JPH09147392A - Optical disk reproducing method and optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk reproducing method and an optical disk device capable of normally performing a reproducing even in an optical disk having errors exceeding a specification and capable of constantly performing a reproducing even in the reproducing of a normal optical disk. SOLUTION: A focusing servo control part 21 is provided with a servo amplifier 23 having a servo gain setting circuit 24, an amplitude detector 26 detecting the quantity of the face wobbling of an optical disk and a controller 15 managing operations of respective means. Then, the controller 15 detects the quantity of the face wobbling of the optical disk by preliminarily with the amplitude detector 26 rotating the disk and reproduces the information of the optical disk after changing the amplification factor of the servo amplifier 23 by operating the servo gain setting circuit 24 based on the detection output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing method and an optical disk device for reproducing information on a CD-ROM or the like.

[0002]

2. Description of the Related Art Optical discs such as audio CDs, CD-ROMs, write-once optical disc devices, and the like have already become widespread, and efforts are being made to apply them and improve their performance in various fields. In particular, since a large amount of data can be recorded / reproduced at high speed, a CD-ROM drive has recently been rapidly spread as a center of multimedia as a data reproduction device for a computer.

Therefore, a conventional optical disk device will be described below by taking a CD-ROM as an example. FIG. 6 is a configuration block diagram of a conventional optical disk device. Reference numeral 1 is an optical disk (CD-ROM), 2 is a spindle motor, and 3 is an optical pickup.

The optical pickup 3 is composed of a mechanical section and an optical section. The mechanical section has an objective lens 4 for focusing light on the recording surface of the optical disc 1 and a direction perpendicular to the surface of the optical disc 1 (hereinafter referred to as "objective lens 4"). The objective lens actuator 5 is configured integrally with an actuator for moving in the focus direction) and the radial direction of the optical disc 1 (hereinafter referred to as the tracking direction). The optical unit includes various prisms such as a semiconductor laser and an optical sensor 6.

A sled motor 7 is used for tracking a movable range that cannot be handled by the objective lens actuator 5 and for making a large movement between tracks (access operation). The access operation is controlled by the access control unit 10.

The signal of the optical sensor 6 is supplied to the focus servo control unit 8, the tracking servo control unit 9, and the information signal detection unit 11 to generate a focus error signal, a tracking error signal and an information detection signal, respectively, and the objective Focus control of the lens 4, tracking control, and signal processing by the signal processing circuit 12 are performed.

Reference numeral 13 is an interface control unit,
The read signal processed by the controller 15 is sent to the host device via the interface control unit 13.

Further, the information detection signal is supplied to the spindle motor controller 14 to drive the spindle motor 2 to rotate at a constant rotation speed. The controller 15 controls the operation of the entire optical disc device.

With respect to the conventional optical disk device configured as described above, the servo control operation thereof will be described in particular. An information track on which an information signal is recorded is formed in a spiral shape on the optical disc 1, and the track pitch thereof is very small (1.6 μm). Therefore, in order to accurately detect the information signal, the It is necessary to control the position of the light spot on the optical disc 1 with high accuracy.

Therefore, FIG. 7 shows a detailed configuration diagram of the conventional focus servo control unit 8. In the figure, 15 is a controller shown in FIG. 6, 16 is a phase compensation filter for stabilizing the servo system, 17 is a servo amplifier, 18 is a servo gain setting circuit, and 19 is a drive circuit.

The operation of the conventional focus servo control unit configured as described above will be described below. The focus error signal obtained from the optical pickup 3 is input to a phase compensation filter 16 for stabilizing the servo system, passes through a servo amplifier 17 and a drive circuit 19, and a signal for driving the objective lens actuator 5 is output. .

The servo gain setting circuit 1 keeps the servo gain constant regardless of variations in the optical signal of the optical pickup 3 and the sensitivity of the objective lens actuator 5.
8 is provided, and the amplification factor of the servo amplifier 17 is set by the controller 15 so that a desired value can be obtained from the drive circuit 19.

