JP2009064492A - Optical recording medium drive device, and astigmatism correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent such the situation that fine adjustment is not performed appropriately by performing the coarse adjustment of a spherical aberration correction value with a tracking error signal amplitude value as an evaluation index, which is performed prior to the fine adjustment of spherical aberration correction value-focus bias. <P>SOLUTION: An optimum (e,g, a TE amplitude value is made the maximum) astigmatism correction value is searched in a state in which the spherical aberration correction value-focus bias are fixed based on the result in which the amplitude value of the tracking error signal TE obtained when the astigmatism correction value is changed is obtained, and astigmatism correction is performed by the correcting value. Thereby, a reproduction performance optimum point and a tracking performance optimum point of the focus bias-spherical aberration correction value can be approached so as to coincide, appropriate fine adjustment is performed based on the coarse adjustment result. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical recording medium driving device and an astigmatism correction method.

  As a technique for recording / reproducing digital data, optical disc recording media (including magneto-optical discs) such as CD (Compact Disc), MD (Mini-Disc), DVD (Digital Versatile Disc) are used as recording media. Data recording technology. An optical disk recording medium (also simply referred to as an optical disk) is a generic term for recording media in which a laser beam is irradiated onto a disk on which a signal is recorded by pits or marks, and a signal is read by a change in 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 BD (Blu-ray Disc: registered trademark) has been developed, and the capacity has been significantly increased.

  For a high-density disc such as BD, in a disc structure having a cover layer of about 0.1 mm in the disc thickness direction, a laser with a wavelength of 405 nm (so-called blue laser) and an objective lens with NA (Numerical Aperture) of 0.85 It is assumed that data is reproduced (recorded) under the condition of the combination.

As is already known, in a recording / reproducing apparatus that performs recording / reproducing with respect to an optical disc, a focus servo operation for controlling the focal position of the laser beam to the disc recording surface, or the laser beam by a track (a pit row or a groove) A tracking servo operation is performed to control to track).
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 essential to perform spherical aberration correction in order to cope with the thickness error of the cover layer and the recording layer having a multilayer structure as the adjustment in the focus direction. For example, an optical pickup having a spherical aberration correction mechanism using an expander or a liquid crystal element has been developed.
In particular, in a recording / reproducing apparatus having a high NA lens such as the BD, since the margin of focus bias / spherical aberration is narrow, automatic adjustment of the focus bias and the spherical aberration correction value is essential.

Here, when adjusting the spherical aberration correction value and the focus bias, the adjustment operation is performed using some evaluation value as an evaluation index. Since it is desirable that such adjustment operation is finally performed so as to obtain the best reproduction performance, the evaluation indicators include, for example, an evaluation indicator of reproduction signal quality such as a jitter (Jitter) value and a reproduction error rate. An evaluation value (reproduction performance evaluation value) is used.
Specifically, the reproduction performance evaluation value obtained when the spherical aberration correction value and the focus bias are changed are acquired, and the spherical aberration correction value and the focus bias when the best evaluation value is obtained. It is to adjust to.

Thus, when the reproduction performance evaluation value is used as the evaluation value at the time of adjustment, it is a precondition that the tracking servo is applied and the data can be read out.
However, especially for the spherical aberration correction value, when the value is changed at the time of adjustment as described above, the position may be deteriorated so that the tracking servo is not applied. There was a possibility that could not be done.

For this reason, in the prior art, prior to the adjustment of the spherical aberration correction value and the focus bias, first, the coarse adjustment of the spherical aberration correction value is performed.
Specifically, the tracking error signal amplitude value is obtained when the spherical aberration correction value is changed with only the focus servo turned on, and the amplitude value is better than a predetermined value, that is, the tracking servo can be applied. In other words, the spherical aberration correction value is adjusted so as to be excellent.
By performing such rough adjustment of the spherical aberration correction value, the spherical aberration correction value and the focus bias can be finely adjusted based on the reproduction performance evaluation value as described above. .

In addition, about the related prior art, the following patent documents can be mentioned.
JP 2004-95106 A

However, there is no guarantee that the spherical aberration correction value adjusted by the coarse adjustment as described above is a good position for the reproduction performance evaluation value.
This will be described with reference to FIGS.
First, FIG. 12 shows the position of the spherical aberration correction value roughly adjusted based on the tracking error signal amplitude value on the characteristic map (contour) of the tracking error signal amplitude value with respect to the change between the spherical aberration correction value and the focus bias (FIG. 12). (A)) and a characteristic map (contour line) of a reproduction performance evaluation value (in this case, a jitter value as an example) with respect to changes in the spherical aberration correction value and the focus bias (FIG. 12B), respectively, are compared. Show.
In FIG. 12, the axial direction of the tracking error signal amplitude characteristic shown in FIG. 12A (the dashed line in the figure) and the axial direction of the jitter value characteristic shown in FIG. Shows the case. In such a case, the spherical aberration correction value coarsely adjusted with the tracking error signal amplitude value is a relatively good position in terms of the jitter value characteristics. Can be fine-tuned.

On the other hand, FIG. 13 shows a case where the axial direction of the characteristics as described above is significantly deviated. FIG. 13A shows the position of the spherical aberration correction value roughly adjusted based on the tracking error signal amplitude value on the characteristic map (contour line) of the tracking error signal amplitude value with respect to the change between the spherical aberration correction value and the focus bias. FIG. 13B shows the jitter value on the characteristic map (contour lines).
As can be seen by comparing FIGS. 13 (a) and 13 (b), when the tracking error signal amplitude value characteristic and the jitter value characteristic deviate in the axial direction, coarse adjustment is performed with the tracking error signal amplitude value. The position of the spherical aberration correction value may not be a good position in terms of the jitter value characteristics.
As a result, in some cases, it is not possible to perform data reproduction by performing coarse adjustment, and address detection becomes impossible, or the jitter value at the start of fine adjustment is too bad, and the optimum value is drawn. There is a possibility that fine adjustment itself cannot be performed, for example, it becomes impossible to perform the adjustment.

In recent years, a drive device has been developed that uses a common optical pickup for media having different laser wavelengths, such as CD, DVD, and BD. The pickup may have an axial deviation as shown in FIG. 13 due to problems such as design constraints, and countermeasures are particularly required.
Further, the characteristic deviation as shown in FIG. 13 becomes particularly noticeable when a so-called bad disk with low manufacturing accuracy is loaded, and data reproduction becomes impossible as described above, or jitter value at the start of fine adjustment. Is particularly likely to fall into a situation where it is impossible to pull in the optimum value due to being too bad.

Therefore, in the present invention, in view of the above problems, the optical recording medium driving device is configured as follows.
That is, the optical recording medium is irradiated with laser light and reflected light is detected, and at least head means having a focus servo mechanism, a spherical aberration correction mechanism, and an astigmatism correction mechanism for laser light are provided.
In addition, tracking error signal generation means for generating a tracking error signal based on the reflected light detected by the head means is provided.
Further, focus servo means is provided that drives 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.
In addition, spherical aberration correction means for driving the spherical aberration correction mechanism and executing spherical aberration correction based on the spherical aberration correction value is provided.
Also provided is astigmatism correction means for driving the astigmatism correction mechanism based on the astigmatism correction value to execute astigmatism correction.
Further, a focus bias means for adding a focus bias to a focus servo loop including the focus servo means, and a control means are provided.
The control means is optimized using the amplitude value of the tracking error signal obtained when the astigmatism correction value is sequentially changed while the focus bias and spherical aberration correction value are fixed as an evaluation index. An astigmatism optimum point search process for searching for an astigmatism correction value,
Astigmatism correction processing is executed in which the optimum astigmatism correction value obtained by the astigmatism optimum point search process is set in the astigmatism correction means and astigmatism correction is executed.

Here, as a result of the experiment conducted by the present applicant on the axial deviation of each characteristic as described with reference to FIG. 13, the cause of the occurrence is astigmatism. It was. That is, the astigmatism generated in the laser beam is shifted between the spherical aberration correction value (and focus bias) that maximizes the tracking error signal amplitude and the spherical aberration correction value (and focus bias) that maximizes the reproduction performance evaluation value. It is that it is generated.
Therefore, in the present invention, as described above, the tracking error signal amplitude value obtained when the astigmatism correction value is changed with the focus bias and the spherical aberration correction value being fixed as described above is the optimum value. The astigmatism correction value to be searched is searched, and astigmatism correction is performed with this optimum astigmatism correction value.
Here, for example, when no correction is performed for astigmatism, as shown in FIG. 4A later, the optimum point for reproduction performance (the spherical aberration correction value (and the focus for which the reproduction performance evaluation value is the best) (Bias value)) and tracking performance optimum point (spherical aberration correction value (and focus bias value) with the best (maximum) tracking error signal amplitude value)). On the other hand, by performing astigmatism correction as in the present invention, for example, as shown in FIG. 4B, the optimum point for reproduction performance and the optimum point for tracking performance are matched. Can be closer. That is, the fact that the optimum point for reproduction performance and the optimum point for tracking performance are close in this way means that the axial deviation between the tracking error signal amplitude characteristic and the reproduction performance evaluation value characteristic as shown in FIG. It means being suppressed.

