JP2002342963A - Optical disk device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device that can accurately detect the tilt of the recording face of an optical disk with respective to the optical axis of a light beam through reproducing signals using an optical pickup, without installing a special detector like a tilt sensor, and that can control such tilt of the recording face at an optimum angle. SOLUTION: The optical disk device is provided with a measuring means 20 that measures the amplitude of reproducing signals while a relative tilt (tilt quantity) of the recording face of an optical disk 1 to a light beam is varied at a prescribed step angle centering around a reference angle, a calculating means that approximates the relation between the tilt quantity and the amplitude of the reproducing signals to a secondary function by the method of least square to obtain, as the calculation result, the optimum tilt quantity maximizing the amplitude of the reproducing signals, and a means that discriminates the calculation result as normal/abnormal. If the calculation result is abnormal, the reference angle is shifted by prescribed steps, and resetting, remeasurement and recalculation are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus for recording and reproducing information by irradiating an optical disk with a light beam, and a control method therefor, and more particularly, to controlling a relative inclination of a light beam with a recording surface of the optical disk. This relates to tilt control.

[0002]

2. Description of the Related Art In recent years, as means for recording / reproducing large-capacity data, an optical disk device capable of recording / reproducing at a higher recording density has been demanded. In order to realize an optical disk device for high-density recording, it is necessary to control the inclination (tilt amount) of the recording surface of the optical disk with respect to the optical axis of the light beam to an optimum angle. If the inclination (tilt amount) of the recording surface of the optical disk with respect to the optical axis of the light beam is not maintained at an optimum angle, the light spot when the light beam is focused on the optical disk has aberrations and is recorded at high density. It is difficult to accurately read data and to record high-quality signals at high density. However, since the substrate of an optical disk is generally formed by molding a resin material, warping often occurs due to distortion during molding, storage conditions, and the like.
Conventionally, several methods have been proposed as methods for controlling the inclination (tilt amount) of the optical axis of a light beam with respect to the recording surface of an optical disk having such a warp.

For example, Japanese Utility Model Laid-Open No. 2-72414, Japanese Patent Laid-Open No. 7-272300, and Japanese Patent Laid-Open No. 10-30802.
In Japanese Patent Application Publication No. 3 (1993), a so-called tilt sensor composed of a light emitting element and a light receiving element divided into two is provided on an optical head, and the tilt sensor detects the relative inclination between the optical head and the recording surface of the optical disk. There has been proposed an apparatus that controls the inclination of the recording surface of an optical disk with respect to the optical axis of a light beam while tilting the entire optical head by a driving mechanism based on a detection signal of a tilt sensor. Also, Japanese Patent Application Laid-Open No. 10-812
Japanese Patent Publication No. 564 discloses a device in which a tilt sensor is fixedly provided on a chassis instead of on an optical head, and a tilt amount is corrected by obtaining a warp of an optical disk from a signal detected by the tilt sensor.

[0004]

However, in the conventional configuration, a dedicated tilt sensor is used to detect the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam. Therefore, a space for arranging the tilt sensor is required, and the cost is increased not only for the sensor itself but also for its driving circuit and detecting circuit.
In addition, some tilt sensors do not detect the relative tilt between the optical axis of the light beam and the recording surface of the optical disk itself. become. Furthermore, since it is difficult to make the position where the tilt sensor detects the inclination coincide with the position of the light spot, the inclination of the recording surface of the optical disk at the position of the light spot cannot be detected, and a detection error has occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and the inclination of the recording surface of an optical disk with respect to the optical axis of a light beam is read by an optical pickup without providing a special detection device such as a tilt sensor. It is an object of the present invention to provide an optical disc device capable of accurately detecting a reproduced signal using a reproduction signal and controlling the inclination of a recording surface of the optical disc with respect to the optical axis of a light beam to an optimum angle.

[0006]

To solve the above problems, the present invention has the following arrangement. A first configuration of the present invention focuses and irradiates a light beam on an optical disc having a track formed in a spiral or concentric shape,
An optical pickup for recording or reproducing a signal; a photodetector for receiving reflected light from the optical disk; A reproduction signal processing unit that generates the output signal of the detector, and a command signal for sequentially setting the tilt amount to a plurality of different values in the first mode, and outputs the tilt amount in the second mode. A tilt setting signal generator configured to set an optimum tilt value, a tilt driving mechanism that varies the tilt amount according to an output signal of the tilt setting signal generator, and driving the tilt driving mechanism based on the command signal. A reproduction signal measuring unit for measuring an output value of the reproduction signal processing unit when the tilt amount is sequentially changed; An optical disk apparatus characterized by comprising the optimal tilt amount calculation section for calculating the optimal tilt value based on the measured value of the signal measuring unit.

According to a sixteenth aspect of the present invention, there is provided an optical pickup for focusing and irradiating an optical disk having a spiral or concentric track with a light beam to record or reproduce a signal, and the optical disk. A photodetector that receives reflected light from the optical disc, and a reproduction signal process that generates a signal that changes in accordance with a tilt amount that is a relative inclination between the recording surface of the optical disc and the light beam using an output signal of the photodetector. A playback signal measuring unit that measures an output value of the playback signal processing unit; and a tilt drive mechanism that varies the tilt amount. A command signal to be set to a value is sequentially output, and the tilt drive mechanism is driven in accordance with the command signal to sequentially change the tilt amount, thereby sequentially changing the tilt amount. Measuring the output signal of the reproduction signal processing unit at the time, an optimum tilt amount detection step of calculating an optimum tilt value based on the tilt amount changed by the command signal and the measurement value of the reproduction signal measurement unit, An optimum tilt amount setting step of setting the tilt amount to the optimum tilt value. The tilt of the recording surface of the optical disk with respect to the optical axis of the light beam can be accurately detected by a reproduction signal from the optical head without providing a special detection device such as a tilt sensor, and the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam. Can be controlled to an optimum angle.

A second configuration of the present invention is an optical pickup that focuses and irradiates a light beam on an optical disk having tracks formed in a spiral or concentric shape to record or reproduce signals, and an optical pickup from the optical disk. A photodetector that receives the reflected light, and a reproduction signal processing unit that generates a signal that changes according to a tilt amount that is a relative inclination of the recording surface of the optical disc and the light beam using an output signal of the photodetector; A command signal for sequentially setting the tilt amount to a plurality of different values in the first mode, and a tilt setting signal generating unit for setting the tilt amount to the optimum tilt value in the second mode; A tilt drive mechanism that varies the tilt amount in accordance with an output signal of a setting signal generating unit; and A reproduction signal measurement unit that measures an output value of the reproduction signal processing unit when sequentially changed, and a relationship between the tilt amount changed by the command signal and a measurement value of the reproduction signal measurement unit is determined by a least square method. An optical disc apparatus comprising: an optimum tilt amount calculation unit that approximates a predetermined function and calculates the optimum tilt value based on the function.

In a seventeenth aspect of the present invention, in the optimum tilt amount detecting step, a relationship between the tilt amount changed by the command signal and a measurement value of the reproduction signal measuring unit is determined by a least square method. A method of controlling an optical disc device according to a sixteenth configuration, characterized in that the optimum tilt value is calculated based on the function by approximating the function.
Thus, an accurate optimum tilt value can be obtained based on a small number of measured values. An accurate optimum tilt value can be obtained in a small calculation circuit or in a short calculation time.

[0010] A third configuration of the present invention is the method according to the first aspect, wherein the optimum tilt value calculated by the optimum tilt amount calculation unit exceeds a calculation limit value determined according to a command signal from the tilt setting signal generation unit. If the optimum tilt value exceeds the calculation limit value in the positive direction, a command signal of the tilt setting signal generation unit is changed so that the tilt value determined thereby changes by a predetermined amount in the positive direction. If the optimal tilt value exceeds the calculation limit value in the negative direction, the command signal of the tilt setting signal generation unit is changed so that the tilt value determined thereby changes by a predetermined amount in the negative direction. And further comprising a calculation result determination unit for setting the tilt setting signal generation unit to the optimum tilt value when the optimum tilt value does not exceed the calculation limit value, When the optimum tilt value calculated by the amount calculation unit exceeds the calculation limit value in the positive direction or the negative direction, the tilt setting signal generation unit outputs the reset command signal and outputs the reproduction signal. The measuring unit re-measures the output value of the reproduction signal processing unit when the tilt amount is sequentially changed in accordance with the reset command signal, and the optimal tilt amount calculating unit re-calculates the optimal tilt value. An optical disc device according to the first or second configuration, wherein the optical disc device is characterized by calculating.

In an eighteenth aspect of the present invention, in the optimum tilt amount detecting step, it is determined whether or not the optimum tilt value exceeds a calculation limit value determined according to the command signal. Is larger than the calculation limit value in the positive direction, the command signal is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and the optimum tilt amount detection step is performed again. If the optimum tilt value exceeds the calculation limit value in the negative direction, the command signal is reset so that the tilt value determined thereby changes in the negative direction by a predetermined amount. The optimum tilt amount detecting step is executed again, and if the optimum tilt value does not exceed the calculation limit value, the optimum tilt amount setting step is executed. A control method for forming an optical disc apparatus. It has means for judging whether the optimal tilt value is correct or not, and when the optimal tilt value is abnormal, resets the reference angle by a predetermined step and performs re-measurement / recalculation.
An accurate optimum tilt value can be obtained.

In a fourth configuration of the present invention, when the amount of tilt is X and the value measured by the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X. Y
Is calculated as an optimum tilt value, and it is determined whether a quadratic coefficient of the quadratic function is positive or negative,
In the case of a positive value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount. And a tilt setting signal generating unit that outputs the reset command signal when the quadratic coefficient of the quadratic function is positive. The output value of the reproduction signal processing unit when the tilt amount is sequentially changed according to the set command signal is re-measured, and the optimum tilt amount calculation unit recalculates the optimum tilt value. An optical disc device of the first or second configuration characterized by the following.

In a nineteenth aspect of the present invention, in the optimum tilt amount detecting step, when the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X. The tilt amount at which Y is an extreme value is calculated as an optimum tilt value, and it is determined whether the quadratic coefficient of the quadratic function is positive or negative. If the quadratic coefficient of the quadratic function is positive, The command signal is reset so that the tilt value determined thereby changes by a predetermined amount, and the optimum tilt amount detecting step is re-executed. If the quadratic coefficient of the quadratic function is negative, the optimum tilt A control method for an optical disk device according to a sixteenth or seventeenth configuration, characterized by performing an amount setting step. It has means for judging whether or not the optimum tilt value is correct. If the optimum tilt value is abnormal, the reference angle is shifted by a predetermined step and reset, and remeasurement and recalculation are performed. An accurate optimum tilt value at which the signal becomes maximum can be obtained.

According to a fifth aspect of the present invention, when the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X. Y
Is calculated as an optimum tilt value, and it is determined whether a quadratic coefficient of the quadratic function is positive or negative,
In the case of a negative value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount, and in the case of a positive value, the optimum tilt value is set in the tilt setting signal generation unit. The apparatus further includes a calculation result determining unit for setting, and when the quadratic coefficient of the quadratic function is negative, the tilt setting signal generating unit outputs the reset command signal, and the reproduction signal measuring unit resets the command signal. The output value of the reproduction signal processing unit when the tilt amount is sequentially changed according to the set command signal is re-measured, and the optimum tilt amount calculation unit recalculates the optimum tilt value. An optical disc device having the first or second configuration characterized by the following.

In a twentieth aspect of the present invention, in the optimum tilt amount detecting step, when the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X. The tilt amount where Y is an extreme value is calculated as an optimum tilt value, and it is determined whether the quadratic coefficient of the quadratic function is positive or negative. If the quadratic coefficient of the quadratic function is negative, The command signal is reset so that the tilt value determined thereby changes by a predetermined amount, and the optimum tilt amount detecting step is re-executed. If the quadratic coefficient of the quadratic function is positive, the optimum tilt A control method for an optical disk device according to a sixteenth or seventeenth configuration, wherein an amount setting step is performed. Even when the quality of the reproduced signal is extremely low, such as when the amount of warpage of the optical disk is extremely large, the optimum tilt amount that minimizes the jitter value etc. is accurately detected, and the tilt amount is accurately controlled to the optimum angle. Is possible.

In a sixth configuration of the present invention, the operation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and determines a plurality of tilt amounts set by the command signal. It is determined whether the optimum tilt value is located in the positive direction or the negative direction with reference to the reference angle which is the center value. If the quadratic coefficient is positive and the optimal tilt value is located in the positive direction with respect to the reference angle, the tilt setting signal generation unit issues a command signal to determine the tilt value. Is reset so as to change by a predetermined amount in the negative direction, and when the quadratic coefficient is positive and the optimum tilt value is located in the negative direction with reference to the reference angle, the tilt setting signal generation unit Command signal An optical disk apparatus of the fourth configuration, wherein a tilt value defined by Re is reconfigured to change in a positive direction by a predetermined amount. It has means for judging whether or not the optimum tilt value is correct. If the optimum tilt value is abnormal, the reference angle is shifted by a predetermined step and reset, and remeasurement and recalculation are performed. An accurate optimum tilt value at which the signal becomes maximum can be obtained.

In a seventh configuration of the present invention, the calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and determines a plurality of tilt amounts set by the command signal. It is determined whether the optimum tilt value is located in a positive direction or a negative direction with reference to a reference angle that is a center value. If the quadratic coefficient is positive, the tilt setting signal generation unit notifies the optimum tilt value If the quadratic coefficient is negative and the optimum tilt value is located in the positive direction with respect to the reference angle, the tilt setting signal generation unit generates a tilt signal determined by the command signal. Is reset so as to change by a predetermined amount in the negative direction, and when the quadratic coefficient is negative and the optimum tilt value is located in the negative direction with reference to the reference angle, the tilt setting signal generation unit Command signal An optical disk apparatus of the fifth configuration, wherein a tilt value defined by Re is reconfigured to change in a positive direction by a predetermined amount. Even when the quality of the reproduced signal is extremely low, such as when the amount of warpage of the optical disk is extremely large, the optimum tilt amount that minimizes the jitter value etc. is accurately detected, and the tilt amount is accurately controlled to the optimum angle. Is possible.