Next, the tracking servo control will be described. FIG. 8 is an open loop characteristic diagram of the tracking servo. For example, the standard value of the maximum eccentricity of a CD-ROM disk is ± 70 μm, but the actual mechanical eccentricity is ± 120 μm in consideration of the eccentricity of the motor shaft and turntable.
About.

On the other hand, in order not to reduce the error rate of the reproduction signal, the positional deviation of the track (optical pit) is ±
It is necessary to suppress the thickness to 0.1 μm or less.

Therefore, the low frequency (30 Hz in the figure)
The low-pass servo gain of (below) is set to 20 log (120 / 0.1) = 61.6 dB.

Regarding the high-frequency servo gain, the maximum eccentric acceleration is 0.4 G in the above-mentioned standard, but in order to improve the vibration resistance of the optical disk device and suppress the higher resonance frequency,
The gain intersection is set to about 1 kHz.

[0017]

As described in the above standard values, the optical disc 1 has an error between the roundness and the flatness, which, together with the error of the optical disc device,
It rotates while vibrating slightly in the radial direction (hereinafter referred to as eccentricity), or rotates while slightly moving up and down (hereinafter referred to as surface runout). Moreover, there are individual variations in the amount of surface runout and the amount of eccentricity of the optical disc 1, and there are some in the market whose amounts exceed the values defined by the standard.

Therefore, if the set value of the servo gain is designed according to the standard, it operates with a fixed set value regardless of the amount of eccentricity and the amount of surface wobbling of the optical disk 1, so that the optical disk 1 is reproduced. At that time, the focus error or tracking error becomes larger than a predetermined allowable value, and normal reproduction cannot be performed. For example, FIG. 9 is a diagram showing a state in which the focus error exceeds the allowable value. As shown in the figure, when the optical disk 1 whose surface deflection exceeds the value defined by the standard is reproduced, the focus error signal does not fall within the allowable value. Therefore,
In order to perform normal reproduction on such an optical disc 1, it is necessary to increase the focus servo gain or change the characteristics of the servo loop gain (or the phase compensation filter 16).

To increase the servo gain, the servo amplifier 1
It is possible to increase the amplification factor of 7. However, in this method, the focus error signal is suppressed by increasing the servo gain, but the gain in the higher range than the servo band also increases, so that it is sensitive to scratches and noise existing on the optical disc 1, and the normal error occurs. Playability with respect to scratches during disk reproduction deteriorates. In addition, since over-control is applied to a normal optical disc 1 having a small amount of surface wobbling, there arises a problem that power consumption increases.

It is also conceivable to change the characteristics of the phase compensation filter 16 to increase the gain only in the low frequency range. With this method, the gain in the high frequency band is almost the same as that of the conventional method, and therefore the playability is not deteriorated. However, if the low-pass gain of the servo system is increased, the stability is deteriorated by that amount, and thus it is not a preferable method, and the problem of excessive control and power consumption for the ordinary optical disk 1 cannot be solved.

The present invention has been made in order to solve the above problems, and can properly reproduce even an optical disk having an error exceeding the standard, and is stable even when reproducing an ordinary optical disk. It is an object of the present invention to provide an optical disc reproducing method and an optical disc device that can be reproduced by performing the following.

[0022]

In order to achieve the above object, the optical disk device of the present invention comprises an optical reproducing means for optically reading information from a track on the optical disk and a rotational driving of the optical disk at a predetermined rotational speed. Rotation control means,
An optical disc device having a servo control unit for causing an optical reproducing unit to follow a track, wherein the servo control unit includes at least one of a servo amplifier having an amplification factor changing unit and a filter unit having a frequency characteristic changing unit. In addition to having the target value fluctuation amount detecting means for detecting the amount of surface deviation or eccentricity of the optical disk, and the controller controlling the operation of each means, the above-mentioned controller amplifies based on the output of the target value fluctuation amount detecting means. It is characterized in that the rate changing means or the frequency characteristic changing means is operated to change the operating characteristics of the servo amplifier or the filter means.

