JP2001067781A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately record/reproduce an optical disk even when eccentricity exists therein. SOLUTION: A bit clock signal BC generated by a PLL circuit 20 synchronized with a fine clock mark signal FCM is frequency divided by frequency dividers 204, 38 to be imparted to a phase comparator 42. The phase comparator 42 performs spindle servo control with a CLV(constant linear velocity) system in response to the bit clock signal BC2. A microcomputer 56 switches from ZCAV(zone constant angular velocity) servo control to CLV servo control by the fine clock mark signal FCM at need.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical disk device, and more particularly, to an optical disk device that records and / or reproduces a signal in synchronization with a fine clock mark formed at regular intervals on a track.

[0002]

2. Description of the Related Art In an optical disk apparatus for recording a signal on or reproducing a signal from an optical disk by irradiating the optical disk with a laser beam, spindle servo control is performed to rotate the optical disk at a predetermined speed. Have been. The spindle servo control method includes a CAV (Constant Angular Velocity) method,
LV (Constant Linear Velocity) method, ZCAV (Zo
ne Constant Angular Velocity) method.

As shown in FIG. 7, in the CAV method, an optical disk is always rotated at a constant angular velocity ω. Accordingly, as shown in FIG. 8, the linear velocity v (= rω; r is the radius of the access track) is faster toward the outer circumference and slower toward the inner circumference. In the CAV method, the control is simplified, but the recording density becomes lower toward the outer periphery.

On the other hand, in the CLV system, as shown in FIG. 8, the optical disk is rotated so that the linear velocity v is constant both on the outer circumference and the inner circumference. Therefore, as shown in FIG. 7, the optical disk must be rotated so that the angular velocity ω is slower toward the outer periphery and faster toward the inner periphery. Therefore, C
In the LV system, the recording density can be the same at the outer circumference and the inner circumference, but the control becomes complicated.

[0005] The ZCAV system takes advantage of the advantages of both systems. In the ZCAV system, the optical disk is divided into a plurality of concentric zones, and as shown in FIG. 9, the angular velocity ω is constant in each of the zones Z1 to Z4, and
As shown by 0, the optical disc is rotated so that the linear velocity (generally, “average linear velocity”) v of the center track in each of the zones Z1 to Z4 is constant both on the outer circumference and the inner circumference.

[0006]

SUMMARY OF THE INVENTION As described above, CLV
In the method, the linear velocity is always constant, and in the ZCAV method, the average linear velocity is always constant. However, as shown in FIG. 11, the optical disc 1 has eccentricity. That is, the center Cdk of the optical disc 1 is often shifted from the rotation center Csp of the spindle motor during chucking. Also, the center hole of the optical disc 1 is often shifted from the true center.

As described above, since the optical disk is eccentric due to the chucking deviation and the processing error, the linear velocity v does not become exactly constant as shown in FIG. Assuming that the eccentric distance is d and the radius of the access track is r, the amplitude width Δv is proportional to d / r. Therefore, the unevenness of the linear velocity becomes larger as the track has a smaller radius r. Further, such linear velocity unevenness appears at the same cycle as the rotation cycle T of the optical disc 1.

Incidentally, AS-MO (Advanced Storage)
dMagneto Optics) generally employs the ZCAV method. In AS-MO, a fine clock mark is preformatted on a disc. Recording of signals on AS-MO and AS-MO
Is reproduced in synchronization with the bit clock signal generated by detecting the fine clock mark.

However, since the linear velocity becomes uneven due to the eccentricity of the disk as described above, the detection of the fine clock mark fluctuates periodically. As a result, there is a problem that the jitter of the bit clock signal increases, which adversely affects the recording and reproduction of the signal.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an optical disk apparatus capable of accurately recording / reproducing a signal by reducing unevenness in linear velocity. .

[0011]

An optical disk device according to the present invention includes a spindle motor, fine clock mark detecting means, and spindle servo control means.
The spindle motor rotates the optical disk. The fine clock mark detecting means detects the fine clock mark and generates a fine clock mark signal. The spindle servo means includes CLV control means for controlling a spindle motor so that the optical disc rotates at a constant linear velocity in response to the fine clock mark signal.

