JP2006179037A - Optical disk device and tilt correction method of optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device capable of adjusting the tilt correction amount in a short time by an easy method even when a revolving speed of the optical disk is changed. <P>SOLUTION: This optical disk device is equipped with: a means for detecting the tilt correction amount at the optional position of the optical disk revolving with a predetermined revolving speed; a means for calculating the change amount of the tilt correction amount due to the change of revolving speed in accordance with the detected tilt correction amount and the revolving speed of the optical disk, of which the preliminarily set tilt correction amount becomes almost zero; and a means for correcting the tilt in accordance with the detected tilt correction amount when the revolving speed of the optical disk is the predetermined one, and also for re-correcting the tilt correction amount in accordance with the change amount of the calculated tilt correction amount when the revolving speed is changed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus, and more particularly to an optical disc apparatus suitable for tilt correction and an optical disc tilt correction method.

  Conventionally, in order to accurately read recorded information from an optical disc, it is necessary to irradiate a read beam from an optical pickup perpendicular to the recording surface of the optical disc. However, if the optical disc itself is warped or the assembly error of the mechanical system becomes large, it becomes impossible to irradiate the read beam from the optical pickup perpendicular to the recording surface of the optical disc, and tilt occurs. There has been a problem that the accuracy of reading information from or writing information to the optical disk decreases (see FIG. 7).

In order to deal with such problems, in an optical disc apparatus that controls the optical pickup track direction by a push-pull method, a tilt correction signal is generated based on a push-pull signal obtained from the optical pickup, and the generated tilt correction signal is generated. Has been proposed to correct tilt by supplying a tilt correction circuit (see, for example, Patent Document 1).
JP 2002-170265 A (page 2-11, FIG. 1)

  However, according to the above method, the tilt caused by the warp of the optical disc itself or the assembly error of the mechanical system can be suppressed to some extent. However, this tilt correction amount varies depending on the number of rotations of the optical disc. The tilt correction value obtained from the rotational speed cannot be used at another rotational speed. Further, if the tilt correction is performed for each position of the optical pickup with respect to the optical disk and for each rotation speed of the optical disk, the processing value becomes complicated, and the commercial value may decrease, for example, the reproduction time of the optical disk becomes longer.

  Therefore, the present invention has been made in view of the above-described problems, and even when the rotational speed of the optical disk changes, the optical disk apparatus and the optical disk tilt capable of adjusting the tilt correction amount in a short time by a simple method. An object is to provide a correction method.

In order to solve the above problems, the present invention proposes the following means.
According to the first aspect of the present invention, there is provided a tilt correction amount detecting means for detecting a tilt correction amount at an arbitrary position of an optical disk rotating at a predetermined rotational speed, the detected tilt correction amount, and a preset tilt correction. A tilt change amount calculating means for calculating a change amount of a tilt correction amount due to a change in the number of rotations based on the number of rotations of the optical disk whose amount is substantially zero, and the number of rotations of the optical disk is the predetermined number of rotations When the tilt correction is performed based on the detected tilt correction amount, and the tilt correction amount is recorrected based on the calculated change amount of the tilt correction amount when the rotation speed changes. An optical disc apparatus characterized by comprising correction means is proposed.

  According to a fourth aspect of the present invention, there is provided a step of detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed, and at the detected arbitrary rotational speed at the arbitrary position of the optical disk. Based on the tilt correction amount and the rotation speed of the optical disc at which the preset tilt correction amount is substantially zero, calculating the change amount of the tilt correction amount due to the change in the rotation speed; and A step of performing tilt correction based on the detected tilt correction amount when the rotation speed is the predetermined number of rotations, and based on the calculated tilt change amount when the rotation number of the optical disk changes. And a method of re-correcting the tilt correction amount, and a method of correcting the tilt of the optical disc, characterized in that it is provided.