In the optical disk device of the present invention configured as described above, the target value fluctuation amount detecting means can detect the surface runout amount and the eccentricity amount of each optical disk by checking the fluctuation amount of the optical disk in advance. Therefore, the optimum amplification factor of the servo amplifier or the frequency characteristic of the phase compensation filter can be set for each optical disk.

Therefore, even an optical disk having an error exceeding the standard can be normally reproduced, and even an ordinary optical disk can be stably reproduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises an optical reproduction step of optically reading information from a track on an optical disk, and a servo control step of following the track in the optical reproduction step. In the optical disc reproducing method having, the servo control step includes a step of changing at least one of an amplification factor and a frequency characteristic of a servo amplifier, and a target value fluctuation amount detection step of detecting a surface deflection amount or an eccentricity amount of the optical disc. Have,
In advance, the optical disc is rotated, and the amount of surface deflection or the amount of eccentricity of the optical disc is detected by the target value variation amount detection step,
It is characterized in that the servo control step is operated based on these detection results to change the servo control step of the amplification factor or frequency characteristic suitable for the optical disc, and then the information of the optical disc is reproduced.

According to the second to sixth aspects of the present invention, there are provided an optical reproducing means for optically reading information from a track on the optical disk, and a rotation control means for rotationally driving the optical disk at a predetermined rotation speed. An optical disc apparatus having a servo control unit that causes an optical reproducing unit to follow a track, wherein the servo control unit includes a servo characteristic changing unit that changes a servo characteristic, and changes in a control target value when the optical disc is rotated. Target value fluctuation amount detecting means for detecting the amount,
The controller controls the operation of each means, and the controller rotates the optical disk in advance by the rotation control means, operates the target value fluctuation amount detection means to detect the fluctuation amount of the control target value, and based on the fluctuation amount. The servo characteristic changing means is operated to change to a servo control means having a servo characteristic suitable for the optical disk, and then the information on the optical disk is controlled to be reproduced. The amplitude value based on the tracking error signal, or the number of tracks counting the number of tracks traversed by the light spot, and the above-mentioned servo characteristic is the amplification factor of the servo amplifier or the frequency characteristic of the phase compensation filter. It is a feature.

The invention described in claims 7 to 11 of the present invention is an optical reproducing means for optically reading information from a track on an optical disk, and a tracking shift for shifting the optical reproducing means among a plurality of tracks. Means, sled moving means for moving the optical reproducing means in the radial direction of the optical disk, rotation control means for rotationally driving the optical disk at a predetermined rotational speed, tracking servo control means for causing the tracking displacement means to follow the track, and sled movement. An optical disc device having a sled servo control means for causing the means to follow a track, wherein the tracking servo control means includes a tracking servo characteristic changing means for changing a servo characteristic, and the sled servo control means is a sled servo for changing a servo characteristic. Rotate the optical disc, including the characteristic changing means. The target value fluctuation amount detecting means for detecting the fluctuation amount of the control target value at the time of the operation, and the controller controlling the operation of each means, the controller rotates the optical disk in advance by the rotation control means to set the target value fluctuation amount. After the detection means is operated to detect the variation amount of the control target value, the servo characteristic changing means is operated based on the variation amount, and after changing to the tracking servo control means and the sled servo control means having the servo characteristics suitable for the optical disc. , Characterized in that it is controlled to reproduce the information of the optical disc, the fluctuation amount is the amplitude value based on the focus error signal or the tracking error signal, or the number of tracks that counted the number of tracks the optical spot crossed, The servo characteristic is the amplification factor of the servo amplifier of the tracking servo control means and the sled servo control means, , It is characterized in that a frequency characteristic of the phase compensation filter of the tracking servo control means and sled servo control means.

(Embodiment 1) An optical disk device according to Embodiment 1 of the present invention will be described below with reference to the drawings. The block diagram of the entire optical disk device is the same as the block diagram shown in FIG. The present invention relates to the focus servo control unit 8, the tracking servo control unit 9, and the controller 15 in FIG.