According to an eighth aspect of the present invention, in the arithmetic operation result judging section, it is determined whether a quadratic coefficient of the quadratic function is positive or negative, and a plurality of tilt amounts set by the command signal are determined. With reference to a reference angle that is a center value, a positive average value that is an average of the measured values measured when the tilt amount set by the command signal is located in a positive direction with respect to the reference angle, Comparing the magnitude relationship with a negative average value, which is the average of the measured values measured when the tilt amount set by the command signal is located in the negative direction with respect to the reference angle, the second order coefficient Is positive and the positive average value is larger than the negative average value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction. And the quadratic coefficient If the average value is positive and the average value on the negative side is larger than the average value on the positive side, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes in the negative direction by a predetermined amount. An optical disc apparatus according to a fourth configuration, characterized in that when the quadratic coefficient is negative, the tilt setting signal generation section sets the optimum tilt value. It has means for judging whether or not the optimum tilt value is correct. If the optimum tilt value is abnormal, the reference angle is shifted by a predetermined step and reset, and remeasurement and recalculation are performed. An accurate optimum tilt value at which the signal becomes maximum can be obtained.

According to a ninth aspect of the present invention, in the arithmetic operation result judging section, it is determined whether a quadratic coefficient of the quadratic function is positive or negative, and a plurality of tilt amounts set by the command signal are determined. With reference to a reference angle that is a center value, a positive average value that is an average of the measured values measured when the tilt amount set by the command signal is located in a positive direction with respect to the reference angle, Comparing the magnitude relationship with a negative average value, which is the average of the measured values measured when the tilt amount set by the command signal is located in the negative direction with respect to the reference angle, the second order coefficient Is negative and the positive average value is greater than the negative average value, the tilt setting signal generation unit command signal is reset so that the tilt value determined thereby changes in the negative direction by a predetermined amount. And the quadratic coefficient If the average value is negative and the average value on the negative side is greater than the average value on the positive side, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction. An optical disc apparatus according to a fifth configuration, wherein when the secondary coefficient is positive, the tilt setting signal generation section sets the optimum tilt value. Even when the quality of the reproduced signal is extremely low, such as when the amount of warpage of the optical disk is extremely large, the optimum tilt amount that minimizes the jitter value etc. is accurately detected, and the tilt amount is accurately controlled to the optimum angle. Is possible.

In a tenth aspect of the present invention, the operation result determination section determines whether a quadratic coefficient of the quadratic function is positive or negative, and determines a plurality of tilt amounts set by the command signal. With reference to a reference angle that is a center value, a positive average value that is an average of the measured values measured when the tilt amount set by the command signal is located in a positive direction with respect to the reference angle, The tilt amount set by the command signal is compared with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, and the optimum tilt amount is calculated. When the optimum tilt value calculated by the calculation unit is located in the positive direction with respect to the reference angle and the negative side average value is larger than the positive side average value, a command signal of the tilt setting signal generation unit Is determined by it Is reset so that the tilt value changes in the negative direction by a predetermined amount, the optimal tilt value is located in the negative direction with respect to the reference angle, and the positive average value is larger than the negative average value. In the case of resetting the command signal of the tilt setting signal generation unit so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and when the command signal of the tilt setting signal generation unit is reset, ,
The tilt setting signal generation unit outputs the reset command signal, and the reproduction signal measurement unit outputs the reproduction signal processing unit when the tilt amount is sequentially changed in accordance with the reset command signal. The optical disc apparatus according to a fourth configuration, wherein the value is re-measured, and the optimum tilt amount calculating unit recalculates the optimum tilt value. It has means for judging whether or not the optimum tilt value is correct. If the optimum tilt value is abnormal, the reference angle is shifted by a predetermined step and reset, and remeasurement and recalculation are performed. An accurate optimum tilt value at which the signal becomes maximum can be obtained.

According to an eleventh configuration of the present invention, the calculation result determination section determines whether a quadratic coefficient of the quadratic function is positive or negative, and determines a plurality of tilt amounts set by the command signal. With reference to a reference angle that is a center value, a positive average value that is an average of the measured values measured when the tilt amount set by the command signal is located in a positive direction with respect to the reference angle, The tilt amount set by the command signal is compared with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, and the optimum tilt amount is calculated. When the optimum tilt value calculated by the calculation unit is located in the positive direction with respect to the reference angle and the positive average value is larger than the negative average value, a command signal of the tilt setting signal generation unit Is determined by it The optimal tilt value is located in the negative direction with respect to the reference angle, and the negative average value is larger than the positive average value. In the case of resetting the command signal of the tilt setting signal generation unit so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and when the command signal of the tilt setting signal generation unit is reset, ,
The tilt setting signal generation unit outputs the reset command signal, and the reproduction signal measurement unit outputs the reproduction signal processing unit when the tilt amount is sequentially changed in accordance with the reset command signal. The optical disc apparatus according to the fifth configuration, wherein the value is re-measured, and the optimum tilt amount calculating unit recalculates the optimum tilt value. Even when the quality of the reproduced signal is extremely low, such as when the amount of warpage of the optical disk is extremely large, the optimum tilt amount that minimizes the jitter value etc. is accurately detected, and the tilt amount is accurately controlled to the optimum angle. Is possible.

According to a twelfth aspect of the present invention, the output value of the reproduction signal processing section is a tracking error signal, and the reproduction signal measurement section is a tracking error signal amplitude measurement section. 2, 3, 4, 6, 8 or 1
0 is an optical disk device. An accurate optimum tilt value can be obtained based on the tracking error signal.

According to a thirteenth configuration of the present invention, the output value of the reproduction signal processing unit is an output value corresponding to an addition signal of output signals of a plurality of light emitting elements included in the photodetector, A first, second, third, fourth, or first feature wherein the measuring unit is an added signal amplitude measuring unit that measures the amplitude of the added signal.
An optical disk device having a configuration of 6, 8, or 10. An accurate optimum tilt value can be obtained based on the RF signal.

According to a fourteenth aspect of the present invention, in the optical disk apparatus having the first, second, third, fifth, seventh, ninth, or eleventh configuration, the reproduction signal measuring section is a jitter signal measuring section. It is. An accurate optimum tilt value can be obtained based on the jitter signal.

A fifteenth aspect of the present invention is the optical disc apparatus according to any one of the first to fourteenth aspects, wherein the tilt drive mechanism changes the angle of an objective lens for focusing a light beam. . The structure of the tilt drive mechanism is simplified, and the size, thickness, and cost are reduced.

[0026]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a preferred embodiment of the present invention.

Embodiment 1 Hereinafter, an optical disk device according to Embodiment 1 of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of the optical disk device according to the first embodiment of the present invention. In FIG. 1, an optical disc 1 is driven to rotate by a spindle motor 2, and a rotation frequency of the spindle motor 2 is controlled by a spindle servo circuit (not shown).
Is controlled by The optical pickup 3 (including the objective lens 4 mounted thereon) focuses a light beam on the recording surface of the optical disc 1 to record or reproduce data. The binary signal to be recorded is converted into a recording signal by a recording signal processing circuit (not shown), sent to the optical pickup 3, and recorded on the optical disc 1. Optical disk 1
The reproduction signal read from the is processed into a binary signal by the reproduction signal processing circuit 19.

The objective lens 4 of the optical pickup 3 is driven in the optical axis direction (focus direction) of the light beam by a focus actuator 7 composed of a magnet 8 and a focus drive coil 9. The focus servo circuit 6 controls the voltage applied to the focus drive coil 9 to control the focal position of the objective lens 4 in order to focus the light beam emitted from the optical pickup 3 on the recording surface of the optical disc 1. Similarly, the objective lens 4 is driven in the radial direction (tracking direction) of the optical disc 3 by a tracking actuator 11 composed of a magnet 8 and a tracking drive coil 10. The tracking servo circuit 12 controls the voltage applied to the tracking drive coil 10 so that the light beam emitted from the optical pickup 3 follows the track formed on the recording surface, and controls the optical axis position of the objective lens 4. A focus error signal indicating a shift in the focal position of the light beam,
A tracking error signal indicating the deviation in the track direction is generated by the reproduction signal processing circuit 19 based on the reproduction signal from the optical pickup 3 and sent to the focus servo circuit 6 and the tracking servo circuit 12.

The optical pickup moving means 13 for moving the optical pickup to a different radial position is composed of a traverse motor 14, a lead screw 15, a rack 16, and a guide shaft 17, and a lead screw 15 formed on the rotation shaft of the traverse motor 14. Is the optical pickup 3
The optical pickup 3 is supported by a guide shaft 17 so as to be able to move straight. The optical pickup 3 is composed of a lead screw 1
5 and traverse motor 1 transmitted via rack 16
The optical disk 1 is moved in the radial direction by the rotation torque of No. 4.

The tilt driving mechanism 26 (tilt varying means) shown in FIG. 1 changes the height of the outer peripheral end of a guide shaft 17 that supports the optical pickup 3 so as to be movable in the radial direction of the optical disk 1, thereby changing the height of the optical pickup. 3 is a mechanism for changing the relative tilt with respect to the optical disk 1 and includes a motor gear 27, a chill track 28, a tilt cam 29, a tilt follower 30, a guide shaft fixing plate 31, and a guide shaft 17. The tilt motor 24 is rotated by the tilt drive voltage from the tilt servo circuit 21, and the tilt cam 29 is translated via the motor gear 27 and the chill track 28. The translation of the tilt cam 29 causes the tilt cam 29 to move.
The tilt follower 30 abutting on the inclined surface moves up and down, and the vertical movement of the tilt follower 30 causes the guide shaft fixing plate 31 formed integrally with the tilt follower 30 to move up and down. The outer peripheral end of the guide shaft 17 is fixed to the guide shaft fixing plate 31, and the guide shaft 17 is rotatably supported about its inner peripheral end. Therefore, the inclination of the guide shaft 17 changes due to the vertical movement of the guide shaft fixing plate 31, and as a result, the inclination of the optical pickup 3 changes. By rotating the tilt motor 24 as described above, the optical pickup 3
Is changed, and the irradiation angle of the light beam applied to the optical disc 1 can be changed. That is, by controlling the rotation of the tilt motor 24, the irradiation angle of the light beam irradiated on the optical disc 1 can be controlled to be a desired angle.

FIG. 2 shows the structure of the tilt servo circuit 21. The tilt servo circuit 21 is a circuit for controlling the tilt of the optical pickup 3 so that the irradiation angle of the light beam irradiated on the optical disc 1 becomes a desired angle. A tilt servo signal generator 23 that outputs a tilt servo signal based on the tilt setting signal from the signal generator 33, and a tilt drive voltage based on the tilt servo signal
And a tilt motor drive circuit 25 for supplying the motor 4 to the motor.

Next, the photodetector 34 and the reproduction signal processing circuit 19 provided in the optical pickup 3 will be described with reference to FIGS. FIG. 3 shows the relationship between the configuration of the photodetector 34 and the light reflected from the optical disc 1. The photodetector 34 includes four divided light receiving elements A, B, C, and D. The detection signal of each light receiving element is amplified by an amplifier. The output signals a, b, c, d of each amplifier are transmitted to the reproduction signal processing circuit 19. FIG. 4 shows the reproduction signal processing circuit 19. From the output signals a, b, c, and d of the photodetector 34, the reproduction signal processing circuit 19 calculates a tracking error (TE) signal = (a + d)-(b + c) and a focus error (FE).
Signal = (a + c)-(b + d), RF signal = (a + b +
c + d). The TE signal is sent to the tracking servo circuit 12 and used for tracking servo for causing the light spot to follow the track of the optical disk. The FE signal is sent to a focus servo circuit 6 and used for focus servo for controlling the focal position of the objective lens 4 to focus the light spot on the recording surface of the optical disc 1.

FIG. 5 shows the structure of the tilt detecting section 20. The tilt detection unit 20 includes a TE signal amplitude measurement unit 35, a tilt setting signal generation unit 33, an optimum tilt amount calculation unit 36, and a calculation result determination unit 37. The tilt detection unit 20 that calculates the optimum tilt amount based on the reproduction signal of the optical pickup 3 and outputs a tilt setting signal is a unique block of the present invention. The tilt detection unit 20 has two operation modes: an optimum tilt amount detection mode and an optimum tilt amount setting mode. The optimum tilt amount detection mode is a mode for detecting the optimum tilt amount by changing the tilt amount, and the optimum tilt amount setting mode is a mode for fixing the tilt amount to the optimum tilt amount.

The operation mode of the tilt setting signal generator 33 is determined. The determined operation mode is transmitted to each block (not shown). The tilt setting signal generation unit 33 sequentially outputs three or more (seven in the present embodiment) different tilt setting signals in the optimum tilt amount detection mode. As a result, different tilt amounts are sequentially set (a constant tilt amount is set for each tilt setting signal). The TE signal amplitude measurement unit 35 measures the amplitude value of the TE signal at each tilt amount (details will be described later). The tilt setting signal generation unit 33 includes:
In the optimum tilt amount setting mode, a tilt setting signal of the optimum tilt amount is output based on the calculation result output by the optimum tilt amount calculating unit 36. Thereby, the optimum tilt amount is set.

The TE signal amplitude measuring section 35 measures the amplitude of the tracking error signal (TE signal) generated by the reproduction signal processing circuit 19. The optimum tilt amount calculation unit 36 calculates the relationship between three or more tilt setting signals in the optimum tilt amount detection mode and the amplitude value of the TE signal measured for each tilt amount (tilt setting signal) by the least square method. It approximates to a quadratic function, and calculates a tilt amount (or a tilt setting signal) at which the amplitude value of the TE signal becomes an extreme value (maximum value) based on the quadratic function as a calculation result. At the optimum tilt angle, the amount of reflected light input to the optical pickup 3 is maximized, so that the amplitude value of the TE signal is also maximized.

The calculation result determination section 37 determines whether or not the calculation result calculated by the optimum tilt amount calculation section 36 exceeds a predetermined calculation limit value. If the calculation result exceeds the calculation limit value, the calculation result and a command to remeasure the relationship between the tilt setting signal (tilt amount) and the amplitude value of the TE signal are output to the tilt setting signal generation unit 33. The tilt setting signal generator 33 performs re-measurement by a method described later. If the calculation result does not exceed the calculation limit value, the calculation result and
Information indicating that the calculation result does not exceed the calculation limit value is transmitted to the tilt setting signal generation unit 33. The tilt setting signal generator 33 changes the operation mode to the optimum tilt amount setting mode, and outputs a tilt setting signal corresponding to the calculation result (optimum value).

The tilt setting signal generator 33 outputs to the tilt servo circuit 21 a tilt setting signal for setting the relative inclination (tilt amount) between the optical disk 1 and the light beam to a desired angle. As described above, the tilt setting signal generation unit 33 sets the 3 set for measurement in the optimum tilt amount detection mode.
One or more tilt setting signals are sequentially output, and in the optimum tilt amount setting mode, a tilt setting signal corresponding to the calculation result (optimum value) output by the optimum tilt amount calculation unit 36 is output. The tilt servo circuit 21 drives the tilt drive mechanism 26 based on the tilt setting signal, and the relative inclination (tilt amount) between the optical disk 1 and the light beam is set to a desired angle (optimal tilt value).

