JP2008299939A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly correct a tilt of an objective lens within a short time during recording or reproducing. <P>SOLUTION: This drive obtains a first tilt drive signal from an optional optical disk 1 to correct a tilt caused by the assembling errors of the objective lens 3. Before recording or reproducing the optical disk to be recorded or reproduced, a second approximate expression is obtained for showing a relation of each focus drive signal and the radial position of the pickup by moving the optical pickup 4 radially on the optical disk. During recording or reproducing, second tilt drive signals are obtained from the second approximate expression, the current radial position of the optical pickup, the sensitivity of moving amount of the objective lens to the focus drive signals, and the sensitivity of tilt angle of the objective lens to the tilt drive signal. Then, the tilt is corrected by using the tilt drive signal obtained by adding the first and second tilt drive signals as the third tilt drive signal at the current radial position of the optical pickup. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical disk drive device that performs tilt correction so that the optical axis of an objective lens of an optical pickup is perpendicular to the surface of an optical disk by a tilt drive signal when the optical disk is warped or tilted.

  The optical beam for recording / reproducing information with respect to the optical disc is set so that the optical axis is perpendicular to the optical disc surface, so that information can be recorded with high density at a fine track pitch. Information can be reproduced from a track having a fine track pitch. However, if there is a warp in the radial direction of the optical disk or the surface of the optical disk is tilted, the surface of the optical disk will not be perpendicular to the optical axis of the light beam, and high-density recording / reproduction will not be possible. Conventionally, tilt correction for correcting the curvature of the optical disc in the radial direction and the tilt of the optical disc surface has been performed.

In the tilt correction method described in Patent Document 1, focus servo is executed at several positions from the inner periphery to the outer periphery of the disc in order to correct the warp in the radial direction of the disc and the tilt of the disc. The focus drive signal applied to the disk is measured, and the tilt angle at the disk radial position is obtained using the difference between the measured values of adjacent focus drive signals and the difference between the disk radial positions. The focus drive signal here is a signal equivalent to a parameter representing the amount of shift in the focus direction. From the initial state of the objective lens for focusing the light beam on the optical disc (the state where no voltage is applied to the actuator), the focus drive signal is focused. This parameter represents the voltage applied to the focus actuator during servo execution. If the distance between the initial position of the objective lens and the disk is large, the drive voltage increases. If the distance is small, the drive voltage decreases. That is, the angle at each position is calculated from the difference between the measured adjacent focus shift amounts and the difference between the disk radial positions, and the correlation between the angle value and the disk position is obtained.
JP-A-10-177729 (FIG. 3)

  However, in the method in the prior art, the tilt angle is derived from the difference between the focus drive signal and the disc radial position, so that the tilt angle is not step-like and smooth, and the measurement error of the focus drive signal remains as it is. Therefore, there is a problem that the tilt angle is inaccurate and it is difficult to represent the actual warp or tilt of the disc. If the warp and tilt of the disk are to be measured accurately, a large number of measurements are required, and each measurement accuracy must be increased.

  In addition, the tilt drive signal is obtained only from the relationship between the focus drive signal and the disk radial position. In this case, the tilt of the guide rail in the disk radial direction of the optical pickup, the tilt of the installation surface of the optical disk, and the warp of the optical disk However, in reality, since an inclination due to an assembly error of the objective lens remains, it is not possible to derive an optimum tilt angle to which the amount is added.

  Furthermore, there is a method of measuring the jitter and error rate, which are the quality of the reproduction signal, to obtain the total tilt angle including the tilt of the objective lens in the optical pickup, but a high-density disk using a blue laser ( In the case of Blu-ray (registered trademark) Disc, the disc cover layer has a thickness of 100 [μm], which is thinner than conventional DVDs, and jitter and error rate changes with respect to the tilt angle are less likely to occur. In order to derive a signal, it is necessary to measure while tilting the tilt angle until a change appears, and there is a risk that the servo will be lost, which is not suitable for performing during reproduction.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical disk drive device that can appropriately perform optimum tilt correction of an objective lens during recording and reproduction in a short time.
In particular, an object of the present invention is to provide an optical disk drive device that can obtain an accurate tilt angle without requiring a large number of measurements and without increasing the accuracy of each measurement.
It is another object of the present invention to provide an optical disk drive device that can obtain an accurate tilt angle corresponding to the tilt due to the assembly error of the objective lens.
It is another object of the present invention to provide an optical disc drive apparatus that can obtain an accurate tilt angle corresponding to the sensitivity of an objective lens with respect to a focus drive signal and a tilt drive signal.