  As described above, according to the present invention, by performing astigmatism correction using the tracking error signal as an evaluation index, the optimum point for reproduction performance and the optimum point for tracking performance for the focus bias and spherical aberration correction value are obtained. It is possible to make them closer to each other and to suppress axial deviation between the tracking error signal amplitude characteristic and the reproduction performance evaluation value characteristic with respect to the focus bias / spherical aberration correction value. As a result, the data reproduction cannot be performed by performing coarse adjustment as in the conventional case, and the address detection becomes impossible, and the reproduction performance evaluation value at the start of fine adjustment is too bad and is optimal. It is possible to effectively prevent the occurrence of such a situation that it becomes impossible to pull in a certain value. In other words, it is possible to appropriately adjust the focus bias / spherical aberration correction value.

  In addition, the fact that the optimum point for reproduction performance of the focus bias / spherical aberration correction value and the optimum point for tracking performance are close to each other as described above means that the reproduction performance evaluation value is used as an evaluation index by fine adjustment processing. As long as the focus bias / spherical aberration correction value is adjusted, the tracking performance can be improved as well. In other words, in the conventional case in which astigmatism correction is not performed, tracking performance is sacrificed and deteriorated by performing fine adjustment processing using the reproduction performance evaluation value as an evaluation index. According to the invention, it is possible to achieve both improvement in reproduction performance and improvement in tracking performance by performing fine adjustment processing.

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 an internal configuration of a disk drive device as an embodiment of an optical recording medium driving device of the present invention.
First, the disc drive apparatus of this example is configured to be compatible with each of an optical disc 50 shown in the figure, which is a CD (Compact Disc), a DVD (Digital Versatile Disc), and a BD (Blu-ray Disc: registered trademark). Accordingly, the optical pickup 1 in the drawing is configured to irradiate laser beams having different wavelengths λ = 780 nm, 650 nm, and 405 nm using a common laser diode and a common objective lens. A so-called three-wavelength monocular pickup is employed.
The disk drive device is a reproduction-only device that can only reproduce data. In this case, it is possible to reproduce not only the optical disk 50 as a read-only ROM disk in which data is stored by a combination of pits and lands but also a write-once or rewritable optical disk 50 as a recordable type. For example, in the case of a BD, a BD-R (write-once type), a BD-RE (rewritable type), or the like.

In FIG. 1, an optical disk 50 is loaded on a turntable (not shown) when loaded in a disk drive device, and is rotated at a constant linear velocity (CLV) by a spindle motor 2 during recording / reproducing operations.
At the time of reproduction, information recorded as pits or marks on a track on the optical disk 50 is read by the optical pickup (optical head) 1.
In the optical disk 50, for example, physical information of the disk is recorded as embossed pits or wobbling grooves as reproduction-only management information. The information is also read out by the optical pickup 1. Further, ADIP information embedded as wobbling of the groove track is recorded on the recordable optical disc 50, but the optical pickup 1 can also read the ADIP information.

In the optical pickup 1, 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, a laser beam is irradiated onto the disk recording surface via the objective lens, and An optical system or the like for guiding the reflected light to the photodetector is formed. In this case, the laser diode is configured to be capable of alternatively outputting laser beams having wavelengths of 780 nm, 650 nm, and 405 nm.
In the optical pickup 1, the objective lens is held so as to be movable in a tracking direction and a focus direction by a biaxial mechanism.
The entire optical pickup 1 can be moved in the radial direction of the disk by a thread mechanism 3.
The configuration of the optical system in the optical pickup 1 in this example will be described later.

Reflected light information from the optical disk 50 is detected by a photodetector, and is supplied to the matrix circuit 4 as an electric signal corresponding to the amount of received light.
The matrix circuit 4 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 as photodetectors, and generates necessary signals by matrix calculation processing.
For example, an RF signal (reproduction data signal RF) corresponding to a reproduction signal from the optical disc 50, a focus error signal FE for servo control, a tracking error signal TE, and the like are generated.
Further, a push-pull signal PP is generated as a signal related to groove wobbling, that is, a signal for detecting wobbling.
The RF signal output from the matrix circuit 4 is supplied to the data signal processing circuit 5, the focus error signal FE and the tracking error signal TE are supplied to the servo circuit 11, and the push-pull signal PP is supplied to the wobble signal processing circuit 7, respectively.
Further, in this case, the tracking error signal TE is also supplied to the system controller 10 so as to be used as an evaluation index at the time of coarse adjustment of a spherical aberration correction value, which will be described later, or when searching for an optimum point of astigmatism.

  The data signal processing circuit 5 performs binarization processing on the RF signal and supplies the obtained binary data string to the subsequent decoder 6. The data signal processing circuit 5 also performs A / D conversion processing of the RF signal and reproduction clock generation processing by the PLL in addition to the binarization processing.

At this time, in the data signal processing circuit 5, in response to the case where the above-described BD is loaded as the optical disc 50, PR (Partial Response) equalization processing, Viterbi decoding (maximum likelihood decoding) is performed as the binarization processing. Process. That is, a binary data string is obtained by a partial response maximum likelihood decoding process (PRML detection method: Partial Response Maximum Likelihood detection method).
In particular, the data signal processing circuit 5 in this embodiment has an evaluation value calculation function as shown in the figure. That is, the data signal processing circuit 5 calculates, as this evaluation value calculation function, a reproduction performance evaluation value that serves as an evaluation index for reproduction performance based on the RF signal. There are various reproduction performance evaluation values based on such RF signals. Specifically, in the data signal processing circuit 5 of this example, as the reproduction performance evaluation values, partial processing is performed as binarization processing as described above. Corresponding to the response maximum likelihood decoding process, an evaluation value calculated based on the Euclidean distance between the ideal response and the input signal (equalized signal) is calculated. More specifically, an evaluation value called PRSNR is calculated.
The method and configuration for calculating the PRSNR are described in Reference Document 1 below, for example.

Reference 1. Japanese Patent Publication No. 3857684

  The reproduction performance evaluation value as the PRSNR, which is generated by the data signal processing circuit 5, is supplied to the system controller 10 as an evaluation value used at the time of adjusting the focus bias and the spherical aberration correction value, which will be described later.

The decoder 6 demodulates the binary data string decoded by the data signal processing circuit 5. That is, data demodulation, deinterleaving, ECC decoding, address decoding, etc. are performed. Thereby, reproduction data from the optical disk 50 is obtained.
The data decoded to the reproduction data by the decoder 6 is transferred to the host interface 8 and transferred to the host device 100 based on an instruction from the system controller 10.
The host device 100 is, for example, a computer device or an AV (Audio-Visual) system device.

When the optical disc 50 is a recordable disc, ADIP information processing is performed during reproduction.
That is, the push-pull signal PP output from the matrix circuit 4 as a signal related to the wobbling of the groove is converted into wobble data digitized by the wobble signal processing circuit 7. A clock synchronized with the push-pull signal is generated by the PLL process.
The wobble data is MSK demodulated and STW demodulated by the ADIP demodulation circuit 8, demodulated into a data stream constituting an ADIP address, and supplied to the address decoder 9.
The address decoder 9 decodes the supplied data, obtains an address value, and supplies it to the system controller 10.

The servo circuit 11 generates various servo drive signals for focus, tracking, and thread from the focus error signal FE and tracking error signal TE from the matrix circuit 4, and executes the servo operation.
That is, a focus drive signal and a tracking drive signal are generated according to the focus error signal FE and the tracking error signal TE, and the focus coil and tracking coil of the biaxial mechanism in the optical pickup 1 are driven. As a result, an optical pickup 1, a matrix circuit 4, a servo circuit 11, a tracking servo loop and a focus servo loop by a biaxial mechanism are formed.
The servo circuit 11 executes a track jump operation by turning off the tracking servo loop and outputting a jump drive signal in response to a track jump command from the system controller 10.

The servo circuit 11 gives a focus bias to the focus servo loop in accordance with an instruction from the system controller 10.
In addition, the servo circuit 11 supplies a drive signal Sd for correcting spherical aberration to a spherical aberration correction mechanism, which will be described later, provided in the optical pickup 1 in response to an instruction from the system controller 10.
Further, the servo circuit 11 supplies a drive signal AS for astigmatism correction to an astigmatism correction mechanism (to be described later) included in the optical pickup 1 in accordance with an instruction from the system controller 10.

  The servo circuit 11 generates a thread drive signal based on a thread error signal obtained as a low frequency component of the tracking error signal TE, an access execution control from the system controller 10, and the like, and drives the thread mechanism 3 by the thread driver 14. To do. Although not shown, the sled mechanism 3 has a mechanism including a main shaft that holds the optical pickup 1, a sled motor, a transmission gear, and the like. The sled mechanism 3 drives the sled motor according to a sled drive signal. The slide movement is performed.

