JPH10241177A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disc device which enables servo control stably even if scratches, dusts, etc., exist on a disc. SOLUTION: The outputs S2 of a phase compensation circuit 5 which compensates the phases of servo error signals are successively stored in a memory circuit 10 and held at least while an optical disc 2 makes one turn. A disc abnormality detector 8 detects the abnormalities such as scratches, dusts, etc., on the optical disc 2. When the disc abnormality detector 8 detects an abnormality, the memory circuit 10 outputs a memory data, concerning the signal S2 which is previously generated at the rotation position approximately same as the abnormality detection position, to an optical system driving means 7 as a driving signal S3. If these is no abnormality, the output S2 of the phase compensation circuit 5 is outputted as it is to the optical system driving means 7 as the driving signal S3. The optical system driving means 7 drives an optical system 1 in accordance with the driving signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device having a servo mechanism for a light beam spot, and more particularly to an optical disk device capable of performing stable servo control even when a scratch or dust is present on the disk surface. About.

[0002]

2. Description of the Related Art In recent years, an optical disk, which is a recording medium widely used, records, reproduces or erases information by irradiating a focused light beam onto the disk surface.
The irradiation state of the light beam (spot position on the disk, focus state) is controlled by a focus servo signal and a tracking servo signal based on the reflected light from the disk. However, if there is a scratch or dust on the surface of the disk, the reflected light is disturbed, so that a correct servo signal cannot be obtained, the servo cannot be performed, and a data reproduction error or data error occurs. A recording error occurs.

In order to solve the above problem, a conventional optical disk device detects a scratch or dust on a disk from a signal obtained from reflected light, and a period during which such detection is performed is as follows.
The servo disabled state is prevented by lowering the servo gain or holding the servo error signal.

[0004]

However, even if the servo gain is lowered or the servo error signal is held,
If the period during which a flaw or dust is detected becomes long, the amount of deviation of the trajectory in the focus direction or the tracking direction becomes large, and may exceed the servo pull-in range. In this case, it is impossible to return the objective lens to the position of the just focus or just track after the end of the period in which the scratch or dust is detected.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide an optical disk device capable of performing servo control stably even when a scratch or dust is present on the disk.

[0006]

According to a first aspect of the present invention, there is provided an optical disk apparatus comprising: an optical system for guiding a light beam to an optical disk; and a servo for generating a servo signal for controlling a spot position of the light beam based on light reflected from the optical disk. Signal generating means, and driving means for moving an optical system by a drive signal based on a servo signal to move an optical beam spot position on the optical disk in the vertical direction of the disk surface and in the radial direction of the disk. In the optical disk device, the generated servo signals are sequentially stored, and at least until the optical disk rotates once, the storage means and the abnormality detecting the presence of an abnormality such as a scratch or dust on the optical disk. When the detecting means and the abnormality detecting means detect an abnormality, the servo signal is read from the storage means at a rotational position substantially the same as the abnormality detecting position. And it reads the already-stored signals generated by the abnormal drive signal generating means for outputting to the driving means as the driving signal is made a.

According to a second aspect of the present invention, there is provided the optical disk device according to the first aspect, wherein the rotation period of the optical disk is detected, and a servo signal is stored in the storage means in correspondence with each disk rotation position. It has a period detecting means.

According to a third aspect of the present invention, there is provided the optical disk device according to the first or second aspect,
The servo signal is a servo error signal of focus servo and tracking servo of the light beam spot.

[0009] Claim 1 or Claim 2 of Claim 4
Wherein the servo signal is a phase compensation signal obtained by compensating a servo error signal of focus servo and tracking servo of the light beam spot by a phase compensator.

According to a fifth aspect of the present invention, in the optical disk device of the fourth aspect, the stored signal read from the storage means is replaced with a servo error signal while the abnormality detection means detects the abnormality. An abnormal time input means for inputting to the phase compensation means is provided.