In order to achieve the above object, the present invention tilts the objective lens with a tilt drive signal to correct the tilt of the objective lens so that the optical axis of the objective lens in the optical pickup is perpendicular to the surface of the optical disc. In an optical disc drive device that corrects tilt to
With the optical pickup fixed to the reproducible area of the optical disc, the objective lens is tilted by N (N is a natural number of 3 or more) tilt drive signals, and the reproduction signal of the optical pickup in each tilt drive signal is A jitter value is measured to obtain a first approximate expression indicating a relationship between each tilt drive signal and the measured jitter value, and a tilt drive signal having a minimum jitter value in the first approximate expression is obtained from the objective lens. Means for obtaining and storing as a first tilt drive signal for correcting the tilt;
Before recording or reproducing an optical disk to be recorded or reproduced, the focus pickup signals at M (M is a natural number of 3 or more) radial positions are measured while moving the optical pickup in the radial direction of the optical disk. Means for obtaining a second approximate expression indicating the relationship between each focus drive signal and the radial position of the pickup;
During recording or reproduction of the optical disk to be recorded or reproduced, the second approximate expression, the current radial position of the optical pickup, the sensitivity of the displacement amount of the objective lens with respect to a focus drive signal, and tilt drive A second tilt drive signal is obtained from the sensitivity of the tilt angle of the objective lens to the signal, and the tilt drive signal obtained by adding the first and second tilt drive signals is obtained as a third radial drive position at the current radial position of the optical pickup. Means for tilt correction as a tilt drive signal of
Prepared.

In order to achieve the above object, the present invention tilts the objective lens with a tilt drive signal to correct the tilt of the objective lens, and the optical axis of the objective lens in the optical pickup is perpendicular to the surface of the optical disc. In the optical disk drive device for tilt correction so that
With the optical pickup fixed to the reproducible area of the optical disc, the objective lens is tilted by N (N is a natural number of 3 or more) tilt drive signals, and the reproduction signal of the optical pickup in each tilt drive signal is The error rate is measured to obtain a first approximate expression indicating the relationship between each tilt drive signal and the measured error rate, and the tilt drive signal that minimizes the error rate in the first approximate expression is obtained from the objective lens. Means for obtaining and storing as a first tilt drive signal for correcting the tilt;
Before recording or reproducing an optical disk to be recorded or reproduced, the focus pickup signals at M (M is a natural number of 3 or more) radial positions are measured while moving the optical pickup in the radial direction of the optical disk. Means for obtaining a second approximate expression indicating the relationship between each focus drive signal and the radial position of the pickup;
During recording or reproduction of the optical disk to be recorded or reproduced, the second approximate expression, the current radial position of the optical pickup, the sensitivity of the displacement amount of the objective lens with respect to a focus drive signal, and tilt drive A second tilt drive signal is obtained from the sensitivity of the tilt angle of the objective lens to the signal, and the tilt drive signal obtained by adding the first and second tilt drive signals is obtained as a third radial drive position at the current radial position of the optical pickup. Means for tilt correction as a tilt drive signal of
Prepared.