FIG. 1 is a detailed block diagram of the focus servo control unit 21 in the first embodiment of the present invention. FIG.
Reference numeral 21 is a focus servo control unit, 15 is a controller, 22 is a phase compensation filter for stabilizing the servo system, 23 is a servo amplifier, 24 is a servo gain setting circuit, 25 is a drive circuit, and 26 is an amplitude detector.

The operation of the focus servo control unit 21 of the present invention having the above structure will be described below. First, the focus error signal obtained from the optical pickup 3 is a phase compensation filter 2 for stabilizing the servo system.
A signal for driving the objective lens actuator 5 of the optical pickup 3 is output via the servo amplifier 23 and the drive circuit 25.

Further, in order to keep the servo gain constant regardless of variations in the optical signal of the optical pickup 3 and the sensitivity of the objective lens actuator 5, the servo gain setting circuit 2
Reference numeral 4 adjusts the amplification factor of the servo amplifier 23 to set the servo gain to a desired value.

The controller 15 controls the operation of the entire optical disc device, and controls the servo gain setting circuit 24 and the drive circuit 25 which will be described below.

When the power is turned on or the optical disc 1 is exchanged, the focus servo is first turned on to rotate the optical disc 1. In this state, the amplitude detector 26 detects the amplitude of the focus error signal and outputs the detection result to the controller 15. Controller 1
5 increases the gain of the servo amplifier 23 by a preset amount when the detection result of the focus error signal exceeds a predetermined allowable value.

That is, when the amount of surface wobbling of the optical disk 1 is small, the conventional servo gain is set, but when the amount of surface wobbling of the optical disk 1 is large, the servo gain is increased and the focus error signal is suppressed below a predetermined allowable value. It

FIG. 2 is a diagram showing the relationship between the focus error signal and the allowable value. In the figure, the dotted line represents the focus error signal when the optical disc 1 having a large amount of surface wobbling is set and read with a normal servo gain.

At this time, the amplitude value of the focus error signal detected by the amplitude detector 26 exceeds the allowable value shown in the figure. Therefore, the controller 15 controls the servo gain setting circuit 24 to increase the gain of the servo amplifier 23 by a predetermined amount. As a result, the focus servo gain becomes high, and the focus error signal becomes below the allowable value as shown by the solid line.

In the optical disc 1 having a small amount of normal surface wobbling, since the focus error signal falls within the allowable value with the normal servo gain, the operation with the normal servo gain is continued.

(Second Embodiment) The focus servo system has been described above, but the same control method can be applied to the tracking servo system.

FIG. 3 is a detailed block diagram of the tracking servo control unit 31 in the second embodiment of the present invention. In FIG. 3, 31 is a tracking servo control unit, 15 is a controller, 32 is a phase compensation filter for stabilizing the servo system, 33 is a servo amplifier, 34 is a servo gain setting circuit, 35 is a drive circuit, and 36 is the number of transverse tracks. It is a vessel. The operation of the tracking servo control unit 31 in the other embodiment of the present invention configured as described above will be described below. First, the tracking error signal obtained from the optical pickup 3 is input to the phase compensation filter 32 for stabilizing the servo system, passes through the servo amplifier 33 and the drive circuit 35, and drives the objective lens actuator 5 of the optical pickup 3. Signal is output.

Further, in order to keep the servo gain constant regardless of variations in the optical signal of the optical pickup 3 and the sensitivity of the objective lens actuator 5, the servo gain setting circuit 3
Reference numeral 4 adjusts the amplification factor of the servo amplifier 33 to set the servo gain to a desired value.

The controller 15 controls the operation of the entire optical disk apparatus, controls the servo gain setting circuit 34, changes the amplification factor of the servo amplifier 33, and turns the operation of the drive circuit 35 on and off. .

When the power is turned on or the optical disc 1 is exchanged, the tracking servo is turned off and the optical disc 1 is rotated after setting the focus servo.
In this state, the number of traverse tracks detector 36 detects the number of tracks traversed by the optical spot while the optical disk 1 makes one revolution, and the detection result is detected by the controller 1
5 is output. The controller 15 increases the amplification factor of the servo amplifier 23 by a preset amount when the detection result of the number of crossing tracks exceeds a predetermined allowable number of tracks.

