JP2002042354A - Servo circuit for optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a servo circuit for an optical disk device, capable of performing stable servo control by simple circuit constitution, even when performing high double-speed reproduction to an optical disk with flaws on its surface. SOLUTION: The device is provided with a spindle motor 102 for rotating the optical disk 101, an optical pickup 103 for reading reflected light from the disk 101, a high-frequency amplifier 106 for obtaining a high-frequency signal from the reflected light, a defect-detecting circuit 107 for detecting the flaw on the disk 101 from the high-frequency signal and outputting a defect- detecting signal, a counting counter 108, a count value storing register 109 and a comparing circuit 110 for predicting the position of the flaw and outputting a defect-predicting signal, a hold circuit 112 for holding movement of the pickup 103, based on the defect detection signal and the defect-predicting signal, the servo circuit 113 and an optical pickup drive circuit 114.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pickup servo circuit for an optical disk device, and more particularly, to an optical pickup servo circuit for an optical disk device that performs stable servo control for scratches on an optical disk.

[0002]

2. Description of the Related Art An optical disc apparatus performs focus servo control using a focus error signal to accurately converge a laser beam of an optical pickup on an optical disc during recording or reproduction, and a laser spot on a track on the optical disc. Tracking servo control using a tracking error signal is performed in order to accurately follow the tracking error signal. The focus error signal and the tracking error signal are obtained from the reflected light of the optical disk. Therefore, if there is a scratch on the optical disc, a stable focus error signal and tracking error signal cannot be obtained, and stable focus servo control and tracking servo control cannot be performed.

Therefore, as described in Japanese Patent Application Laid-Open No. 4-364233, there is provided a defect detection circuit for detecting a flaw on an optical disk, and when a flaw is detected by the defect detection circuit, reflected light from the optical disk is detected. There has been proposed a servo circuit for an optical disc device that switches a servo band by predicting the position of a flaw to be detected next based on read time information and performs stable focus servo control and tracking servo control.

The configuration and operation of a conventional servo circuit for an optical disk device will be described below with reference to FIG. The spindle motor 502 rotates the optical disk 501, and the optical pickup 503 reads reflected light from the optical disk 501. The high-frequency amplifier 506 outputs a high-frequency component of the reflected light
RF signal). Data processor 507
Performs binarization of RF signal and clock recovery,
Data is read, for example, in a music CD, the elapsed time (hereinafter referred to as absolute time) from the innermost circumference of the optical disk obtained from the subcode read from the optical disk is read. The defect detection circuits 508 and 509 detect a scratch on the optical disk 501 and output a defect detection signal. The defect position prediction circuit 510 is a defect detection circuit 5
When a flaw is detected in steps 08 and 509, the rotation period of the optical disk is obtained using the absolute time, the timing of the flaw when the optical disk 501 makes one rotation is predicted, and a defect prediction signal is output. Focusing equalizer 51
3 and the tracking equalizer 514 can change the servo characteristics in three stages of a wide band, a normal band, and a narrow band.
The servo characteristic switching circuits 511 and 512 are based on the defect detection signals output from the defect detection circuits 508 and 509 and the defect prediction signal output from the flaw position prediction circuit 510, and the focusing equalizer 5 is used.
13 and the servo characteristics of the tracking equalizer 514 are switched. The focusing driver 515 drives the focusing actuator 504 in the direction perpendicular to the surface of the optical disk 501, and the tracking driver 516 drives the tracking actuator 505 in the radial direction of the optical disk 501.

[0005] The conventional servo circuit for an optical disk apparatus configured as described above switches the servo characteristics of the focusing equalizer 513 and the tracking equalizer 514 to a wide band when the surface of the optical disk 501 is normal without any scratches. When a flaw is detected in 508 or 509, the flaw position prediction circuit 510 obtains the rotation cycle of the optical disc 501 from the absolute time read from the optical disc 501 by the data processor 507, and the optical disc 501 is rotated once. It predicts the timing of the damage and outputs a defect prediction signal. Then, the servo characteristic switching circuits 511 and 512 switch the servo characteristics of the focusing equalizer 513 and the tracking equalizer 514 to the normal band immediately before the flaw according to the defect prediction signal which is the output signal of the flaw position prediction circuit 510. During the detection, the focusing equalizer 513 and the tracking equalizer 5
When the servo characteristic of the servo servo 14 is switched to a narrow band, and there is no damage again, the servo characteristics of the focus servo equalizer 513 and the tracking servo equalizer 514 are switched to a wide band, so that servo malfunction due to the scratch can be reduced and servo control can be stabilized. Had been.

[0006]

However, the conventional servo circuit for an optical disk device described above uses the absolute time read from the optical disk to predict the position of a scratch on the surface of the optical disk by using the absolute time read from the optical disk. Need to ask. Therefore, for example, in order to calculate the rotation cycle using a DSP, the number of execution steps of the servo control program increases, and the calculation processing performed during one execution cycle of the servo control program increases when the rotation number of the optical disk increases. However, there has been a problem that high-speed reproduction of the optical disc cannot be performed.