In this optical disk apparatus, the optical disk rotates at a constant linear velocity in response to the fine clock mark signal. Therefore, even if the optical disk is eccentric, the jitter of the bit clock can be suppressed, and the signal can be accurately recorded / reproduced. Is possible.

Preferably, the optical disk has a plurality of concentric zones. The spindle servo control means further includes a ZCAV control means and a switching means. Z
The CAV control means controls the spindle motor so that the average linear velocity in each zone becomes the same as the constant linear velocity and the optical disk rotates at a constant angular velocity for each zone. The switching means alternately switches between the CLV control means and the ZCAV control means.

In this optical disk device, the spindle servo control system is switched between the CLV system using fine clock marks and the ZCAV system as required, so that stable spindle servo control is always possible.

More preferably, the switching means switches to the CLV control means when the linear velocity of the optical disk is close to the constant linear velocity, and switches to the ZCAV control means when the linear velocity of the optical disk is far from the constant linear velocity.

In this optical disk apparatus, when the spindle motor is started, when track access or jump is performed, or when the rotation of the optical disk is disturbed by disturbance, the spindle servo control is performed by the ZCAV method, and the actual line of the optical disk is controlled. When the speed approaches the target linear speed and lock is detected, spindle servo control is performed by the CLV method.

Alternatively, the switching means switches to the CLV control means on the inner circumference of the optical disk from a predetermined radius, and switches to the ZCAV control means on the outer circumference of the optical disk beyond the predetermined radius.

In this optical disk apparatus, since the spindle servo control is performed by the CLV method on the inner circumference where the influence of the eccentricity of the optical disk is large, the unevenness of the linear velocity on the inner circumference is reduced.

Alternatively, the optical disk device further comprises:
A PLL circuit for generating a bit clock signal in response to the fine clock mark signal; The switching means,
When the jitter of the bit clock signal is larger than a predetermined threshold value, the mode is switched to the CLV control means, and when the jitter is smaller than the threshold value, the mode is switched to the ZCAV control means.

In this optical disk device, when the jitter of the bit clock signal increases, the spindle servo control is performed by the CLV method, so that the increase of the jitter of the bit clock signal can be suppressed.

Alternatively, the optical disk device further comprises:
An error correction circuit is provided for correcting an error in a signal reproduced from the optical disk. When the error correction rate by the error correction circuit is higher than a predetermined threshold,
Switching to LV control means, and switching to ZCAV control means when the error correction rate is lower than the threshold value.

In this optical disk apparatus, when the error correction rate increases, the spindle servo control is performed by the CLV method, so that the increase in the error correction rate is suppressed.

Alternatively, the CLV control means and the ZC
The AV control means commonly includes a phase comparator for comparing the phase of the bit clock signal or the frequency tachogenerator signal output from the spindle motor with the phase of the reference clock signal.

In this optical disk device, since one phase comparator is shared by the CLV control means and the ZCAV control means, the number of circuits required for such a phase comparison is reduced.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the drawings, the same or corresponding portions have the same reference characters allotted, and description thereof will not be repeated.

Before describing the optical disk apparatus according to the embodiment of the present invention, a magneto-optical disk such as an AS-MO used here will be described.

Referring to FIG. 1, this magneto-optical disk 10
Has a plurality of concentric zones Z1 to Z22. Also, a number of spiral or concentric tracks (not shown) are formed over the entire magneto-optical disk 10. Each zone Zi (i = 1 to 22) has about 2
500 to 2600 tracks are included. At the center of the magneto-optical disk 10, a hole 101 for mounting on a spindle motor is formed.

Referring to FIG. 13, the track of magneto-optical disk 10 is composed of land 103 and groove 104. The track is address segment A
S and data segment DS. The side wall of the groove 104 in the address segment AS is wobbled according to the address. Land 103
Fine clock marks 102 are formed on tracks of the groove 104 at regular intervals. The fine clock mark 102 in the land 103 is a groove-shaped discontinuous region, and the fine clock mark 102 in the groove 104 is a land-shaped discontinuous region.