  According to these inventions, the tilt correction amount detection means detects the tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed. The tilt change amount calculation means calculates the rotation number based on the tilt correction amount at a predetermined rotation number at an arbitrary position of the detected optical disc and the rotation number of the optical disc at which the preset tilt correction amount becomes substantially zero. The amount of change in tilt correction amount due to the change in is calculated. The tilt correction means performs tilt correction based on the detected tilt correction amount when the rotation speed of the optical disk is a predetermined rotation speed, and calculates the calculated tilt correction when the rotation speed of the optical disk changes. The tilt correction amount is recorrected based on the amount change amount.

  According to a second aspect of the present invention, there is provided a tilt correction amount detecting means for detecting a tilt correction amount at an arbitrary position of an optical disk rotating at a predetermined rotational speed, and when the rotational speed of the optical disk is the predetermined rotational speed. In addition to performing the tilt correction based on the detected tilt correction amount, the tilt correction amount is recorrected based on the change amount of the tilt correction amount due to the change in the preset rotation number when the rotation number changes. An optical disc apparatus characterized by including a tilt correcting means is proposed.

  According to a fifth aspect of the invention, there is provided a step of detecting a tilt correction amount at an arbitrary position of an optical disk rotating at a predetermined rotational speed, and the detection is performed when the rotational speed of the optical disk is the predetermined rotational speed. Performing a tilt correction based on the tilt correction amount, and re-correcting the tilt correction amount based on a change amount of the tilt correction amount due to a change in the preset rotation speed when the rotation speed changes. An optical disk tilt correction method characterized by comprising:

  According to these inventions, the tilt correction amount is detected by the tilt correction amount detection means at an arbitrary position of the optical disk that rotates at a predetermined rotational speed. The tilt correction means performs tilt correction based on the detected tilt correction amount when the rotation speed of the optical disc is a predetermined rotation speed, and when the rotation speed changes, the tilt correction means The tilt correction amount is recorrected based on the change amount of the tilt correction amount due to the change.

  The invention according to claim 3 detects the tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed, and changes the rotational speed of the optical disk at one of the arbitrary positions. The tilt correction amount detecting means for detecting the tilt correction amount and the tilt correction by linear approximation from two tilt correction amounts when the rotational speed of the optical disk is changed at one of the arbitrary positions. Based on the calculation means for calculating the rotational speed at which the amount becomes substantially zero, the tilt correction amount for the arbitrary rotational speed at the arbitrary position, and the rotational speed at which the tilt correction amount becomes substantially zero, the change in the rotational speed And a tilt change amount calculating means for calculating a change amount of the tilt correction amount by the optical disc based on the detected tilt correction amount when the rotational speed of the optical disc is the predetermined rotational speed. An optical disc apparatus comprising: tilt correction means that performs tilt correction and recorrects the tilt correction amount based on the calculated change amount of the tilt correction amount when the rotation speed changes. is suggesting.

  According to a sixth aspect of the invention, there is provided a step of detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed, and changing the rotational speed of the optical disk at one of the arbitrary positions. The tilt correction amount becomes substantially zero by linear approximation from the two tilt correction amounts when the rotational speed of the optical disk is changed at one of the arbitrary positions. The amount of change in the tilt correction amount due to the change in the number of rotations based on the step of calculating the number of rotations, and the tilt correction amount at the arbitrary number of rotations and the number of rotations at which the tilt correction amount is substantially zero at the arbitrary position. Calculating a tilt correction based on the detected tilt correction amount when the rotation speed of the optical disc is the predetermined rotation speed, When the rotational speed of the optical disc is changed, based on the tilt variation issued the calculated proposes a tilt correction method for an optical disc characterized by comprising the step of re-correcting the tilt correction amount.