That is, when the amount of eccentricity of the optical disc 1 is small, the conventional normal servo gain is set, but when the amount of eccentricity of the optical disc 1 is large, the servo gain is increased and the tracking error signal is suppressed to a predetermined allowable number of tracks or less. To be done.

When the gain setting of the tracking servo control section 31 is completed, the tracking servo is turned on and the reading of information from the optical disc 1 is started.

FIG. 4A is a diagram showing a tracking error signal for reproducing the optical disk 1 with a normal eccentricity amount due to the tracking servo OFF, and FIG. 4B is a tracking error signal for reproducing the optical disk 1 with a large eccentricity amount due to the tracking servo OFF. It is a figure showing a signal. In the figure, in the case of a disc with a large eccentricity, the number of tracks traversed by the optical pickup increases during a fixed time. Therefore, when the number of crossing tracks detected by the crossing track number detector 36 is less than the predetermined allowable number of tracks, the servo gain setting circuit 34 sets the servo amplifier 33 to a normal amplification factor, but exceeds the allowable number of tracks. Sometimes, the servo gain setting circuit 34 sets the amplification factor of the servo amplifier 33 to a higher value by a predetermined amount under the control of the controller 15. Therefore, as in the case of the focus servo control unit 21, the tracking error signal can be suppressed to the allowable number of tracks or less.

(Third Embodiment) The embodiment of the tracking servo focusing on the control of the objective lens actuator has been described above, but the two-step tracking servo which also refers to the control of the sled motor will be described below as an example. FIG. 5 is a detailed block diagram of a two-step tracking servo control unit according to another embodiment of the present invention. 5, 41 is a two-stage tracking servo control unit, 15 is a controller, 42 is a tracking phase compensation filter for stabilizing the tracking servo system, 43 is the first servo amplifier of the tracking servo system, 44 is a servo gain setting circuit, Reference numeral 45 is an actuator drive circuit, 46 is a transverse track number detector, 47 is a sled phase compensation filter for stabilizing the sled servo system, 48 is a second servo amplifier of the sled servo system, and 49 is a sled motor drive circuit.

The operation of the two-step tracking servo control unit 41 in the third embodiment of the present invention configured as above will be described below. First, the tracking error signal obtained from the optical pickup 3 is input to the tracking phase compensation filter 42 for stabilizing the tracking servo system, passes through the first servo amplifier 43 and the actuator drive circuit 45, and then passes through the objective lens of the optical pickup 3. It is output as a signal for driving the actuator 5.

Further, in order to keep the servo gain constant regardless of variations in the optical signal of the optical pickup 3 and the sensitivity of the objective lens actuator 5, the servo gain setting circuit 4
Reference numeral 4 adjusts the amplification factor of the first servo amplifier 43 to set the servo gain to a desired value. Further, the output signal of the first servo amplifier 43 is input to the sled phase compensation filter 47 for stabilizing the sled servo system, and drives the sled motor 7 via the second servo amplifier 48 and the sled motor drive circuit 49. Is output as a signal for. With this configuration, the objective lens actuator 5 and the sled motor 7 are simultaneously driven based on the tracking error signal. Note that normally, the tracking phase compensation filter 42 and the sled phase compensation filter 47 are set so that the objective lens actuator follows the high speed range and the sled motor 7 follows the low speed range.

The controller 15 controls the operation of the entire optical disk device, controls the servo gain setting circuit 44 described below, changes the setting of the amplification factor of the second servo amplifier 48, and turns on the operation of the drive circuits 45, 48.・ Off control.