Further, when the calculation for obtaining the rotation cycle of the optical disk is performed by hardware using a DSP, there has been a problem that the circuit scale becomes large. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a servo circuit for an optical disk device capable of performing stable servo control with a simple circuit configuration even when reproducing an optical disk having a scratch on the surface at a high speed.

[0008]

According to a first aspect of the present invention, there is provided a servo circuit for an optical disk device, comprising: a servo circuit capable of changing servo characteristics; and a reflected light obtained from an optical disk via an optical pickup. A defect detection circuit for detecting a defect in the optical disc and outputting a defect detection signal; and, when a defect is detected by the defect detection circuit, predicting a position of the defect detected by the defect detection circuit. A defect time estimating means for outputting a signal, and when no defect is detected by the defect detection circuit, the servo characteristic of the servo circuit is set to a wide band, and when a defect is detected by the defect detection circuit, the defect time estimating means is Hoist the servo circuit just before the next detected scratch As well as de, the while the flaw in defect detection circuit is detected is characterized in that and a hold means for holding the servo circuit.

According to a second aspect of the present invention, in the servo circuit for an optical disk device according to the first aspect, the defect time estimating means includes:
A count counter for measuring the time from the detection of the flaw by the defect detection circuit to the start position of the flaw after one rotation of the optical disc; and a count value storage register for storing the count value of the count counter when the flaw is detected. A comparison circuit that compares a count value of the count counter with a value stored in the count value storage register and outputs a defect prediction signal.

According to a third aspect of the present invention, in the servo circuit for an optical disk device according to the first aspect, the holding means includes a logical sum of the defect prediction signal and the defect detection signal. And a hold circuit that holds the servo circuit based on an output signal of the OR circuit and holds a drive value of the optical pickup.

According to a fourth aspect of the present invention, there is provided a servo circuit for an optical disk apparatus, wherein a servo circuit capable of changing servo characteristics, an optical disk is rotated, and an FG signal is output at a constant rotation angle via a spindle driver. A spindle motor, a defect detection circuit that detects a scratch on the optical disc based on reflected light obtained from the optical disc via an optical pickup, and outputs a defect detection signal; and when the defect detection circuit detects the scratch, A defect position estimating means for estimating a position of a flaw to be detected by the defect detection circuit by counting an FG signal; and when the flaw is not detected by the defect detection circuit, a servo characteristic of the servo circuit is broadened. And the flaw is detected by the defect detection circuit. Hold means for holding the servo circuit immediately before the next defect detected according to the prediction of the defect position prediction means when detected, and holding the servo circuit while the defect is detected by the defect detection circuit And the following.

According to a fifth aspect of the present invention, in the servo circuit for an optical disk device according to the fourth aspect, the defect position predicting means comprises:
A first method for measuring the time from the rising edge of the FG signal to the detection of the rising edge of the next FG signal.
Count counter, a first count value storage register for storing a count value output from the first count counter when a defect is detected by the defect detection circuit, and a count value of the first count counter A first comparison circuit that compares the stored value of the first count value storage register with a second count counter that counts the rising edge of the FG signal, and a counter that detects when a defect is detected by the defect detection circuit. A second count value storage register for storing a count value output from the second count counter, and a second count value comparing the count value of the second count counter with the stored value of the second count value storage register. 2
And a logical product circuit that outputs the logical product of the output signal of the first comparator circuit and the output signal of the second comparator circuit as a defect prediction signal.

According to a sixth aspect of the present invention, in the servo circuit for an optical disk device according to the fourth aspect, the hold means performs a logical sum of the defect prediction signal and the defect detection signal. And a hold circuit that holds the servo circuit based on an output signal of the OR circuit and holds a drive value of the optical pickup.

According to a seventh aspect of the present invention, in the servo circuit for an optical disk device according to the fifth aspect, the first count value storage register and the second count value storage register are provided. , Are provided two or more.

[0015]

(Embodiment 1) Hereinafter, Embodiment 1 will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a block diagram of a pickup and tracking servo control device of the servo circuit for an optical disk device according to the first embodiment. FIG. 2 is a time chart illustrating the generation of a defect prediction signal when a scratch on the optical disk surface is detected for the first time in the optical disk device servo circuit.