  According to these inventions, the tilt correction amount detecting means detects the tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed, and the rotation of the optical disk at one of the arbitrary positions. The amount of tilt correction when the number is changed is detected. Then, the rotation speed at which the tilt correction amount becomes substantially zero is calculated from the tilt correction amount when the rotation speed of the optical disk is changed at one of the arbitrary positions by the calculating means. The tilt change amount calculation means calculates the change amount of the tilt correction amount due to the change in the rotation number based on the tilt correction amount at the arbitrary rotation number at the detected arbitrary position and the rotation number at which the tilt correction amount becomes substantially zero. Is calculated. The tilt correction means performs tilt correction based on the detected tilt correction amount when the rotation number of the optical disk is a predetermined rotation number, and calculates the tilt change amount when the rotation number of the optical disk changes. The tilt correction amount is corrected again based on the above.

  According to the present invention, an optical disk device in which the rotation speed of the optical disk changes during recording or reproduction operation, and even when the rotation speed of the optical disk changes for some reason during recording or reproduction operation, it corresponds to the rotation speed of the optical disk at that time Thus, an appropriate tilt correction can be realized in a short time.

  As shown in FIG. 1, an optical disc apparatus according to an embodiment of the present invention includes an optical disc 1, an optical pickup 2, a photodetector 3, an RF amplifier 4, a signal processing circuit 5, a driver 6, a CPU ( A CPU (Central Processing Unit) 7, a RAM (RAM: Random Access Memory) 8, a tilt correction driver 9, and a rotation speed detection unit 10 are provided.

  The optical disc 1 is a recording medium on which information can be recorded, reproduced, and erased by a semiconductor laser, and examples thereof include a CD-R, a CD-RW, a DVD-R, and a DVD-RW. Hereinafter, in this embodiment, a DVD will be described as an example.

  The optical pickup 2 includes a laser light source such as a laser diode (not shown), an optical lens such as an objective lens driven by a collimator lens, a focus actuator, or a tracking actuator, a polarization beam splitter, and a cylindrical lens.

  The photodetector 3 is built in an optical pickup, and is divided into four regions A, B, C, and D, and includes a four-divided photodetector (PD) that converts light into an electric signal, a sub-beam photodetector, and the like. .

  The RF amplifier 4 detects the reflected light from the optical disc 1, calculates the amount of reflected light from the detected reflected light, generates an RF signal indicating the total amount of reflected light to each region of the four-divided PD, and optical pickup A focus error signal (FE) that is a signal that detects the defocus of the irradiation laser of 1 is generated by the astigmatism method. Further, a tracking error signal (TE), which is a signal that detects the track deviation of the irradiation laser of the optical pickup 1, is generated by the push-pull method.

  The servo circuit 5 generates a focus drive signal (FODRV) and a tracking drive signal (TRDRV) based on FE, TE, and RF generated by the analog signal processing unit 4.

  Further, a peak / bottom detection circuit (not shown) is provided in the RF amplifier 4 to detect the envelope of the generated RF signal. Furthermore, the top level and the bottom level of the envelope signal that changes in accordance with the intensity of the reflected light from the groove and land are detected from the detected envelope signal, and the difference value is calculated (see FIG. 8).

The calculated value is output to the CPU 7 to calculate the radial contrast. Incidentally, the radial contrast level I _l of the land _signal, when the level of the groove signal and I _g, although shown as such in the normalized equation (1) to an average value, in the present invention, as described above In addition, (I _g -I _l ) is also included in the radial contrast in a broad sense.
2 (I _g −I _l ) / (I _l + I _g ) (1)

  The signal processing circuit 5 receives the EFM signal generated from the RF signal and processes data, and includes a PLL circuit (not shown) to control the rotation of the spindle motor. In addition, a servo circuit including a phase compensation circuit and the like is incorporated, and the servo circuit is turned on / off.

  The driver 6 inputs a focus drive signal (FODRV), a tracking drive signal (TRDRV) generated by the RF amplifier 4 or a spindle control signal generated by the signal processing circuit 5 and amplifies it to a desired size. After that, it is supplied to a focus actuator, tracking actuator or spindle motor (not shown).

  The CPU 7 controls the entire apparatus based on a control program stored in a ROM (ROM: Read Only Memory) or the like. In the present embodiment, the radial contrast is calculated from the difference value between the peak and the bottom based on the envelope of the RF signal input from the RF amplifier 4.