The operation of the optical disk device of Embodiment 1 configured as described above will be described with reference to FIG. FIG. 26 is a flowchart illustrating the operation of the tilt detection unit 20. First, when the power of the optical disk device is turned on or the optical disk is mounted on the optical disk device, the tilt setting signal generation unit 33 sets the tilt detection unit 20 to the optimum tilt amount detection mode (step 260).
1). In the optimum tilt amount detection mode, the tracking servo is turned off so that the light spot crosses the track. Next, the tilt setting signal generating section 33 sequentially outputs seven predetermined tilt setting signals, and the TE signal amplitude measuring section 35 measures the amplitude value of each TE signal (Step 2602). Based on the seven tilt setting signals, the inclination of the optical pickup 3 is changed by three steps in the positive direction and the negative direction at a constant angle pitch S degrees with a predetermined reference inclination set to a reference angle of 0 degree. That is, the amplitude of the TE signal is measured while changing the tilt amount, which is the relative inclination between the recording surface of the optical disc 1 and the light beam. First, the tilt setting signal generator 33 outputs a tilt setting signal for setting the tilt of the optical pickup 3 to the reference angle 0 to the tilt servo circuit 21. While the tilt X1 of the optical pickup 3 is controlled to the reference angle 0, the TE signal amplitude measuring unit 35 measures the TE signal amplitude value Y (X1). Subsequently, the tilt of the optical pickup 3 is set to +1 step, and the amplitude value Y (X2) of the TE signal is measured. Similarly, while changing the inclination of the optical pickup 3 to +2 steps, +3 steps, -1 step, -2 steps, and -3 steps, the amplitude value Y of the TE signal with respect to each tilt amount.
(X3), Y (X4), Y (X5), Y (X6), Y
(X7) is measured seven times in total.

The reference angle 0 ° is set in advance in the assembly process of the manufacturing factory as follows. In the assembling process, the tilt of the optical pickup 3 is adjusted so that the light beam is emitted almost perpendicularly to the reference disk while rotating the flat reference disk having almost no warp by the spindle motor 2, and the reference is made to the reference. The angle is defined as 0 degree. That is, for an optical disk having a warp amount of approximately 0 degrees, the relative inclination (tilt amount) between the recording surface of the optical disk and the light beam at the reference angle of 0 degrees is an optimum value. Then, a rotation angle detection sensor (not shown) is attached to the rotation shaft of the tilt motor 24 so as to output a zero point signal when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Alternatively, the output circuit of the rotation angle detection sensor is adjusted so that the zero point signal is output when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Therefore, if the rotation angle of the tilt motor 24 is set to the angle at which the zero point signal is output, the tilt of the optical pickup 3 becomes the reference angle of 0 degree, and the rotation angle of the tilt motor 24 can be controlled based on the output of the rotation angle detection sensor. For example, the tilt of the optical pickup 3 can be set to a tilt shifted from the reference angle of 0 degree by a predetermined angle.

Next, the optimum tilt amount is calculated based on the measured value (step 2603). Here, FIG. 6 shows a change in the amplitude of the TE signal with respect to the inclination of the optical pickup 3.
As shown in FIG. 6, since the change in the TE signal amplitude is small near the angle at which the TE signal amplitude is maximum, when the inclination of the optical pickup 3 is changed at the constant step angle S degree pitch as described above, the change is small. Unless a large number of measurements are performed at the step angle, the true angle at which the TE signal amplitude becomes maximum cannot be accurately detected. However, focusing on the fact that the change in the TE signal amplitude with respect to the inclination of the optical pickup 3 shows a characteristic substantially close to a quadratic function, the change in the TE signal amplitude is approximated to a quadratic function by the least square method, and the TE signal amplitude is maximized. Find the angle This makes it possible to obtain the maximum angle without reducing the step angle and without increasing the number of measurements. Therefore, the ratio of the inclination (tilt amount) of the optical pickup to the step angle S is represented by X (X = −3,...
.0..3), the TE signal amplitude is Y (X), and Y
(X) is approximated by a quadratic function of equation (1).

[0041]

(Equation 1)

Assuming that the measured value of the TE signal amplitude when the tilt amount X at the j-th measurement is Xj is Yj, the approximated value of equation (1) and the actual measured value Yj are equal to the noise and the like mixed in the signal. They do not completely match due to the effects. Assuming that the error amount at that time is vj, the error amount vj is shown in Expression (2).

[0043]

(Equation 2)

In the least square method, the coefficients a, b, and c are determined so as to minimize the sum of squares E of the error vj as shown in equation (3). N indicates a predetermined number of measured samples.

[0045]

(Equation 3)

In the least-squares method, the values of a, b, and c can be obtained by solving the determinant of equation (4) that is satisfied when E is minimized.

[0047]

(Equation 4)

Here, each function P (k), Q in equation (4)
(K) and Y1 are as shown in Formula (5), Formula (6), and Formula (7).

[0049]

(Equation 5)

[0050]

(Equation 6)

[0051]

(Equation 7)

Here, the tilt amounts are X1 = 0, X2 = +
1, X3 = + 2, X4 = + 3, X5 = -1, X6 =-
2, X7 = -3, so X2 and X5, X3 and X
6, and since X4 and X7 are opposite in sign,
(1), P (3) becomes 0, and equation (4) is simplified to equation (8).

[0053]

(Equation 8)

In the quadratic function of equation (1), X at which Y is the maximum value
Is obtained by Expression (9). Secondary coefficient a and primary coefficient b
Can be calculated from the measured TE signal amplitude value Yj and equation (8).

[0055]

(Equation 9)

When these are summarized, Xmax of the equation (9) is obtained.
(The value of X at which Y is the maximum value) is expressed by equation (10). Further, the quadratic coefficient a can be obtained by Expression (11).

[0057]

(Equation 10)

[0058]

[Equation 11]

As described above, the angle θ of the tilt amount at which the amplitude value of the TE signal becomes the maximum value is determined by the step angle S degrees and the equation (9).
Can be obtained by the product of Xmax calculated by
S × Xmax). For example, FIG.
Plotting the amplitude value of the TE signal measured while changing the amount of tilt in degrees, and using the least squares method
This shows a quadratic curve approximating a quadratic function, in which the calculated Xmax is 1.05 steps.
At this time, the tilt amount at which the TE signal amplitude value becomes maximum is 0.2
Once. As described above, the optimum tilt amount calculating unit 36 calculates the tilt amount set based on the tilt setting signal output from the tilt setting signal generating unit 33 and the amplitude value of the TE signal measured by the TE signal amplitude measuring unit 35. The relationship is approximated to a quadratic function by the least squares method as described above, and a tilt amount at which the amplitude value of the TE signal with respect to a change in the tilt amount becomes maximum is calculated as a calculation result.

Next, the calculation result judging section 37 determines whether the calculation result calculated by the optimum tilt amount calculation section 36 is equal to a predetermined calculation limit value in order to accurately obtain the true optimum tilt amount that maximizes the TE signal amplitude. Is determined (step 2604). FIG. 8 shows the change in the TE signal amplitude with respect to the tilt amount when the true optimum tilt amount at which the TE signal amplitude becomes the maximum is about 2.75 times the step angle of 0.2 degrees, by a broken line. For example, such a state occurs when the amount of warpage of the optical disk 1 is extremely large and is about -0.55 degrees. In this case, the measured value of the TE signal amplitude measured by changing the amount of tilt by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degrees is indicated by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line. As is clear from FIG. 8, the true extreme value (TE
Since the tilt amount at which the signal amplitude becomes maximum) is near −3 steps, which is the maximum step on the minus side, the extreme value calculated from the measured values in ± 3 steps is affected by the measurement error, and the extreme value is −3.6 steps. Will be.

In order to prevent the erroneous calculation of the optimum tilt amount when the optimum tilt amount at which the TE signal amplitude becomes maximum deviates greatly from the reference angle, a calculation limit value is set in advance, and the calculation result is determined by the calculation limit value. If it exceeds the value, the process proceeds to step 2605. In step 2605, the reference angle is shifted and reset in the direction in which the calculation result is shifted. Specifically, if the calculation limit value is ± 2 steps and the calculation result exceeds the negative calculation limit value of −3.6 steps as in the present embodiment, the calculation result determination unit 37 sets the tilt. A command is issued to shift the reference angle of the tilt setting signal output from the signal generation unit 33 to the minus side by two steps. That is, the reference angle is reset to an angle of -0.4 degrees, and the measurement is performed again. Returning again to step 2602, the tilt setting signal generation unit 33 sets the new reference angle at 0 step, +1 step, +2 step, +3 step,-
A tilt setting signal changed to one step, -2 steps, and -3 steps is output. The amplitude value of the TE signal for each tilt amount (tilt setting signal) is measured seven times in total.

The plot of black circles in FIG. 8 is the re-measured TE signal amplitude value, and the extreme value (maximum value) is calculated by approximation using the measured value by the least squares method (step 260).
3). The calculated extreme value matches the true extreme value at which the TE signal amplitude becomes maximum, that is, the optimum tilt amount. Again, the calculation result determination unit 37 determines whether the calculation result calculated by the optimal tilt amount calculation unit 36 exceeds a predetermined calculation limit value (step 2604). If the calculation result is within the calculation limit value, the process proceeds to step 2606. In step 2606, the tilt setting signal generation unit 33 sets the tilt detection unit 2
0 is set to the optimum tilt amount setting mode. Next, the tilt setting signal generator 33 outputs an optimal tilt setting signal according to the input calculation result (step 2607). The tilt drive mechanism 26 tilts the optical disc 1 optimally.

Conversely, when the result of measurement / computation in ± 3 steps using 0 ° as the reference angle exceeds the plus computation limit value (+2 steps), such as when the amount of warpage of the optical disc 1 is large on the plus side. In step 2605, the reference angle is shifted to the positive side by +2 steps,
Recalculation is performed (steps 2602 and 2603). Due to these, when the amount of warpage of the optical disk is extremely large,
Even when the optimal tilt amount is greatly deviated from the reference angle,
By resetting the reference angle and performing re-measurement and re-calculation, the optimum tilt amount can be accurately obtained.

As described above, in the first embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is set as the inclination at which the amplitude of the TE signal is maximized. In order to find the relationship, the relationship between the tilt amount and the amplitude value of the TE signal is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle, and the amplitude value of the TE signal becomes an extreme value. Is calculated as the calculation result. And the optical disk 1
In order to obtain the optimum tilt amount without error even if the amount of warpage is large, first determine whether the calculation result exceeds the ± 2 steps set as the calculation limit value, and determine whether the calculation result is the plus side calculation limit value. Is exceeded, the reference angle is shifted by +2 steps and reset, and if the calculation result exceeds the minus calculation limit value, the reference angle is set to -2.
Re-set by shifting the steps, and perform re-measurement and re-calculation.

Therefore, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by performing re-measurement and re-calculation. Tilt setting signal generator 33
Stores the correct calculation result as the optimum tilt amount. At the time of the recording or reproducing operation (the optimum tilt amount setting mode is set), the tilt setting signal generation unit 33 outputs a tilt setting signal for setting the optimum tilt amount to the tilt servo circuit 21, and the tilt servo circuit By 21, the relative tilt between the optical disk 1 and the light beam is controlled to the optimum tilt amount. As described above, according to the configuration of the first embodiment of the present invention, even if the amount of warpage of the optical disk is large, the recording surface of the optical disk with respect to the optical axis of the optical beam can be provided without providing a special detection device such as a tilt sensor. Provided is an optical disk device capable of accurately detecting the inclination and controlling the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam to an optimum angle with high accuracy. In the conventional example using a separate tilt sensor, an error between the tilt angle in the tilt sensor and the tilt angle in the optical pickup 3 has been a problem. However, the optimum tilt amount is calculated based on the reflected light input by the optical pickup 3. Such an error cannot occur in the optical disk device of the present invention.

Embodiment 2 Hereinafter, an optical disk device according to Embodiment 2 of the present invention will be described with reference to the drawings.
The optical disc device according to the second embodiment of the present invention is different from the optical disc device according to the first embodiment only in the operation of the calculation result determination unit 37 in the first embodiment. The calculation result determination unit of the second embodiment is 137. The other components and their operations are the same as those in the first embodiment, and therefore the same reference numerals are given and the detailed description is omitted. Also in the second embodiment, the optimum tilt amount calculation unit 36 is configured to determine the tilt amount set based on the tilt setting signal output from the tilt setting signal generation unit 33 and the TE signal measured by the TE signal amplitude measurement unit 35. Is approximated to a quadratic function by the least square method as described above, and the extreme value of the change in the TE signal amplitude value with respect to the change in the tilt amount is calculated as the calculation result.

The calculation result determination unit 137 according to the second embodiment determines whether the quadratic coefficient of the quadratic function approximated by the least square method by the optimum tilt calculation unit 36 is positive or negative, and Is positive, the direction in which the reference angle should be shifted is determined based on the sign of the calculation result calculated as the extreme value. FIG. 9 shows a case where the true optimum tilt amount at which the TE signal amplitude is the maximum is about 3.7 times the step angle S = 0.2 degrees, that is, the true optimum tilt amount is
The change of the TE signal amplitude with respect to the tilt amount when the magnitude is larger than that shown in FIG. 8 is indicated by a broken line. In this case, the tilt amount is set to 0.2 in one step with respect to the reference angle of 0 degree.
The measured value obtained by measuring the TE signal amplitude by changing the degree by ± 3 steps is shown by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line.

When the true optimum tilt amount deviates greatly from the reference angle to the minus side as described above, the TE amplitude value when the tilt amount is on the plus side becomes very small, and is easily affected by noise or the like. The error increases. Further, the change cannot always be approximated by a quadratic function. Therefore, for example, as shown in FIG. 9, there is a possibility that the TE amplitude at the +3 step angle is measured to be larger than the true value. Would. Therefore, the quadratic coefficient a shown in Expression (11) is calculated as a positive value, and the calculation result is calculated as a value completely deviated from the true optimum tilt amount. In this case, specifically, the quadratic coefficient a = 6.71 and the calculation result Xmax =
It is calculated as 8.8 steps.

In order to prevent such inconvenience, the calculation result determination unit 137 determines whether the calculation is erroneous due to the positive or negative of the secondary coefficient. If the secondary coefficient is positive, the calculation result is incorrect. And reset the reference angle. In resetting the reference angle, the direction in which the reference angle should be shifted is determined based on the sign of the calculation result calculated as the extreme value. If the calculation result is positive, the reference angle is shifted by two steps to the minus side, and if negative, the reference angle is shifted by two steps to the plus side. In the case shown in FIG. 9, since the calculation result is positive, re-measurement and re-calculation are performed by shifting the reference angle by two steps to the minus side. The black circle plot in FIG. 9 is the TE signal amplitude value re-measured by shifting the reference angle to the minus side,
The measured value is approximated by the least squares method, and the calculated extreme value coincides with the true extreme value at which the TE signal amplitude becomes maximum, that is, the optimum tilt amount.