According to the present invention, since the second approximate expression indicating the relationship between each focus drive signal and the radial position of the pickup is obtained, it is necessary to increase the measurement accuracy without requiring a large number of measurements. Therefore, the warp in the radial direction of the disc and the tilt of the disc can be obtained, and an accurate tilt angle can be obtained.
In addition, since the first tilt drive signal for correcting the tilt due to the assembly error of the objective lens is obtained and tilt correction is performed, an accurate tilt angle corresponding to the tilt due to the assembly error of the objective lens can be obtained.
The second tilt drive signal is calculated from the second approximate expression, the current radial position of the optical pickup, the sensitivity of the displacement amount of the objective lens with respect to the focus drive signal, and the sensitivity of the tilt angle of the objective lens with respect to the tilt drive signal. Therefore, an accurate tilt angle corresponding to the sensitivity of the objective lens with respect to the focus drive signal and the tilt drive signal can be obtained.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
FIG. 1 is a block diagram showing an optical information recording / reproducing apparatus according to a first embodiment of an optical disk drive apparatus according to the present invention. As shown in FIG. 1, this optical information recording / reproducing apparatus applies laser light 2 emitted from a light source such as a semiconductor laser element (not shown) to an optical recording medium such as an optical disc 1 via an objective lens 3. An optical pickup 4 that guides and detects the reflected light by the photodetector 21 through the objective lens 3 is provided. Although not shown, the optical pickup 4 also includes a tilt actuator (hereinafter referred to as ACT) for correcting the tilt (tilt) of the optical axis of the objective lens 3 and the direction of the objective lens 3 relative to the surface of the optical disc 1 (focus). A focus ACT for driving in a direction) and a tracking ACT for driving the objective lens 3 in a direction crossing a track (not shown) of the optical disc 1 for tracking. These tilt ACT, focus ACT, and tracking ACT are driven by drive signals from the tilt ACT driver 9, the focus ACT driver 10, and the tracking ACT driver 11, respectively. The controller 14 includes an equalizer circuit 15, a focus drive signal measurement circuit 16, a jitter measurement unit 18, and a tilt control unit 19.

  The servo signals are obtained by calculating the focus error signal F and the tracking error signal T based on the detection signal of the photodetector 21 in the optical pickup 4 by the focus error calculation circuit 12 and the tracking error calculation circuit 13, respectively. . The focus error signal F obtained by the focus error calculation circuit 12 is applied to a phase compensation circuit (not shown) in the equalizer circuit 15 where a focus drive signal is generated and supplied to a focus ACT (actuator) driver 9. And measured and stored by the focus drive signal measurement circuit 16. The focus drive signal measurement circuit 16 can average the sampling values obtained by extracting the focus drive signal through a filter circuit (not shown) at regular time intervals and read the numerical values. The tracking error signal T is applied to a phase compensation circuit (not shown) in the equalizer circuit 15 where a tracking drive signal is generated and supplied to the tracking ACT driver 10.

  The jitter measurement unit 18 measures the jitter of the reproduction signal obtained by optimizing the reproduction signal extracted from the photodetector 21 by the reproduction signal equalizer 17, and the tilt control unit 19 reads the numerical value. The tilt control unit 19 realizes an operation for obtaining the current tilt correction value by describing a hardware hardware constituted by a microcomputer or the like. The tilt control unit 19 performs an operation as described later, and outputs an optimum tilt value at an arbitrary position of the disk 1 to the tilt ACT driver 8.

  The spindle driver 11 receives the rotation control of the disk 1 from the controller 14 and controls the spindle motor 11a. The thread motor 6 is a stepping motor or the like, and a lead screw 5 is connected to its main shaft, and the optical pickup 4 is moved along a guide rail (not shown) installed in parallel with the lead screw 5 by the rotation of the lead screw 5. The disk 1 is moved in the radial direction. The thread driver 7 controls the thread motor 6 and controls the number of rotation steps and the rotation direction by the controller 14 so that the positioning control can be performed at an arbitrary position from the inner periphery to the outer periphery of the disk 1.