Referring to FIG. 2, each track is (n + 1)
It consists of frames F0 to Fn. Since each track is longer toward the outer periphery, the outer periphery has more frames F0 to Fn. For example, each track in the outermost peripheral zone Z1 has 73 frames F0 to F72,
Each track in 22 has 31 frames F0 to F30.

Each frame Fi includes an address segment AS of 532 DCB (data channel bits) and 202
It has 16 DCB data segments DS0 to DS37. Therefore, each frame Fi is 20748D
It has a length of CB.

A fine clock mark 102 is provided at the head of each of the address segment AS and the data segments DS0 to DS37. Here, one address segment AS and 38 data segments DS0 to DS0 are used.
Since the DS 37 exists, each frame Fi has 39 fine clock marks 102. Since the outer track has more frames F0 to Fn,
The number of fine clock marks 102 is larger on the outer track and smaller on the inner track. The fine clock marks 102 are formed at regular intervals on the track.

Next, an optical disk device according to an embodiment of the present invention will be described with reference to FIG. This optical disk device records a signal on the magneto-optical disk 10 in synchronization with the fine clock mark 102 and reproduces a signal from the magneto-optical disk 10 in synchronization with the fine clock mark 102.

Referring to FIG. 3, this optical disk device comprises:
Spindle motor 12 for rotating magneto-optical disk 10
An optical pickup (PU) 14 for irradiating the magneto-optical disk 10 with a laser beam and detecting a reflected light thereof; and a magnetic head 16 for applying a magnetic field to the magneto-optical disk 10.

The optical disk device further includes a fine clock mark 102 based on the output signal of the optical pickup 14.
A fine clock mark (FCM) detecting circuit 18 for detecting a clock signal and generating a fine clock mark signal FCM;
A phase locked loop (PLL) circuit 20 for generating a bit clock signal BC in response to the fine clock mark signal FCM.

The PLL circuit 20 includes a phase comparator 201,
It includes a low pass filter (LPF) 202, a voltage controlled oscillator (VCO) 203, and a 1/532 frequency divider 204. The frequency divider 204 divides the bit clock signal BC output from the voltage controlled oscillator 203 into 1/532.
The phase comparator 201 compares the phase of the bit clock signal BC1 divided by the frequency divider 204 with the phase of the fine clock mark signal FCM, and generates an error voltage according to the phase difference. Therefore, this PLL circuit 20
As shown in FIG. 4, the fine clock mark signal FC
M and 1 of the fine clock mark signal FCM
A bit clock signal BC having a period of / 532 is generated.

The optical disk apparatus further includes, as a data recording system, an encoder 22 for adding an error correction code to the input data signal, and a magnetic head driver for driving the magnetic head 16 in response to the data signal from the encoder 22. 24. The optical disk device further includes:
As a data reproducing system, an A / D converter 26 for digitizing an analog magneto-optical signal MO output from the optical pickup 14, an equalizer (EQ) 28, and a Vidabi complex 30
, Unformatter 32 and NRZI + demodulation circuit 3
4 and an error correction circuit 36 for correcting an error in the reproduced data signal and outputting the corrected data signal. These recording and reproducing systems operate in synchronization with the bit clock signal BC. At the time of data recording, a magnetic field is applied by the magnetic head 16 in accordance with the input data while irradiating the laser light with the optical pickup 14, thereby recording the data signal in synchronization with the bit clock signal BC. On the other hand, at the time of data reproduction, the optical pickup 14 detects the magneto-optical signal MO, and thereby reproduces the data signal in synchronization with the bit clock signal BC.