As described above, according to the second embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is set as the inclination at which the TE signal amplitude becomes maximum, and the accuracy is high. In order to find the relationship, the relationship between the tilt amount and the amplitude value of the TE signal is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle, and the amplitude value of the TE signal becomes an extreme value. Is calculated as the calculation result. And the approximated 2
Determine whether the quadratic coefficient in the quadratic function is positive or negative, and
The operation result is determined in the positive direction or the negative direction based on the reference angle. When the secondary coefficient is positive, it is determined that there is an error in the operation result, and the reference angle is reset. If the calculation result is in the plus direction with respect to the reference angle, the reference angle is shifted by -2 steps and reset, and if the calculation result is in the minus direction with respect to the reference angle, the reference angle is shifted by +2 steps and reset. Set and perform remeasurement and recalculation.

As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by remeasurement and recalculation. And the calculation result determination unit 13
7 sets the correct calculation result as the optimum tilt amount, and outputs the result to the tilt setting signal generation unit 33 to store it. And
At the time of a recording or reproducing operation, the tilt setting signal generating section 33 outputs a tilt setting signal for setting an optimum tilt amount to the tilt servo circuit 21 and the tilt servo circuit 2
1 controls the relative tilt between the optical disk 1 and the light beam to the optimum tilt amount. As described above, Embodiment 2 of the present invention
According to the configuration of the above, without providing a special detection device such as a tilt sensor, even when the amount of warpage of the optical disk is large, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam is accurately detected by the TE signal, and Provided is an optical disk device capable of accurately controlling the inclination of a recording surface of an optical disk with respect to the optical axis of a light beam to an optimum angle.

Embodiment 3 Hereinafter, an optical disk device according to Embodiment 3 of the present invention will be described with reference to the drawings.
The optical disc device according to the third embodiment of the present invention is different from the optical disc device according to the first embodiment only in the operation of the calculation result determination unit 37. The calculation result determination unit of the third embodiment is 237. The other components and their operations are the same as those in the first embodiment, and therefore the same reference numerals are given and the detailed description is omitted. Also in the third embodiment, the optimum tilt amount calculation unit 36 is configured to determine the tilt amount set based on the tilt setting signal output from the tilt setting signal generation unit 33 and the TE signal measured by the TE signal amplitude measurement unit 35. Is approximated to a quadratic function by the least squares method as described above, and an extreme value of a change in the TE signal amplitude value with respect to a change in the tilt amount is calculated as a calculation result. Then, the calculation result determination unit 237 in the third embodiment
Determines whether the quadratic coefficient in the quadratic function approximated by the least squares method by the optimal tilt calculator 36 is positive or negative, and when the quadratic coefficient is positive, the tilt amount becomes the reference angle. From the average value of the TE signal amplitude measured in three steps in the positive direction and the average value of the TE signal amplitude measured in the three steps in the negative direction to determine the direction in which the reference angle should be shifted I do.

FIG. 10 shows a case where the true optimum tilt amount at which the TE signal amplitude becomes the maximum is about 3.7 times the step angle of 0.2 degrees, similarly to FIG. 9 used in the description of the second embodiment. That is, the change of the TE signal amplitude with respect to the tilt amount when the true optimum tilt amount is large is indicated by a broken line. In this case, as in FIG. 9, the measured value obtained by measuring the TE signal amplitude by changing the amount of tilt by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degrees is shown by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line.
As described above, when the true optimum tilt amount is largely deviated from the reference angle to the minus side, it is greatly affected by a measurement error and the like. In some cases. In such a case,
The secondary coefficient a is calculated as a positive value, and the calculation result is calculated as a value completely deviated from the true optimum tilt amount.

In order to prevent such inconveniences, the operation result determination unit 237 first determines whether or not there is an error in the operation due to the positive or negative of the secondary coefficient, as in the second embodiment. Is determined to be incorrect, and the reference angle is reset. Then, in resetting the reference angle, the calculation result determination unit 237 of the present embodiment determines whether the tilt amount is an average value (positive average value) of the TE signal amplitudes measured in three steps on the plus side from the reference angle, and a minus value. By comparing the magnitude relationship with the average value (negative average value) of the TE signal amplitude measured in the three steps on the side, the direction in which the reference angle should be shifted is determined. When the average value of the three steps on the plus side is large, the reference angle is shifted by two steps to the plus side, and when the average value of the three steps on the minus side is large, the reference angle is shifted by two steps to the minus side. In the case shown in FIG.
Since the average value of the steps is larger, the reference angle is shifted to the minus side by two steps, and remeasurement and recalculation are performed. Similar to FIG. 9, a black circle plot indicates a TE signal amplitude value re-measured by shifting the reference angle to the minus side. The measured value is approximated by the least squares method, and the calculated extreme value is the TE signal amplitude. Is equal to the true extremal value at which the maximum is obtained, that is, the optimum tilt amount.

As described above, in the third embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is set as the inclination at which the TE signal amplitude becomes the maximum, and the accuracy is high. In order to find the relationship, the relationship between the tilt amount and the amplitude value of the TE signal is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle, and the amplitude value of the TE signal becomes an extreme value. Is calculated as the calculation result. And the approximated 2
In addition to determining whether the quadratic coefficient in the quadratic function is positive or negative,
The magnitude relationship between the positive average value and the negative average value is compared. If the secondary coefficient is positive, it is determined that there is an error in the calculation result, and the reference angle is reset. If the average value on the positive side is larger than the average value on the negative side, the reference angle is shifted and reset by +2 steps. If the average value on the positive side is smaller than the average value on the negative side, the reference angle is shifted by -2 steps and reset. Set and perform remeasurement and recalculation.

As described above, even when the amount of warpage of the optical disk 1 is large, a correct calculation result is finally obtained by re-measurement and re-calculation. And the calculation result determination unit 23
7 sets the correct calculation result as the optimum tilt amount, and outputs the result to the tilt setting signal generation unit 33 to store it. And
At the time of a recording or reproducing operation, the tilt setting signal generating section 33 outputs a tilt setting signal for setting an optimum tilt amount to the tilt servo circuit 21 and the tilt servo circuit 2
1 controls the relative tilt between the optical disk 1 and the light beam to the optimum tilt amount. As described above, Embodiment 3 of the present invention
According to the configuration of the above, without providing a special detection device such as a tilt sensor, even when the amount of warpage of the optical disk is large, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam is accurately detected by the TE signal, and Provided is an optical disk device capable of accurately controlling the inclination of a recording surface of an optical disk with respect to the optical axis of a light beam to an optimum angle.

Embodiment 4 An optical disk device according to Embodiment 4 of the present invention will be described below. The optical disc device according to the fourth embodiment of the present invention is different from the optical disc device according to the first embodiment in that the calculation result determination unit 37
Is different from the first embodiment. The calculation result determination unit of the fourth embodiment is 337. The other components and their operations are the same as those in the first embodiment, and therefore the same reference numerals are given and the detailed description is omitted. Also in the fourth embodiment, the optimum tilt amount calculation unit 36 determines the tilt amount set based on the tilt setting signal output from the tilt setting signal generation unit 33 and T
The relationship between the amplitude values of the TE signals measured by the E signal amplitude measurement unit 35 is approximated to a quadratic function by the least squares method as described above, and the extreme value of the change in the TE signal amplitude value with respect to the change in the tilt amount is calculated. Is calculated as

The calculation result determination unit 337 in the fourth embodiment determines whether the calculation result calculated as the extreme value by the optimum tilt calculation unit 36 is positive or negative (whether the tilt amount of the extreme value is a positive value with respect to the reference angle). The tilt amount is measured in three steps on the plus side from the reference angle, and the tilt amount is measured in three steps on the minus side. By comparing the magnitude relationship with the average value (negative average value) of the TE signal amplitude, it is determined whether the calculation result is correct or not and the direction in which the reference angle should be shifted.
If the calculation result is in the plus direction (the extreme tilt amount is a positive value with respect to the reference angle) and the negative average value is large, the reference angle is reset by changing the reference angle by a predetermined amount in the minus direction. If the calculation result is in the negative direction (the extreme tilt amount is a negative value with respect to the reference angle) and the average value on the positive side is large, the reference angle is changed from the reference angle by a predetermined amount in the positive direction to change the reference angle. If the calculation result is positive (the tilt value of the extreme value is a positive value with respect to the reference angle) and the average value on the positive side is large, and if the calculation result is negative (the tilt amount of the extreme value is If the angle is a negative value and the average value on the negative side is large, it is determined that the calculation result is correct, and the calculation result is set as the optimum tilt amount. The average value of the TE signal amplitude measured in three steps on the plus side from the reference angle and the TE measured in the three steps on the minus side
If the absolute value of the difference from the average value of the signal amplitude is equal to or less than a certain value, or if the calculation result (the amount of extreme tilt) is within a certain range from the reference angle, the above determination step is not performed. May be.

For example, in FIG. 10 used in the description of the third embodiment, the true optimum tilt amount at which the TE signal amplitude becomes maximum is −3.7 steps in the minus direction. In this case, the tilt amount is set to 0.2 in one step with respect to the reference angle of 0 degree.
The extreme value Xmax calculated from the measurement values (white circle plots) measured by changing ± 3 steps in degrees is a value +8 completely deviated from the true optimum tilt amount due to the influence of the measurement error as described above. .8 steps. In this case, the calculation result (extreme tilt amount) is +8.8.
The step is in the plus direction, and the average value of the TE signal amplitude measured in three steps on the plus side from the reference angle is 102 mV, and the average value of the TE signal amplitude measured in three steps on the minus side is 609 mV. . Therefore, this case corresponds to a case where the calculation result is in the plus direction (the tilt amount of the extreme value is a positive value with respect to the reference angle) and the average value on the negative side is large, and the reference angle is shifted by two steps in the minus direction and reset. , Re-measurement and recalculation. Similar to the third embodiment, the black circle plots the TE signal amplitude values re-measured by shifting the reference angle to the minus side. The measured values are used to approximate the least square method, and the calculated extreme value is the TE signal amplitude. Is equal to the true extremal value at which the maximum is obtained, that is, the optimum tilt amount.

As described above, in the fourth embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is set as the inclination at which the TE signal amplitude becomes maximum, and the accuracy is high. In order to find the relationship, the relationship between the tilt amount and the amplitude value of the TE signal is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle, and the amplitude value of the TE signal becomes an extreme value. Is calculated as the calculation result. The optimum tilt amount calculation unit 36 determines whether the calculation result calculated as the extreme value is positive or negative, and determines whether the tilt amount is equal to the average value of the TE signal amplitude measured in three steps on the plus side from the reference angle, and the minus side. By comparing the magnitude relationship between the average value of the TE signal amplitudes measured in three steps, the correctness of the calculation result and the direction in which the reference angle should be shifted are determined. If the calculation result is determined to be incorrect, the reference angle is determined. Is reset, and remeasurement and recalculation are performed.

As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by remeasurement and recalculation. And the calculation result determination unit 33
7 sets the correct calculation result as the optimum tilt amount, and outputs the result to the tilt setting signal generation unit 33 to store it. And
At the time of a recording or reproducing operation, the tilt setting signal generating section 33 outputs a tilt setting signal for setting an optimum tilt amount to the tilt servo circuit 21 and the tilt servo circuit 2
1 controls the relative tilt between the optical disk 1 and the light beam to the optimum tilt amount. As described above, Embodiment 4 of the present invention
According to the configuration of the above, without providing a special detection device such as a tilt sensor, even when the amount of warpage of the optical disk is large, the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam is accurately detected by the TE signal, and Provided is an optical disk device capable of accurately controlling the inclination of a recording surface of an optical disk with respect to the optical axis of a light beam to an optimum angle.

Embodiment 5 Hereinafter, an optical disk device according to Embodiment 5 of the present invention will be described with reference to the drawings.
The optical disc apparatus according to the fifth embodiment of the present invention detects the relative tilt (tilt amount) between the recording surface of the optical disc 1 and the light beam at which the amplitude of the RF signal is maximum as the optimum tilt amount, and detects the tilt of the optical pickup. By changing
Measure the amplitude value of the RF signal while changing the amount of tilt,
The relationship between the tilt amount and the amplitude value of the RF signal is approximated by a quadratic function by the least square method, and the tilt amount at which the RF signal amplitude value with respect to the change in the tilt amount becomes maximum is calculated as the optimum tilt amount. Therefore, the difference from the first to fourth embodiments is that TE
The point is that the amplitude value of the RF signal is used instead of the amplitude value of the signal. Hereinafter, the same components and operations as those in the first to fourth embodiments are denoted by the same reference numerals, and the detailed description thereof will be omitted.

FIG. 11 is a block diagram showing the configuration of an optical disk device according to Embodiment 5 of the present invention. The optical disk device of FIG. 11 includes a tilt detection unit 420 instead of the tilt detection unit 20 of FIG. This is the same as the first embodiment shown in FIG. 1 except that the RF signal output from the reproduction signal processing circuit 19 is sent to the tilt detection unit 420. The divided four light detectors 34 in the optical head 3 shown in FIG.
Output signals a, b, c, d of the two light receiving elements A, B, C, D
Are added by the reproduction signal processing circuit 19 shown in FIG. 4 to generate an RF signal = (a + b + c + d). FIG. 12 shows a configuration of the tilt detection unit 420 according to the fifth embodiment of the present invention. The tilt detection unit 420 is provided with the RF signal amplitude measurement unit 43
8, tilt setting signal generator 33, optimum tilt amount calculator 4
36, and an operation result determination unit 437.

The tilt detecting section 420 has two operation modes: an optimum tilt amount detection mode and an optimum tilt amount setting mode. The optimum tilt amount detection mode is a mode for detecting the optimum tilt amount by changing the tilt amount, and the optimum tilt amount setting mode is a mode for fixing the tilt amount to the optimum tilt amount. Tilt setting signal generator 33
Determines in which operation mode to operate. The determined operation mode is transmitted to each block (not shown). In the optimum tilt amount detection mode, three or more tilt setting signal generation units 33 (in the embodiment, 7 or more).
) Sequentially output different tilt setting signals. Thereby, different tilt amounts are sequentially set (a constant tilt amount is set for each tilt setting signal). The RF signal amplitude measurement unit 438 measures the amplitude value of the RF signal at each tilt amount (details will be described later). In the optimum tilt amount setting mode, the tilt setting signal generation unit 33 outputs a tilt setting signal of the optimum tilt amount based on the calculation result output from the optimum tilt amount calculation unit 436. Thereby, the optimum tilt amount is set.