The spindle motor 102 is used for the optical disc 1
01, the optical pickup 103 is driven by the focus actuator 104 and the tracking actuator 1
05, and optically detects a recording signal of the optical disk 101. The high frequency amplifier 106 includes the optical pickup 103
Is subjected to predetermined signal processing on the detection output to obtain an RF signal 115 and a focus error signal (hereinafter referred to as F
E signal), tracking error signal (hereinafter TE)
Abbreviated as a signal). Tracking servo circuit 11
3 is a TE signal 11 output from the high-frequency amplifier 106
7 for gain correction and phase compensation. The tracking drive circuit 114 includes the tracking servo circuit 11
3 based on the tracking control value 118 output from the optical pickup 103.
5 is driven. The defect detection circuit 107 detects a scratch on the surface of the optical disc 101 from the RF signal 115,
When a flaw is detected, the defect detection signal 116 is set to logic high.
To The count counter 108 counts the time from when a defect is detected by the defect detection circuit 107 to when the next defect is detected at regular time intervals, and the count value storage register 109 indicates that the defect detection signal 116 has a logic high level. The value obtained by subtracting 1 from the count value of the counter 108 at the time of is stored. The comparison circuit 110 compares the value of the count counter 108 with the value of the count value storage register 109, and if they match, the defect prediction signal 11
9 is set to logic high. The OR circuit 111 outputs a logical sum of the defect prediction signal 119 and the defect detection signal 116. The tracking hold circuit 112 generates and outputs a tracking hold signal 120 for holding a tracking control value 118 from the tracking servo circuit 113 to the tracking drive circuit 114 based on the output signal of the OR circuit 111, and outputs the signal.
The movement of the third tracking actuator 105 in the track direction is held.

As described above, in the first embodiment,
When a defect is detected by the defect detection circuit 107,
Next, a defect time estimating means for estimating a position of a flaw detected by the defect detecting circuit 107 is constituted by a count counter 108, a count value storing register 109, and a comparing circuit 110. Further, a holding means for holding the driving of the tracking actuator 105 of the optical pickup 103 based on the defect detection signal 116 and the defect prediction signal 119 is constituted by an OR circuit 111 and a tracking hold circuit 112.

In the servo circuit for an optical disk device according to the first embodiment configured as described above, a method of predicting a defect and a defect prediction when a plurality of tracks adjacent in the radial direction of the optical disk 101 are damaged. The generation of the signal 119 will be described with reference to FIGS.

In section 1 of FIG. 2 where the surface of the optical disc 101 has no flaw, the defect detection signal 116 which is the detection output signal of the defect detection circuit 107 is logic low.
In addition, the defect prediction signal 119 is also a logical low.
w. In this case, the tracking hold signal 120
Is also a logic low, the tracking servo circuit 11
3 is a tracking control value 1 for making the TE signal 117 zero.
18 is output to the tracking drive circuit 114.

On the other hand, when the surface of the optical disk 101 has a flaw, if the defect detection circuit 107 detects a flaw in the section 2 of FIG. 2 due to the lack of the RF signal 115, the defect detection circuit 107 outputs a defect detection signal. Signal 116 goes to a logic high. The logic-high defect detection signal 116 is input to the tracking hold circuit 112 via the OR circuit 111. The tracking hold circuit 112 is provided with a logical high OR circuit 11.
When the output signal of "1" is input, the tracking hold signal 120 is set to logic high and output. The tracking servo circuit 113 holds the tracking control value 118 based on the tracking hold signal 120 of logic High.

When the laser beam of the optical pickup 103 passes through the flaw, the defect detection signal 116 becomes logic low.
At this time, the tracking hold signal 120
Also becomes a logic low, and the tracking servo circuit 113 changes from a state where the tracking control value 118 is held to
The tracking control value 118 corresponding to the TE signal 117 is output to the tracking drive circuit 114. By the operation described above, when the laser beam passes through the flaw, even if disturbance components due to the flaw are generated in the TE signal 117, the tracking servo does not follow these components, and
Immediately after the laser beam passes through the scratch, the servo returns to a normal state, and tracking errors can be reliably suppressed.

Hereinafter, the defect detection circuit 11
7, the tracking hold circuit 112 outputs the tracking control value 11 by the tracking servo circuit 113 after the logic High defect detection signal 116 is output.
The operation until 8 is held will be described in detail.
When the first logic high defect detection signal 116 is input to the count counter 108, the count counter 108
As shown in section 2, until the second rising edge of the defect detection signal 116 is detected in section 3,
Counting is performed at fixed time intervals, and when the second rising edge of the defect detection signal 116 is detected,
The count value n0 is transferred to the count value storage register 109. After that, the count value of the count counter 108 is cleared to zero, and the count value storage register 109 stores a value obtained by subtracting 1 from the count value n0 transferred from the count counter 108 in order to predict the position of the flaw. Then, the count value of the count counter 108 is compared with the value stored in the count value storage register 109 by the comparison circuit 110. If they match, the scratch position is expected to be immediately before one rotation of the optical disk 101. Thus, the defect prediction signal 119 is set to logic high as shown in the section 4. As a result, when the laser beam of the optical pickup 103 again reaches a scratch on the surface of the optical disc 101, a defect prediction signal 119 of logic high is input to the OR circuit 111 immediately before, and the OR circuit 111 tracks and holds the logic high signal. Output to the circuit 112. The tracking hold circuit 112 sets the tracking hold signal 120 to logic high and sets the tracking servo circuit 1
13 so that the tracking servo circuit 113
Hold the tracking control value 118 to the tracking drive circuit 114. Then, immediately after that, when the laser beam approaches the flaw, the defect detection circuit 107
Outputs a logic high defect detection signal 116, and the tracking control value 118 continues to be held. When the laser beam passes through the flaw and the defect detection signal 116 becomes logic low, the comparison circuit 110 outputs a logic low defect prediction signal 119 in conjunction with this. As a result, the OR circuit 111 outputs a logical low signal, the tracking hold signal 120 also becomes logical low, and the tracking control value 118 is released from the hold state.