The spindle servo circuit 12 performs control to rotate the spindle motor 2 at CLV.
The spindle servo circuit 12 generates the spindle error signal by obtaining the clock generated by the PLL processing for the wobble signal as the current rotational speed information of the spindle motor 2 and comparing it with predetermined CLV reference speed information. To do.
Alternatively, when the optical disk 50 is a read-only ROM disk, the reproduction clock generated by the PLL in the data signal processing circuit 5 becomes the current rotational speed information of the spindle motor 2, and this is used as a predetermined CLV reference speed. A spindle error signal is generated by comparing with the information.
The spindle servo circuit 12 outputs a spindle drive signal generated according to the spindle error signal, and causes the spindle driver 13 to execute CLV rotation of the spindle motor 2.
Further, the spindle servo circuit 12 generates a spindle drive signal in response to a spindle kick / brake control signal from the system controller 10, and also 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 10 formed by a microcomputer.
The system controller 10 executes various processes in accordance with commands from the host device 100 given via the host interface 8.
For example, when a read command requesting transfer of certain data recorded on the optical disk 50 is supplied from the host device 100, the system controller 10 first performs seek operation control using the instructed address as a target. . That is, the servo circuit 11 is instructed to execute the access operation of the optical pickup 1 that targets the address specified by the read command.
Thereafter, operation control necessary for transferring the data in the designated data section to the host device 100 is performed. That is, signal reading from the optical disc 50 and reproduction processing for the read signal in the data signal processing circuit 5 and the decoder unit 7 are executed, and the requested data is transferred.

  Further, a memory 16 is provided for the system controller 10. In this example, the memory 16 stores the optimum astigmatism correction value (optimal AS correction value 16a) obtained by the astigmatism optimum point search process performed at the timing before factory shipment as described later. Will be.

Although the example of FIG. 1 has been described as a disk drive device connected to the host device 100, the disk drive device of the present invention may have 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 reproduction is performed in accordance with a user operation and a terminal portion for inputting / outputting various data is formed.
Of course, there are various other examples of the configuration of the disk drive device. For example, a configuration capable of recording can be used. That is, the disk drive device of the present invention may be in the form of a recording / reproducing device or a recording-only device.

[Optical pickup optical system]
FIG. 2 shows the configuration of the optical system of the optical pickup 1 shown in FIG.
In FIG. 2, laser light output from a semiconductor laser (laser diode) 81 is made parallel light by a collimator lens 82 and then enters a liquid crystal panel 86 as an astigmatism correction mechanism.
The liquid crystal panel 86 is configured such that a region through which laser light is transmitted is divided into a plurality of panel portions along the circumferential direction, for example, and an applied voltage can be controlled for each panel portion. As described above, since the applied voltage level can be controlled for each panel unit, the phase given to the transmitted light can be controlled for each panel unit, and thereby, for example, 0 degrees (90 degrees). It is possible to adjust (correct) astigmatism in a required angular direction such as a direction or 45 degrees (135 degrees). In this case, the driving signal Ad in the figure is a driving signal for each panel unit, and the driving signal for each panel unit corresponding to the astigmatism correction value set based on the instruction from the system controller 10 as described later is used. The drive signal Ad is supplied to the liquid crystal panel 86.

  The laser light that has passed through the liquid crystal panel 86 passes through the beam splitter 83, travels through the movable lens 87 and the fixed lens 88 as a spherical aberration correction lens group, and is irradiated from the objective lens 84 onto the optical disk 50. The movable lens 87 and the fixed lens 88 as the spherical aberration correction lens group are called expanders. For this reason, in particular, the movable lens 87 and the fixed lens 88 may be referred to as expander lenses 87 and 88.

  Reflected light from the optical disk 50 is reflected by the beam splitter 83 through the objective lens 84 → the fixed lens 88 → the movable lens 87 and is incident on the detector 92 through the collimator lens (condensing lens) 85.

In this 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 a focus servo operation and a tracking servo operation are performed.
The expander lenses 87 and 88 have a function of changing the diameter of the laser beam. That is, the movable lens 87 is movable in the J direction, which is the optical axis direction, by the actuator 90, and the diameter of the laser light applied to the optical disc 50 is adjusted by this movement.
In other words, the spherical aberration correction can be executed by performing the control for causing the actuator 90 to move back and forth.

[Servo circuit configuration example]
Next, FIG. 3 shows an internal configuration example of the servo circuit 11 shown in FIG.
3, the focus error signal FE and the tracking error signal TE from the matrix circuit 4 shown in FIG. 1 are converted into digital data by the A / D converters 20 and 21 in the servo circuit 11 and inputted to the DSP 35, respectively. The
The DSP 35 has functions as a focus servo calculation unit 25 and a tracking servo calculation unit 28.

The focus error signal FE from the A / D converter 20 is input to the focus servo calculation unit 25 via the adder 22.
The focus servo calculation unit 25 performs predetermined calculations such as filtering for phase compensation and loop gain processing on the focus error signal FE input as digital data, and generates and outputs a focus servo signal. . The focus servo signal is converted into an analog signal by the D / A converter 30 (including PWM and PDM), and then input to the focus driver 33 to drive the focus actuator. That is, a current is supplied to the focus coil of the biaxial mechanism 91 that holds the objective lens 84 in the optical pickup 1 to execute the focus servo operation.

  The tracking servo calculation unit 28 performs predetermined calculations such as filtering for phase compensation and loop gain processing on the tracking error signal TE input as digital data to generate and output a tracking servo signal. . The tracking servo signal is converted into an analog signal by the D / A converter 31 (including PWM and PDM) and then input to the tracking driver 34 to drive the tracking actuator. That is, a current is supplied to the tracking coil of the biaxial mechanism 91 that holds the objective lens 84 in the optical pickup 1 to execute the tracking servo operation.

In the DSP 35, functional parts for focus bias addition, spherical aberration correction value setting, and astigmatism correction value setting are provided.
The adder 22 adds a focus bias to the focus error signal FE. The focus bias value to be added is such that an appropriate focus bias is added to the focus servo loop when the focus bias setting unit 23 outputs a focus bias value set in an adjustment process described later.

In the spherical aberration correction value setting unit 24, the setting control unit 26 sets a spherical aberration correction value for the spherical aberration correction mechanism. The set spherical aberration correction value is converted into an analog signal by the D / A converter 29 and supplied to the spherical aberration correction driver 32.
The spherical aberration correction driver 32 is a circuit that supplies the drive signal Sd to the actuator 90 that moves the expander lens 87 shown in FIG. That is, with such a configuration, the spherical aberration correction driver 32 drives the spherical aberration correction mechanism in the optical pickup 1 based on the spherical aberration correction value supplied from the spherical aberration correction value setting unit 24.

In the astigmatism correction value setting unit 36, the astigmatism correction value for the astigmatism correction mechanism is set by the setting control unit 26. The astigmatism correction value setting unit 36 determines the value of the drive signal of each panel unit of the liquid crystal panel 86 shown in FIG. 2 from the set astigmatism correction value. Then, the drive signals of the respective panel units whose values are determined in this way are converted into analog signals by the D / A converter 37 and supplied to the astigmatism correction driver 38.
The astigmatism correction driver 38 supplies a drive signal to each panel unit. That is, the drive signal Ad is supplied to the liquid crystal panel 86. With this configuration, the astigmatism correction driver 38 drives the astigmatism correction mechanism in the optical pickup 1 based on the set astigmatism correction value.

  The setting control unit 26 sets a setting value in the focus bias setting unit 23, a setting value in the spherical aberration correction value setting unit 24, and a setting value in the astigmatism correction value setting unit 36. For example, it is set to a value stored in the illustrated non-volatile memory 27, or each set value is changed in accordance with an instruction from the system controller 10.

[Astigmatism correction]
Here, the disk drive apparatus of the present example described above includes a focus bias / spherical aberration correction mechanism, and can adjust (correct) the focus bias / spherical aberration correction value. As described above, the correction of the focus bias / spherical aberration correction value is to be performed especially for the BD, and the correction of the focus bias / spherical aberration correction value is also performed in the disk drive apparatus of this example. The processing is to be executed in response to loading of a BD.
For confirmation, the focus bias / spherical aberration correction value correction processing (including the astigmatism correction processing associated therewith) as an embodiment described below is loaded as a BD as the optical disc 50. Specifically, after the optical disc 50 is loaded, it is first determined whether or not it is a BD (whether it is at least a CD / DVD or a BD). The determination is performed, and the optical disk 50 loaded by this determination is executed in response to the case where the optical disk 50 is BD (any one of BD-ROM, BD-R, and BD-RE).

  By the way, as described above, when adjusting the focus bias / spherical aberration correction value as described above, rough adjustment of the spherical aberration correction value using the tracking error signal TE as an evaluation index is performed in advance. The In other words, by performing rough adjustment of spherical aberration correction value using the tracking error signal amplitude as an evaluation index, spherical aberration correction deteriorated so that tracking servo is not required when fine adjustment of focus bias and spherical aberration correction value is performed. It is possible to prevent the value from being selected, and to perform the fine adjustment operation appropriately.

  However, as described with reference to FIG. 13, the spherical aberration correction value adjusted by such coarse adjustment is not necessarily a good position for the reproduction performance evaluation value. It is not possible to reproduce the data by performing the above, making fine adjustments such as impossible to detect the address, or the position at the start of the fine adjustment is too bad to be drawn to the optimum value. There was a possibility that it would be impossible to do it.