This optical disk device further reduces the bit clock signal BC1 divided by the frequency divider 204 by one third in order to servo-control the spindle motor 12.
The 1/39 frequency divider 38 for dividing the frequency by 9; the crystal oscillator 40 for generating the reference clock signal RC0; and the phase of the bit clock signal BC2 divided by the frequency divider 38 are compared with the phase of the reference clock signal RC0. A phase comparator 42 for outputting an error voltage corresponding to the phase difference, a crystal oscillator 44 for generating a reference clock signal RC1, and a 1 / N variable frequency divider for dividing the reference clock signal RC1 by 1 / N 46, a phase for comparing the phase of the frequency tachogenerator signal FG output from the spindle motor 12 with the phase of the reference clock signal RC2 divided by the variable frequency divider 46, and outputting an error voltage corresponding to the phase difference. A comparator 48, a switching circuit 50 for switching between the output of the phase comparator 42 and the output of the phase comparator 48, and an error voltage output from the phase comparator 42 or 48. The phase difference between the motor driver 52 for driving the pin dollars motor 12, a bit clock signal BC1 and fine clock mark signal FCM in response to the output from the phase comparator 201, i.e. the bit clock signal BC
A jitter detection circuit 54 for detecting the jitter of the address, an address detected by the optical pickup 14, and an error correction circuit 36.
The switching of the switching circuit 50 is controlled based on the correction rate of the reproduced data corrected by the above, the jitter detected by the jitter detection circuit 54, the phase lock signal PL output from the phase comparator 201, etc. And a microcomputer 56 for controlling the frequency division ratio of the detector 46.

Next, the operation of the optical disk device will be described. First, in brief, the optical disk device controls the spindle motor 12 in a CLV manner so that the magneto-optical disk 10 rotates at a constant linear speed in response to the fine clock mark signal FCM. In order to perform spindle servo control in response to the fine clock mark signal FCM in this manner, the PLL circuit 20 must be locked. Therefore, this optical disk device is
Until the L circuit 20 is locked, the spindle motor 12 is controlled by the ZCAV system so that the magneto-optical disk 10 rotates at a constant angular speed in response to the frequency tachogenerator signal FG. Thereby, when the magneto-optical disk 10 rotates at a substantially predetermined speed and the PLL circuit 20 locks,
The servo control is switched from ZCAV servo control (hereinafter referred to as “FG servo control”) using the frequency tach generator signal FG to CLV (hereinafter referred to as “FCM servo control”) using the fine clock mark signal FCM.

If the rotational speed of the spindle motor 12 changes abruptly during the FCM servo control, the PLL circuit 20 cannot follow, and the phase of the bit clock signal BC deviates from the phase of the fine clock mark signal FCM. Still, if the FCM servo control is continued, the spindle servomotor 12 will run away. Therefore, in the following cases (1) to (3), it is necessary to switch from FCM servo control to FG servo control.

(1) When the spindle motor 12 starts up When the spindle motor 12 starts up, the magneto-optical disk 10
Is not rotating at a predetermined speed, the FCM detection circuit 1
8 detects the fine clock mark signal FCM.
Is too low, and the PLL circuit 20 is not locked. Accordingly, the microcomputer 56 switches the switching circuit 50 to the phase comparator 48 side in response to the phase lock signal PL output from the phase comparator 201 and indicating the unlocked state. In the ZCAV method, a required constant angular velocity is predetermined for each of the zones Z1 to Z22 so that the average linear velocity in each of the zones Z1 to Z22 of the magneto-optical disk 10 is the same. The microcomputer 56 determines the frequency division ratio 1 / N of the variable frequency divider 46 corresponding to these constant angular velocities.
I remember. Since it is necessary to reduce the angular velocity of the outer peripheral zone, the frequency division ratio is reduced by 1 / N corresponding to the outer peripheral zone.

The microcomputer 56 has a zone Z1.
To access a desired zone among the optical pickups 14 through a thread feed mechanism (not shown).
To the desired zone. The microcomputer 56 sets the frequency division ratio 1 / N of the variable frequency divider 46 to the frequency division ratio corresponding to the desired zone. Therefore, the reference clock signal RC1 from the crystal oscillator 44 is frequency-divided at the set frequency division ratio, and supplied to the phase comparator 48 as the reference clock signal RC2.

On the other hand, a frequency tachogenerator signal FG corresponding to the rotation speed of the spindle motor 12 is given from the spindle motor 12 to the phase comparator 48. Phase comparator 4
8 compares the phase of the frequency tachogenerator signal FG with the phase of the reference clock signal RC2, and provides an error voltage corresponding to the phase difference to the motor driver 52 via the switching circuit 50. As a result, the motor driver 52 drives the spindle motor 12 so that the magneto-optical disk 10 rotates at a constant angular speed required for the desired zone.