Thus, the second time the optical pickup 103
When the laser beam of the optical disk 101 hits a scratch on the surface of the optical disc 101, the tracking control value 118 is held immediately before, so that the disturbance component due to the scratch of the TE signal is reduced as compared with the scratch of the optical disc at the first time. Is stabilized. In the section 4, the count counter 108 to which the third rising edge of the defect detection signal 116 has been input transfers the count value n 1 to the count value storage register 109. Thereafter, the counting counter 108
Is cleared to zero, and the count value storage register 109 stores the count counter 10 in order to predict the position of the flaw.
A value obtained by subtracting 1 from the count value n1 transferred from 8 is stored. Then, the comparison circuit 1 compares the count value of the counter 108 with the value stored in the count value storage register 109.
10 and if they match, the optical disc 1
01 is predicted to be just before one rotation, so that the defect prediction signal 1
By setting 19 to a logic high and holding the tracking control value 118, the malfunction of the servo due to disturbance when the laser beam immediately hits a flaw is reduced.

Thereafter, the same operation is repeated, so that the defect detection circuit 107 does not detect a scratch after one rotation of the optical disk 101, and the defect detection signal
6 is no longer output, the comparison circuit 110
The prediction of the position of the flaw and the output of the defect prediction signal 119 of logic High are stopped. Although the contents described above are specific to the tracking servo circuit, the focus servo circuit can be considered in the same manner as the tracking servo circuit.

As described above, according to the servo circuit for an optical disk device according to the first embodiment, the defect detection signal 116 for predicting the position of a scratch on the surface of the optical disk 101 is provided.
Counter 1 that measures the time between rising edges of
08, a count value storage register 109 for storing the count value of the count counter 108 at the time of flaw detection, and the count value of the count counter 108 and the count value storage register 10.
9 is provided with a defect time estimating means including a comparison circuit 110 for comparing the stored value of No. 9, so that the tracking drive value can be held immediately before the flaw is detected, that is, the tracking actuator 105 of the optical pickup 103 can be held. Servo can be stabilized without causing the servo to follow the TE signal immediately after being performed. Therefore,
Unlike the conventional servo circuit for optical disk devices, there is no need to perform an arithmetic process to determine the rotation period of the optical disk from the absolute time read from the optical disk, so even when playing back an optical disk with a scratched surface at high speed, stable servo control It can be performed.

Further, according to the servo circuit for an optical disk device of the first embodiment, it is not necessary to have an arithmetic circuit for determining the rotation period of the optical disk, so that the circuit scale of hardware can be reduced.

(Embodiment 2) A servo circuit for an optical disk device according to Embodiment 2 will be described below with reference to FIGS. FIG. 3 is a block diagram of a pickup and tracking servo control device of a servo circuit for an optical disk device according to claim 4 of the present invention. FIG. 4 is a time chart showing the generation of a defect prediction signal when a scratch on the optical disk surface is detected for the first time in the servo circuit for the optical disk device.

The optical pickup 303 includes a focus actuator 304 and a tracking actuator 305.
And optically detects a recording signal of the optical disk 301. The spindle motor 302 rotates the optical disc 301, and outputs a fixed number of FG signals when the optical disc 301 makes one rotation via the spindle driver 325. The high-frequency amplifier 306 performs predetermined signal processing on the detection output of the optical pickup 303 to obtain the RF signal 320 and to extract the FE signal and the TE signal 319.

The tracking servo circuit 317 receives the TE signal 319 from the high frequency amplifier 306 and performs gain correction and phase compensation. Tracking drive circuit 318
Drives the tracking actuator 305 of the optical pickup 303 based on the tracking control value 324 output from the tracking servo circuit 317.