  Here, the tilt correction method will be described. First, the sled motor 6 moves the optical pickup 4 to the innermost position in the reproducible area of the optical disc 1. Here, focus servo, tracking servo, and spindle servo are executed, and the first process is executed. The first process is that the tilt control unit 19 gives different N (N is a natural number of 3 or more) tilt drive signals to the tilt ACT driver 8 and measures jitter of the reproduced signal in each state. Measured by unit 18 and stored. This is a process of calculating and storing the first tilt drive signal 1 having the smallest jitter value based on the measured N jitter measurement values using the first approximate expression. This process may be performed once in a manufacturing process using a standard disk with less warpage, which is not a disk to be recorded or reproduced.

  In the second process, the controller 14 instructs the thread driver 7 to move the position of the optical pickup 4 to different M positions (M is a natural number of 3 or more) by the thread motor 6. Then, focus servo is executed at each position, and the focus drive signal is measured by the focus drive signal measurement circuit 16. This is a process of obtaining the second approximate expression from the measured M focus drive signals and the position of the optical pickup 4 and storing the coefficient of the second approximate expression. If the M positions to be moved extend from the inner periphery to the outer periphery of the disk 1, an equation representing the inclination at an arbitrary position of the disk 1 can be obtained. This process is performed as a part of the initial adjustment executed every time the disc 1 to be recorded or reproduced is inserted.

  Thereafter, after moving to a normal reproduction or recording operation, the position of the optical pickup 4 on the disk 1 is calculated from the physical address of the disk 1 or the number of steps from the origin position of the optical pickup 4. The second tilt drive signal 2 at the position of the optical pickup 4 during reproduction or recording is calculated from the coefficient of the second approximate expression obtained in the second process, and obtained from the first process obtained earlier. By adding the first tilt drive signal 1 and setting it from the controller 14 toward the tilt ACT driver 8, the tilt correction with respect to the warp and tilt of the disc is always kept optimal.

  Next, the operation of the embodiment of the present invention configured as described above will be described. The first process will be described with reference to the flowchart of FIG. After power-on and disk loading, initial preparation 1 is executed (step S1). In this initial preparation 1, the optical pickup 4 is moved to the inner periphery side, and the number of movement steps of the optical pickup 4 is set to “0” at this position. Subsequently, in order to set parameters necessary for performing focus servo, the optical pickup 4 is moved to a predetermined position, and at this position, focus error offset adjustment, tracking error offset adjustment, focus error gain adjustment, tracking Adjust the error gain and set servo parameters so that focus servo and tracking servo can be executed.

  Next, the optical pickup 4 is moved to the innermost periphery of the reproducible area of the optical disc 1 (step S2). At this position, focus servo ON (step S3) and tracking servo ON (step S4) are executed, spindle linear velocity constant control (CLV) ON (step S5), still ON (jump forward one track after one rotation) (Step S6) is operated, and the reproduction track of the optical pickup 4 is fixed.

  Next, the N tilt drive signals are given to the tilt ACT driver 8, and the process proceeds to the process of measuring the jitter value of the reproduction signal in each state by the jitter measuring unit 18. First, a variable n indicating the number of tilt drive signals is set to an initial value “1” (step S7), and then the tilt drive signal is set to the nth (= 1) state and applied to the tilt ACT driver (step S8). ). The jitter value in this state is measured and stored by the jitter measuring unit 18 (step S9). Subsequently, it is determined whether or not the variable n is N (step S10). If it is not N, the variable n is incremented by “1” (step S11), and then steps S8 to S10 are repeated until the variable n becomes N. repeat.

If the variable n is repeated until the variable n becomes N in this way, N tilt drive signals and jitter values are stored. Thus, approximate expression 1 is obtained based on these N sets of measured values. The approximate expression is an n-order function obtained by the method of least squares. If approximate expression 1 to be obtained is a quadratic function as shown in FIG.
Y = A · X ² + B · X + C
Coefficients A, B, and C are obtained (step S12). Here, the X axis in FIG. 3 is the tilt drive signal, and the Y axis is the jitter value. Next, the tilt drive signal that minimizes the jitter value Y is obtained as the tilt drive signal 1 from the obtained approximate expression 1 (step S13). Since this is the extreme value of the approximate expression 1, X that satisfies the first-order differential equation = 0 of the approximate expression 1 is obtained. Therefore,
X ₁ = −B / 2 · A
X ₁ is obtained and stored as tilt drive signal 1, and the first process is terminated. In addition, this first process is for correcting the tilt due to the assembly error of the objective lens 3 in the pickup 4, so it may be performed during the manufacturing process and is performed every time the disk 1 to be recorded or reproduced is replaced. There is no need.