Here, the cause of occurrence of such a problem, the tracking error signal characteristic with respect to the focus bias / spherical aberration correction value as shown in FIG. 13 and the characteristic of the reproduction performance evaluation value in the axial direction are shown. The applicant has ascertained that the cause of the deviation is astigmatism from the experiment.
FIG. 4A shows a change characteristic of PRSNR (reproduction performance evaluation value) with respect to the change of the spherical aberration correction value (SA) (black circle plot in the figure) and tracking error when no correction is made for astigmatism. An example of the change characteristic of the signal TE (black square plot) is shown.
As shown in FIG. 4A, when no astigmatism correction is performed, the spherical aberration correction value (the optimum point for reproduction performance in the figure) with the reproduction performance evaluation value being the best (maximum) and Therefore, there is a deviation from the spherical aberration correction value (the optimum point for tracking performance in the figure) that makes the tracking error signal amplitude the best (maximum).
In this figure, as an example, only the reproduction performance evaluation value / tracking error signal TE change characteristic with respect to the change in the spherical aberration correction value is illustrated, but the reproduction performance evaluation value / tracking error signal TE change characteristic with respect to the focus bias change. However, when the astigmatism correction is not performed, similarly, a deviation occurs between the optimum point for reproduction performance and the optimum point for tracking performance. That is, when astigmatism correction is not performed, there is a difference between the optimum point for reproduction performance of the focus bias / spherical aberration correction value and the optimum point for tracking performance of the focus bias / spherical aberration correction value.

By the way, as can be understood from the above description, in the adjustment of the focus bias / spherical aberration correction value, the order of “rough adjustment of the spherical aberration correction value → fine adjustment of the focus bias / spherical aberration correction value” is performed. Will be adjusted. According to this, in the disc drive apparatus, the actual reproduction operation is performed after the fine bias adjustment is finally adjusted to the focus bias / spherical aberration correction value that provides the best reproduction performance evaluation value. It will be.
Considering that the device is used with the focus bias / spherical aberration correction value adjusted to the optimum reproduction performance evaluation value in this way, astigmatism correction in this case is tracking. It can be considered that the performance optimum point may be performed so as to match the reproduction performance optimum point.

  Therefore, in this example, the focus bias / spherical aberration correction value is fixed at a value that optimizes the reproduction performance evaluation value, and the optimum point for tracking performance is not attracted to the optimum point for reproduction performance. Perform point aberration correction. Specifically, the astigmatism correction value is sequentially changed in a state where the focus bias / spherical aberration correction value is fixed to the best value for the reproduction performance evaluation value, and the amplitude value of the tracking error signal TE obtained at that time is changed. As an evaluation index, the optimum point of the astigmatism correction value is searched. That is, for example, an astigmatism correction value that maximizes the amplitude value of the tracking error signal TE is searched as an optimum astigmatism correction value (optimum astigmatism correction value), and the searched correction value Astigmatism correction is performed.

By performing astigmatism correction by such a method, the optimum point for reproduction performance and the optimum point for tracking performance can be brought closer to each other as shown in FIG. it can.
FIG. 4B also illustrates only the change characteristic of the reproduction performance evaluation value / tracking error signal TE with respect to the change in the spherical aberration correction value, but the reproduction performance evaluation value / tracking error signal TE with respect to the change in the focus bias is illustrated. Similarly, when the astigmatism correction is performed as described above, the optimum point for reproduction performance and the optimum point for tracking performance are also brought close to each other. That is, by performing the astigmatism correction described above, the optimum point for tracking performance and the optimum point for tracking performance of the focus bias / spherical aberration correction value can be brought closer to each other.

For confirmation, the astigmatism optimum point search process performed in the above astigmatism correction will be described with reference to FIG. FIG. 5 shows an operation example corresponding to the case of correcting astigmatism (AS0) in the 0 degree direction as an example.
As can be understood from the above description, in searching for the optimum point of astigmatism in this case, first, the focus bias / spherical aberration correction value is fixed at a value that optimizes the reproduction performance evaluation value. In this state, the amplitude value of the tracking error signal TE when a plurality of astigmatism correction values are shaken as shown in the figure is acquired. Then, the astigmatism correction value when the maximum amplitude value of the tracking error signal TE is obtained based on the amplitude value of the tracking error signal TE obtained in the setting state of each astigmatism correction value in this way. Is obtained as an optimum astigmatism correction value.

By setting the optimum astigmatism correction value obtained by such search processing and performing astigmatism correction, as described above, the optimum point for reproduction performance and the tracking performance for the focus bias / spherical aberration correction value Although the optimum point can be brought closer to each other by matching, the object of the first embodiment is to roughly adjust the spherical aberration correction value as understood from the above description. In other words, it is intended to prevent the occurrence of a situation that hinders the subsequent fine adjustment.
Here, in order to achieve such a target, it is required that the astigmatism correction process described above is executed at least before the coarse adjustment of the spherical aberration correction value is performed.
However, as described above, the adjustment sequence is performed in the order of coarse adjustment of spherical aberration correction value in consideration of tracking servo deviation at the time of fine adjustment → then fine adjustment of focus bias and spherical aberration correction value. There is a need. According to the above description, in order to perform astigmatism correction in this example, it is necessary to fix the focus bias / spherical aberration correction value to a value that optimizes the reproduction performance evaluation value (optimized value). However, the optimum focus bias / spherical aberration correction value is obtained when the fine adjustment is completed. In other words, from this point, it is not possible to obtain the focus bias / spherical aberration correction value that optimizes the reproduction performance evaluation value before the coarse adjustment of the spherical aberration correction value. As described above, the astigmatism correction of this example cannot be performed before the coarse adjustment, and the problem cannot be solved.

Therefore, for the purpose of the first embodiment described above (in order to prevent the occurrence of a situation that hinders subsequent fine adjustment by performing rough adjustment), the optimum astigmatism correction value is set. A method of searching in advance before shipment from the factory is adopted.
Specifically, at the stage before factory shipment,
1) Coarse adjustment of spherical aberration correction value
2) After executing fine adjustment of the focus bias / spherical aberration correction value, and obtaining the setting state of the focus bias / spherical aberration correction value with the best reproduction performance evaluation value,
3) Search for optimal astigmatism correction value (search for optimal astigmatism point)
Execute. Moreover,
4) The optimum astigmatism correction value obtained by the search process is stored in a required storage means (in this case, the memory 16) in the drive device.

  By executing such processing, astigmatism correction using the optimum astigmatism correction value stored in 4) is performed before coarse adjustment of the spherical aberration correction value is performed after factory shipment and when the actual device is used. It can be carried out. That is, at this point, when the spherical aberration correction value is roughly adjusted, the deviation between the optimum point for reproduction performance and the optimum point for tracking performance can be corrected, and thus the coarse adjustment is performed. On the contrary, it is possible to effectively prevent the occurrence of a situation that hinders the subsequent fine adjustment.

  Here, the coarse adjustment of the spherical aberration correction value 1) before factory shipment is performed in a state where astigmatism is not corrected, so the axial directions of the respective characteristics as shown in FIG. However, in various adjustment processes performed on, for example, a production line before factory shipment, the adjustment optical disc 50 manufactured with relatively high accuracy can be used. The rough adjustment of 1) makes it impossible to reproduce data, or the initial position at the time of fine adjustment is so bad that the reproduction performance evaluation value cannot be drawn to the best value. You can never fall. In other words, the axial deviation of each characteristic in this case cannot be as great as when a bad disk is loaded, so that the spherical aberration correction value is slightly disadvantageous in terms of reproduction performance due to the coarse adjustment in 1) above. Although the image is shaken in the correct direction, the focus bias / spherical aberration correction value that provides the best reproduction performance evaluation value can be appropriately searched by the subsequent fine adjustment in 2).

[Processing behavior]
6 and 7 are flowcharts showing processing operations to be performed in order to realize astigmatism correction as the present example described above. FIG. 6 shows a processing operation that should be performed at the time of factory shipment, and FIG. 7 shows a processing operation that should be performed at the time of actual use.
The processing operations shown in FIGS. 6 and 7 are executed by the system controller 10 shown in FIG. 1 based on, for example, a program stored in an internal ROM or the like.
Further, when the processing operations shown in these figures are executed, it is assumed that the optical disk 50 (in particular, the above-described adjustment disk in the case of FIG. 6) is already loaded in the disk drive device. Further, as described above, a determination process for the type of the loaded optical disk 50 (at least whether it is a BD) is performed, and the determination process determines that the disk is a BD. Suppose there is. Further, it is assumed that the focus servo is already turned on.

In FIG. 6, first, in step S101, the generation of an astigmatism optimum point search start trigger is awaited. That is, it waits for the occurrence of a predetermined trigger (for example, input of a predetermined command, etc.) determined in advance to execute the processing from step S102 shown in FIG.
If a search start trigger occurs, rough adjustment processing of the spherical aberration correction value (SA) is executed in step S102. That is, based on the result of obtaining the amplitude value of the tracking error signal TE obtained when the spherical aberration correction value is changed, the spherical aberration correction value when the best amplitude value of the tracking error signal TE is obtained is obtained. Explore.
Specifically, different spherical aberration correction values are sequentially instructed to the setting control unit 26 in the servo circuit 11 shown in FIG. 3 so that different spherical aberration correction values are sequentially given to the spherical aberration correction value setting unit 24. To be set. Then, the amplitude value of the tracking error signal TE obtained in the setting state of each spherical aberration correction value is acquired, and the spherical aberration correction value set when the maximum amplitude value of the tracking error signal TE is obtained is obtained. Obtained as the optimum spherical aberration correction value by coarse adjustment.