The RF signal amplitude measuring section 438 measures the amplitude of the RF signal generated by the reproduction signal processing circuit 19. The optimum tilt amount calculation unit 436 is provided in the tilt setting signal generation unit 33.
The relationship between the amount of tilt set based on the tilt setting signal output from and the amplitude value of the RF signal measured by the RF signal amplitude measuring unit 438 is approximated by a least square method to a quadratic function. Based on the quadratic function, a tilt amount at which the amplitude value of the RF signal with respect to the change in the tilt amount becomes an extreme value (maximum value) is calculated as a calculation result. Calculation result determination unit 43
7 determines whether the calculation result calculated by the optimum tilt amount calculation unit 436 exceeds a predetermined calculation limit value. If the calculation result exceeds the calculation limit value, the calculation result, the tilt amount and A command to re-measure the relationship between the amplitude values of the RF signals is output to the tilt setting signal generation unit 33. If the calculation result does not exceed the calculation limit value, the calculation result and information indicating that the calculation result is within the calculation limit value are transmitted to the tilt setting signal generation unit 33. The tilt setting signal generator 33 sets the input calculation result as the optimum tilt value.

The operation of the optical disk device of Embodiment 5 configured as described above will be described with reference to FIG. FIG. 27 is a flowchart illustrating the operation of the tilt detection unit 420. First, when the power of the optical disk device is turned on or the optical disk is mounted on the optical disk device, the tilt setting signal generation unit 33 causes the tilt detection unit 420
Is set to the optimum tilt amount detection mode (step 270).
1). In the optimal tilt amount detection mode, with both the focus servo and tracking servo turned on,
The tilt setting signal generation unit 33 sequentially outputs seven predetermined tilt setting signals, and the RF signal amplitude measurement unit 438 measures the amplitude value of each TE signal (step 27).
02). In accordance with the seven tilt setting signals, a predetermined reference inclination is set to a reference angle of 0 ° as in the first to fourth embodiments, and the inclination of the optical pickup 3 is set to a constant angle pitch S.
The angle is changed by three steps in the positive and negative directions. That is, the amplitude of the RF signal is measured while changing the tilt amount, which is the relative tilt between the recording surface of the optical disc and the light beam.
First, the tilt setting signal generator 33 outputs a tilt setting signal for setting the tilt of the optical pickup 3 to the reference angle 0 to the tilt servo circuit 21. Tilt X of optical pickup 3
The RF signal amplitude measurement unit 438 measures the RF signal amplitude value Y (X1) while 1 is controlled to the reference angle 0. Subsequently, the inclination of the optical pickup 3 is set to +1 step, and the amplitude value Y (X2) of the RF signal is measured. Similarly, while changing the tilt of the optical pickup 3 to +2 steps, +3 steps, -1 step, -2 steps, and -3 steps, the amplitude value Y (X) of the RF signal with respect to each tilt amount.
3), Y (X4), Y (X5), Y (X6), Y (X
7) is measured 7 times in total.

The reference angle 0 ° is set in advance in the assembling process of the manufacturing factory as follows. In the assembling process, the tilt of the optical pickup 3 is adjusted so that the light beam is emitted almost perpendicularly to the reference disk while rotating the flat reference disk with almost no warp by the spindle motor, and the tilt is set to the reference angle. Defined as 0 degrees. That is, for an optical disk having a warp amount of approximately 0 degrees, the relative inclination (tilt amount) between the recording surface of the optical disk and the light beam at the reference angle of 0 degrees is an optimum value. Then, a rotation angle detection sensor (not shown) is attached to the rotation shaft of the tilt motor 24 so as to output a zero point signal when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Alternatively, the output circuit of the rotation angle detection sensor is adjusted so that the zero point signal is output when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Therefore, if the rotation angle of the tilt motor 24 is set to the angle at which the zero point signal is output, the inclination of the optical pickup 3 becomes the reference angle of 0 degree, and the rotation angle of the tilt motor 24 can be controlled based on the output of the rotation angle detection sensor. For example, the tilt of the optical pickup 3 can be set to a tilt shifted from the reference angle of 0 degree by a predetermined angle.

Next, the optimum tilt amount is calculated based on the measured value (step 2703). Here, FIG. 13 shows a change in RF signal amplitude with respect to the inclination of the optical pickup 3. As shown in FIG. 13, the change in the RF signal amplitude with respect to the inclination of the optical pickup 3 shows a characteristic almost similar to a quadratic function, like the change in the TE signal amplitude. Therefore, the change in the RF signal amplitude is approximated to a quadratic function by the least squares method, and the angle at which the RF signal amplitude is maximized is obtained. Therefore, the ratio of the inclination (tilt amount) of the optical pickup to the step angle S is represented by X (X = −3,... 0.
3) Assuming that the RF signal amplitude is Y (X), it approximates the quadratic function of equation (1). The calculation method is the same as that of the first embodiment. Assuming that the measured value of the RF signal amplitude when the tilt amount X at the jth measurement is Xj is Yj, the value of the approximate expression (1) and the actual measured value Yj Equation (2) shows the error amount vj. The coefficients a, b and c are determined so as to minimize the sum of squares E of the error vj shown in the equation (3). The coefficients a, b, c, and d can be obtained by solving the determinant of equation (4). Here, each function P (k), Q (k),
Y1 is as shown in Expression (5), Expression (6), and Expression (7). The tilt amount is X1 = 0, X2 = + 1, X3 = + 2,
Since X4 = + 3, X5 = -1, X6 = -2, and X7 = -3, X2 and X5, X3 and X6, and X4 and X7
Have opposite signs, P (1) and P (3) become 0, and equation (4) is simplified to equation (8).
X at which Y is the maximum value in the quadratic function of Expression (1) is expressed by Expression (9)
Is required. The secondary coefficient a and the primary coefficient b are the measured R
It can be calculated from the amplitude value Yj of the F signal and equation (8). Summarizing these, Xmax of the equation (9) is represented by the equation (10). Further, the quadratic coefficient a can be obtained by Expression (11).

As described above, the angle θ of the tilt amount at which the amplitude value of the RF signal becomes the maximum value is determined by the step angle S degrees and the equation (9).
Can be obtained by the product of Xmax calculated by
S × Xmax). For example, FIG.
FIG. 9 shows a plot of RF signal amplitude measured while changing the tilt amount at two degrees, and a quadratic curve approximated to a quadratic function by the least square method based on the measured value. .05 step. At this time, the tilt amount at which the RF signal amplitude value becomes maximum is 0.21.
Degree. As described above, the optimum tilt amount calculation unit 436 calculates the tilt amount set based on the tilt setting signal output from the tilt setting signal generation unit 33 and the amplitude value of the RF signal measured by the RF signal amplitude measurement unit 438. The relationship is approximated to a quadratic function by the least squares method as described above, and the tilt amount at which the amplitude value of the TE signal with respect to the change in the tilt amount becomes maximum is calculated as the calculation result.

Next, in order to accurately obtain the true optimum tilt amount at which the RF signal amplitude becomes maximum, the calculation result determination unit 437 determines whether the calculation result calculated by the optimum tilt amount calculation unit 436 is a predetermined calculation limit value. It is determined whether or not it has exceeded (step 2704). FIG. 15 shows the change of the RF signal amplitude with respect to the tilt amount when the true optimum tilt amount at which the RF signal amplitude becomes the maximum is about 2.75 times the step angle of 0.2 degrees, by a broken line. For example, such a state occurs when the amount of warpage of the optical disc 1 is extremely large and is about -0.55 degrees. In this case, the tilt amount is changed by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degrees, and RF is changed.
The measured value of the signal amplitude is shown by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line. As is apparent from FIG. 15, the true extreme value (R
Since the tilt amount at which the F signal amplitude becomes maximum) is near the negative maximum step, ie, −3 step, the extreme value calculated from the measured value in ± 3 steps is affected by the measurement error. It becomes a step.

In order to prevent an erroneous calculation of the optimum tilt amount when the optimum tilt amount at which the RF signal amplitude becomes maximum deviates greatly from the reference angle, a calculation limit value is set in advance, and the calculation result is determined by the calculation limit value. If it exceeds the value, the process proceeds to step 2705. In step 2705, the reference angle is shifted and reset in the direction in which the calculation result is shifted. Specifically, when the calculation limit value is ± 2 steps, and the calculation result exceeds the negative calculation limit value of −3.6 steps as in the present embodiment, the calculation result determination unit 437 sets the tilt. A command is issued to shift the reference angle of the tilt setting signal output by the signal generation unit 33 to the minus side by two steps. That is, the reference angle is reset to an angle of -0.4 degrees, and the measurement is performed again. Returning to step 2702 again, the tilt setting signal generator 33 sets the new reference angle at 0 step, +1 step, +2 step, +3 step,
It outputs a tilt setting signal changed to -1 step, -2 step, and -3 step. The amplitude value of the TE signal for each tilt amount (tilt setting signal) is measured seven times in total.

The plot of the black circle in FIG. 15 is the re-measured RF signal amplitude value, and the extreme value (maximum value) is calculated by approximation using the measured value by the least squares method (step 27).
03). The calculated extreme value matches the true extreme value at which the RF signal amplitude becomes maximum, that is, the optimum tilt amount. Again, the calculation result determination unit 437 determines whether the calculation result calculated by the optimal tilt amount calculation unit 436 exceeds a predetermined calculation limit value (step 2704). If the calculation result is within the calculation limit value, the process proceeds to step 2706. Step 27
In 06, the tilt setting signal generation unit 33 sets the tilt detection unit 20 to the optimum tilt amount setting mode. next,
The tilt setting signal generator 33 outputs an optimum tilt setting signal according to the input calculation result (step 270).
7). The tilt drive mechanism 26 tilts the optical disc 1 optimally.

Conversely, when the result of measurement / computation in ± 3 steps using 0 ° as the reference angle exceeds the plus computation limit value (+2 steps), such as when the amount of warpage of the optical disc 1 is large on the plus side. In step 2705, the reference angle is shifted to the plus side by +2 steps,
Recalculation is performed (steps 2702 and 2703). Due to these, when the amount of warpage of the optical disk is extremely large,
Even when the optimal tilt amount is greatly deviated from the reference angle,
By resetting the reference angle and performing re-measurement and re-calculation, the optimum tilt amount can be accurately obtained.

Further, the calculation result determination unit 437 determines whether the quadratic coefficient of the quadratic function approximated by the least squares method is positive or negative. FIG. 16 shows a case where the true optimum tilt amount at which the RF signal amplitude becomes the maximum is about 3.7 times the step angle of 0.2 degrees, that is, the true optimum tilt amount is larger than the case shown in FIG. The dashed line indicates the change in the RF signal amplitude with respect to the amount of tilt in the case of a larger value. In this case, the measured value of the RF signal amplitude measured by changing the amount of tilt by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degrees is indicated by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line.

When the true optimum tilt amount deviates greatly from the reference angle to the minus side as described above, the RF signal amplitude value when the tilt amount is on the plus side becomes very small, and the influence of noise or the like is increased. Measurement error increases.
Further, the change cannot always be approximated by a quadratic function.
Therefore, for example, as shown in FIG. 16, there is a possibility that the RF amplitude at the +3 step angle is measured to be larger than the true value, and when the approximation is performed by the least squares method, an erroneous approximation is performed to the downwardly convex quadratic curve. Would. Therefore, the quadratic coefficient a shown in Expression (11) is calculated as a positive value, and the calculation result is calculated as a value completely deviated from the true optimum tilt amount. In this case, specifically, the calculation result Xm is set to the secondary coefficient a = 6.71.
ax = 8.8 steps.

In order to prevent such inconvenience, the calculation result determination unit 437 determines whether the calculation has an error due to the positive or negative of the secondary coefficient. If the secondary coefficient is positive, the calculation result is incorrect. And reset the reference angle. In resetting the reference angle, the direction in which the reference angle should be shifted is determined based on the sign of the calculation result calculated as the extreme value. If the calculation result is positive, the reference angle is shifted by two steps to the minus side, and if negative, the reference angle is shifted by two steps to the plus side. In the case shown in FIG. 16, since the calculation result is positive, re-measurement / recalculation is performed by shifting the reference angle by two steps to the minus side. The plot of the black circle in FIG. 16 is the RF signal amplitude value re-measured by shifting the reference angle to the minus side, and the measured value is approximated by the least squares method. Is equal to the true extreme value, that is, the optimum tilt amount.

As described above, in the fifth embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is set as the inclination at which the RF signal amplitude is maximized. In order to find the relation, the relationship between the tilt amount and the amplitude value of the RF signal is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle, and the amplitude value of the RF signal becomes an extreme value. Is calculated as the calculation result. And the optical disk 1
In order to obtain the optimum tilt amount without error even if the amount of warpage is large, first determine whether the calculation result exceeds the ± 2 steps set as the calculation limit value, and determine whether the calculation result is the plus side calculation limit value. If the value exceeds the limit, reset the reference angle by +2 steps, and if the calculation result exceeds the minus calculation limit, reset the value by -2 steps, and then re-measure / recalculate I do. As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by performing re-measurement and re-calculation.

Further, it is determined whether the quadratic coefficient in the approximated quadratic function is positive or negative, and whether the calculation result is positive or negative with respect to the reference angle (the amount of tilt at the extreme value is Positive value or negative value). 2
If the next coefficient is positive, it is determined that there is an error in the operation result,
Reset the reference angle. If the calculation result is in the plus direction with respect to the reference angle (the tilt amount at the extreme value is a positive value with respect to the reference angle), the reference angle is shifted by -2 steps and reset, and the calculation result is based on the reference angle. In the negative direction (the tilt amount at the extreme value is a negative value with respect to the reference angle), the reference angle is shifted by +2 steps and reset, and the measurement and recalculation are performed. As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by remeasurement and recalculation.

The tilt setting signal generator 33 stores a correct calculation result as an optimum tilt amount. At the time of the recording or reproducing operation (the optimum tilt amount setting mode is set), the tilt setting signal generating unit 33 outputs a tilt setting signal for setting the optimum tilt amount to the tilt servo circuit 21.
To the optical disk 1 by the tilt servo circuit 21.
And the relative tilt of the light beam is controlled to the optimum tilt amount. As described above, according to the configuration of the fifth embodiment of the present invention, even if the amount of warpage of the optical disk is large, the recording surface of the optical disk with respect to the optical axis of the optical beam can be provided without providing a special detection device such as a tilt sensor. Provided is an optical disk apparatus capable of accurately detecting the inclination by an RF signal and controlling the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam to an optimum angle with high accuracy. In the conventional example using a separate tilt sensor, an error between the tilt angle of the tilt sensor and the tilt angle of the optical pickup 3 is a problem. Such an error cannot occur in the optical disk device of the present invention.