  Next, a 2nd process is demonstrated with reference to the flowchart of FIG. After the power is turned on and the disk is loaded, the initial preparation 2 is executed. In this initial preparation 2 (step S21), the optical pickup 4 is moved to the inner peripheral side, and the number of movement steps of the optical pickup 4 is set to “0” at this position. Subsequently, in order to set parameters necessary for performing the focus servo, the optical pickup 4 is moved to a predetermined position, and focus error offset adjustment and focus error gain adjustment are performed at this position to execute the focus servo. Servo parameters are set as described above, and then focus servo is executed (step S22).

  Next, the process moves to a process in which the focus drive signal measurement circuit 16 measures the focus drive signal at each position while moving the optical pickup 4 to M radial positions. First, the variable n indicating the position of the optical pickup 4 is set to an initial value “1” (step S23), the position of the optical pickup is moved to the nth (= 1) position (step S24), and the focus at this position is set. The drive signal is measured and stored by the focus drive signal measurement circuit 16 (step S25). Subsequently, it is determined whether or not the variable n is M (step S26). If not, the variable n is incremented by “1” (step S27), and then steps S24 to S26 are repeated again until the variable n becomes M. .

If the variable n is repeated until the variable n becomes M in this way, the M positions of the optical pickup 4 and the focus drive signal are stored. Therefore, the approximate expression 2 is obtained based on these M sets of measured values. The approximate expression is an n-order function obtained by the method of least squares. If approximate expression 2 to be obtained is a cubic function as shown in FIG.
Y = A · X ³ + B · X ² + C · X + D
The coefficients A, B, C, and D to be obtained are obtained and stored (step S28), and the second process is terminated. Here, the X axis in FIG. 5 is the radial position of the optical disk 1 obtained from the position of the optical pickup 4 (disk radial position), and the Y axis is the focus drive signal. The second process needs to be performed every time the optical disk 1 to be recorded or reproduced is inserted, and is preferably executed in the initial automatic adjustment.

Next, the operation during recording / reproduction will be described with reference to the flowchart of FIG. First, the current disk address is read to determine the radius position X (step S31). The approximate expression 2 obtained in the second process is multiplied by a sensitivity value K1 representing a focus shift amount with respect to a focus drive signal that is known in advance, and the X axis is obtained from the position of the optical pickup 4, and the radial position of the optical disk and the Y axis are obtained. Conversion to approximate expression 3 as the focus shift amount is performed (step S32).
Approximation formula 3:
Focus shift amount Y = K1 × Approximation formula 2
= K1 × (A ・ X ³ + B ・ X ² + C ・ X + D)

Next, approximate expression 3 is first-order differentiated to obtain a first-order differential equation, the X-axis is the radial position of optical disk 1 obtained from the position of optical pickup 4, and the approximate expression is that the Y-axis is the inclination of optical disk relative to optical pickup 4. 4 is obtained (step S33).
Approximation formula 4:
Optical disk tilt Y = K1 × (3A · X ² + 2B · X + C)

An inclination Δ is obtained from the approximate expression 4 and the radial position X of the optical disk obtained from the position of the optical pickup 4 (step S34), the inclination is converted into an angle θ (step S35), and an objective lens for a known tilt drive signal is obtained. Is multiplied by the angle θ to obtain the tilt drive signal 2 (= K2 × angle θ) for correcting the tilt amount at the radial position of the optical disk obtained from the position of the optical pickup 4 (step S36). ). Then, as shown in FIG. 7, an optimum tilt correction amount (tilt drive signal 3) obtained by adding the tilt drive signal 1 and the tilt drive signal 2 obtained from the first process is calculated (step S37).
Tilt drive signal 3 = tilt drive signal 1 + tilt drive signal 2
= −B / 2 ・ A + K2 × θ
By outputting the tilt drive signal 3 to the tilt ACT driver 8 (step S38), it is possible to perform optimum tilt correction at an arbitrary position on the optical disc.