When the power is turned on or the optical disc 1 is exchanged, after setting the focus servo, the sled servo and tracking servo are turned off and the optical disc 1 is rotated. In this state, for example, the number of tracks traversed by the light spot during one rotation of the optical disc 1 is detected by the traverse track number detector 36, and the detection result is output to the controller 15. Where, for example,
If the number of crossed tracks detected exceeds the predetermined allowable number of tracks (that is, the amount of eccentricity is large), the controller 1
5 increases the amplification factor of the second servo amplifier 48 by a preset amount. That is, when the eccentricity of the optical disc 1 is small, the conventional normal sled servo gain is set, but when the eccentricity of the optical disc 1 is large, the sled servo gain is increased and the sled motor 7 is controlled to follow the eccentricity. To

By doing so, the tracking error signal can be suppressed below the allowable value. Here, since the amplification factor of the second servo amplifier 48 does not have to be set in advance corresponding to a large eccentricity amount, the current consumption of the sled motor is suppressed for a general disk. It can be configured to reduce the system consumption.

Further, when the amount of eccentricity is large, on the contrary, the amplification factor of the second servo amplifier 48 may be lowered and the amplification factor of the first servo amplifier 43 may be increased.
In this case, the tracking error signal can be suppressed below the allowable value by increasing the amplification factor of the first servo amplifier 43, and the sled motor, which consumes a large amount of current, is not moved so much that the drive is consumed. The current becomes smaller. Therefore, if the sled servo gain is set low, the response to scratches on the disk surface decreases, but if low power consumption characteristics are emphasized, this setting will reduce the current consumption of the optical disk device when eccentricity is large. It is possible to suppress it significantly.

In the embodiment, the example in which the amplification factors of the servo amplifiers 23 and 33, the first servo amplifier 43 and the second servo amplifier 48 are controlled has been described, but the servo gain setting circuits 24, 34 and 44 are described. Control of the phase compensation filters 22 and 32 and the tracking phase compensation filter 4
2. Setting the frequency characteristic of the sled phase compensation filter 47 can be realized by exactly the same control. Further, the phase characteristics of the servo amplifiers 23 and 33, the first servo amplifier 43, and the second servo amplifier 48 can be set. Setting both of the compensation filters 22 and 32, the tracking phase compensation filter 42, and the sled phase compensation filter 47 can also be easily realized in the same manner. Since any application is obvious, duplicated description will be omitted. .

As described above, according to the present invention, the focus error signal and the tracking error can be maintained even for an optical disc having a large amount of surface wobbling or eccentricity while maintaining the performance concerning the power consumption and the stability during the normal disc reproduction. By suppressing the signal to the allowable value or less, it is possible to provide an optical disk device capable of stable reproduction of the optical disk.

[0055]

As described above, according to the present invention, the focus servo control unit and the tracking servo control unit are provided with means for detecting the amount of surface deviation and eccentricity of each optical disk and means for changing the servo gain. Since the optimum servo gain for the optical disk can be set, it is possible to normally play even an optical disk having an error exceeding the standard, and to stably play even an ordinary optical disk. It is possible to provide an optical disk device capable of performing the above.

[Brief description of the drawings]

FIG. 1 is a detailed block diagram of a focus servo control unit according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a focus error signal and an allowable value.

FIG. 3 is a detailed block diagram of a tracking servo control unit according to the second embodiment of the present invention.

FIG. 4A is a diagram showing a tracking error signal reproduced from an optical disc having a normal eccentricity amount when the tracking servo is OFF, and FIG. 4B is a diagram showing a tracking error signal reproduced from an optical disc having a large eccentricity amount when the tracking servo is OFF.

FIG. 5 is a detailed block diagram of a two-step tracking servo control unit according to the third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional optical disk device.

FIG. 7 is a detailed configuration diagram of a conventional focus servo control unit.

FIG. 8 is an open loop characteristic diagram of tracking servo.

FIG. 9 is a diagram showing a state in which a focus error exceeds an allowable value.