According to a sixth aspect of the present invention, in the optical disk device according to any one of the first to fifth aspects, the high frequency removing means for removing the high frequency component of the servo signal and outputting it to the storage means. It is what you have.

The operation of the present invention will be described below.

A major component of the servo error is an error caused by eccentricity and surface runout of the disk, and is an error synchronized with the rotation cycle of the disk. Therefore, the drive signal for driving the drive means in the vertical direction on the surface of the disk indicates the deflection of the surface of the disk, and the drive signal for driving in the radial direction of the disk indicates the eccentricity of the disk. The eccentricity and runout of the disk can be considered to be unique to the disk, and the movement of the eccentricity and runout for each rotation of the disk is considered to be almost the same when viewed from several tens to several hundreds of rotations. Good.

Therefore, in the present invention, the servo signal is stored in the storage means at least during one rotation of the disk, and the information (the servo signal is stored during the period when the disk has an abnormality such as a scratch or dust). Servo control is performed by substituting the previously generated servo signal at substantially the same rotational position. As a result, even if there is an abnormality such as a scratch or dust on the disk, stable servo control can be performed reliably in response to eccentricity and runout of the disk.

Further, by detecting the disk rotation period and associating the servo signal with each of the generated rotation positions, it is possible to accurately read the storage information from the storage means in the event of an abnormality.

Furthermore, by inputting the output from the storage means without inputting the abnormal servo error signal to the phase compensation means in the event of an error, malfunctions after the error is eliminated can be suppressed.

Further, by removing the high-frequency component of the servo signal input to the storage means, the period of the servo signal stored in the storage means can be increased, and the memory capacity required by the storage means can be reduced. Can be reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk device according to the present invention will be described. FIG. 1 is a block diagram illustrating a configuration example of a main part of the optical disc device according to the present embodiment.

The optical system 1 comprises a laser, a lens, a beam splitter, etc., and condenses the light emitted from the laser on the disk 2 and a photo diode for reflecting the light from the disk 2. And the like. The servo error signal generation circuit 4 generates servo error signals such as a focus servo error signal and a tracking servo error signal from the output signal of the photoelectric converter 3. The phase compensation circuit 5
The servo error signal generation circuit 4 comprises a low-pass filter, a filter for compensating for a phase lead, and compensating for a low-frequency gain increase.
And generates a drive signal s2 for the optical system drive means 7 in response to the servo error signal from. The optical system driving means 7 includes an actuator, a power amplifier, and the like. For example, by driving the objective lens of the optical system 1, the beam spot on the disk is driven in the focus direction and the tracking direction.

The disk abnormality detector 8 detects an abnormality such as a scratch or dust on the disk 2 based on the amplitude of the output signal of the photoelectric converter 3 and outputs a disk abnormality detection signal s1. For example, if a waveform as shown in the figure is obtained as a data reproduction signal from the output signal as shown in FIG. 2 from the photoelectric converter 3, the peak value of the data reproduction signal waveform is held. A circuit and a circuit for holding the bottom value are provided, and the amplitude of the data reproduction signal waveform is obtained by taking the difference between the respective hold values. By determining that there is an abnormality such as a scratch or dust, the abnormality of the disk is detected.

The rotation period detector 9 of the motor has, for example, one reflector attached to the rotor of the motor and a reflection type interrupter attached to the fixed side. Such a pulse can be generated according to the rotation of the motor.

The storage circuit 10 is provided with a memory capable of storing a signal corresponding to one rotation of the motor. In a normal state, one rotation of the output signal of the phase compensating circuit for one rotation of the motor is provided for each rotation of the motor. Update and store.

In the optical disk device of the present embodiment having the above configuration, when the disk abnormality detector 8 does not detect any abnormality, the drive signal s generated by the phase compensation circuit 5
2 becomes an output signal s3 of the storage circuit 10 and is input to the optical system driving means 7. Then, the optical system 1 is driven based on the signal s3 (s2), and the light beam is controlled. Therefore, when a disk abnormality is not detected, focus servo and tracking servo are performed based on the reflected light from the disk 2 as usual.