The defect detection circuit 307 detects a scratch on the surface of the optical disc 301, and when the scratch is detected, a logic
The high defect detection signal 322 is output. The first count counter 308 is a counter to which an FG signal is input, and counts at a fixed time interval from when a rising edge of the FG signal is detected to when a rising edge of the next FG signal is detected. The first count value storage register 309 stores a value obtained by subtracting 1 from the count value output by the first count counter 308 when the defect detection signal 322 becomes logic high. The first comparison circuit 310 compares the value stored in the first count value storage register 309 with the count value of the first counter 308, and
If the two input values match, a logic high signal is output. The second count counter 311 is a counter that counts the rising edge of the FG signal, clears the FG number that is the count value when the optical disc 301 makes one rotation, and counts again. The second count value storage register 312 receives the FG number of the second count counter 311 and the defect detection signal as inputs, and stores the FG number when the defect detection signal becomes logic high. The second comparison circuit 313 is provided in the second count value storage register 31.
The stored value of 2 is compared with the counter value of the second counter 311. If the two input values match, a logical high signal is output. The logical product circuit 314 outputs the logical product of the output signals of the first comparison circuit 310 and the second comparison circuit 313 as a defect prediction signal 321. The OR circuit 315 outputs a logical OR of the defect prediction signal 321 and the defect detection signal 322. The tracking hold circuit 316 generates and outputs a tracking hold signal 323 for holding the tracking control value 324 from the tracking servo circuit 317 to the tracking drive circuit 318 based on the output signal of the OR circuit 315, and outputs the tracking hold signal 323 to the tracking actuator of the optical pickup 303. The movement of 305 in the track direction is held.

As described above, in the second embodiment,
When a defect is detected by the defect detection circuit 307,
Next, the position of the flaw detected by the defect detection circuit 307 is determined by F which is a cycle detection signal of the spindle motor 302.
Defect position estimating means for estimating by counting the G signal includes first and second counting counters 308 and 3.
11, the first and second count value storage registers 309,
312 and first and second comparison circuits 310 and 313. Further, a holding means for holding the driving of the tracking actuator 305 of the optical pickup 303 based on the defect detection signal 322 and the defect prediction signal 321 is composed of an OR circuit 315 and a tracking hold circuit 316.

In the servo circuit for an optical disk device according to the second embodiment configured as described above, a method for predicting a defect and a defect prediction when a plurality of tracks adjacent to each other in the radial direction of the optical disk 301 are damaged. The generation of the signal 321 will be described with reference to FIGS.

In the section 10 of FIG. 4 where the surface of the optical disc 301 has no flaw, the defect detection signal 322 which is the detection output signal of the defect detection circuit 307 is logic low.
, And the defect prediction signal 321 is also logic low. In this case, the tracking hold signal 323 is also logical.
Since the signal is Low, the tracking servo circuit 317
A tracking control value 324 that makes the E signal 319 zero is output to the tracking drive circuit 318.

On the other hand, when the surface of the optical disc 301 has a flaw, if the defect detection circuit 307 detects a flaw in the section 11 of FIG. 4 due to the lack of the RF signal 320, the defect detection circuit 307 outputs a defect. Signal 322 goes to logic high. The logic high defect detection signal 322 is input to the tracking hold circuit 316 via the OR circuit 315. The tracking hold circuit 316 changes the tracking hold signal 323 to logic High when the logic High defect detection signal 322 is input, and outputs the tracking servo circuit 317 based on the tracking control signal 324 based on the logic High tracking hold signal 323. Hold.

When the laser beam of the optical pickup 303 has passed through the flaw, the defect detection signal 322 becomes logically low.
3 also becomes a logic low, so the tracking servo circuit 3
Reference numeral 17 denotes a state where the output of the tracking control value 324 is held and the tracking control value 324 is output to the tracking drive circuit based on the TE signal 319. With the above operation, when the laser beam passes through the flaw, even if disturbance components due to the flaw are generated in the TE signal 319, the tracking servo does not follow these components, and immediately after the laser beam passes through the flaw. Thus, the servo is in a normal state, and the tracking error can be surely suppressed.

Hereinafter, the defect detection circuit 30
7, the tracking hold circuit 316 outputs the tracking control value 32 by the tracking servo circuit 317 after the logic High defect detection signal 322 is output.
The operation up to holding 4 will be described in detail.
Second count value storage register 31 for storing FG number
2 is the first logic high defect detection signal 322
Is input, the FG number is stored. Here, FG
The case where the number is output for six cycles in one rotation of the spindle motor 302 will be described as an example. That is, if the FG number is represented by 0 to 5, the FG number 3 when the defect detection signal 322 becomes logic High in the section 11 is stored. At this time, the first count value storage register 30
9, a count value m0 counted at a fixed time interval after the rising edge of the FG number 3 is detected is the first count value m0.
From the count counter 308 of FIG. Then, the first count value storage register 309 stores a value obtained by subtracting 1 from the counter value m0 in order to predict the position of the flaw. Thereafter, the FG number of the second counter 311 and the value stored in the second count value storage register 312 are stored in the second comparison circuit 3.
13 and the first counter 3
08 count value and first count value storage register 30
9 are compared by the first comparing circuit 310, and if they match, it is predicted that the position of the flaw is immediately before, so here, as shown in the section 11, the defect prediction signal 3
21 is set to logic high. As a result, when the laser beam of the optical pickup 303 again reaches a scratch on the surface of the optical disk 301, the defect prediction signal 321 of logic High is input to the OR circuit 315 immediately before, and the OR circuit 315 tracks the signal of logic High. Output to the hold circuit 316. Tracking hold circuit 316
The tracking servo circuit 317 changes the logic level of the tracking hold signal 323 to logic high and outputs it to the tracking servo circuit 317.
The tracking control value 324 to 18 is held. Immediately thereafter, the laser beam hits the flaw, and the defect detection circuit 307 further outputs a defect detection signal 322 of a logic high, and the tracking control value 324 is kept held. When the laser beam passes through the flaw and the defect detection signal 322 becomes logic low, the AND circuit 314 sets the defect prediction signal 321 to logic low and outputs it in conjunction with this. As a result,
The OR circuit 315 outputs a signal of logic low, the tracking hold signal 323 also becomes logic low, and the tracking control value 324 is released from the hold state.

Thus, when the laser beam hits the scratch on the surface of the optical disc 301 for the second time, the tracking control value 324 can be held immediately before the laser beam hits, and the TE signal 319 can be held rather than the scratch for the first time.
As a result, disturbance components due to the scratches are reduced, and the servo is stabilized.

When the second rising edge of the defect detection signal 322 is detected in the section 12, the logical sum circuit 315 supplies the logic high defect detection signal 32
2, the second count value storage register 312 stores the FG number from the second count counter 311, and the first count value storage register 309 stores the count value m 1 output from the first count counter 308. The value obtained by subtracting 1 from is stored. The prediction of the position of the flaw is performed by the FG number of the second counter 311 and the second count value storage register 31.
The stored value of 2 is compared by the second comparison circuit 313 and while the values match, the count value of the first
If the values stored in the count value storage register 309 are compared and matched by the first comparison circuit 310, it is predicted that the laser beam is immediately before the position of the flaw. The defect prediction signal 321 is logically Hig
h, and the tracking hold signal 323 is also logic
By setting the value to High and holding the tracking control value 324, the malfunction of the servo due to disturbance when the laser beam of the optical pickup 303 immediately hits the flaw is reduced.

Thereafter, the same operation is repeated, and the defect detection circuit 307 does not detect the scratches after one rotation of the optical disk 301.
2 is no longer output, the AND circuit 314
Stops the prediction of the position of the flaw and the output of the defect prediction signal 321 of logic High. The contents explained above are
Although the content is specially described for the tracking servo circuit, the focus servo circuit can be considered similarly to the tracking servo circuit.

As described above, according to the servo circuit for the optical disk device of the second embodiment, the FG number and the time from the rising edge of the FG signal to the position of the scratch when the surface of the optical disk 301 is detected are determined. Holding the optical disk 30
Even when a scratch on one surface is scratched on a plurality of tracks adjacent in the radial direction of the optical disc 301, the first and second count counters 308 and 311 can predict the position of the scratch to be detected next. And a defect position predicting means including first and second count value storage registers 309 and 312 and first and second comparing circuits 310 and 313, so that the tracking drive value can be obtained immediately before a flaw is detected. , Ie, the tracking actuator 305 of the optical pickup 303 can be held, and the servo can be stabilized without following the TE signal immediately after the flaw is detected. This eliminates the need to perform an arithmetic process for calculating the rotation period of the optical disk from the absolute time read from the optical disk as in the conventional servo circuit for an optical disk device. Servo control can be performed.

Further, according to the servo circuit for the optical disk device of the second embodiment, it is not necessary to have an arithmetic circuit for determining the rotation period of the optical disk, so that the hardware circuit scale can be reduced.

In the conventional servo circuit for an optical disk device, the position of a scratch is predicted by the rotation cycle of the optical disk, so that only one scratch can be predicted per rotation of the optical disk. In the servo circuit for an optical disk device according to the second embodiment, since the position of a specific scratch on the optical disk is predicted based on the FG number on one track, the first and second count value storage registers 309, 31
By preparing a plurality of two, the positions of a plurality of scratches during one rotation of the optical disk can be predicted by the number of the first and second count value storage registers 309 and 312, and a plurality of scratches can be provided in one track. Stable servo control can be performed even when a scratched optical disk is reproduced at a high speed.

[0043]

As described above, according to the servo circuit for the optical disk according to the first aspect, the servo circuit capable of changing the servo characteristics and the optical disk based on the reflected light obtained from the optical disk via the optical pickup. Detects scratches on
A defect detection circuit for outputting a defect detection signal; and a defect time prediction means for predicting a position of a flaw detected by the defect detection circuit when a defect is detected by the defect detection circuit and outputting a defect prediction signal. When the defect is not detected by the defect detection circuit, the servo characteristic of the servo circuit is set to a wide band, and when the defect is detected by the defect detection circuit, the defect is detected next according to the prediction of the defect time prediction means. And a holding means for holding the servo circuit immediately before the defect is detected and for holding the servo circuit while the defect is detected by the defect detection circuit. The position of the scratch on the surface of the optical disk It was predicted by the door time prediction means,
Since the servo circuit can be held immediately before the scratch, even when the surface of the optical disc has a scratch, stable servo control can be performed without causing the servo to follow an error signal due to the scratch.