  Further, the tilt correction amount is changed, and the corresponding radial contrast is stored in the RAM 8, and the maximum value is obtained by comparing these radial contrast values, and the tilt correction amount at that time is calculated as the tilt correction driver 9. To supply.

  Further, in the present embodiment, the CPU 7 performs the tilt correction amount at a predetermined rotation number at an arbitrary position of the optical disc 1 and the rotation number of the optical disc 1 or an arbitrary position at which the preset tilt correction amount is substantially zero. Based on the rotation number of the optical disc 1 at which the tilt correction amount obtained from the tilt correction amount when the rotation number is changed becomes substantially zero, the change amount of the tilt correction amount due to the change in the rotation number is calculated. Further, when the rotation speed of the optical disk changes, a recorrection value of the tilt correction amount is calculated by adding a change amount corresponding to the change in the rotation number to the tilt correction amount obtained from the radial contrast.

  The RAM 8 is a rewritable storage device and has a data table that stores a radial contrast and a tilt correction amount corresponding to the radial contrast in association with each other. Further, a data table relating to a predetermined track address of the optical disc 1 and a tilt correction amount corresponding to the predetermined track address is also provided. Further, a change amount of the tilt correction amount when the rotation speed of the optical disc 1 is changed at a predetermined track address is stored.

  The tilt correction driver 9 supplies a voltage corresponding to the tilt correction amount input from the CPU 7 to a tilt actuator (not shown) in the optical pickup 2 to perform tilt correction. In the present embodiment, a tilt actuator is exemplified and described as the tilt correction means, but the present invention is not limited to this, and for example, a liquid crystal panel method may be used. Furthermore, any method such as a method of tilting the pickup itself or a method of tilting only the objective lens may be used for the tilt actuator.

  The rotational speed detection unit 10 receives a signal from, for example, a PLL circuit in the signal processing circuit 5 to detect the current rotational speed of the optical disc 1 and outputs it to the CPU 7.

Next, the operation of the first embodiment will be described with reference to FIG.
First, when the insertion of the optical disk is confirmed (step 101), the CPU 7 instructs a setup operation (step 102). When the setup operation is completed, the CPU 7 measures the amount of tilt correction for a plurality of tracks, for example, at the steady rotational speed of the optical disc 1 (step 103). The operation of step 103 will be described later with reference to FIG.

  When the CPU 7 completes the measurement of the tilt correction amount for a plurality of tracks, the CPU 7 calculates the change amount of the tilt correction amount based on the change in the rotation number from the rotation number of the optical disc 1 at which the previously obtained tilt correction amount becomes substantially zero. (Step 104).

Here, a method of calculating the amount of change in the tilt correction amount will be described with reference to FIG.
FIG. 5 shows a case where the rotational speed of the optical disk at a predetermined position of the optical disk is sequentially changed using the disk 1 that is warped with respect to the outer periphery of the disk and the disk 2 that is warped with respect to the outer periphery of the disk. This shows how the tilt angle (tilt correction amount) changes. According to this figure, in any case, the tilt angle changes substantially linearly according to the change in the rotational speed, and there is a point where the tilt angle becomes zero at substantially the same point.

Therefore, if the rotation speed of the optical disk at which the tilt angle is zero is obtained in advance, the tilt angle at a predetermined rotation speed can be measured, and the amount of change in the tilt correction amount can be calculated using the following Equation 1.
θ = (R−Rp) * θ1 / (R1−Rp)
Here, θ1 is a tilt angle (tilt correction amount) at a predetermined rotational speed (R1), θ is a tilt angle (tilt correction amount) in actual recording / reproduction, and Rp is a rotational speed at which θ = 0. ing.
Note that the rotation speed of the optical disc 1 at which the tilt correction amount is substantially zero is set to a different value depending on the type of the optical disc 1.