  FIG. 3 is a diagram showing the relationship between the tilt drive signal obtained from the first process and the jitter value. From the approximate expression 1, the tilt drive signal 1 with the smallest jitter can be derived. FIG. 5 is a diagram showing the relationship between the disk radial position and the focus drive signal obtained from the second process. From this approximate expression 2, the warp and the inclination with respect to the disk radial position can be expressed according to the above procedure. As shown in FIG. 7, an optimum tilt drive signal 3 at an arbitrary disk radial position can be derived.

<Second Embodiment>
FIG. 8 is a block diagram showing an optical information recording / reproducing apparatus according to a second embodiment of the optical disk drive apparatus according to the present invention. In the second embodiment, an error rate measurement unit 20 is provided instead of the jitter measurement unit 18 shown in FIG. The error rate measurement unit 20 measures the error rate of the reproduction signal obtained by optimizing the reproduction signal extracted from the photodetector 21 by the reproduction signal equalizer 17, and the tilt control unit 19 reads the numerical value. The other configurations are the same except that the tilt drive is performed based on the error rate of the reproduction signal, and thus the description thereof is omitted.

FIG. 9 shows the process of the first process in the second embodiment. Steps 9a, 12a, and 13a are different from FIG. 2, and the other processes are the same. In step 9a, the error rate measuring unit 20 measures and stores the error rate of the reproduction signal. In step 12a, when N tilt drive signals and error rates are stored, approximate expression 1 is obtained based on these N sets of measured values. The approximate expression is an n-order function obtained by the method of least squares. If approximate expression 1 to be obtained is a quadratic function as shown in FIG.
Y = A · X ² + B · X + C
Coefficients A, B, and C are obtained. Here, the X axis in FIG. 10A is the tilt drive signal, and the Y axis is the error rate. Next, the tilt drive signal 1 that minimizes the error rate is obtained from the obtained approximate expression 1 (step S13a). Since this is the extreme value of the approximate expression 1, X is calculated so that the first-order differential equation = 0 of the approximate expression. Therefore,
X ₁ = −B / 2 · A
X ₁ is obtained and stored as tilt drive signal 1, and the first process is terminated.

The processing in the second process in the second embodiment is the same as that in the first embodiment (FIG. 4). Further, the processing during recording / reproduction is the same as that in the first embodiment (FIG. 6), but in step S37 in FIG.
Tilt drive signal 3 = tilt drive signal 1 + tilt drive signal 2
= −B / 2 ・ A + K2 × θ
The tilt drive signal 1 for obtaining is different from that obtained based on the error rate in FIG.

  Here, FIG. 10A is a diagram showing the relationship between the tilt drive signal obtained from the first process and the error rate. From the approximate expression 1, the tilt drive signal 1 with the minimum error rate can be derived. FIG. 10B is the same as FIG. 5 and shows the relationship between the disk radius position obtained from the second process and the focus drive signal. From this approximate expression 2, the disk radius position is obtained according to the above procedure. It is possible to express the warp and inclination with respect to. FIG. 10C is the same as FIG. 7, and the optimum tilt drive signal 3 can be derived at an arbitrary disk radial position.