Embodiment 6 Hereinafter, an optical disk device according to Embodiment 6 of the present invention will be described with reference to the drawings.
The optical disc apparatus according to the sixth embodiment of the present invention detects the relative tilt (tilt amount) between the recording surface of the optical disc 1 and the light beam at which the jitter value of the RF signal with respect to the reference clock is minimum as the optimum tilt amount. By changing the tilt of the pickup, the jitter value is measured while changing the tilt amount, and the relationship between the tilt amount and the jitter value is approximated to a quadratic function by the least squares method. The tilt amount is calculated as the optimum tilt amount. Therefore, the difference from the first to fourth embodiments is that TE
The point is that a jitter value is used instead of the signal amplitude value. Hereinafter, the same components and operations as those in the first to fourth embodiments are denoted by the same reference numerals, and the detailed description thereof will be omitted.

FIG. 17 is a block diagram showing a configuration of an optical disk device according to Embodiment 6 of the present invention. The optical disc device of FIG. 17 includes a jitter measuring unit 539 and a tilt detecting unit 520 instead of the tilt detecting unit 20 of FIG. The RF signal output from the reproduction signal processing circuit 19 is
9, and the jitter value measured by the jitter measuring unit 539 is sent to the tilt detecting unit 520. Other than that, it is the same as the first embodiment shown in FIG. The outputs a, b, c, and d of the four divided light receiving elements A, B, C, and D of the photodetector 34 in the optical pickup 3 shown in FIG. The signals are added by the signal processing circuit 19,
An RF signal is generated as (a + b + c + d). The jitter measuring unit 539 converts the RF signal into a binary signal, measures a jitter value of the binary signal with respect to a reference clock, and outputs a voltage proportional to the jitter value as a jitter voltage.

FIG. 18 shows the structure of the tilt detector 520 according to the sixth embodiment of the present invention. The tilt detection section 520 includes a jitter signal measurement section 540, a tilt setting signal generation section 33, an optimum tilt amount calculation section 536, and a calculation result determination section 537. The tilt detection section 420 has two operation modes: an optimum tilt amount detection mode and an optimum tilt amount setting mode. The optimum tilt amount detection mode is a mode for detecting the optimum tilt amount by changing the tilt amount, and the optimum tilt amount setting mode is a mode for fixing the tilt amount to the optimum tilt amount. Tilt setting signal generator 33
Determines in which operation mode to operate. The determined operation mode is transmitted to each block (not shown). In the optimum tilt amount detection mode, three or more tilt setting signal generation units 33 (in the embodiment, 7 or more).
) Sequentially output different tilt setting signals. Thereby, different tilt amounts are sequentially set (a constant tilt amount is set for each tilt setting signal). The jitter signal measuring unit 540 measures a jitter signal at each tilt amount (details will be described later). In the optimum tilt amount setting mode, the tilt setting signal generation unit 33 outputs a tilt setting signal of the optimum tilt amount based on the calculation result output by the optimum tilt amount calculating unit 536. Thereby, the optimum tilt amount is set.

The jitter signal measuring section 540 measures the jitter voltage value generated by the jitter measuring section 539 as a jitter value. The tilt setting signal generator 33 outputs a tilt setting signal for setting the relative inclination (tilt amount) between the optical disk 1 and the light beam to a desired angle to the tilt servo circuit 21. The optimum tilt amount calculating unit 536 calculates the relationship between the tilt amount set based on the tilt setting signal output from the tilt setting signal generating unit 33 and the jitter value measured by the jitter signal measuring unit 540 by the least square method. Approximate the following function. Based on the quadratic function, the tilt amount at which the jitter value with respect to the change in the tilt amount becomes an extreme value (minimum value) is calculated as a calculation result. The calculation result determination unit 537 determines whether the calculation result calculated by the optimum tilt amount calculation unit 536 exceeds a predetermined calculation limit value, and when the calculation result exceeds the calculation limit value, the calculation result And a command to re-measure the relationship between the tilt amount and the jitter value are output to the tilt setting signal generation unit 33. If the calculation result does not exceed the calculation limit value, the calculation result and information indicating that the calculation result is within the calculation limit value are transmitted to the tilt setting signal generation unit 33. The tilt setting signal generator 33 sets the input calculation result as the optimum tilt value.

The operation of the optical disk device of Embodiment 6 configured as described above will be described with reference to FIG. FIG. 28 is a flowchart illustrating the operation of the tilt detection unit 520. First, when the power of the optical disk device is turned on or the optical disk is mounted on the optical disk device, the tilt setting signal generation unit 33 causes the tilt detection unit 520
Is set to the optimum tilt amount detection mode (step 280).
1). In the optimal tilt amount detection mode, with both the focus servo and tracking servo turned on,
The tilt setting signal generating section 33 sequentially outputs seven predetermined tilt setting signals, and the jitter signal measuring section 540 measures each jitter value (step 2802). 7
With the two tilt setting signals, the inclination of the optical pickup 3 is set at a constant angle pitch S degree in three steps in the positive direction and the negative direction, with the predetermined reference inclination as the reference angle of 0 degree as in the first to fourth embodiments. Change in steps. That is, the jitter value is measured while changing the tilt amount, which is the relative inclination between the recording surface of the optical disc and the light beam.

First, the tilt setting signal generator 33 outputs a tilt setting signal for setting the tilt of the optical pickup 3 to the reference angle 0 to the tilt servo circuit 21. The jitter value Y (X1) is measured by the jitter signal measuring unit 540 in a state where the tilt X1 of the optical pickup 3 is controlled to the reference angle 0. Subsequently, the tilt of the optical pickup 3 is set to +1 step, and the jitter value Y (X2) is measured. Similarly, tilt of the optical pickup 3 +2 steps, +3 steps, -1
The jitter values Y (X3), Y (X
4) Y (X5), Y (X6), and Y (X7) are measured seven times in total.

The reference angle 0 ° is set in advance in the assembling process of the manufacturing factory as follows. In the assembling process, the inclination of the optical pickup 3 is adjusted so that the light beam is irradiated almost perpendicularly to the reference disk while rotating the flat reference disk having almost no warp by the spindle motor, and the inclination is set to the reference angle. Defined as 0 degrees. That is, for an optical disk having a warp amount of approximately 0 degrees, the relative inclination (tilt amount) between the recording surface of the optical disk and the light beam at the reference angle of 0 degrees is an optimum value. Then, a rotation angle detection sensor (not shown) is attached to the rotation shaft of the tilt motor 24 so as to output a zero point signal when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Alternatively, the output circuit of the rotation angle detection sensor is adjusted so that the zero point signal is output when the inclination of the optical pickup 3 matches the reference angle of 0 degree. Therefore, if the rotation angle of the tilt motor 24 is set to the angle at which the zero point signal is output, the tilt of the optical pickup 3 becomes the reference angle of 0 degree, and the rotation angle of the tilt motor 24 can be controlled based on the output of the rotation angle detection sensor. For example, the tilt of the optical pickup 3 can be set to a tilt shifted from the reference angle of 0 degree by a predetermined angle.

Next, the optimum tilt amount is calculated based on the measured value (step 2803). Here, FIG. 19 shows a change in the jitter value with respect to the inclination of the optical pickup 3. As shown in FIG. 19, the change in the jitter value with respect to the inclination of the optical pickup 3 shows a characteristic almost similar to a quadratic function, like the change in the TE signal amplitude. However, the tilt amount at which the secondary coefficient becomes a positive downwardly convex quadratic curve and the jitter is minimized is the optimum tilt amount. Therefore, the change in the jitter value with respect to the tilt amount is approximated to a quadratic function by the least square method, and the angle at which the jitter value is minimized is obtained. Therefore, the ratio of the inclination (tilt amount) of the optical pickup to the step angle S is X (X = −3,... 0... 3 in the case of the above-described seven-step measurement).
The jitter value is approximated to a quadratic function of Expression (1), where Y (X) is used. The calculation method is the same as that of the first embodiment. When the tilt amount X at the j-th measurement is Xj, the measured value of the jitter value is Y
Let j be the approximate value of equation (1) and the actual measured value Yj
Equation (2) shows the error amount vj.

The coefficients a, b and c are determined so as to minimize the sum of squares E of the error vj shown in the equation (3). Coefficients a, b,
c and d can be obtained by solving the determinant of equation (4). Here, each function P (k), Q in equation (4)
(K) and Y1 are as shown in Formula (5), Formula (6), and Formula (7). X1 = 0, X2 = + 1, X3
= + 2, X4 = + 3, X5 = -1, X6 = -2, X7 =
-3, X2 and X5, X3 and X6, and X
4 and X7 have opposite signs, so that P (1), P
(3) becomes 0, and equation (4) is simplified to equation (8)
become. X at which Y is the maximum in the quadratic function of equation (1) is
The secondary coefficient a and the primary coefficient b, which are obtained by the equation (9), can be calculated from the measured jitter value Yj and the equation (8). Summarizing these, Xmin (the value of X at which Y is the minimum value) is represented by an expression obtained by replacing Xmax in Expressions (9) and (10) with Xmin. Further, the quadratic coefficient a can be obtained by Expression (11).

As described above, the tilt angle θ at which the jitter value becomes the minimum value can be obtained by the product of the step angle S degrees and Xmin calculated by the equation (9) (θ = S × Xm
in). For example, FIG. 20 shows a plot of a jitter voltage value measured while changing the amount of tilt at a step angle S of 0.2 degree, and a quadratic curve approximated to a quadratic function by the least square method based on the measured value. Xm
This is the case where in is 1.05 steps. At this time, the tilt amount at which the jitter value becomes the minimum is 0.21 degrees. As described above, the optimum tilt amount calculation unit 536 determines the relationship between the tilt amount set based on the tilt setting signal output from the tilt setting signal generation unit 33 and the jitter voltage value measured by the jitter signal measurement unit 540. Then, a tilt function is approximated by a least-squares method as a quadratic function, and a tilt amount that minimizes a jitter value with respect to a change in the tilt amount is calculated as a calculation result.

Next, the operation of the calculation result determination section 537 will be described. First, the calculation result determination unit 537 determines whether the calculation result calculated by the optimum tilt amount calculation unit 536 exceeds a predetermined calculation limit value in order to accurately obtain the true optimum tilt amount that minimizes the jitter value. (Step 280)
4). FIG. 21 shows a change of the jitter value with respect to the tilt amount when the true optimum tilt amount at which the jitter value becomes the minimum is about 2.75 times the step angle S = 0.2 degrees by a broken line. For example, the amount of warpage of the optical disc 1 is extremely large, and -0.5
Such a state occurs when there is about 5 degrees. In this case, the measured value of the jitter voltage value obtained by changing the amount of tilt by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degree is shown by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line.
As is clear from FIG. 21, the true extreme value (the tilt amount at which the jitter value becomes the minimum) is the maximum step on the minus side, −3.
Because it is near the step, it is affected by the measurement error, and ± 3
The extreme value calculated from the measured value in the step is -3.6 steps.

In order to prevent the erroneous calculation of the optimum tilt amount when the optimum tilt amount at which the jitter value is minimized greatly deviates from the reference angle, a calculation limit value is set in advance, and the calculation result is set to the calculation limit value. If it has exceeded, the process proceeds to step 2805. In step 2805, the reference angle is shifted and reset in the direction in which the calculation result is shifted.
Specifically, when the calculation limit value is ± 2 steps, and the calculation result exceeds the negative calculation limit value of −3.6 steps as in this embodiment, the calculation result determination unit 537
Instructs the reference angle of the tilt setting signal output from the tilt setting signal generation unit 33 to be shifted by two steps to the minus side. That is, the reference angle is reset to an angle of -0.4 degrees, and the measurement is performed again. Returning again to step 2802, the tilt setting signal generator 33 sets the new reference angle at 0 step, +1 step, +2 step, +3 step, -1 step.
A tilt setting signal changed to step, -2 step, and -3 step is output. A jitter value for each tilt amount (tilt setting signal) is measured seven times in total.

The plot of the black circle in FIG. 21 is the remeasured jitter voltage value. The measured extreme value is approximated by the least squares method, and the calculated extreme value is the true extreme value at which the jitter value is minimized, that is, It matches the optimum tilt amount. Again, the calculation result determination unit 537 determines whether the calculation result calculated by the optimal tilt amount calculation unit 536 exceeds a predetermined calculation limit value (step 2804). If the calculation result is within the calculation limit value, the process proceeds to step 2806. Step 280
In 6, the tilt setting signal generation unit 33 sets the tilt detection unit 520 to the optimum tilt amount setting mode. next,
The tilt setting signal generator 33 outputs an optimum tilt setting signal according to the input calculation result (step 280).
7). The tilt drive mechanism 26 tilts the optical disc 1 optimally.

Conversely, when the result of measurement / calculation in ± 3 steps with 0 ° as the reference angle exceeds the plus calculation limit (+2 steps), such as when the amount of warpage of the optical disc 1 is large on the plus side. In step 2805, the reference angle is shifted to the plus side by +2 steps,
Recalculation is performed (steps 2802, 2803). Due to these, when the amount of warpage of the optical disk is extremely large,
Even when the optimal tilt amount is greatly deviated from the reference angle,
By resetting the reference angle and performing re-measurement and re-calculation, the optimum tilt amount can be accurately obtained.

Further, the calculation result determination unit 537 determines whether the quadratic coefficient of the quadratic function approximated by the least squares method is positive or negative. FIG. 22 shows a case where the true optimum tilt amount at which the jitter value is minimum is about 3.7 times the step angle S = 0.2 degrees, that is, the true optimum tilt amount is smaller than the case shown in FIG. The change in the jitter voltage value with respect to the amount of tilt when the value of ジ ッ タ is even larger is indicated by a broken line. In this case, the measured value of the jitter voltage value obtained by changing the amount of tilt by ± 3 steps at 0.2 degrees per step with respect to the reference angle of 0 degree is shown by a white circle plot. Further, a quadratic curve approximated by the least square method using the measured values is shown by a solid line.

When the true optimum tilt amount deviates greatly from the reference angle to the minus side as described above, the jitter value becomes a monotonically increasing curve, and the coefficient of the quadratic curve approximated by the least squares method is affected by noise and the like. More easily. For example, FIG.
As shown in FIG. 2, when the jitter value at the +3 step angle is measured to be smaller than the true value, if Y (X) is approximated by the least square method, an erroneous approximation is performed to the upwardly convex quadratic curve. I will. Therefore, the quadratic coefficient a shown in Expression (11) is calculated as a negative value, and the calculation result is calculated as a value completely deviated from the true optimum tilt amount. In this case, specifically, the calculation result Xmin = + 8.8 steps is calculated for the secondary coefficient a = -6.71.