When the magneto-optical disk 10 starts rotating at a desired angular velocity by the FG servo control as described above, the PLL
The circuit 20 locks and the fine clock mark signal FC
A bit clock signal BC synchronized with M is generated. The microcomputer 56 responds to the phase lock signal PL indicating the locked state from the phase comparator 201 to switch the switching circuit 5.
0 is switched to the phase comparator 42 side. The phase comparator 42
The phase of bit clock signal BC2 from frequency divider 38 is compared with the phase of reference clock signal RC0 from crystal oscillator 40, and an error voltage corresponding to the phase difference is provided to motor driver 52 via switching circuit 50. Therefore, the motor driver 52 controls the spindle motor 12 so that the magneto-optical disk 10 rotates at a constant linear speed.

(2) At the time of access or jump When the activation of the spindle motor 12 is completed as described above, this optical disc apparatus performs FCM servo control. When accessing or jumping to a desired track in such a state, this optical disc apparatus is used in FIG.
Operate according to the flowchart shown in FIG.

When access to a desired track is started in step S1, the microcomputer 56 switches the switching circuit 50 from the phase comparator 42 side to the phase comparator 48 side in step S2.
Switch to servo control.

Subsequently, at step S3, the microcomputer 56 also controls the optical pickup 14 to move to the position of the desired track by the microcomputer 56. Is moved toward the position of the target track.

While the optical pickup 14 is moved over a plurality of zones, the FG servo control is performed, and the spindle motor is rotated so that the magneto-optical disk 10 rotates at an angular velocity corresponding to the desired track zone. 12 is controlled.

When the access to the desired track is completed in step S4, the microcomputer 56 checks in step S5 whether or not the PLL circuit 20 is locked.
When the access is completed, the magneto-optical disk 10 is rotating at a predetermined angular velocity, and thus the PLL circuit 20 is locked.

Therefore, in step S6, the microcomputer 56 outputs the phase lock signal PL indicating the locked state.
, The switching circuit 50 is switched from the phase comparator 48 side to the phase comparator 42 side. As a result, the mode is switched from the FG servo control to the FCM servo control.

Then, in step S7, the access or jump operation to the desired track ends.

(3) When PLL Lock is Lost Due to Disturbance Even when the FCM servo control is performed, the rotation of the magneto-optical disk 10 is disturbed due to a disturbance such as an impact.
The lock of the LL circuit 20 may be released. in this case,
The microcomputer 56 switches the switching circuit 50 to the phase comparator 42 in response to the phase lock signal PL indicating the unlocked state.
Side is switched to the phase comparator 48 side. With this, FC
The mode is switched from the M servo control to the FG servo control.

When the angular velocity of the magneto-optical disk 10 substantially returns to its original state, the PLL circuit 20 locks again, and the FG
Return from servo control to FCM servo control.

When the access zone is switched to the adjacent zone, it is not necessary to switch from the FCM servo control to the FG servo control because the jump is only a few tracks.

At the time of the above-described track access or transistor jump, access is made several tracks before the target address, and the PLL circuit 2 is accessed before reaching the target address.
It is desirable that 0 is locked so that the FG servo control is switched to the FCM servo control.

In order to stabilize the PLL circuit 20 and suppress the jitter of the bit clock signal BC, it is preferable to perform the FCM servo control over the entire circumference of the magneto-optical disk 10. However, the FG servo control also has advantages that high-speed access is possible and that the spindle servomotor 12 does not run away even if the phase of the bit clock signal BC is out of phase due to disturbance or the like. Therefore, FG servo control may be performed in a range where recording / reproduction of the magneto-optical signal MO is possible, and in the following cases (1) to (3), switching from FG servo control to FCM servo control may be performed.