1 is a configuration diagram showing an example of an optical information recording / reproducing apparatus according to a first embodiment of an optical disc drive apparatus according to the present invention. It is a flowchart showing the 1st process in 1st Embodiment. It is a graph which shows the relationship between the tilt drive signal and jitter measured value in 1st Embodiment. It is a flowchart showing the 2nd process in 1st Embodiment. 6 is a graph showing a relationship between a disk radial position and a focus drive signal in the first embodiment. 6 is a flowchart showing an operation during recording / reproduction in the first embodiment. 6 is a graph showing a relationship between a disk radial position and a tilt drive signal in the first embodiment. It is a block diagram which shows an example of the optical information recording / reproducing apparatus which is 2nd Embodiment of the optical disk drive device based on this invention. It is a flowchart showing the 1st process in 2nd Embodiment. 6 is a graph showing a relationship between a tilt drive signal and an error rate measurement value, a relationship between a disc radius position and a focus drive signal, and a relationship between a disc radius position and a tilt drive signal in the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Laser beam 3 Objective lens 4 Optical pick-up 5 Lead screw 6 Thread motor 7 Thread driver 8 Tilt actuator driver 9 Focus actuator driver 10 Tracking actuator driver 11 Spindle driver 12 Focus error calculation circuit 13 Tracking error calculation circuit 14 Controller 15 Equalizer circuit 16 Focus Drive Signal Measurement Unit 17 Playback Signal Equalizer 18 Jitter Measurement Unit 19 Tilt Control Unit 20 Error Rate Measurement Unit 21 Photodetector

Claims (2)

In an optical disc drive apparatus that tilts the objective lens with a tilt drive signal to correct the tilt of the objective lens and corrects the tilt so that the optical axis of the objective lens in an optical pickup is perpendicular to the surface of the optical disc.
With the optical pickup fixed to the reproducible area of the optical disc, the objective lens is tilted by N (N is a natural number of 3 or more) tilt drive signals, and the reproduction signal of the optical pickup in each tilt drive signal is A jitter value is measured to obtain a first approximate expression indicating a relationship between each tilt drive signal and the measured jitter value, and a tilt drive signal having a minimum jitter value in the first approximate expression is obtained from the objective lens. Means for obtaining and storing as a first tilt drive signal for correcting the tilt;
Before recording or reproducing an optical disk to be recorded or reproduced, the focus pickup signals at M (M is a natural number of 3 or more) radial positions are measured while moving the optical pickup in the radial direction of the optical disk. Means for obtaining a second approximate expression indicating the relationship between each focus drive signal and the radial position of the pickup;
During recording or reproduction of the optical disk to be recorded or reproduced, the second approximate expression, the current radial position of the optical pickup, the sensitivity of the displacement amount of the objective lens with respect to a focus drive signal, and tilt drive A second tilt drive signal is obtained from the sensitivity of the tilt angle of the objective lens to the signal, and the tilt drive signal obtained by adding the first and second tilt drive signals is obtained as a third radial drive position at the current radial position of the optical pickup. Means for tilt correction as a tilt drive signal of
Optical disk drive device provided. In an optical disc drive apparatus that tilts the objective lens with a tilt drive signal to correct the tilt of the objective lens and corrects the tilt so that the optical axis of the objective lens in an optical pickup is perpendicular to the surface of the optical disc.
With the optical pickup fixed to the reproducible area of the optical disc, the objective lens is tilted by N (N is a natural number of 3 or more) tilt drive signals, and the reproduction signal of the optical pickup in each tilt drive signal is The error rate is measured to obtain a first approximate expression indicating the relationship between each tilt drive signal and the measured error rate, and the tilt drive signal that minimizes the error rate in the first approximate expression is obtained from the objective lens. Means for obtaining and storing as a first tilt drive signal for correcting the tilt;
Before recording or reproducing an optical disk to be recorded or reproduced, the focus pickup signals at M (M is a natural number of 3 or more) radial positions are measured while moving the optical pickup in the radial direction of the optical disk. Means for obtaining a second approximate expression indicating the relationship between each focus drive signal and the radial position of the pickup;
During recording or reproduction of the optical disk to be recorded or reproduced, the second approximate expression, the current radial position of the optical pickup, the sensitivity of the displacement amount of the objective lens with respect to a focus drive signal, and tilt drive A second tilt drive signal is obtained from the sensitivity of the tilt angle of the objective lens to the signal, and the tilt drive signal obtained by adding the first and second tilt drive signals is obtained as a third radial drive position at the current radial position of the optical pickup. Means for tilt correction as a tilt drive signal of
Optical disk drive device provided.

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