On the other hand, when the disk abnormality detector 8 detects an abnormality, a signal s1 indicating the occurrence of the abnormality is input to the storage circuit 10. Upon receiving the disk abnormality detection signal s1, the storage circuit 10 outputs a signal (stored signal) stored therein as a signal s3 to the optical system driving means 7 instead of the output s2 of the phase compensation circuit 5. . Then, the optical system driving means 7 moves the optical system 1 based on the driving signal (stored signal). Therefore, the focus servo and the tracking servo are performed based on the drive signal for one rotation stored in the storage circuit 10.

Next, an example of the configuration of the storage circuit 10 in such an optical disk device and a specific example of the servo control operation when the storage circuit 10 is used will be described.

Here, a description will be given of a case where the phase compensating circuit 5 performs digital arithmetic processing by a DSP or the like.

FIG. 3 is a block diagram showing a configuration example of the storage circuit 10. The storage area 100 is an area for storing the output s2 of the phase compensation circuit 5, and uses, for example, a RAM.
The storage position generator 101 determines a position for storing data from the rotation period signal and the phase compensation circuit output period signal. Lee
The write / write switching unit 102 outputs the disk abnormality detection signal s1
, The storage area 100 is switched to a data storable state or a data output state. That is, when the disk abnormality detection signal s1 does not indicate an abnormality, the storage area 10
The output s2 from the phase compensation circuit can be stored by setting 0 to a write state, and when the disk abnormality detection signal s1 indicates an abnormality, the storage area 100 is set to a read state so that data in the storage area 100 can be read. The signal switching unit 103 switches between the drive signal s3 to be the phase compensation circuit output s2 and the already stored signal in the storage area 100 according to the disk abnormality detection signal s1. That is, when the disk abnormality detection signal s1 does not indicate abnormality, the phase compensation circuit output s2 is selected, and when the disk abnormality detection signal s1 indicates abnormality, the stored signal in the storage area 100 is selected.

Regarding the size of the storage area 100, for example, when the rotation speed of the disk is 2400 rpm, the rotation cycle is 25 msec, and the output of the phase compensation circuit 5 is 25 msec.
Assuming that the phase compensation circuit is used for each usec, the phase compensation circuit 5 for one rotation
Requires 1000 storage areas to store the output. When the number of rotations of the disk is constant, the number of necessary storage areas is fixed, but when the number of rotations of the motor changes depending on the location of the disk, such as a CD, the size of the required storage area changes. For example, as described above, when the output of the phase compensating circuit 5 is every 25 usec and the rotation speed becomes 1200 rpm, 2,000 storage positions are required. Therefore, the necessary maximum storage area is prepared in consideration of the range of the number of rotations to be used and the output cycle of the phase compensation circuit 5. For example, if the output of the phase compensation circuit 5 is used every 25 usec and the disk rotation speed is in a range of 1200 rpm to 2400 rpm, 2,000 storage areas are prepared.

The data storage location is set, for example, as shown in FIG. Here, a rotation cycle signal of one pulse is output for one rotation of the motor, and the data storage position at the time when the pulse from the rotation cycle detector 9 is input is set to the position of 0 ', and the phase compensation is performed. The data storage position is shifted by one for each data output of the circuit 5 and stored, and the storage position is returned to 0 'when the next rotation cycle signal is output.

In the example of FIG. 4, the rotational speed is 2 under the above conditions.
This corresponds to the case of 400 rpm. By storing in this manner, the cycle of the rotation cycle signal becomes longer as the number of rotations becomes slower, the number of data stored in one rotation increases, and the rotation cycle signal becomes shorter as the number of rotations increases, and the number of rotations becomes one. The number of data to be stored is reduced. In this way, the normal state is always 1
The output of the phase compensation circuit 5 before rotation is stored based on the rotation period signal.