(1) At the time of recording / reproducing the inner track As described above, the influence of the eccentricity due to chucking and the like becomes larger toward the inner circumference of the disk, and the linear velocity unevenness becomes larger. Therefore, when the microcomputer 56 moves the optical pickup 14 inside the radius 25 mm of the magneto-optical disk 10 or beyond the zone Z21 according to the AS-MO standard, the switching circuit 50 switches the phase comparator 48 side to the phase comparator 42 side. To change from FG servo control to FC
Switching to M servo control may be performed. in this case,
FG servo control is always performed outside the radius of 25 mm or below the zone Z20 in the AS-MO standard.

(2) When Clock Jitter Exceeds Allowable Range FIG. 6 shows the jitter of the bit clock signal BC with respect to the radius of the access track when the linear velocity is 5 m / s and the eccentricity is 70 μm. Here, -35 dB,-
The noise of 38dB, -41dB and 0dB is deliberately F
It was mixed in the CM detection circuit 18 and the jitter of the bit clock signal BC in these cases was measured.

As is apparent from the experimental results, the jitter of the bit clock signal BC becomes smaller toward the outer periphery and becomes larger toward the inner periphery.

Therefore, a threshold value is set in advance in accordance with the magnitude of the allowable jitter, and when the jitter of the bit clock signal BC exceeds this threshold value, the FG servo control switches to F
The control may be switched to CM servo control. In the optical disk device shown in FIG. 3, the jitter detection circuit 5 is controlled in accordance with the phase difference between the bit clock signal BC1 detected by the phase comparator 201 and the fine clock mark signal FCM.
4, the jitter of the bit clock signal BC is detected.
When the detected jitter exceeds a predetermined threshold, the microcomputer 56 switches the switching circuit 50 from the phase comparator 48 to the phase comparator 42, thereby switching from FG servo control to FCm servo control. .

(3) When the Error Correction Rate Increases When the linear velocity unevenness increases, the number of errors of the magneto-optical signal MO reproduced from the magneto-optical disk 10 increases, and the error correction rate by the error correction circuit 36 increases. . Therefore, when the error correction rate exceeds a predetermined threshold value, the FG servo control may be switched to the FCM servo control.
It is desirable to set this threshold slightly lower than the error correction rate allowed by the system.

In the optical disk device shown in FIG. 3, the error correction rate is supplied from the error correction circuit 36 to the microcomputer 5.
6 given. The microcomputer 56 switches the switching circuit 50 when the error correction rate exceeds a predetermined threshold.
Is switched from the phase comparator 48 side to the phase comparator 42 side, thereby switching from FG servo control to FCM servo control.

Further, the PLL circuit 20 shown in FIG. 3 divides the frequency of the bit clock signal BC by 1/532, and compares the phases in units of the segment period shown in FIG. On the other hand, in the phase comparator 42 for the FCM servo control, the bit clock signal B divided by 1/532 is used.
C1 is further frequency-divided by 1/39, and the phase comparison is performed for each frame period shown in FIG. Therefore, FCM servo control suitable for the response speed of the spindle motor 12 can be performed. Further, since the frame period is common to each zone, appropriate FCM servo can be performed in any zone.

In the optical disk apparatus shown in FIG. 3, a phase comparator 42 for FCM servo control and a phase comparator 48 for FG servo control are provided separately. By making the frequency of the bit clock signal BC2 divided by the frequency divider 38 and the frequency close to each other, the phase comparators 42 and 48 can be shared by one phase comparator. In this case, one phase comparator is shared for FCM servo control and FG servo control.

As described above, according to the embodiment of the present invention, since the FG servo control is switched to the FCM servo control as necessary, accurate recording / reproduction can be performed even if the magneto-optical disk 10 is eccentric. It is possible.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0066]

According to the present invention, since the CLV servo control is performed in response to the fine clock mark signal, accurate recording / reproduction can be performed even if the optical disk is eccentric.

[Brief description of the drawings]

FIG. 1 is a plan view showing a zone configuration of a magneto-optical disk such as an AS-MO.

FIG. 2 is a layout diagram showing a track format of the magneto-optical disk shown in FIG.

FIG. 3 is a block diagram showing an overall configuration of the optical disc device according to the embodiment of the present invention.