According to the servo circuit for an optical disk according to the second aspect of the present invention, in the servo circuit for the optical disk according to the first aspect, the defect time estimating means determines whether or not the defect has been detected by the defect detection circuit. A counter for measuring the time until the start position of the wound after rotation; a count value storage register for storing a count value of the count counter when a scratch is detected; a count value of the count counter and the count value storage register And a comparison circuit for comparing the stored values of the defect prediction signal and outputting the defect prediction signal. Thus, the defect prediction signal is calculated without performing the calculation for obtaining the rotation period of the optical disk from the absolute time read from the optical disk as in the conventional example. Can be used to measure the rotation period of the optical disc to accurately predict the start position of the scratch. Therefore, it is possible to perform the servo control stable even when high-speed reproduction of the optical disc have scratches on the surface. Further, since it is not necessary to have an arithmetic circuit for performing a calculation for determining the rotation cycle of the optical disk, the circuit scale of the hardware can be reduced.

Further, according to the servo circuit for an optical disk device of the present invention, a servo circuit capable of changing servo characteristics, an optical disk is rotated, and an FG signal is transmitted at a constant rotation angle via a spindle driver. A spindle motor for outputting, a defect detection circuit for detecting a scratch on the optical disc based on reflected light obtained from the optical disc via an optical pickup, and outputting a defect detection signal; and when a defect is detected by the defect detection circuit. A defect position estimating means for estimating a position of a flaw detected by the defect detection circuit by counting the FG signal; and a servo characteristic of the servo circuit when no flaw is detected by the defect detection circuit. To a wide band, and the defect detection circuit When a flaw is detected, the servo circuit is held immediately before the next flaw detected according to the prediction of the defect position prediction means, and the servo circuit is held while the flaw is detected by the defect detection circuit. And a holding unit for performing the following operations: when there is a flaw on the surface of the optical disc, predicting the position of the flaw on the surface of the optical disc by the defect position prediction means, and holding the servo circuit immediately before the flaw. Therefore, even when the surface of the optical disk has a scratch, stable servo control can be performed without causing the servo to follow an error signal due to the scratch.

According to a fifth aspect of the present invention, in the servo circuit for an optical disk device according to the fourth aspect, the defect position estimating means includes the FG.
A first counting counter for measuring a time from a rising edge of the signal to a rising edge of the next FG signal is detected; and a first counter output when the defect detection circuit detects a flaw. A first count value storage register for storing a count value, a first comparison circuit for comparing a count value of the first count counter with a value stored in the first count value storage register,
A second count counter for counting a rising edge of the FG signal; and a second count value storage register for storing a count value output from the second count counter when a defect is detected by the defect detection circuit. When,
A second comparison circuit that compares the count value of the second count counter with a value stored in the second count value storage register; an output signal of the first comparison circuit and an output signal of the second comparison circuit And an AND circuit that outputs a logical product of the two as a defect prediction signal, without calculating the rotation period of the optical disk from the absolute time read from the optical disk as in the conventional example. The position of a flaw can be predicted by counting the output FG signal by the first and second counters, and stable servo control can be performed even when an optical disk having a flaw on the surface is reproduced at a high speed. Can be. Further, since it is not necessary to have an arithmetic circuit for performing a calculation for determining the rotation cycle of the optical disk, the circuit scale of the hardware can be reduced.

The servo circuit for an optical disk device according to claim 7 is the servo circuit for an optical disk device according to claim 5, wherein the first count value storage register and the second count value storage register are provided. And two or more, respectively, so that the position of a plurality of scratches during one rotation of the optical disc can be predicted by the number of the first and second count value storage registers. Even when a scratched optical disc is reproduced at a high speed, stable servo control can be performed.

[Brief description of the drawings]

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

FIG. 2 is a time chart illustrating generation of a defect prediction signal in the servo circuit for the optical disk device according to the first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a configuration of a servo circuit for an optical disk device according to a second embodiment of the present invention.

FIG. 4 is a time chart illustrating generation of a defect prediction signal in a servo circuit for an optical disk device according to a second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a conventional servo circuit for an optical disk device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Optical disk 102 Spindle motor 103 Optical pickup 104 Focus actuator 105 Tracking actuator 106 High frequency amplifier 107 Defect detection circuit 108 Count counter 109 Count value storage register 110 Comparison circuit 111 OR circuit 112 Tracking hold circuit 113 Tracking servo circuit 114 Tracking drive circuit 115 RF Signal 116 Defect detection signal 117 TE signal 118 Tracking control value 119 Defect prediction signal 301 Optical disk 302 Spindle motor 303 Optical pickup 304 Focus actuator 305 Tracking actuator 306 High frequency amplifier 307 Defect detection circuit 308 Count counter 309 Store count value Register 310 Comparison circuit 311 Count counter 312 Count value storage register 313 Comparison circuit 314 Logical product circuit 315 Logical sum circuit 316 Tracking hold circuit 317 Tracking servo circuit 318 Tracking drive circuit 319 TE signal 320 RF signal 321 Defect prediction signal 322 Defect detection signal 323 Tracking hold signal 324 Tracking control value 325 Spindle driver 501 Optical disk 502 Spindle motor 503 Optical pickup 504 Focusing actuator 505 Tracking actuator 506 High frequency amplifier 507 Data processor 508 Defect detection circuit 509 Defect detection circuit 510 Flaw position prediction circuit 511 Servo characteristic switching circuit 512 Servo Sex switching circuit 513 focusing equalizer 514 tracking equalizer 515 focusing driver 516 tracking driver

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Yasushi Yasushi 8-8 Koshinmachi, Takamatsu City, Kagawa Prefecture Matsushita Hisashi Denshi Kogyo Co., Ltd. F term (reference) 5D118 AA17 BA01 CA02 CA04 CA08 CB05 CD02 CD03 CD14 CD17

Claims (7)

[Claims] A servo circuit capable of changing servo characteristics; a defect detection circuit for detecting a scratch on the optical disk based on reflected light obtained from the optical disk via an optical pickup and outputting a defect detection signal; When a flaw is detected by the detection circuit, a defect time prediction means for predicting a flaw position detected by the defect detection circuit and outputting a defect prediction signal; and no flaw is detected by the defect detection circuit. Sometimes, the servo characteristics of the servo circuit is set to a wide band, and when a flaw is detected by the defect detection circuit, the servo circuit is held immediately before a flaw to be detected next according to the prediction of the defect time prediction means, While a defect is detected by the defect detection circuit, A servo circuit for an optical disk device, comprising: a holding means for holding the servo circuit. 2. The servo circuit for an optical disk device according to claim 1, wherein the defect time estimating means measures a time from when a defect is detected by the defect detection circuit to a start position of the defect after one rotation of the optical disk. A count counter that stores the count value of the count counter when a flaw is detected; compares the count value of the count counter with the stored value of the count value register to output a defect prediction signal A servo circuit for an optical disk device, comprising: 3. The servo circuit for an optical disk device according to claim 1, wherein the hold unit performs a logical sum of the defect prediction signal and the defect detection signal, and an output signal of the logical sum circuit. And a hold circuit for holding the drive value of the optical pickup by holding the servo circuit on the basis of (1). 4. A servo circuit capable of changing servo characteristics, a spindle motor for rotating an optical disk, and outputting a period detection signal (hereinafter, referred to as an FG signal) every fixed rotation angle via a spindle driver, and an optical disk. A defect detection circuit for detecting a flaw in the optical disk based on reflected light obtained from the optical pickup through the optical pickup, and outputting a defect detection signal; and counting the FG signal when the flaw is detected by the defect detection circuit. The defect position prediction means for predicting the position of the flaw next detected by the defect detection circuit, and when the flaw is not detected by the defect detection circuit, the servo characteristics of the servo circuit are set to a wide band, When a defect is detected by the defect detection circuit, Holding means for holding the servo circuit immediately before a flaw detected next according to the prediction of the defect position prediction means and holding the servo circuit while the flaw is detected by the defect detection circuit. A servo circuit for an optical disk device, comprising: 5. The servo circuit for an optical disk device according to claim 4, wherein the defect position predicting unit measures a time from a rising edge of the FG signal to a detection of a rising edge of the next FG signal. 1
A count counter, a first count value storage register for storing a count value output from the first count counter when a defect is detected by the defect detection circuit, and a count value of the first count counter. A first comparison circuit that compares the value stored in the first count value storage register with a second count counter that counts the rising edge of the FG signal; and when a defect is detected by the defect detection circuit. A second count value storage register that stores a count value output from the second count counter, and a second value counter that compares the count value of the second count counter with the value stored in the second count value storage register. And a logical product of an output signal of the first comparison circuit and an output signal of the second comparison circuit as a defect prediction signal. Servo circuit for an optical disk apparatus characterized by comprising a logical product circuit, the that. 6. The optical disk control servo circuit according to claim 4, wherein the hold unit performs a logical sum of the defect prediction signal and the defect detection signal, and an output signal of the logical sum circuit. And a hold circuit for holding the drive value of the optical pickup by holding the servo circuit on the basis of (1). 7. The optical disk drive according to claim 5, wherein each of the first count value storage register and the second count value storage register is two or more. Servo circuit for equipment.