Servo control operation using storage circuit 10 A method for inputting and outputting data to and from the storage circuit 10 will be specifically described with reference to FIG.

FIG. 5 shows an example in which the number of data stored in one rotation of the disk is twelve. In the case of FIG.
After storing the data in the storage position 4 'of the rotation, an abnormality of the disk is detected, and the state of the abnormality is determined by the data output period of the phase compensation circuit 5 as 3
This is an example of a case where a batch is continued. In the example shown in FIG. 5, data "8" is stored at the storage location 0 'and data "1" is stored at the storage location 1' in the example of FIG.
0 ". When the data" 8 "is stored in the storage location 11 ', the motor rotation period signal is input and the next data (the first data of the second rotation) is input. ) Is set to 0 ', that is, the data of the second rotation is written from the data of the first rotation. The servo operation is performed based on the write data (phase compensation circuit output s2).

After recording the data at the storage position 4 'in the second rotation, when the phase compensating circuit 5 outputs the next data, the signal switching section 103 has detected that the disk is abnormal. Is the output s3 to the optical system driving means 7,
The data "9" stored in the storage location 5 'of the storage circuit 10 is output instead of the output s2 of the phase compensation circuit 5, and the storage content is not updated. Similarly, after the disk abnormality detection is stopped, the outputs for the two subsequent times are stored at the storage locations 6 ',
7 '("7" in FIG. 5, "
6 ″) is output, and the stored content retains the previous value.

After the abnormality detection of the disk is stopped, the output of the phase compensation circuit 5 is outputted to the optical system driving means 7 and the output value of the phase compensation circuit 5 is stored in the storage position 8 'as usual.

In the next rotation, even if a disk abnormality is detected at the same position (the position corresponding to the storage positions 5 ', 6', 7 'in the example of FIG. 5), the storage positions 5',
The data stored in 6 'and 7', that is, the data two rotations before, is output. As described above, the data at the position where the disk abnormality is once detected is not updated until the data becomes normal.

When the above method is applied to a disk such as a CD having a different rotational speed according to the radial position of the disk, the number of data differs for each track. The number of storage areas is different. For this reason, even if the data stored one rotation before is read when an abnormality occurs, the data is not exactly the same data (circumferential position) as one rotation before and the data is shifted. However, since the difference in the number of data between adjacent tracks is at most about one, the above-mentioned deviation is minute and does not pose a problem.

The above is an example in which the output value of the phase compensation circuit 5 in FIG. 1 is stored in the storage circuit 10, but the present invention is not limited to this, and the configuration shown in FIG. The output value of the servo error signal generation circuit 4 may be stored in the storage circuit 10. In this case, it is preferable that the storage means store the servo error signal as digital data by sampling the servo error signal at an appropriate cycle. The operation of the servo mechanism of this optical disk device is substantially the same as the servo operation of the servo mechanism of FIG.

Further, a configuration shown in FIG. 7 in which data stored in the storage circuit 10 can be input to the phase compensation circuit 5 may be employed. If the disc has an abnormality such as a scratch or dust, the servo error signal is not output with a normal amplitude.
In particular, in the case of a disk abnormality in which the amplitude of the servo error signal becomes large, when the signal is input to the phase compensation circuit 5 and the disk abnormality ends, the output of the phase compensation circuit 5 becomes unstable. There is. Therefore, in the optical disk apparatus shown in FIG. 7, when an abnormality of the disk is detected, the output data of the phase compensation circuit 5 stored in the storage circuit 10 is output to the optical system driving means 7 and the phase compensation circuit 5 An abnormal signal is prevented from being input to the phase compensation circuit 5 as an input signal. This makes it possible to stabilize the operation of the phase compensation circuit 5 when a disk abnormality is detected.