FIG. 4 is a timing chart showing a fine clock mark signal and a bit clock signal in FIG. 3;

5 is a flowchart showing a track access operation or a track jump operation of the optical disk device shown in FIG.

FIG. 6 is a diagram illustrating jitter of a bit clock signal with respect to a radius of an access track.

FIG. 7 is a diagram showing a change in angular velocity with respect to a radial position of an optical disc according to the CAV and CLV methods.

FIG. 8 is a diagram showing a change in linear velocity with respect to a radial position of an optical disc according to the CAV and CLV methods.

FIG. 9 is a diagram showing a change in angular velocity with respect to a radial position of an optical disk according to the ZCAV method.

FIG. 10 is a diagram showing a change in linear velocity with respect to a radial position of an optical disc according to the ZCAV method.

FIG. 11 is a diagram for explaining the eccentricity of the optical disc.

FIG. 12 is a diagram showing unevenness of linear velocity due to the eccentricity shown in FIG. 11;

FIG. 13 is a plan view showing a track structure of the magneto-optical disk shown in FIG.

[Explanation of symbols]

10 magneto-optical disk, Z1 to Z22 zone, 12
Spindle motor, 14 optical pickup, 16 magnetic head, 18 fine clock mark detection circuit, 20
PLL circuit, 36 error correction circuit, 42, 48 phase comparator, 50 switching circuit, 52 motor driver, 56
Microcomputer.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Watanabe 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term in Sanyo Electric Co., Ltd. 5D066 AA05 DA03 DA04 FA01 SA07 SC04 SE06 5D090 AA01 CC12 DD03 FF07 FF43 GG26 HH03 5D109 AA12 KA02 KA04 KB23 KB26 KB27 KD11 KD14 KD18 KD34

Claims (7)

[Claims] 1. An optical disk device for recording and / or reproducing a signal in synchronization with a fine clock mark formed at regular intervals on a track, comprising: a spindle motor for rotating an optical disk; and detecting the fine clock mark. Spindle servo control including fine clock mark detection means for generating a fine clock mark signal, and CLV control means for controlling the spindle motor so that the optical disc rotates at a constant linear speed in response to the fine clock mark signal An optical disc device comprising: 2. The optical disc has a plurality of concentric zones, and the spindle servo control means further comprises: an average linear velocity in each zone being equal to the constant linear velocity and being constant for each zone. Z for controlling the spindle motor so that the optical disc rotates at an angular velocity
2. The optical disk device according to claim 1, further comprising: a CAV control unit; and a switching unit that alternately switches between the CLV control unit and the ZCAV control unit. 3. The switching means switches to the CLV control means when the linear velocity of the optical disk is close to the constant linear velocity, and switches to the ZCAV control means when the linear velocity of the optical disk is far from the constant linear velocity. The optical disk device according to claim 2. 4. The optical disc apparatus according to claim 2, wherein the switching means switches to the CLV control means on an inner circumference of the optical disk from a predetermined radius, and switches to the ZCAV control means on an outer circumference of the optical disk from the predetermined radius. 5. The optical disk device further includes a PLL circuit that generates a bit clock signal in response to the fine clock mark signal, and wherein the switching unit includes a threshold value that determines a jitter of the bit clock signal. 3. The optical disk device according to claim 2, wherein the switch is made to said CLV control means when the value is larger than the threshold value, and to said ZCAV control means when said jitter is smaller than said threshold value. 6. The optical disk device further includes an error correction circuit for correcting an error of a signal reproduced from the optical disk, and the switching unit includes a threshold value for setting an error correction rate by the error correction circuit to a predetermined value. 3. The optical disk apparatus according to claim 2, wherein when the error correction rate is lower than the threshold value, the mode is switched to the ZCAV control means. 7. The optical disk device further includes a PLL circuit that generates a bit clock signal in response to the fine clock mark signal, wherein the CLV control unit and the ZCAV control unit are configured to control the bit clock signal or the spindle motor. Including in common a phase comparator for comparing the phase of the frequency tachogenerator signal output from the phase with the phase of the reference clock signal,
The optical disk device according to claim 2.