In order to prevent such inconvenience, the operation result determination unit 537 determines whether the operation is erroneous due to the positive or negative of the secondary coefficient. If the secondary coefficient is negative, the operation result is incorrect. And reset the reference angle. In resetting the reference angle, the direction in which the reference angle should be shifted is determined based on the sign of the calculation result calculated as the extreme value. If the calculation result is positive, the reference angle is shifted by two steps to the minus side, and if negative, the reference angle is shifted by two steps to the plus side. In the case shown in FIG. 22, since the calculation result is positive, re-measurement / recalculation is performed by shifting the reference angle by two steps to the minus side. The plot of the black circle in FIG. 22 is the jitter voltage value re-measured while shifting the reference angle to the minus side, and the measured value is approximated by the least squares method, and the calculated extreme value is the true value at which the jitter value becomes the minimum. , That is, the optimum tilt amount.

As described above, in the sixth embodiment, even when the amount of warpage of the optical disk 1 is large, the optimum value of the relative inclination between the recording surface of the optical disk and the light beam is accurately determined as the inclination with the minimum jitter. The relationship between the tilt amount and the jitter value is approximated to a quadratic function by the least squares method while changing the tilt amount by ± 3 step angles around the reference angle.
The optimum tilt amount at which the jitter value becomes an extreme value is calculated as a calculation result. Then, in order to obtain the optimum tilt amount without error even when the amount of warpage of the optical disk 1 is large, it is first determined whether or not the calculation result exceeds ± 2 steps set as the calculation limit value, If the calculation limit value is exceeded, the reference angle is shifted by +2 steps and reset, and if the calculation result exceeds the minus calculation limit value, the reference angle is reset by -2 steps and reset. Perform measurement and recalculation. As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by remeasurement and recalculation.

Further, it is determined whether the quadratic coefficient of the approximated quadratic function is positive or negative, and whether the calculation result is positive or negative with respect to the reference angle (the tilt amount at the extreme value is Positive value or negative value). 2
If the next coefficient is negative, it is determined that there is an error in the operation result,
Reset the reference angle. If the calculation result is in the plus direction with respect to the reference angle (the tilt amount at the extreme value is a positive value with respect to the reference angle), the reference angle is shifted by -2 steps and reset, and the calculation result is based on the reference angle. In the negative direction (the tilt amount at the extreme value is a negative value with respect to the reference angle), the reference angle is shifted by +2 steps and reset, and the measurement and recalculation are performed. As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by remeasurement and recalculation.

The tilt setting signal generator 33 stores a correct calculation result as an optimum tilt amount. At the time of a recording or reproducing operation (the optimum tilt amount setting mode is set), the tilt setting signal generation unit 33 outputs a tilt setting signal for setting the optimum tilt amount to the tilt servo circuit 21.
To the optical disk 1 by the tilt servo circuit 21.
And the relative tilt of the light beam is controlled to the optimum tilt amount. As described above, according to the configuration of Embodiment 6 of the present invention, even if the amount of warpage of the optical disk is large, the recording surface of the optical disk with respect to the optical axis of the optical beam can be provided without providing a special detection device such as a tilt sensor. Provided is an optical disk apparatus capable of accurately detecting the inclination by a jitter signal and controlling the inclination of the recording surface of the optical disk with respect to the optical axis of the light beam to an optimum angle with high accuracy. In the conventional example using a separate tilt sensor, an error between the tilt angle in the tilt sensor and the tilt angle in the optical pickup 3 has been a problem. However, the optimum tilt amount is calculated based on the reflected light input by the optical pickup 3. Such an error cannot occur in the optical disk device of the present invention.

Embodiment 7 An optical disk device according to Embodiment 7 of the present invention will be described below with reference to the drawings.
In the seventh embodiment, the tilt drive mechanism is configured to change the angle of the objective lens 4 that focuses the light beam. Example 1
In Nos. 1 to 6, the tilt of the optical pickup 3 was changed to change the tilt amount. However, the same effect can be obtained by changing the tilt of the objective lens 4. That is, by changing the inclination of the objective lens 4, the angle at which the light beam enters the recording surface of the optical disc 3 can be changed. Therefore, in the seventh embodiment, the TE is changed while changing the tilt amount of the objective lens 4 as in the first embodiment.
The optimum tilt amount that maximizes the signal amplitude can be obtained.

FIG. 23 shows the structure of a tilt actuator for tilting the objective lens 4. The tilt actuator includes a magnet 8, an inner focus driving coil 641, and an outer focus driving coil 642. When a voltage having the same phase is applied to the inner focus driving coil 641 and the outer focus coil 642, the objective lens 4 is driven in the focus direction (up and down direction). The inner focus driving coil 641 and the outer focus coil 6
When an opposite-phase voltage is applied to 42, the objective lens 4 tilts, and the tilt angle of the objective lens 4 can be controlled by controlling the voltage input to these coils.

FIG. 24 is a block diagram showing a configuration of an optical disk device according to Embodiment 7 of the present invention. Compared to the configuration of FIG. 1, the optical disc apparatus of the seventh embodiment varies the tilt by changing the angle of the objective lens 4 of the optical pickup 3 and has a tilt servo unit 621 instead of the tilt servo circuit 21. It is characteristic. The output signal of the tilt servo circuit section 621 is added to the output signal of the focus servo circuit 6, and the objective lens 4 is driven by the added signal.

FIG. 25 shows the structure of the tilt servo circuit 621. The tilt servo circuit 621 controls the tilt of the objective lens 4 so that the irradiation angle of the light beam irradiated on the optical disc 1 becomes a desired angle. A tilt servo signal generator 623 that outputs a tilt servo signal based on the tilt setting signal from the tilt setting signal generator 33;
And a tilt drive circuit 643 for applying a voltage to the outer peripheral side focus coil 642. Other configurations are the same as those of the first embodiment, and the tilt detection unit 20 has the same configuration as that of FIG. It is configured by a result determination unit 637 (having a calculation result determination unit 637 instead of the calculation result determination unit 37 in FIG. 5). The TE signal amplitude measuring section 35 is a tracking error signal (TE signal) generated by the reproduction signal processing circuit 19.
Measure the amplitude of

The tilt setting signal generating section 33 outputs a tilt setting signal for setting the relative inclination (tilt amount) between the optical disk 1 and the light beam to a desired angle.
Output to The optimum tilt amount calculating section 36 calculates the relationship between the tilt amount set based on the tilt setting signal output from the tilt setting signal generating section 33 and the amplitude value of the TE signal measured by the TE signal amplitude measuring section 35. It approximates to a quadratic function by the least square method. Using the quadratic function, a tilt amount at which the amplitude value of the TE signal with respect to the change in the tilt amount becomes an extreme value is calculated as a calculation result. Calculation result determination unit 637
Determines whether or not the calculation result calculated by the optimum tilt amount calculation unit exceeds a predetermined calculation limit value. If the calculation result exceeds the calculation limit value, the calculation result, the tilt amount and TE An instruction to re-measure the relationship between the signal amplitude values is output to the tilt setting signal generation unit 33. If the calculation result does not exceed the calculation limit value, the calculation result and information indicating that the calculation result is within the calculation limit value are used as the tilt setting signal generation unit 3.
Transmit to 3. The tilt setting signal generator 33 sets the calculation result as the optimum tilt value.

As described above, even when the amount of warpage of the optical disc 1 is large, a correct calculation result is finally obtained by re-measurement and recalculation. Then, the tilt setting signal generation unit 33 stores a correct calculation result as the optimum tilt amount. At the time of the recording or reproducing operation (in the optimum tilt amount setting mode), the tilt setting signal generation unit 33
Outputs a tilt setting signal for setting the optimum tilt amount to the tilt servo circuit 21, and outputs the tilt servo circuit 621.
By controlling the tilt of the objective lens 4, the relative tilt between the optical disk 1 and the light beam can be controlled to the optimum tilt amount. As described above, according to the configuration of the seventh embodiment of the present invention, even if the amount of warpage of the optical disk is large without providing a special detection device such as a tilt sensor or a tilt drive mechanism such as a tilt motor, Provided is an optical disk apparatus capable of accurately detecting the inclination of a recording surface of an optical disk with respect to an optical axis by a jitter signal and controlling the inclination of the recording surface of the optical disk with respect to the optical axis of a light beam to an optimum angle with high accuracy. In the conventional example using a separate tilt sensor, an error between the tilt angle in the tilt sensor and the tilt angle in the optical pickup 3 has been a problem. However, the optimum tilt amount is calculated based on the reflected light input by the optical pickup 3. Such an error cannot occur in the optical disk device of the present invention.

As described above, the optical disk device of the present invention can reliably detect the optimum tilt amount even when the optical disk has a large amount of warp without providing a special detection device such as a tilt sensor. Highly accurate and highly reliable tilt servo can be realized. Therefore, the configuration of the optical disk device of the present invention is a DVD-R device, a DVD-RAM
Device, DVD-RW device, CD-R device, optical disk recording / reproducing device for performing both recording and reproduction, such as CD-RW device and magneto-optical recording device, and DVD-ROM for reproduction only
The present invention is suitable for any optical disk device such as an optical disk reproducing device such as a CD-ROM device or a read-only MD device, and an optical disk recording device that performs only recording.

[0127]

As described above, the optical disk apparatus of the present invention detects the amount of tilt, which is the relative inclination between the recording surface of the optical disk and the light beam, using the reproduction signal of the optical pickup. By changing the tilt of the optical pickup and the tilt of the objective lens, the amplitude and jitter of the reproduced signal are measured while changing the amount of tilt, and the relationship between the amount of tilt and the amplitude of the reproduced signal is quadratic using the least square method. Approximate function. The tilt amount that maximizes the amplitude value of the reproduced signal or the tilt amount that minimizes the jitter value with respect to the change in the tilt amount is calculated as the optimum tilt amount. Further, in order to cope with a case where the quality of the reproduced signal is significantly reduced, such as when the amount of warpage of the optical disk is extremely large, means for determining whether the calculated optimum tilt amount is correct is provided. In this configuration, the tilt amount is changed again in an angle range corresponding to the warp angle of the optical disk, and remeasurement and recalculation are performed. With this configuration, the inclination of the recording surface of the optical disk with respect to the optical axis of the optical beam can be accurately detected regardless of the amount of warpage of the optical disk without providing a special detecting device such as a tilt sensor, and It is possible to control the inclination of the recording surface of the optical disk with respect to the axis to an optimum angle with high accuracy. Therefore, a small, thin, and highly reliable optical disk device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical disk device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a tilt servo circuit 21 of the optical disc device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a photodetector of the optical disc device according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a reproduction signal processing circuit 19 of the optical disc device according to the first embodiment of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a tilt detection unit 20 of the optical disc device according to the first embodiment of the present invention.

FIG. 6 is a graph showing a change in a TE signal amplitude with respect to a tilt of the optical pickup 3 of the optical disc device according to the first embodiment of the present invention.

FIG. 7 is a plot of the TE signal amplitude measured while changing the amount of tilt at a step angle of 0.2 ° in the optical disc device according to the first embodiment of the present invention, and a quadratic function by the least squares method based on the measured value. 9 is a graph showing a quadratic curve approximated to FIG.

FIG. 8 is a plot of the TE signal amplitude when the true optimum tilt amount at which the TE signal amplitude is maximum in the optical disc device according to the first embodiment of the present invention is about 2.75 times the step angle of 0.2 degrees; 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 9 is a plot of the TE signal amplitude when the true optimum tilt amount at which the TE signal amplitude is maximum is about 3.7 times the step angle of 0.2 degrees in the optical disc device according to the second embodiment of the present invention. 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 10 is a plot of the TE signal amplitude when the true optimum tilt amount at which the TE signal amplitude is maximum in the optical disc device according to the third embodiment of the present invention is about 3.7 times the step angle of 0.2 degrees; 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 11 is a block diagram illustrating a configuration of an optical disc device according to a fifth embodiment of the present invention.

FIG. 12 is a block diagram illustrating a configuration of a tilt detection unit 420 of an optical disc device according to a fifth embodiment of the present invention.

FIG. 13 is a graph showing a change in RF signal amplitude with respect to a tilt of an optical pickup 3 of an optical disk device according to a fifth embodiment of the present invention.

FIG. 14 is a plot of an RF signal amplitude measured while changing the amount of tilt at a step angle of 0.2 degrees in the optical disc device according to the fifth embodiment of the present invention, and a quadratic function by the least squares method based on the measured value. 9 is a graph showing a quadratic curve approximated to FIG.

FIG. 15 illustrates an RF when the true optimum tilt amount at which the RF signal amplitude is maximum is about 2.75 times the step angle of 0.2 degrees in the optical disc device according to the fifth embodiment of the present invention.
5 is a graph showing a plot of a signal amplitude and a quadratic curve approximated to a quadratic function by a least squares method based on the measured value.

FIG. 16 is a plot of the RF signal amplitude when the true optimal tilt amount at which the RF signal amplitude is maximum in the optical disc device according to the fifth embodiment of the present invention is about 3.7 times the step angle of 0.2 degrees; 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 17 is a block diagram illustrating a configuration of an optical disc device in Embodiment 6 of the present invention.

FIG. 18 is a block diagram illustrating a configuration of a tilt detection unit 520 of the optical disc device according to the sixth embodiment of the present invention.

FIG. 19 is a graph illustrating a change in a jitter value with respect to a tilt of the optical pickup 3 of the optical disc device according to the sixth embodiment of the present invention.

FIG. 20 is a plot of a jitter voltage value measured while changing the amount of tilt at a step angle of 0.2 ° of the optical disc device in Embodiment 6 of the present invention, and a quadratic function by the least square method based on the measured value. It is the graph which showed the approximated quadratic curve.

FIG. 21 is a plot of a measured jitter voltage value when the true optimum tilt amount at which the jitter value of the optical disk device according to the sixth embodiment of the present invention is minimum is about 2.75 times the step angle of 0.2 degrees. 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 22 is a plot of a measured jitter voltage value when the true optimum tilt amount at which the jitter value of the optical disk device according to the sixth embodiment of the present invention is the minimum is about 3.7 times the step angle of 0.2 degrees. 7 is a graph showing a quadratic curve approximated to a quadratic function by the least squares method based on the measured values.

FIG. 23 is a diagram illustrating a configuration of a tilt actuator for tilting an objective lens 4 of an optical disc device in Embodiment 7 of the present invention.

FIG. 24 is a block diagram illustrating a configuration of an optical disc device according to a seventh embodiment of the present invention.

FIG. 25 is a block diagram illustrating a configuration of a tilt servo circuit 621 of the optical disc device according to the seventh embodiment of the present invention.

FIG. 26 is a flowchart illustrating an operation of the tilt detection unit 20 of the optical disc device according to the first embodiment of the present invention.