  In addition, when the rotation speed of the optical disk at the time of tilt angle (tilt correction amount) measurement and the rotation speed of the optical disk at the time of recording or playback are different, the measurement of the tilt angle is performed at the rotation speed at the lead-in, When recording or reproduction is performed at CLV (constant linear velocity), there may be a case where processing for lowering the recording or reproduction speed is performed due to some trouble.

  When the CPU 7 calculates the amount of change in the tilt correction amount, the CPU 7 proceeds to a recording or reproducing operation (step 105). Then, in the recording or reproducing operation, the current rotational speed of the optical disc 1 is detected based on the signal input from the rotational speed detection unit 10, and when the detected rotational speed is a steady rotational speed, it is calculated in step 103. The tilt correction amount is output to the tilt correction driver 9 to correct the tilt amount (steps 106 and 107).

  On the other hand, when the detected rotation speed is not the steady rotation speed, the correction amount is calculated by adding the tilt correction amount calculated in step 104 to the tilt correction amount calculated in step 103, and this correction amount is calculated as a tilt correction driver. 9 to correct the tilt amount (step 108).

  In the present embodiment, the change amount of the tilt correction amount based on the change in the rotation number is obtained from the rotation number of the optical disc 1 at which the measured tilt correction amount and the previously obtained tilt correction amount are substantially zero. Although the method for calculating the recorrection amount based on the above description has been described, as shown in FIG. 5, the inclination of each straight line, that is, the change amount of the tilt correction amount based on the change in the number of rotations is not significantly different in any case. Therefore, a change amount of the tilt correction amount based on the change in the rotational speed may be set in advance, and the recorrection amount may be obtained from this value and the measured tilt correction amount.

Next, details of the processing in step 103 will be described with reference to FIG.
First, the CPU 7 issues a search command to the signal processing circuit 5 to move the optical pickup 2 to a desired track on the optical disc 1 (step 201).

  When the optical pickup 2 moves to a desired track, the CPU 7 instructs the signal processing circuit 5 to turn off tracking control, and turns off the track servo (step 202). When the track servo is turned off, the objective lens in the optical pickup 2 maintains a neutral position with respect to the tracking direction. Therefore, due to the eccentricity of the optical disk 1, the photodetector 3 receives, for example, from the land portion and the groove portion. Return light appears alternately. Therefore, an RF signal obtained by inputting a signal from the photodetector 3 and calculating in the RF amplifier 4 has a waveform with a wave corresponding to the amount of return light from the land portion and the groove portion (FIG. 8). reference.).

  The generated RF signal is supplied to a peak / bottom detection circuit in the RF amplifier, and a difference value between the peak and the bottom is calculated. The calculated difference value is input to the CPU 7 to calculate the radial contrast. The calculated radial contrast is stored in the RAM 8 together with the tilt amount. Next, the CPU 7 varies the initial tilt amount, supplies it to the tilt correction driver 9 to vary the tilt amount, calculates the radial contrast at this time by the same method as described above, and calculates this. It is stored in the RAM 8 in association with the tilt correction amount. These operations are continuously performed to calculate the maximum radial contrast at a predetermined address of the optical disc 1 (step 203).

  The tilt correction amount that maximizes the radial contrast is stored in a predetermined data table together with the address information of the optical disc 1 (step 204). When the above series of processing is completed at a predetermined address of the optical disk 1, the CPU 7 issues a search command to the signal processing circuit 5 to move the optical pickup 2 to the next desired track, and performs the above series of operations. Thus, a tilt correction amount that maximizes the radial contrast is obtained (step 205). If the track to be searched next is the track searched first, the CPU 7 determines that a series of operations have been completed for all the predetermined tracks on the optical disc 1, ends the processing, and then searches. If the track to be searched is not the track searched first, a series of operations are continued with a predetermined track (step 206).

  The tilt correction amount detection method uses a radial contrast that is not easily affected by the lens shift of the objective lens and the adjustment variation of the light receiving system for the tilt correction. In general, the tilt between the objective lens in the optical pickup and the optical disc is evaluated by the jitter of the reproduced signal. 6 (a) and 6 (b) show the relationship between radial contrast and jitter and tilt correction amounts. From FIG. 6 (a), the radial contrast becomes the maximum when the jitter is minimum, and the radial contrast is the maximum value. As the value decreases, the jitter value also increases accordingly. This relationship is also clear from the fact that, as shown in FIG. 6B, the relationship between the angle at which the radial contrast is maximized and the angle at which the jitter is minimized is substantially a straight line. For this reason, the above-described tilt correction amount detection method calculates an appropriate tilt correction amount using such a relationship.

  As described above, according to the first embodiment, the tilt correction amount based on the change in the rotation speed from the rotation speed of the optical disk at which the tilt correction amount during steady rotation at a predetermined position of the optical disk and the tilt correction amount obtained in advance are substantially zero. Since the change amount of the correction amount is calculated, the tilt correction amount corresponding to the changed rotation speed can be accurately calculated in a short time even when the rotation speed of the optical disk changes.

Next, the operation of the second embodiment will be described with reference to FIG.
First, when the insertion of the optical disk is confirmed (step 301), the CPU 7 instructs a setup operation (step 302). When the setup operation is completed, the CPU 7 measures the tilt correction amount for a plurality of tracks, for example, at the steady rotational speed of the optical disc 1 (step 303). The operation in step 303 is the same as that in the first embodiment, and a description thereof will be omitted.

  When the CPU 7 completes the measurement of the tilt correction amount for a plurality of tracks, the CPU 7 changes the rotation speed of the optical disc 1 in one of the plurality of tracks, and measures the tilt correction amount at that time (step 304). . Next, the rotation number at which the tilt correction amount of the optical disc 1 becomes substantially zero is calculated from both tilt correction amounts when the rotation number of the optical disc 1 is changed, and the value measured in step 304 and the calculated tilt are calculated. A change amount of the tilt correction amount based on the change in the rotation number of the optical disc 1 is calculated from the rotation number at which the correction amount becomes substantially zero (step 305).

  After calculating the amount of change in the tilt correction amount, the CPU 7 proceeds to a recording or reproduction operation (step 306). Then, in the recording or reproducing operation, the current rotational speed of the optical disc 1 is detected based on the signal input from the rotational speed detection unit 10, and when the detected rotational speed is a steady rotational speed, it is calculated in step 103. The tilt correction amount is output to the tilt correction driver 9 to correct the tilt amount (steps 307 and 308).

  On the other hand, when the detected rotation speed is not the steady rotation speed, the correction amount is calculated by adding the tilt correction amount calculated in step 305 to the tilt correction amount calculated in step 303, and this correction amount is calculated as a tilt correction driver. 9 to correct the tilt amount (step 309).

  Therefore, according to the present embodiment, the number of rotations at which the tilt correction amount becomes substantially zero is obtained from the tilt correction amount at the time of steady rotation at a predetermined position of the optical disc and the tilt correction amount when the rotation number is changed. Therefore, even if the rotation speed of the optical disk changes, the tilt correction amount corresponding to the changed rotation speed can be calculated more accurately. Can be calculated.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to these embodiments, and includes design changes and the like without departing from the gist of the present invention. . For example, in the present embodiment, the method of calculating the radial contrast using only the RF signal has been described. However, in tracking control using a push-pull signal, sub-signals such as a DPP signal (DPP: Differential Push Pull) are used. When there is a spot, a radial contrast based on the calculation result of the main spot signal and the sub spot signal may be included.