[Explanation of symbols]

 1 Optical Disc (CD-ROM) 2 Spindle Motor 3 Optical Pickup 4 Objective Lens 5 Objective Lens Actuator 6 Optical Sensor 7 Thread Motor 8, 21 Focus Servo Control Section 9, 31 Tracking Servo Control Section 10 Access Control Section 11 Information Signal Detection Section 12 Signal processing circuit 13 Interface control unit 14 Spindle motor control unit 15 Controller 16, 22, 32 Phase compensation filter 17, 23, 33 Servo amplifier 18, 24, 34, 44 Servo gain setting circuit 19, 25, 35 Drive circuit 26 Amplitude detection Device 36 Cross-track number detector 41 Two-step tracking servo control unit 42 Tracking phase compensation filter 43 First servo amplifier 45 Actuator drive circuit 46 Cross-track number detector 47 Thread phase compensation filter Ruta 48 second servo amplifier 49 thread motor drive circuit

Claims (11)

[Claims] 1. An optical disk reproducing method comprising: an optical reproducing step of optically reading information from a track on the optical disk; and a servo controlling step of following the track in the optical reproducing step, wherein the servo controlling step comprises: It includes a step of changing at least one of the amplification factor and frequency characteristic of the servo amplifier, and has a target value fluctuation amount detecting step for detecting the amount of surface deflection or eccentricity of the optical disk. The fluctuation amount detection step detects the surface runout amount or eccentricity amount of the optical disc,
An optical disk reproducing method characterized in that the servo control step is operated based on these detection results to change to a servo control step having an amplification factor or a frequency characteristic suitable for the optical disk, and then the information of the optical disk is reproduced. 2. Optical reproduction means for optically reading information from a track on an optical disk, rotation control means for rotationally driving the optical disk at a predetermined number of revolutions, and servo control means for causing the optical reproduction means to follow the track. An optical disc device having: a servo control unit that includes a servo characteristic changing unit that changes a servo characteristic, and a target value variation amount detecting unit that detects a variation amount of a control target value when the optical disc is rotated; A controller that controls the operation of each means, wherein the controller rotates the optical disk in advance by the rotation control means, operates the target value variation amount detection means, detects the variation amount of the control target value, and determines the variation amount. The servo characteristic changing means is operated based on the above, and after changing to the servo control means having the servo characteristic suitable for the optical disc, Optical disc apparatus characterized by being controlled so as to reproduce the broadcast. 3. The optical disk device according to claim 2, wherein the fluctuation amount is an amplitude value based on a focus error signal or a tracking error signal. 4. The optical disk device according to claim 2, wherein the fluctuation amount is the number of tracks obtained by counting the number of tracks traversed by the light spot. 5. The optical disk device according to claim 2, wherein the servo characteristic is an amplification factor of a servo amplifier. 6. The optical disk device according to claim 2, wherein the servo characteristic is a frequency characteristic of a phase compensation filter. 7. An optical reproducing means for optically reading information from a track on an optical disk, and a tracking shifting means for shifting the optical reproducing means among a plurality of tracks.
A sled moving means for moving the optical reproducing means in the radial direction of the optical disc, a rotation control means for rotationally driving the optical disc at a predetermined rotational speed, a tracking servo control means for causing the tracking shifting means to follow a track, and the sled movement. An optical disk device having a sled servo control means for causing the means to follow a track, wherein the tracking servo control means includes a tracking servo characteristic changing means for changing a servo characteristic, and the sled servo control means changes the servo characteristic. It includes a target value fluctuation amount detecting means including a sled servo characteristic changing means for detecting a fluctuation amount of a control target value when the optical disc is rotated, and a controller for controlling the operation of each means. The optical disc is rotated by the control means, and the target The tracking servo control means and the sled servo control having the servo characteristics suitable for the optical disc are operated by operating the fluctuation amount detecting means to detect the fluctuation amount of the control target value, and operating the servo characteristic changing means based on the fluctuation amount. An optical disk device, characterized in that after changing to a means, control is performed so as to reproduce information on the optical disk. 8. The optical disk device according to claim 7, wherein the fluctuation amount is an amplitude value based on a focus error signal or a tracking error signal. 9. The optical disk device according to claim 7, wherein the fluctuation amount is the number of tracks obtained by counting the number of tracks traversed by the light spot. 10. The optical disk apparatus according to claim 7, wherein the servo characteristic is an amplification factor of a servo amplifier of the tracking servo control means and the sled servo control means. 11. The optical disk device according to claim 7, wherein the servo characteristic is a frequency characteristic of a phase compensation filter of the tracking servo control means and the sled servo control means.