In the subsequent step S103, fine adjustment processing of the spherical aberration correction value / focus bias (FB) is executed. That is, spherical aberration when the best reproduction performance evaluation value is obtained based on the result of obtaining the reproduction performance evaluation value (in this case, PRSNR) obtained when the spherical aberration correction value and focus bias are changed. Search for correction values.
Specifically, first, the servo circuit 11 is instructed to turn on the tracking servo, the signal reproduction from the optical disc 50 is executed, and the reproduction performance evaluation value (PRSNR) is calculated by the data signal processing unit 5. State Then, the setting control unit 26 in the servo circuit 11 is instructed sequentially for different combinations of spherical aberration correction values and focus biases, and thereby spherical aberrations set in the spherical aberration correction value setting unit 24 and the focus bias setting unit 23. The combination of correction value and focus bias is changed sequentially.
At this time, for each spherical aberration correction value to be sequentially set by the spherical aberration correction value setting unit 24, each value is selected based on the spherical aberration correction value acquired by the coarse adjustment processing in the previous step S102. (For example, the spherical aberration correction value acquired by the coarse adjustment process and values for several steps before and after the value). By doing so, the spherical aberration correction value obtained by the coarse adjustment is reflected at the time of fine adjustment, and it is possible to prevent the servo from being lost at the time of fine adjustment.
Then, as described above, the spherical aberration correction value / focus bias setting of each group is set while sequentially changing the combination of the spherical aberration correction value / focus bias set in the spherical aberration correction value setting unit 24 / focus bias setting unit 23. The playback performance evaluation value obtained in the state is acquired. Further, the focus bias / spherical aberration correction value when the best evaluation value among the obtained evaluation values is obtained is determined as the optimum focus bias / spherical aberration correction value, and these optimum focus biases are determined. By instructing the setting control unit 26 for the spherical aberration correction value, the focus bias setting unit 23 and the spherical aberration correction value setting unit 24 are set with the determined optimum values.
The PRNSR used as the reproduction performance evaluation value in this example is an evaluation value indicating that the larger the value is, the better the reproduction performance is. Therefore, as the optimum focus bias / spherical aberration correction value, the focus bias / spherical aberration correction value when the maximum PRSNR value is obtained is determined.

In the next step S104, an astigmatism optimum point search process is executed.
That is, in this case, the focus bias / spherical aberration correction value has already been set to the best value for the reproduction performance evaluation value by the fine adjustment processing in step S103, and astigmatism correction is performed in this state. Based on the result of acquiring the amplitude value of the tracking error signal TE when the value is changed, an optimum astigmatism correction value is searched for. Specifically, in step S104, different astigmatism correction values are sequentially set in the astigmatism correction value setting unit 36 by sequentially instructing the setting control unit 26 with different astigmatism correction values. On the other hand, the amplitude value of the tracking error signal TE obtained in the setting state of each astigmatism correction value is acquired. Then, the astigmatism correction value when the maximum amplitude value among the acquired amplitude values is obtained is determined as the optimum astigmatism correction value.

In the subsequent step S105, the optimum astigmatism correction value (optimal AS correction value) obtained by the search process in step S104 is stored in the memory. In this case, the optimum astigmatism correction value is stored in the memory 16 as indicated by the dotted line in FIG. 1 (optimal astigmatism correction value 16a in the figure).
As described above, since the optimum astigmatism correction value is stored in the required storage means in the drive device at the time of shipment from the factory, the spherical aberration correction value can be roughly adjusted in actual use as described below. The correction can be made to the optimum astigmatism correction value before it is performed.

FIG. 7 shows processing operations to be performed in response to actual use.
It is assumed that the processing operation shown in FIG. 7 is executed as a part of start-up processing such as focus adjustment after loading the optical disc 50, disc type determination, and various parameter changes corresponding thereto. In this case, the timing at which the processing operation shown in this figure is started at any timing in the series of startup processes may be selected as appropriate, and is not particularly limited here.

  In FIG. 7, first, in step S201, processing for setting the optimum astigmatism correction value stored in the memory is executed. That is, in this case, the optimum astigmatism correction value 16a stored in the memory 16 is instructed to the setting control unit 26 so that the astigmatism correction value setting unit 36 sets the optimum astigmatism correction value 16a. Astigmatism correction is executed with the optimum astigmatism correction value 16a. By performing astigmatism correction based on the setting processing in step S201, a state in which the optimum point for reproduction performance and the optimum point for tracking performance for the focus bias / spherical aberration correction value are brought close to each other is obtained. You can

In the next step S202 → step S203, a spherical aberration correction value coarse adjustment process → a spherical aberration correction value / focus bias fine adjustment process is executed. The contents of the spherical aberration correction value coarse adjustment process and the spherical aberration correction value / focus bias fine adjustment process are the same as those in steps S102 and S103, respectively, and therefore will not be described again.
As the processing operation corresponding to the actual use as the first embodiment, the fine adjustment process in step S203 is executed, and the process ends. The process surrounded by the broken line in the figure will be described later.

  When the astigmatism correction of this example is performed as described above, as shown in FIG. 4B, the optimum point of reproduction performance and the tracking performance of the focus bias / spherical aberration correction value. It can be brought close to match the optimal point. As described above, before the factory shipment, for example, an astigmatism optimum point is searched in advance using an adjustment disk or the like, and the optimum astigmatism correction value is stored in the memory in advance. In some cases, astigmatism correction can be performed before the coarse adjustment process, and as a result, the coarse adjustment process may adversely affect the subsequent fine adjustment process. Can be effectively prevented.

Further, by performing astigmatism correction in this example, the following effects can be obtained in addition to solving the problem related to the rough adjustment.
That is, according to the astigmatism correction of this example, the optimum point for reproduction performance and the optimum point for tracking performance of the focus bias / spherical aberration correction value can be brought close to each other. Are matched, the focus bias / spherical aberration correction value is adjusted using the playback performance evaluation value as an evaluation index as a fine adjustment process. The TE amplitude value can be corrected to the best value.
As can be understood from this, the astigmatism correction of this example can be performed by adjusting the focus bias / spherical aberration correction value to the optimum point for reproduction performance by fine adjustment, and at the same time, tracking performance. It is also possible to improve. In other words, when the fine adjustment to match the optimal point for playback performance was performed at the sacrifice of the tracking performance, this example is improved and the tracking performance is improved. be able to.

Here, by performing the astigmatism correction of this example in this way, only the operation of adjusting the focus bias / spherical aberration correction value to the optimum point for reproduction performance by fine adjustment processing is performed. Although it is possible to improve the performance and the tracking performance at the same time, the optimum astigmatism is obtained when only the processing in actual use as the first embodiment described above is performed. Since the correction value is a value searched with the adjustment disk loaded before shipment from the factory, the astigmatism correction based on the optimum astigmatism correction value can absorb variations among drive devices. However, variations in characteristics for each optical disk 50 to be loaded cannot be absorbed.
Therefore, as a process at the time of actual use, the search for the optimum astigmatism point and the correction process to the searched optimum astigmatism correction value can be performed every time the optical disk 50 is loaded.

When such an operation as a modified example of the first embodiment is realized, the fine adjustment process in step S203 is completed so as to be surrounded by the broken line in FIG. A search process for the optimal aberration point is executed. Then, in the next step S205, processing for setting the optimum astigmatism correction value obtained by the search processing in step S204 is executed, and astigmatism correction using the optimum astigmatism correction value is executed. To be.
Note that the content of the search processing in step S204 is the same as the content of the search processing in step S104 in FIG. The setting process in step S205 is a process of instructing the setting control unit 26 about the optimum astigmatism correction value obtained in step S204.

If such a process as a modified example is executed, the optimum astigmatism correction value 16a based on the fixed value differs from the optimum value on the optical disk 50 due to the characteristic variation for each loaded optical disk 50. Even in such a case, by searching for the optimum astigmatism correction value for each optical disc 50, it is possible to bring the optimum point for reproduction performance and the optimum point for tracking performance closer to each other more reliably. That is, it is possible to absorb the variation for each optical disc 50 and to achieve both the improvement of the reproduction performance by fine adjustment and the improvement of the tracking performance more reliably.

<Second Embodiment>

Next, a second embodiment will be described.
In the second embodiment, the reproduction performance evaluation value used as an evaluation index at the time of fine adjustment of the focus bias / spherical aberration correction value is of the ROM type or the recordable type. Switching is performed according to the determination result.
FIG. 8 is a block diagram showing an example of the internal configuration of the disk drive device according to the second embodiment. In FIG. 8, parts that are the same as those already described with reference to FIG.
In FIG. 8, the disk drive device in this case is different from the disk drive device shown in FIG. 1 in that the RF signal from the matrix circuit 4 is also input to the system controller 10.

Here, in the first embodiment, PRSNR is used as an evaluation index at the time of fine adjustment of the focus bias / spherical aberration correction value. When PRSNR is used as the evaluation index in this way, It was confirmed that the phenomenon shown in FIG. 9 occurred.
FIGS. 9A and 9B show contours of change characteristics of the PRSNR value with respect to changes in the focus bias and the spherical aberration correction value. In these characteristic diagrams, the horizontal axis is the spherical aberration correction value (SA), the vertical axis is the focus bias (FB), and the contour lines indicate that the PRSNR values increase in ascending order of the numbers shown in the figure.

In FIG. 9, FIG. 9 (a) shows the adjacent track on both sides with respect to the range in which signal reproduction is performed when obtaining the reproduction performance evaluation value (in this case, PRSNR) at the time of fine adjustment (the adjustment use range). FIG. 9B shows the characteristics when data is already recorded on both tracks adjacent to the adjustment use range. FIG. 9B shows the characteristics when the data is recorded. As can be seen from the graph, when both tracks in the adjustment use range are unrecorded, the range in which a good value of PRSNR can be obtained with respect to the change in the focus bias / spherical aberration correction value tends to be widened. When the track has been recorded, the range in which a good value of PRSNR can be obtained tends to be narrow with respect to the change in the focus bias / spherical aberration correction value.
That is, according to this, there is a difference in the accuracy of the optimum value of the focus bias / spherical aberration correction value obtained by fine adjustment between the case where data is recorded on the adjacent track in the adjustment use range and the case where data is not recorded. It will be. Specifically, when the adjacent track is not recorded, the adjustment accuracy of the focus bias / spherical aberration correction value by the fine adjustment is remarkably lowered as compared with the case where the adjacent track is recorded.

Here, as an example, the characteristics when PRSNR is used as an evaluation index have been illustrated. However, as a reproduction performance evaluation value, for example, an evaluation calculated based on an error or deviation from an ideal value of a difference metric such as so-called DMj. Even when the value is used, the same characteristics as in FIGS. 9A and 9B can be obtained.
For the DMj, see, for example, Reference Document 2 below.

Reference 2. JP 2007-128622 A

Here, in order to prevent such a difference in adjustment accuracy from occurring, an adjustment use range in which adjacent tracks have been recorded may be used. Specifically, the following methods are conceivable as methods for that purpose.
For example, a plurality of adjustment use range candidates are set in advance, and first, it is checked whether or not data has been recorded for one adjustment use range and a track adjacent thereto. . If the data has been recorded, fine adjustment processing of the focus bias / spherical aberration correction value is performed within the determined adjustment use range. On the other hand, if it has not been recorded, the adjustment use range is determined as a new candidate, and similarly, recorded / unrecorded check including the adjacent track is performed. Finally, when there is an adjustment use range in which data is recorded including adjacent tracks, fine adjustment processing is performed in the adjustment use range.

  However, for example, when such a method is adopted, it is only necessary to check data recorded / unrecorded only for the adjustment use range, but it is not necessary to check recorded / unrecorded for adjacent ranges. As a result, there is a possibility that the processing load required for the fine adjustment processing and the time required to complete the fine adjustment may be increased.

Therefore, in the present embodiment, it is determined whether the loaded optical disk 50 is a ROM type or a recordable type, and when it is a recordable type (that is, there is a possibility that an unrecorded portion of data exists). Adopts a method of switching the evaluation index used at the time of fine adjustment to an evaluation index that hardly changes in characteristics due to recording / unrecording of adjacent tracks as shown in FIG. 9 instead of PRSNR.
Specifically, switching to the RF signal amplitude is performed as an evaluation index that hardly causes the characteristic change due to the recording / unrecording of the adjacent track.

FIGS. 10A and 10B show the characteristics of the RF signal amplitude when the adjacent track is unrecorded / recorded. Also in this case, the characteristics are indicated by contour lines with the spherical axis correction value (SA) on the horizontal axis and the focus bias (FB) on the vertical axis, and indicate that the values are larger in ascending order of the numbers given in the figure. FIG. 10A shows the change characteristic of the RF signal amplitude with respect to the change in the focus bias and the spherical aberration correction value when the adjacent tracks on both sides are unrecorded. FIG. 10B shows the adjacent tracks on both sides. The same characteristics are shown when recorded.
Comparing these figures, when the RF signal amplitude is used as a reproduction performance evaluation index, a good value can be obtained with respect to the change in the focus bias / spherical aberration correction value regardless of whether the adjacent track is recorded or not recorded. It can be confirmed that the range does not substantially change, and the intervals between the contour lines are both well packed. That is, from this, when the RF signal amplitude is used as an evaluation index, there is a difference in the adjustment accuracy of the focus bias / spherical aberration correction value by fine adjustment regardless of whether the adjacent track in the adjustment use range is recorded or not recorded. It can be understood that there is almost no occurrence and adjustment accuracy can be improved.

  As can be understood from this description, according to the method of this example, the evaluation index at the time of fine adjustment is switched to the RF signal amplitude in accordance with the case where a recordable disc is loaded as described above. Regardless of recording / non-recording of adjacent tracks in the range, it is possible to ensure good adjustment accuracy without causing almost any difference in the adjustment accuracy of the focus bias / spherical aberration correction value by fine adjustment. In other words, according to this, as in the method exemplified above, the adjustment accuracy by fine adjustment can be achieved without checking whether the data has been recorded / unrecorded up to the range including the use range during adjustment and the adjacent track. As a result, as compared with the case where the above-described method is employed, it is possible to reduce the processing load required for fine adjustment and shorten the processing time.

FIG. 11 is a flowchart showing the processing operation to be executed in order to realize the operation as the second embodiment described above.
The processing operation shown in FIG. 11 is executed by the system controller 10 shown in FIG. 8 based on a program stored in a built-in ROM or the like, for example.
Further, since the processing operation shown in this figure is processing related to selection of an evaluation index used in the fine adjustment processing of the focus bias / spherical aberration correction value, at least step S203 shown in FIG. 7 (or FIG. 6). In step S103) before the fine adjustment processing of the focus bias / spherical aberration correction value is executed, the selection processing in step S302 or S303 in the drawing is performed at a timing that is completed.
For confirmation, as can be understood from the fact that PRSNR is used as an evaluation index for BD, the processing operation shown in this figure also shows that the loaded optical disc 50 is a BD. It will be done correspondingly. In other words, actually, a determination process is performed before the step S301 to determine whether the loaded optical disk 50 is a BD or not, and a determination result indicating that the optical disk 50 is a BD is obtained by the determination process. In this case, the process shown in this figure is executed.

  In FIG. 11, first, in step S301, it is determined whether or not the loaded optical disk 50 is a ROM type or a recordable type (R, RE). Whether the loaded optical disc 50 is a ROM type or a recordable type can be determined based on, for example, the result of measuring the reflectance of the optical disc 50 or the like. Alternatively, it may be performed based on the result of reproducing information for discriminating the disc type recorded on the optical disc 50.

  If it is determined in step S301 that the loaded optical disk 50 is a ROM type, the process proceeds to step S302, and PRSNR is selected as an evaluation index used during fine adjustment.

  On the other hand, if it is determined in step S301 that the loaded optical disk 50 is a recordable type, the process proceeds to step S303, and the amplitude value of the RF signal is selected as an evaluation index used during fine adjustment.

Although not shown in the figure, in the case of the disk drive apparatus according to the second embodiment, in step S203 (or step S103 in FIG. 6) shown in FIG. The processing content is changed so that the fine adjustment processing using the evaluation index is performed. Specifically, when PRSNR is selected in step S302, fine adjustment processing is executed using the PRSNR supplied from the data signal processing unit 5 as an evaluation index. When the RF signal amplitude is selected in step S303, fine adjustment processing is executed using the amplitude value of the RF signal input from the matrix circuit 4 as an evaluation index.

<Modification>

Although the embodiments of the present invention have been described above, the present invention should not be limited to the specific examples described above.
For example, in the description so far, when performing astigmatism correction, the focus bias / spherical aberration correction value set (fixed) when searching for the optimum point of astigmatism is set to a value as the optimum point for reproduction performance. Although the case of setting is illustrated, the focus bias / spherical aberration correction value set in performing the astigmatism optimum point search process may be fixed to at least a certain value. That is, if the astigmatism correction of the present invention is performed so as to maximize the tracking error signal amplitude with at least a focus bias / spherical aberration correction value fixed at a certain value, FIG. ) Even if the optimal point for tracking performance does not approach the optimal point for reproduction performance, it can still be corrected so that the optimal point for tracking performance approaches the optimal point for reproduction performance. The focus bias / spherical aberration correction value set at the time of search is not the best value of the reproduction performance evaluation value actually searched, but at least a required value such as a fixed value set in advance as the best value. It only has to be set.
However, in actuality, considering that the device is used in a state in which the focus bias / spherical aberration correction value is set to the best value for the reproduction performance evaluation value by fine adjustment, in response to this, Needless to say, when searching for the optimum point aberration, it is preferable to fix the reproduction performance evaluation value at the best focus bias / spherical aberration correction value.

As described above, the present invention searches for the optimum point of astigmatism using the tracking error signal as an evaluation index with the spherical aberration correction value / focus bias side fixed, when performing astigmatism correction. That is, when searching for the optimum point of astigmatism, only the astigmatism correction value is moved.
However, referring to FIG. 4 (a), when trying to match the optimum point for reproduction performance and the optimum point for tracking performance, considering as appropriate, when the astigmatism correction value is changed sequentially, The first step is to find the optimum point for reproduction performance and the optimum tracking performance for the focus bias / spherical aberration correction value and to search for the astigmatism correction value that can match these optimum points. Is done.
Specifically, in the setting state of each astigmatism correction value, search for the optimum point of the focus bias / spherical aberration correction value using the reproduction performance evaluation value as an evaluation index, and the amplitude value of the tracking error signal TE as the evaluation index The optimum point of the focus bias / spherical aberration correction value is searched, and the optimum point when the reproduction performance evaluation value is used as the evaluation index and the optimum point when the amplitude value of the tracking error signal TE is used as the evaluation index are The astigmatism correction value at the time of coincidence is searched for as the optimum astigmatism correction value.

However, when searching for the optimum point of astigmatism, the focus bias and spherical aberration correction value side must be moved together with the astigmatism correction value. The processing load and processing time required for the search will increase significantly.
On the other hand, in the present invention, only the search for the optimum point of astigmatism using the tracking performance side as an evaluation index is performed with the focus bias and the spherical aberration correction value fixed as described above. As a result, the optimum point for reproduction performance and the optimum point for tracking performance of the focus bias / spherical aberration correction value can be brought close to each other.
As described above, the optimum point for reproduction performance and the optimum point for tracking performance can be brought closer by performing astigmatism correction using only the tracking performance side as an evaluation index with the focus bias / spherical aberration correction value side fixed. This is because, by correcting astigmatism, there is mainly a property that the optimum point side of the tracking performance moves. In other words, the present invention uses this property to search for an astigmatism correction value that actually matches the reproduction performance optimum point and the tracking performance optimum point, as in the method exemplified above. The astigmatism optimum point can be searched more efficiently than the case. Specifically, according to the present invention, the processing load and processing time required for searching for the optimum astigmatism point can be significantly reduced as compared with the case where the above-described method is employed.

  In the description so far, the case where the astigmatism correction of the present invention is performed only corresponding to the BD has been exemplified, but the astigmatism correction of the present invention performs adjustment of spherical aberration correction and focus bias. It can be carried out widely and suitably for optical recording media.

Further, even when the spherical aberration correction value is not adjusted, the astigmatism correction method based on the present invention is applied in correspondence with the case where only the focus bias is adjusted as in the case of DVD, for example. You can also Specifically, in that case, the objective is to match the optimum point for reproduction performance and the optimum point for tracking performance with respect to the focus bias. In this case, the astigmatism optimum point search and astigmatism correction are performed with the focus bias fixed.
In this case as well, when the apparatus is actually used, the optimum point of astigmatism is considered if the focus bias value is finally adjusted to a value that makes the reproduction performance evaluation value the best. It is preferable to set the focus bias value set at the time of searching for a value that makes the reproduction performance evaluation value the best.

In the embodiment, as the coarse adjustment processing, the spherical aberration correction value is simply obtained by acquiring the amplitude value of the tracking error signal TE obtained when a plurality of points are shaken, but other methods are adopted. You can also
For example, first, the spherical aberration correction value is shaken in the + direction and the − direction on the basis of the initial value, and it is determined whether the amplitude value of the tracking error signal TE increases in the + direction or the − direction side. The direction in which the spherical aberration correction value is to be shaken is determined. Thereafter, a plurality of spherical aberration correction values are moved in the determined direction, and based on the result, for example, the spherical aberration correction value at which the amplitude value of the tracking error signal TE is maximized is optimized in the coarse adjustment. It is also possible to take a technique such as obtaining as
In any case, the coarse adjustment may be performed by searching for an optimum spherical aberration correction value based on the tracking error signal amplitude value obtained when the spherical aberration correction value is changed. Yes, and should not be limited to the technique exemplified in the embodiment.

  Further, the fine adjustment processing should not be limited to the method exemplified above. For example, various methods proposed so far, methods proposed in the future, and the like are used as a spherical index with a reproduction performance evaluation value as an evaluation index. Any method for adjusting both the aberration correction value and the focus bias can be employed. In other words, as the fine adjustment processing in the present invention, the optimum focus bias / spherical aberration correction value is determined based on the result of obtaining the reproduction performance evaluation value when both the focus bias / spherical aberration correction value is changed. What should be done.

  Similarly, for the search for the optimum astigmatism point, the optimum astigmatism correction value is determined based on the result of obtaining the tracking error signal amplitude value when at least the astigmatism correction value is changed. If it does, other methods other than the method exemplified above can be adopted.

  In the above description, the optimum point of spherical aberration correction value by coarse adjustment, the optimum point of spherical aberration correction value / focus bias by fine adjustment, and the optimum point of astigmatism correction value by searching for the optimum point of astigmatism The value used as the evaluation index is the best (maximum or the minimum when jitter value is used, etc.). However, it is only necessary to find a point that is appropriately optimized according to a specific search method that is actually taken, such as a point that at least the value of the evaluation index is better than a predetermined value.

Further, according to the description of FIG. 6 and FIG. 7 described above, in the embodiment, the drive device executes different processing before factory shipment and during actual use. And processing performed at the time of actual use can be made common.
Specifically, in this case, it is assumed that the astigmatism correction value obtained by an experiment or the like is stored in advance in the memory 16 before the factory shipment. Then, it is assumed that the common processing based on FIG. 7 as described below is executed before factory shipment and during actual use. That is, the common process to be executed in this case is basically the same as the process shown in FIG. 7, but changes are made to the following points. First, as the processing of step S201, processing for setting astigmatism correction stored in the memory is executed. Further, a process of overwriting the astigmatism correction value stored in the memory with the optimum astigmatism correction value obtained by the search process of step S204 between steps S204 and S205 (referred to as step S204.5 for convenience). Insert.

The operation obtained when the processing based on FIG. 7 is performed in common before factory shipment and during actual use will be described. First, the processing of step S201 is executed before factory shipment. Thus, astigmatism correction using the previously stored astigmatism correction value is performed.
Here, the astigmatism correction value stored in advance before shipment from the factory in this way is determined to be an optimum point with respect to the reproduction performance to some extent although it cannot respond to variations among individual drive devices or disks by experiments. It is possible to calculate a value that can bring the anti-tracking performance optimum point closer. That is, first, correction using such an astigmatism correction value is executed in step S201, so that rough adjustment is performed and data reproduction becomes impossible, or the initial position at the time of fine adjustment is set. Therefore, it is possible to prevent the situation where the reproduction performance evaluation value cannot be drawn to the best value because it is too bad. The focus bias / spherical aberration correction value to be searched can be appropriately searched.
As can be understood from this description, in this case, the focus bias / spherical aberration correction value that provides the best reproduction performance evaluation value by fine adjustment can be appropriately searched. It is not necessary to dare to use the adjustment disk used in the illustrated method.

  After such astigmatism correction in step S201, the process of steps S202 → S203 is executed, so that coarse adjustment of the spherical aberration correction value → fine adjustment of the spherical aberration correction value / focus bias is executed. Thus, an optimum astigmatism point is searched (S204), and thereby an astigmatism correction value that absorbs the characteristic variation on the drive device side is obtained. Subsequently, by executing the process of step S204.5, the astigmatism correction value in the memory 16 is replaced with the astigmatism correction value thus obtained.

  For confirmation, the operation obtained at the time of actual use will be described. First, in the process of step S201, astigmatism correction value replaced by the process before factory shipment as described above is set. To be executed. In other words, this allows the optimum point for reproduction performance and the optimum point for tracking performance to be brought close to each other before the coarse adjustment in the next step S202 is performed, and the coarse adjustment is performed instead. It is possible to prevent subsequent fine adjustment processing from being performed properly. For confirmation, in this case as well, the process of step S205 is performed as a process at the time of actual use, so that astigmatism correction that absorbs the characteristic variation for each loaded optical disk 50 can be performed. It will be possible.

  In the description so far, the case where a liquid crystal panel is used as an astigmatism correction mechanism has been exemplified. However, in addition to this, for example, it is inserted into the optical path from the laser diode to the objective lens in the optical system. Other configurations such as a configuration in which the astigmatism is adjusted by deforming the surface shape of the mirror may be employed.

  In the above description, the case of adopting a configuration corresponding to the case where spherical aberration correction is performed by a so-called expander has been exemplified. However, other spherical surfaces by other configurations such as performing spherical aberration correction using a liquid crystal panel are exemplified. An aberration correction value mechanism can also be adopted.

  In the above description, the disk-shaped recording medium is exemplified as the optical recording medium. However, the present invention is an optical recording medium other than the disk-shaped recording medium for guiding the information reproduction (recording) position. The present invention can be widely and suitably applied to optical recording media on which is formed. An optical recording medium is a recording medium on which information is recorded and reproduced by light irradiation.

In the above description, the case where the optical recording medium driving device of the present invention is applied to a reproduction-only device has been exemplified, but the present invention can also be suitably applied to a recording / reproducing device capable of recording on an optical recording medium. .
When the second embodiment of the present invention is applied to the optical recording medium driving apparatus capable of recording in this way, it is possible to further reduce the processing load and the processing time. In other words, when recording is performed on an optical recording medium, data may not be recorded. In this case, when fine adjustment is performed without using the RF signal amplitude, the adjustment to the adjacent track including the adjustment use range is performed. Although it is necessary to write the test data, if the evaluation index is selected as the RF signal amplitude corresponding to the recordable disc as in the second embodiment described above, the test data is written at the time of adjustment. Since it can be limited to the range, as a result, it can be expected that the processing load can be further reduced and the processing time can be shortened more than when applied to a reproduction-only device.