1 is a configuration diagram of an optical disc apparatus according to the present invention. It is a processing flow figure in a 1st embodiment. It is a flowchart figure of the process for tilt correction amount measurement. It is a processing flow figure in a 2nd embodiment. It is the figure which showed the relationship between the change of the rotation speed of an optical disk, and the change of a tilt angle. It is the figure which showed the relationship between a tilt angle, radial contrast, and a jitter value. It is the figure which showed the relationship between an optical disk and an optical pick-up. It is the figure which showed RF signal in an unrecorded area | region and a recorded area | region.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pick-up, 3 ... Optical detector, 4 ... RF amplifier, 5 ... Signal processing circuit, 6 ... Driver, 7 ... CPU, 8 * ..RAM, 9 ... Tilt correction driver, 10 ... Rotation speed detector

Claims (6)

A tilt correction amount detecting means for detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed;
Tilt change amount calculation means for calculating a change amount of the tilt correction amount due to a change in the rotation number based on the detected tilt correction amount and the rotation number of the optical disc at which the preset tilt correction amount becomes substantially zero. When,
When the rotation speed of the optical disk is the predetermined rotation speed, tilt correction is performed based on the detected tilt correction amount, and when the rotation speed changes, the calculated tilt correction amount changes. Tilt correction means for re-correcting the tilt correction amount based on the amount;
An optical disc apparatus comprising: A tilt correction amount detecting means for detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed;
When the rotational speed of the optical disk is the predetermined rotational speed, tilt correction is performed based on the detected tilt correction amount, and when the rotational speed changes, the tilt is caused by a change in the predetermined rotational speed. Tilt correction means for re-correcting the tilt correction amount based on the change amount of the correction amount;
An optical disc apparatus comprising: Tilt for detecting a tilt correction amount at an arbitrary position of an optical disk rotating at a predetermined rotational speed, and detecting the tilt correction amount by changing the rotational speed of the optical disk at one of the arbitrary positions Correction amount detection means;
Calculating means for calculating a rotational speed at which the tilt correction amount becomes substantially zero by linear approximation from two tilt correction amounts when the rotational speed of the optical disc is changed at one of the arbitrary positions; ,
Tilt change amount calculation means for calculating a change amount of the tilt correction amount due to a change in the rotation number based on the tilt correction amount for the arbitrary rotation number at the arbitrary position and the rotation number at which the tilt correction amount becomes substantially zero. When,
When the rotation speed of the optical disk is the predetermined rotation speed, tilt correction is performed based on the detected tilt correction amount, and when the rotation speed changes, the calculated tilt correction amount changes. Tilt correction means for re-correcting the tilt correction amount based on the amount;
An optical disc apparatus comprising: Detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed;
Based on the detected tilt correction amount at the arbitrary rotational speed at the arbitrary position of the optical disc and the rotational speed of the optical disc at which the preset tilt correction amount becomes substantially zero, the change in the rotational speed Calculating the amount of change in tilt correction amount due to,
Performing tilt correction based on the detected tilt correction amount when the rotational speed of the optical disc is the predetermined rotational speed;
Re-correcting the tilt correction amount based on the calculated tilt change amount when the rotation speed of the optical disc changes;
A tilt correction method for an optical disc, comprising: Detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed;
Performing tilt correction based on the detected tilt correction amount when the rotational speed of the optical disc is the predetermined rotational speed;
Re-correcting the tilt correction amount based on a change amount of the tilt correction amount due to a change in the preset rotation number when the rotation number changes;
A tilt correction method for an optical disc, comprising: Detecting a tilt correction amount at an arbitrary position of the optical disk rotating at a predetermined rotational speed;
Detecting a tilt correction amount by changing the rotational speed of the optical disk at one of the arbitrary positions;
Calculating a rotational speed at which the tilt correction amount becomes substantially zero by linear approximation from two tilt correction amounts when the rotational speed of the optical disk is changed at one of the arbitrary positions;
Calculating the amount of change in the tilt correction amount due to the change in the rotation number based on the tilt correction amount at the arbitrary rotation number and the rotation number at which the tilt correction amount is substantially zero at the arbitrary position;
Performing tilt correction based on the detected tilt correction amount when the rotational speed of the optical disc is the predetermined rotational speed;
Re-correcting the tilt correction amount based on the calculated tilt change amount when the rotation speed of the optical disc changes;
A tilt correction method for an optical disc, comprising:

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