtained by the second evaluation signal generation means and the first evaluation signal obtained by the first evaluation signal generation means at least according to the timing at which the optical disc recording medium is loaded. The result of detecting the value while changing both the focus bias value set for the focus bias means and the spherical aberration correction value set for the spherical aberration correction means with the tracking servo by the tracking servo means turned on. Based on the above, the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best are calculated. Indexing process during loading,
The value of the difference between the focus bias value at which the value of the second evaluation signal obtained by the loading indexing process is the best and the focus bias value at which the value of the first evaluation signal is the best. A first difference value calculation process for calculating the difference value as the first difference value;
The focus bias value and the spherical aberration correction value at which the value of the second evaluation signal determined by the loading index process is the best are set in the focus bias unit and the spherical aberration correction unit, respectively. the optical disk apparatus according to claim 12 control the loading time setting control process for performing, you perform further to. Further, the control means includes
A spherical aberration correction value that optimizes the value of the first evaluation signal from the level of the spherical aberration correction value set in the spherical aberration correction means at least with the tracking servo by the tracking servo means turned on. The spherical aberration correction value that increases or decreases at the same level around the level shifted by the second difference value obtained so as to represent the difference from the spherical aberration correction value is controlled to be set in the spherical aberration correction means. And a second measurement process for measuring the value of the first evaluation signal obtained by the first evaluation signal generating means in accordance with the setting of the spherical aberration correction value that increases or decreases at the same level,
Determining the difference between the value of the first evaluation signal on the increase side of the spherical aberration correction value and the value of the first evaluation signal on the decrease side of the spherical aberration correction value, measured by the second measurement process; A second determination process for determining whether the value is positive or negative, and
Furthermore, in the above setting control process,
Based on the discrimination result of the second discrimination process, the spherical aberration correction value obtained by adding or subtracting a predetermined step value to the spherical aberration correction value set in the spherical aberration correction unit is given to the spherical aberration correction unit. the optical disk apparatus according controlling the row intends claim 12 as configured. Further, the control means includes
The focus bias value set in the focus bias means and the spherical aberration correction means are set at least in a state where the tracking servo by the tracking servo means is turned on at least according to the timing when the optical disc recording medium is loaded. Based on the result of detecting the value of the first evaluation signal obtained by the first evaluation signal generation means while changing both the spherical aberration correction values, the focus bias value and the spherical surface where the value of the first evaluation signal is the best A loading indexing process for determining an aberration correction value;
The focus bias value indexing by the loader during indexing process, the value obtained by subtracting or adding the first difference value relative to the value and controls so as to set to the focus bias means, said loading during indexing the spherical aberration correction value indexing the processing, execution, and a loading time of setting control process for controlling so as to set a value obtained by subtracting or adding the second difference value to the spherical aberration correcting means with respect to the value the optical disk apparatus according to claim 15 you. Further, an evaluation signal that is an index of reproduction signal quality different from the first evaluation signal based on the reflected light obtained by the head means, and has the best value compared to the first evaluation signal. A second evaluation signal generating means for generating a second evaluation signal that is closer to the focus bias value and the spherical aberration correction value at which the focus bias value and the spherical aberration correction value are respectively optimized .
The control means includes
At least the second evaluation signal obtained by the second evaluation signal generation means and the first evaluation signal obtained by the first evaluation signal generation means at least according to the timing at which the optical disc recording medium is loaded. The result of detecting the value while changing both the focus bias value set for the focus bias means and the spherical aberration correction value set for the spherical aberration correction means with the tracking servo by the tracking servo means turned on. Based on the above, the focus bias value and the spherical aberration correction value at which the value of the first evaluation signal is the best, and the focus bias value and the spherical aberration correction value at which the value of the second evaluation signal is the best are calculated. Indexing process during loading,
A value of a difference between the spherical aberration correction value with the best value of the second evaluation signal calculated by the loading indexing process and the spherical aberration correction value with the best value of the first evaluation signal Second difference value calculation processing for calculating as the second difference value,
The focus bias value and the spherical aberration correction value at which the value of the second evaluation signal determined by the loading index process is the best are set in the focus bias unit and the spherical aberration correction unit, respectively. the optical disk apparatus according to claim 15 and the loading setting control process, you perform further performing control such that.

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