Further, particularly for the first embodiment, as the reproduction performance evaluation value used as an evaluation index during fine adjustment, an evaluation value calculated based on the Euclidean distance between the ideal response and the equalized signal, such as PRSNR, is exemplified. However, besides this, an RF signal amplitude value or the like can also be used.
In any case, the reproduction performance evaluation value used for fine adjustment may be a value that serves as an evaluation index for reproduction signal quality, and should not be limited to those exemplified in the embodiment.

  Here, in the present invention, the RF signal only needs to be calculated as a reproduction signal from an optical recording medium. For example, when a quadrant detector is used, the RF signal corresponds to a sum signal of detection signals from each detector. It becomes.

  In the present invention, the tracking error signal may be a value calculated as a value representing an error from the track center position of the laser spot position on the optical recording medium, and is specific based on the reflected light signal from each detector. A specific calculation method is not particularly limited. For example, a push-pull signal can be selected as the tracking error signal of the present invention.

1 is a block diagram showing an internal configuration of an optical recording medium driving device as a first embodiment of the present invention. It is the figure which illustrated about the structure of the optical system of the optical pick-up with which the optical recording medium drive device of embodiment is equipped. It is the block diagram shown about the internal structure of the servo circuit with which the optical recording medium drive device of embodiment is equipped. As a diagram for explaining the effect obtained by the astigmatism correction as the embodiment, the PRSNR (reproduction performance evaluation value) with respect to the change of the spherical aberration correction value (SA) when the astigmatism correction is not performed / when it is performed ) And the change characteristic of the tracking error signal TE in comparison with each other. It is a figure for demonstrating the search process of an astigmatism optimal point. It is a flowchart for demonstrating the processing operation (processing before factory shipment) for implement | achieving astigmatism correction as 1st Embodiment. It is a flowchart for demonstrating the processing operation (process at the time of actual use) for implement | achieving astigmatism correction as 1st Embodiment. It is the block diagram shown about the internal structure of the optical recording medium drive device as 2nd Embodiment. FIG. 7 is a diagram showing a change characteristic of a PRSNR value with respect to changes in a focus bias and a spherical aberration correction value by contour lines. It is the figure which showed the change characteristic of RF signal amplitude value with respect to the change of a focus bias and a spherical aberration correction value by the contour line. It is a figure for demonstrating the processing operation for implement | achieving the operation | movement as 2nd Embodiment. The position of the spherical aberration correction value roughly adjusted based on the tracking error signal amplitude value is displayed on the characteristic map (contour) of the tracking error signal amplitude value with respect to the change between the spherical aberration correction value and the focus bias, and the characteristic map of the reproduction performance evaluation value. It is the figure shown by contrasting with (contour line) top. As a diagram for explaining a case where a deviation occurs in the axial direction between the characteristic of the tracking error signal amplitude value and the characteristic of the reproduction performance evaluation value, the position of the spherical aberration correction value roughly adjusted based on the tracking error signal amplitude value is shown. FIG. 5 is a diagram showing a comparison between a tracking error signal amplitude value characteristic map (contour line) and a reproduction performance evaluation value characteristic map (contour line) with respect to changes in spherical aberration correction value and focus bias.

Explanation of symbols

  1 optical pickup, 2 spindle motor, 3 thread mechanism, 4 matrix circuit, 5 data signal processing circuit, 6 decoder, 7 wobble signal processing circuit, 8 ADIP demodulation circuit, 9 address decoder, 10 system controller, 11 servo circuit, 12 spindle Servo circuit, 13 spindle motor, 14 thread driver, 15 host I / F, 16 memory, 16a optimum astigmatism (AS) correction value, 22 adder, 23 focus bias setting unit, 24 spherical aberration correction value setting unit, 25 Focus servo calculation unit, 26 setting control unit, 27 nonvolatile memory, 28 tracking servo calculation unit, 32 spherical aberration correction driver, 33 focus driver, 34 tracking driver, 35 DSP, 36 astigmatism correction value setting unit, 3 8 Astigmatism correction driver, 50 Optical disk, 84 Objective lens, 86 Liquid crystal panel (Astigmatism correction mechanism), 87 Expander, 90 Actuator, 91 Biaxial mechanism, 100 Host device

Claims (6)

Head means for performing laser light irradiation and reflected light detection on the optical recording medium, and having at least a laser beam focus servo mechanism, a spherical aberration correction mechanism, and an astigmatism correction mechanism;
Tracking error signal generating means for generating a tracking error signal based on reflected light detected 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;
Spherical aberration correction means for performing spherical aberration correction by driving the spherical aberration correction mechanism based on the spherical aberration correction value;
Astigmatism correction means for driving the astigmatism correction mechanism based on the astigmatism correction value to execute astigmatism correction;
A focus bias means for adding a focus bias to a focus servo loop including the focus servo means;
A control means,
The control means includes
Using the tracking error signal amplitude value obtained when the astigmatism correction value is sequentially changed with the focus bias and spherical aberration correction value fixed, the optimum astigmatism correction value is obtained as an evaluation index. Astigmatism optimal point search processing to search,
Performing an astigmatism correction process in which the optimum astigmatism correction value obtained by the astigmatism optimum point search process is set in the astigmatism correction means and the astigmatism correction is executed.
An optical recording medium driving device. An evaluation value calculation unit that calculates a reproduction performance evaluation value that is a quality evaluation index of a reproduction signal based on the reflected light detected by the head unit;
The control means includes
A spherical aberration coarse adjustment process for searching for an optimal spherical aberration correction value using the amplitude value of the tracking error signal obtained when the spherical aberration correction value is sequentially changed as an evaluation index;
As fine adjustment processing for the focus bias and spherical aberration correction value, the spherical aberration correction value is based on the spherical aberration correction value obtained by the spherical aberration coarse adjustment processing, and the focus bias is based on a predetermined initial value. Based on the reproduction performance evaluation value obtained when the spherical aberration correction value and the focus bias are changed, the optimum spherical aberration correction value and focus bias are searched for, and the adjustment value is corrected for the spherical aberration correction. And a fine adjustment process set in the focus bias means,
The astigmatism optimum point search process is executed in a state where the spherical aberration correction value and the focus bias are set to the optimum values based on the reproduction performance evaluation value by the fine adjustment process.
The optical recording medium driving device according to claim 1. The control means includes
A storage process for storing the optimum astigmatism correction value obtained by the astigmatism optimum point search process is performed, and
In the astigmatism correction process,
Setting the optimum astigmatism correction value stored by the storage process in the astigmatism correction means to execute astigmatism correction;
The optical recording medium driving device according to claim 2. The control means includes
After performing astigmatism correction by the astigmatism correction process, the spherical aberration coarse adjustment process is performed again, and after the spherical aberration coarse adjustment process, the fine adjustment process is performed again, and then again Performing the astigmatism optimum point search process and the astigmatism correction process,
The optical recording medium driving device according to claim 3. The evaluation value calculation means is
A first evaluation value calculating means for calculating an amplitude value of an RF signal as a reproduction signal from the optical recording medium as a first reproduction performance evaluation value; and a second reproduction performance evaluation different from the amplitude value of the RF signal. Two types of evaluation value calculating means for calculating a value are provided,
The control means includes
A medium type determination process for determining whether the loaded optical recording medium is a read-only ROM type recording medium or a recordable type recording medium,
RF signal amplitude value calculated by the first evaluation value calculation means as a reproduction performance evaluation value used in the fine adjustment process when the optical recording medium is a recordable type by the medium type determination process Execute the evaluation value selection process to select
The optical recording medium driving device according to claim 2. Based on the reflected light detected by the head means, which performs laser light irradiation and reflected light detection on the optical recording medium, and has at least a focus servo mechanism, a spherical aberration correction mechanism and an astigmatism correction mechanism for the laser light. Tracking error signal generating means for generating a tracking error signal, and focus servo means for driving the focus servo mechanism and executing focus servo based on a focus error signal generated as a signal based on reflected light obtained by the head means A spherical aberration correction means for driving the spherical aberration correction mechanism based on the spherical aberration correction value to execute the spherical aberration correction, and an astigmatism driving the astigmatism correction mechanism based on the astigmatism correction value. Astigmatism correction means for performing aberration correction, and a focus servo means including the focus servo means. And the focus bias means for adding the focus bias Kas servo loop,
An astigmatism correction method for correcting astigmatism for an optical recording medium driving device comprising:
Using the tracking error signal amplitude value obtained when the astigmatism correction value is sequentially changed with the focus bias and spherical aberration correction value fixed, the optimum astigmatism correction value is obtained as an evaluation index. Astigmatism optimal point search procedure to search,
An astigmatism correction procedure for executing the astigmatism correction by setting the optimum astigmatism correction value obtained by the astigmatism optimum point search procedure in the astigmatism correction means;
An astigmatism correction method comprising:

Images