FIG. 27 is a flowchart illustrating an operation of the tilt detection unit 420 of the optical disc device according to the fifth embodiment of the present invention.

FIG. 28 is a flowchart illustrating an operation of the tilt detection unit 520 of the optical disc device according to the sixth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Spindle motor 3 Optical pickup 4 Objective lens 6 Focus servo circuit 7 Focus actuator 8 Magnet 9 Focus drive coil 10 Tracking drive coil 11 Tracking actuator 12 Tracking servo circuit 17 Guide axis 19 Reproduction signal processing circuit 20, 420, 520 Tilt detection Unit 21, 621 Tilt servo circuit 23 Tilt servo signal generation unit 24 Tilt motor 25 Tilt motor drive circuit 27 Motor gear 28 Til track 29 Tilt cam 30 Tilt follower 31 Guide shaft fixing plate 31 34 Photodetector 33 Tilt setting signal generation unit 35 TE signal amplitude measurement Units 36, 436, 536 Optimal tilt amount calculation units 37, 137, 237, 337, 437, 537, 63
7 Calculation result determination unit 438 RF signal amplitude measurement unit 539 Jitter measurement unit 540 Jitter signal measurement unit 623 Tilt servo signal generation unit 643 Tilt drive circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Katsumi Morita 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F-term (reference) 5D118 AA13 BA01 CB03 CC12 CD03 CD04 CF05

Claims (20)

[Claims] An optical pickup for focusing and irradiating a light beam on an optical disk having a spiral or concentric track, and recording or reproducing a signal, and a light detector for receiving reflected light from the optical disk A reproduction signal processing unit that generates a signal that changes according to a tilt amount that is a relative inclination of the recording surface of the optical disc and the light beam using an output signal of the photodetector; A command signal for sequentially setting the tilt amount to a plurality of different values, and a tilt setting signal generating unit for setting the tilt amount to an optimum tilt value in a second mode; and an output signal of the tilt setting signal generating unit. And a tilt drive mechanism that varies the tilt amount according to the tilt drive mechanism based on the command signal to sequentially change the tilt amount. A reproduction signal measuring unit that measures an output value of the reproduction signal processing unit; and an optimum tilt that calculates the optimum tilt value based on the tilt amount changed by the command signal and a measurement value of the reproduction signal measuring unit. An optical disc device comprising: a quantity calculation unit. 2. An optical pickup for focusing and irradiating an optical disc having tracks formed in a spiral or concentric shape to record or reproduce a signal, and a photodetector for receiving reflected light from the optical disc. A reproduction signal processing unit that generates a signal that changes according to a tilt amount that is a relative inclination of the recording surface of the optical disc and the light beam using an output signal of the photodetector; A command signal for sequentially setting the tilt amount to a plurality of different values, and a tilt setting signal generating unit for setting the tilt amount to an optimum tilt value in a second mode; and an output signal of the tilt setting signal generating unit. And a tilt drive mechanism that varies the tilt amount according to the tilt drive mechanism based on the command signal to sequentially change the tilt amount. A reproduction signal measurement unit that measures an output value of the reproduction signal processing unit; and a relationship between the tilt amount changed by the command signal and a measurement value of the reproduction signal measurement unit approximated to a predetermined function by a least square method. An optical disc drive, comprising: an optimum tilt amount calculator that calculates the optimum tilt value based on the function. Determining whether or not the optimum tilt value calculated by the optimum tilt amount calculation unit exceeds a calculation limit value determined in accordance with a command signal of the tilt setting signal generation unit; When the tilt value exceeds the calculation limit value in the positive direction, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction, When the tilt value exceeds the calculation limit value in the negative direction, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the negative direction, When the tilt value does not exceed the calculation limit value, the tilt setting signal generation unit further includes a calculation result determination unit that sets the optimum tilt value. If the optimum tilt value has exceeded the calculation limit value in the positive or negative direction, the tilt setting signal generation unit outputs the reset command signal, and the reproduction signal measurement unit has been reset. The output value of the reproduction signal processing unit when the tilt amount is sequentially changed according to the command signal is re-measured, and the optimum tilt amount calculation unit recalculates the optimum tilt value. An optical disk device according to claim 1. 4. When the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X, and the optimum tilt amount calculating unit sets the tilt value to be an extreme value. The tilt amount is calculated as an optimum tilt value, and it is determined whether the quadratic coefficient of the quadratic function is positive or negative. If the quadratic coefficient is positive, the tilt value determined by the command signal of the tilt setting signal generation unit is determined. The apparatus further includes an operation result determination unit that resets the value by a predetermined amount and causes the tilt setting signal generation unit to set the optimum tilt value when the value is negative, wherein the quadratic coefficient of the quadratic function is positive. In this case, the tilt setting signal generation unit outputs the reset command signal, and the reproduction signal measurement unit outputs the reproduction signal when the tilt amount is sequentially changed according to the reset command signal. Re-measure the output value of the processing unit, and DOO amount calculation unit recalculates the optimum tilt value, the optical disk apparatus according to claim 1 or claim 2, characterized in that. 5. When the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X, and the optimum tilt amount calculating unit determines that the Y is an extreme value. The tilt amount is calculated as an optimum tilt value, and it is determined whether the quadratic coefficient of the quadratic function is positive or negative. The apparatus further includes a calculation result determining unit that resets the value by a predetermined amount and, when positive, sets the tilt setting signal generating unit to set the optimal tilt value. In this case, the tilt setting signal generation unit outputs the reset command signal, and the reproduction signal measurement unit outputs the reproduction signal when the tilt amount is sequentially changed according to the reset command signal. Re-measure the output value of the processing unit, and DOO amount calculation unit recalculates the optimum tilt value, the optical disk apparatus according to claim 1 or claim 2, characterized in that. 6. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and sets a reference angle that is a center value of the plurality of tilt amounts set by the command signal. It is determined whether the optimum tilt value is located in the positive direction or the negative direction as a reference. If the secondary coefficient is negative, the tilt setting signal generation unit sets the optimum tilt value. When the next coefficient is positive and the optimum tilt value is located in the positive direction with respect to the reference angle, the tilt signal determined by the command signal of the tilt setting signal generation unit is shifted by a predetermined amount in the negative direction. If the quadratic coefficient is positive and the optimum tilt value is located in a negative direction with respect to the reference angle, the command signal of the tilt setting signal generation unit is determined accordingly. Be 5. The optical disc device according to claim 4, wherein the tilt value is reset so as to change by a predetermined amount in the positive direction. 7. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and sets a reference angle that is a center value of the plurality of tilt amounts set by the command signal. As a criterion, it is determined whether the optimum tilt value is located in the positive direction or the negative direction. If the secondary coefficient is positive, the tilt setting signal generation unit sets the optimum tilt value. When the next coefficient is negative and the optimum tilt value is located in the positive direction with respect to the reference angle, the tilt signal determined by the command signal of the tilt setting signal generation unit is reduced by a predetermined amount in the negative direction. If the quadratic coefficient is negative and the optimum tilt value is located in the negative direction with respect to the reference angle, the command signal of the tilt setting signal generation unit is determined accordingly. Be 6. The optical disk device according to claim 5, wherein the tilt value is reset so as to change by a predetermined amount in the positive direction. 8. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative and sets a reference angle that is a center value of the plurality of tilt amounts set by the command signal. As a reference, a positive average value which is an average of the measured values measured when the tilt amount set by the command signal is located in the positive direction with respect to the reference angle, is set by the command signal. Compare the magnitude relationship with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, the secondary coefficient is positive and the positive side If the average value is larger than the negative average value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and the secondary coefficient is Positive and negative average When the value is larger than the positive side average value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the negative direction, and the secondary coefficient becomes negative. 5. The optical disc apparatus according to claim 4, wherein in the case of (1), the tilt setting signal generation section sets the optimum tilt value. 9. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and sets a reference angle that is a center value of the plurality of tilt amounts set by the command signal. As a reference, a positive average value which is an average of the measured values measured when the tilt amount set by the command signal is located in the positive direction with respect to the reference angle, is set by the command signal. Compare the magnitude relationship with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, the secondary coefficient is negative and the positive side When the average value is larger than the negative side average value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the negative direction, and the secondary coefficient is Negative and negative average If the value is larger than the positive average value, the command signal of the tilt setting signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and the secondary coefficient becomes positive. 6. The optical disk device according to claim 5, wherein in the case of (1), the tilt setting signal generation section sets the optimum tilt value. 10. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and sets a reference angle that is a center value of the plurality of tilt amounts set by the command signal. As a reference, a positive average value which is an average of the measured values measured when the tilt amount set by the command signal is located in the positive direction with respect to the reference angle, is set by the command signal. The tilt amount is compared with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, and the tilt amount calculated by the optimal tilt amount calculation unit When the optimum tilt value is located in the positive direction with respect to the reference angle and the negative average value is larger than the positive average value, the tilt setting signal generation unit generates a command signal according to the tilt value. Is negative The tilt setting is reset if the optimum tilt value is located in the negative direction with respect to the reference angle and the positive average value is larger than the negative average value. The command signal of the signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction. When the command signal of the tilt setting signal generation unit is reset, the tilt setting signal is set. The generation unit outputs the reset command signal, and the reproduction signal measurement unit re-measures the output value of the reproduction signal processing unit when the tilt amount is sequentially changed according to the reset command signal. The optical disc device according to claim 4, wherein the optimum tilt amount calculation unit recalculates the optimum tilt value. 11. The calculation result determination unit determines whether a quadratic coefficient of the quadratic function is positive or negative, and determines a reference angle that is a center value of the plurality of tilt amounts set by the command signal. As a reference, a positive average value which is an average of the measured values measured when the tilt amount set by the command signal is located in the positive direction with respect to the reference angle, is set by the command signal. The tilt amount is compared with the negative average value, which is the average of the measured values measured when the tilt amount is located in the negative direction with respect to the reference angle, and the tilt amount calculated by the optimal tilt amount calculation unit is compared. When the optimum tilt value is located in the positive direction with respect to the reference angle and the positive average value is larger than the negative average value, the tilt setting signal generation unit generates a command signal according to the tilt value. Is negative The tilt setting is reset when the optimum tilt value is located in the negative direction with respect to the reference angle and the negative average value is larger than the positive average value. The command signal of the signal generation unit is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction. When the command signal of the tilt setting signal generation unit is reset, the tilt setting signal is set. The generation unit outputs the reset command signal, and the reproduction signal measurement unit re-measures the output value of the reproduction signal processing unit when the tilt amount is sequentially changed according to the reset command signal. The optical disc device according to claim 5, wherein the optimum tilt amount calculation unit recalculates the optimum tilt value. 12. The reproduction signal processing unit according to claim 1, wherein an output value of the reproduction signal processing unit is a tracking error signal, and the reproduction signal measurement unit is a tracking error signal amplitude measurement unit. 3, claim 4, claim 6,
The optical disk device according to claim 8. 13. An output value of the reproduction signal processing unit, which is an output value corresponding to an addition signal of output signals of a plurality of light emitting elements included in the photodetector, wherein the reproduction signal measurement unit outputs 11. The optical disk device according to claim 1, wherein the optical disk device is an addition signal amplitude measuring unit for measuring an amplitude. 14. The apparatus according to claim 1, wherein said reproduction signal measuring section is a jitter signal measuring section.
Claim 3, Claim 5, Claim 7, Claim 9, or Claim 1
2. The optical disc device according to 1. 15. The optical disk device according to claim 1, wherein the tilt drive mechanism has a configuration that changes an angle of an objective lens that focuses the light beam. 16. An optical pickup for focusing and irradiating a light beam on an optical disc having tracks formed in a spiral or concentric shape to record or reproduce a signal, and a photodetector for receiving reflected light from the optical disc. A reproduction signal processing unit that generates a signal that changes according to a tilt amount that is a relative inclination of the recording surface of the optical disc and the light beam using an output signal of the photodetector; A method for controlling an optical disc device, comprising: a reproduction signal measuring unit for measuring an output value; and a tilt drive mechanism for varying the tilt amount, wherein a command signal for setting the tilt amount to a plurality of different values is sequentially output. Driving the tilt drive mechanism in response to the command signal to sequentially change the tilt amount, and performing the reproduction signal processing when the tilt amount is sequentially changed. Measuring an output signal of the reproducing unit, and calculating an optimum tilt value based on the tilt amount changed by the command signal and a measurement value of the reproduction signal measuring unit; An optimal tilt amount setting step of setting a tilt value. A method for controlling an optical disk device, comprising: 17. In the optimum tilt amount detecting step, a relationship between the tilt amount changed by the command signal and a measurement value of the reproduction signal measuring unit is approximated to a predetermined function by a least square method, and 17. The method according to claim 16, wherein the optimum tilt value is calculated based on the calculated tilt value. 18. The method according to claim 18, wherein in the optimum tilt amount detecting step, it is determined whether or not the optimum tilt value exceeds a calculation limit value determined in accordance with the command signal. If the value exceeds the threshold value, the command signal is reset so that the tilt value determined thereby changes by a predetermined amount in the positive direction, and the optimum tilt amount detecting step is re-executed. Is larger than the calculation limit value in the negative direction, the command signal is reset so that the tilt value determined thereby changes in the negative direction by a predetermined amount, and the optimum tilt amount detection step is performed again. 18. The light according to claim 16, wherein an optimum tilt amount setting step is performed when the optimum tilt value does not exceed the calculation limit value. Control method of the disk apparatus. 19. In the optimum tilt amount detecting step, assuming that the tilt amount is X and the measured value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X, and the Y becomes an extreme value. The tilt amount is calculated as an optimum tilt value, and it is determined whether the quadratic coefficient of the quadratic function is positive or negative. If the quadratic coefficient of the quadratic function is positive, the command signal is determined accordingly. Resetting the tilt value to be changed by a predetermined amount, re-executing the optimum tilt amount detecting step, and executing the optimum tilt amount setting step when the quadratic coefficient of the quadratic function is negative. 18. The method for controlling an optical disk device according to claim 16, wherein: 20. In the optimum tilt amount detecting step, assuming that the tilt amount is X and the measurement value of the reproduction signal measuring unit is Y, Y is represented by a quadratic function of X, and the Y becomes an extreme value. A tilt amount is calculated as an optimum tilt value, and it is determined whether a quadratic coefficient of the quadratic function is positive or negative. If the quadratic coefficient of the quadratic function is negative, the command signal is determined accordingly. Resetting the tilt value to be changed by a predetermined amount, re-executing the optimal tilt amount detecting step, and executing the optimal tilt amount setting step when the quadratic coefficient of the quadratic function is positive, 18. The method for controlling an optical disk device according to claim 16, wherein: