JPH02210621A - Focus servo device - Google Patents

Abstract

PURPOSE:To return the phase characteristic of an equalizer gradually and to stabilize servocontrol even if an abnormal part is present on a recording surface by deviating the phase characteristic of the equalizer gradually from a specific characteristic when the abnormal part on the recording part is detected and varying a coefficient which determines the characteristics of the equalizer gradually after the abnormality detection. CONSTITUTION:When the signal processor 9 of a focus servo device is in normal processing, an error signal is fetched from an A/D converter 8, phase compensation for the data is performed based upon a preset equalizer characteristics, and error data after the compensation is outputted to a D/A converter 11. When this processor 9 performs equalizing processing for the phase compensation of a focus signal, an abnormality signal is supplied from a comparator 18. Then the coefficient for determining the characteristic of the equalizer is controlled under the control of a microcomputer 10, the phase characteristic is deviated gradually from the specific characteristic to a specific characteristics in the case of abnormality occurrence in response to the abnormality signal from the comparator 8, and the phase characteristic is returned gradually to the specific characteristic at the end of the abnormality detection.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a focus servo device in a disc player.

BACKGROUND ART Disc players that play information recording discs (hereinafter simply referred to as discs) such as video discs and digital audio discs are equipped with an optical system for reading information from a pickup on the information recording surface of the disc, regardless of the warpage of the disc. A focus servo device is essential for adjusting the degree of focus of a spot (hereinafter referred to as a pickup spot).

In this focus servo device, a focus error signal corresponding to the deviation amount of the objective lens of the pickup with respect to a reference position (focus position) from the information recording surface of the disk is generated using a well-known method such as the astigmatism method from the output signal of the pickup. generated by the method. The signal level of this focus error signal shows a nearly constant value regardless of the disc difference if the disc is within the standard, so the characteristics of the equalizer that compensates for the phase characteristics of the focus error signal correspond to the error signal level. It is set and fixed.

However, during focus servo, if there is an abnormal part such as a scratch on the information recording surface of the disk, the signal level of the focus error signal changes greatly in that part, making the servo unstable.

Summary of the Invention The present invention has been made in view of the above-mentioned points, and it is possible to perform stable servo even if there is an abnormal part such as a scratch on the information recording surface of the disk during focus servo. The purpose of this invention is to provide a focus servo device.

The focus servo device according to the present invention includes an equalizer having a variable phase characteristic in a servo loop that adjusts the focusing degree of a pickup spot on the information recording surface of the disk according to a focus error signal, and When detected, the phase characteristics of the equalizer are gradually deviated from the predetermined characteristics, and when the detection of the abnormal portion is completed, the coefficients that determine the characteristics of the equalizer are changed in order to gradually return the phase characteristics to the predetermined characteristics.

Example Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, there are three beam spots obtained by converging the laser beam, namely a pickup spot S1 for reading recorded information and this spot S1.
A pair of spots S for detecting tracking information that precede and follow each other when moving relative to the disk.
2+83 with the positional relationship shown, the pickup (
(not shown) onto the recording track T of the disk. The light reflected from the disk by these beam spots is transmitted to photoelectric conversion elements 1 and 2 built into the pickup.
, 3.

The photoelectric conversion element 1 is composed of four mutually independent light-receiving elements arranged so that the light-receiving surface is divided into four parts, and the total output of these elements is the read RF multiplied signal. Further, the sum of outputs of elements facing each other with respect to the center of the light-receiving surface is obtained by adders 4 and 5, and the difference between the respective addition outputs of these adders 4 and 5 is obtained by a subtracter 6, and this subtracted output is the focus Derived as an error signal. This focus error signal is sampled by a sample and hold circuit 7, digitized by an A/D converter 8, and supplied to a signal processor 9 as, for example, 8-bit data. The signal processor 9 is controlled by the microcomputer 10 to perform signal processing such as phase compensation for the focus error signal. That is, the signal processor 9 functions as a digital equalizer. This signal processor 9
The 8-bit data outputted from the D/A converter 11 is converted into analog data and is supplied to the focus actuator 13 via the driver 12.

The signal processor 9 supplies a sample timing pulse to the sample hold circuit 7, an A/D timing pulse to the A/D converter 8, and a D/A timing pulse to the D/A converter 11. be done.

Predetermined data is stored in the ROM 14 in advance, and R
Data obtained in the signal processing process is temporarily stored in the AM15.

On the other hand, the difference between the respective outputs of the pair of photoelectric conversion cables 2 and 3 is obtained by a subtracter 16, and this subtracted output is derived as a tracking error signal. Further, the sum of each output of the pair of photoelectric conversion elements 2 and 3 is obtained by an adder 17, and this added output becomes a comparison input of a comparator 18. The comparator 18 uses a predetermined reference level vth as a comparison reference input, and if there is an abnormal part such as a scratch on the information recording surface of the disc, the addition output level of the adder 17 decreases according to the degree of abnormality, so the addition output level When the value becomes below the reference level Vth, an abnormality detection signal indicating that an abnormal part such as a scratch exists on the information recording surface is output. This abnormality detection signal is supplied to the signal processor 9 described earlier.

In the process of equalizing processing that performs phase compensation on the focus error signal, the signal processor 9
When an abnormality detection signal is supplied from the comparator 18, control is performed so that the phase characteristic is gradually shifted in the phase advance direction from a predetermined characteristic when an abnormality is detected, and the phase characteristic is gradually returned to the predetermined characteristic when detection of the abnormal portion is completed. In equalizing processing by the signal processor 9, if the human input data is X(z), the output data is Y(z), and the equalizer characteristic is EQ(Z), the input/output relationship is Y(z)-EQ.
(z) ·X(z), and E Q (z) is expressed as KBO-KB, Z-'+Ka2Z-2. Here, KAo is the 0th-order term coefficient, KA□ is the 1st-order term coefficient, KA□ is the 2nd-order term coefficient, KXI is the integral term coefficient, (1-KRZ-') is the 1st-order low-pass filter, and (K
ao-Ks+Z-'+KB2Z-2) respectively represent second-order low-pass filters, Z-1 indicates the previous sampling value, and Z-2 indicates the sampling value before the previous one. In such equalizer characteristics, the phase characteristics can be controlled by changing the integral term coefficient KXI.

Next, the procedure of the focus process executed by the signal processor 9 when detecting an abnormal part such as a scratch will be explained according to the flowcharts shown in FIGS. 2 to 4.

FIG. 2 shows the processing procedure during normal play, and this processing has a sampling period Ts (for example, 31.7
78 μ5 ec). The processor first takes in the error data digitized by the A/D converter 8 (step S1), performs phase compensation on this error data using preset equalizer characteristics (step S2), and converts the error data after compensation. The error data is output to the D/A converter 11 (step S3). Next, it is determined whether or not an abnormality detection signal has been input from the comparator 18 (step S4), and if not, the current process is ended. When an abnormality detection signal is input, a focus-in counter (hereinafter referred to as (COUNTl)) for measuring the time in the focus-in state and a defocus counter (hereinafter referred to as "COUNTl") for measuring the time in the defocus state are used. , (denoted as COUNT2)) and further determines the characteristics of the equalizer.
A flag indicating up (0)/down (1) of
LG) is set as up/down FLG-1 in step S5), then the processing vector is set as "B" in step S6), and the current processing ends.

By setting the processing vector to "B" in step S6, the interrupt service of the processor jumps to a specific location, and processing and pull-in processing when detecting an abnormal part such as a flaw are executed. In addition, if the processing vector is "8",
The above-described processing during normal play is executed.

FIG. 3 shows the procedure of processing at the time of abnormality detection and pull-in processing, and this processing is also repeatedly executed at the sampling period Ts. As in the case of normal processing, the processor first takes in the error data digitized by the A/D converter 8 (step 5ll), and applies phase compensation to this error data using preset equalizer characteristics. (step 512), and outputs the compensated error data to the D/A converter 11 (step 813).

Next, it is determined whether or not an abnormality detection signal has been input from the comparator 18 (step 514), and if it is determined that it has been input, (COUNTI) is reset and (COUNT2) is incremented (step 5).
15). Next, it is determined whether the count value of (COUNT2) has reached a predetermined value of 12 or more (step 516).
, if the predetermined value T2 has not been reached, the current process ends. The predetermined value T2 is set to 640, for example, corresponding to about 20 l1sec. If the count value of (COUNT2) is equal to or greater than the predetermined value 12, set a flag for defocus processing to perform focus adjustment again.Step 51
7), end the current process.

If it is determined in step S14 that no abnormal signal is input, (COUNT2) is reset and (CO
UNTI) is incremented (step 518).

Next, it is determined whether the count value of (COUNTI) has reached a predetermined value T1 or more (step 519), and if it has not reached the predetermined value T1, the current process is ended.

For example, the predetermined value T1 is 409, corresponding to about 130 ssec.
Set to 5. If the count value of (COUNTI) is equal to or greater than the predetermined value T1, the up/down FLG is set to "0" (step 520), the processing vector is set to "A" (step 521), and the current processing ends.

FIG. 4 shows a procedure for adjusting the phase characteristics of the equalizer, and this process is executed by an interrupt with a cycle of, for example, 1 a+sec in the normal play process (FIG. 2). The processor first uses up/down FLG.
In step 531), it is determined whether FLG is "1" or not.
-1, that is, in the down mode of the integral term coefficient KXI, it is determined whether the count value of the equalizer conversion counter (hereinafter referred to as (TIMER)) is 0 (step 532). Note that the initial value N of (TIMER) is set to "5" corresponding to, for example, 5 m5ec.

(TIMER) If it is not -0, the value obtained by subtracting the value of 1/H of this initial value from the initial value of the integral term coefficient KXI (for example, 1.585 step 333), followed by (TIMER)
is decremented (step 534), and then returns to the main flow. This process is performed in step S32 (TIME
R) Repeat until it is determined to be -0, (TIMER) -0
If so, the integral term coefficient KXI is set to "0" (step 535), and then the process returns to the main flow.

On the other hand, in the up mode of FLG-0, that is, the integral term coefficient Kx1, the count value of (TIMER) is the initial value N
It is determined whether or not this is the case (step 536). (T
IMER) - If not N, the integral term coefficient KX at that point
The value obtained by adding 1/N of the initial value to the value of I "0" is set as the new integral term coefficient KXI (step 537),
Next, increment (TIMER) in step 5.
38), then return to the main flow. This process is repeated until it is determined in step S36 that (TIMER)≧N, and when (TIMER)≧N, the integral term coefficient KXI
is set to the initial value (step 539), and then returns to the main flow.

Through the above-described processing, as shown in FIG. 5, the integral term coefficient KXI changes in 5 steps every 1 m5 ec during a period of 5 m5 ec from the time of detection of an abnormal part such as a scratch based on the abnormality detection signal output from the comparator 18. Initial value (1, 5
The integral term coefficient KXI gradually changes from 85X10- to the final value '0', and after approximately 130a+sec as measured by (COUNTI) has passed since the end of detection of the abnormal part, the integral term coefficient KXI changes to "0" in 5 steps every 1a+sec. degree gradually changes to the initial value (1,585X to-'). As a result, when an abnormal part is detected, the phase characteristic changes to KXI-
The predetermined characteristic determined by the initial value (1,5G5X 10-") gradually deviates in the advancing direction and shifts to the characteristic determined by Kx+-0, and when the detection of the abnormal part is finished, the phase characteristic changes to the one after the transition. The characteristic gradually returns to the above-mentioned predetermined characteristic.In Fig. 6, which shows the overall oven loop characteristic of the focus servo, the solid line indicates the characteristic during normal play, and the - dotted chain line indicates the characteristic at the end of the transition. ing.

During focus servo, if there is an abnormal part such as a scratch on the information recording surface of the disk, the servo becomes unstable.

In such cases, stability can be improved by changing the phase characteristics of the equalizer in the forward direction, but rapid equalizer conversion can cause a sudden change in the drive output and cause a shock to the focus unit. Become. However, as described above, in the present invention, when an abnormality is detected, the phase characteristic of the equalizer is gradually advanced to convert it into an equalizer with a high pull-in ability, and when the abnormality detection is finished, it is gradually returned to an equalizer with a predetermined phase characteristic. Therefore, it is possible to always perform stable servo without giving a shock to the focus unit. Furthermore, since the phase characteristic can be advanced or delayed simply by changing the integral term coefficient Kx■, equalizer conversion can be easily performed.

As described in detail, the focus servo device according to the present invention gradually deviates the phase characteristics of the equalizer from the predetermined characteristics when an abnormal portion of the information recording surface is detected, and changes the phase characteristics when the abnormal portion is detected. The structure is such that the coefficients that determine the characteristics of the equalizer are changed in order to gradually restore the above-mentioned predetermined characteristics, so even if there is an abnormality such as a scratch on the information recording surface of the disk during focus servo, it will remain stable. Can perform servo.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 to 4 are flowcharts showing the procedure of focus processing when detecting an abnormal part, FIG. 5 is a timing chart thereof, and FIG. 6 is a focus This is a diagram showing the overall open loop characteristics of the servo, where the solid line represents the characteristics during normal play.
- The dashed and dotted lines indicate the characteristics at the end of the transition. Explanation of symbols of main parts 1 to 3...Photoelectric conversion element 7...Sample hold circuit 9...Signal processor 13...Focus actuator Applicant
Pioneer Corporation

Claims (3)

[Claims] (1) A focus servo device that adjusts the focusing degree of a pickup spot on an information recording surface of an information recording disk according to a focus error signal passed through an equalizer having variable phase characteristics, an abnormality detection means for detecting an abnormality, and a control means for controlling a coefficient that determines a characteristic of the equalizer, and the control means gradually deviates the phase characteristic from a predetermined characteristic when the abnormality detection means detects an abnormality, and detects the abnormality. A focus servo device characterized in that the coefficient is changed to gradually return the phase characteristic to the predetermined characteristic at the end of the process. (2) The focus servo device according to claim 1, wherein the deviation from the predetermined characteristic is in a phase advance direction. (3) The focus servo device according to claim 1, wherein the coefficient is an integral term coefficient.