The main causes of the servo error of the optical disk servo are surface runout and eccentricity of the disk. Therefore, it is considered that the servo error has the largest frequency component equal to the rotational frequency of the disk (about several tens Hz).
Therefore, if a high frequency component is removed from a signal input to the storage circuit 10 through a low-pass filter having a frequency band of about several times the rotation frequency, the storage period of data stored in the storage circuit 10 is reduced. The number of data to be stored in one rotation of the disk can be reduced by setting the period corresponding to a frequency several times as large as that of the above band. Thereby, the memory capacity required for the storage circuit 10 can be reduced.

In the above description, the rotation of the optical disk is detected, and the servo error signal and the output of the phase compensation circuit are stored based on the result. However, the present invention is not limited to this.
For example, the number of data to be stored may be counted, the rotation of the disk may be determined based on the count result, and the servo error signal and the output of the phase compensation circuit may be stored.

[0041]

The present invention focuses on the fact that the main causes of the servo error are the disk runout and the eccentric disk,
A servo signal (for example, a servo error signal or an output of a phase compensation circuit) corresponding to at least one rotation of the disk is stored in a storage circuit, and when there is an abnormality such as a scratch or dust on the disk, the storage circuit stores the signal. Servo control such as focus control and tracking control of the light beam is performed based on the servo signal thus obtained. For this reason, the servo operation can be stably performed irrespective of an abnormality such as a scratch or dust on the disk.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an optical disc device according to the present invention.

FIG. 2 is an explanatory diagram illustrating an input signal of an optical system driving unit when an abnormality of a disk is detected.

FIG. 3 is a block diagram illustrating a configuration example of a storage circuit.

FIG. 4 is a diagram showing a relationship between a storage position and a motor rotation period signal when 1000 data are stored.

FIG. 5 is an explanatory diagram showing an example of a disk abnormality detection method.

FIG. 6 is a block diagram showing another configuration example of the optical disc device of the present invention.

FIG. 7 is a block diagram showing still another configuration example of the optical disc device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical system 2 Optical disk 3 Photoelectric converter 4 Servo error signal generation circuit 5 Phase compensation circuit 7 Optical system drive means 8 Disk abnormality detector 9 Rotation period detector 10 Storage circuit

Claims (6)

[Claims] An optical system for guiding a light beam to an optical disk;
Servo signal generating means for generating a servo signal for controlling the spot position of the light beam based on the reflected light from the optical disc; and moving the optical system by a drive signal based on the servo signal, thereby forming an optical beam on the optical disc. And a driving means for moving the disk spot position in the vertical direction of the disk surface and in the radial direction of the disk. In the optical disk device, the servo signals sequentially generated are stored until at least one rotation of the optical disk. Storage means for holding the optical disk for an abnormality such as a scratch or dust, and an abnormality detection position from the storage means when the abnormality detection means detects an abnormality. Read the stored signal previously generated as a servo signal at the same rotational position as
An abnormal time drive signal generating means for outputting the drive signal to the drive means. 2. The optical disk apparatus according to claim 1, further comprising: a rotation period detecting unit that detects a rotation period of the optical disk and stores the servo signal in the storage unit in correspondence with each disk rotation position. An optical disk device characterized by comprising: 3. The optical disk device according to claim 1, wherein the servo signal is a servo error signal of focus servo and tracking servo of a light beam spot. 4. The optical disk device according to claim 1, wherein the servo signal is a phase compensation signal obtained by phase-compensating a servo error signal of a focus servo and a tracking servo of a light beam spot by a phase compensator. An optical disc device characterized by the above-mentioned. 5. The optical disk device according to claim 4, wherein said stored signal read from said storage means instead of said servo error signal while said abnormality detection means detects an abnormality. An optical disk device comprising an abnormal time input means for inputting an error. 6. The optical disk device according to claim 1, further comprising: a high-frequency removing unit that removes a high-frequency component of the servo signal and outputs the servo signal to the storage unit. Characteristic optical disk device.