JPH09204662A - Optical disc player and play back method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set servo parameters optimal to respective drives by detecting a flaw on a disc. SOLUTION: When a flaw is detected by a flaw detection means 1, a selector 3 is switched and positive and negative peak values of focus error signal are detected by an focus error signal peak detection means 5. When it is higher than a reference error signal preset by a peak value comparing means 6, gain of a high frequency component cur means 4 is varied by a preset amount through a controller 2 and the focus error signal is balanced immediately after a flaw section thus preventing detuning of servo.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reproducing device and an optical disk reproducing method used for servo control operation of information reading of an optical disk drive device.

[0002]

2. Description of the Related Art In recent years, optical discs have attracted attention as recording media, and compact discs (CDs), laser discs (LDs) and the like are known in particular. As a device for reproducing this CD, there is a CD drive, and the development of this CD drive has become popular. Although the CD drive is specialized for reading, it has become widespread as an external storage device for a personal computer because of its merit such as a large amount of information on a disc as a medium and low manufacturing cost. In this CD drive, feedback control is performed so as to minimize the servo error signal read from the track on the disc (consisting of a focus error signal indicating a shift in the focus direction with respect to the disc and a tracking error signal). The pickup is following the upper track. If there are scratches on the disc, the pickup will follow the scratches, the servo error signal will increase, and the servo may deviate from the track that is currently following, causing skipping when playing a music CD. was there. As one of means for solving this problem, it has been proposed to use a scratch detecting means for detecting scratches on the disk and a high frequency component cutting means in a section where the disk has scratches.

FIG. 5 is a block diagram showing the structure of a conventional flaw correction servo apparatus. In the figure, the flaw correction servo device is configured to include a flaw detection unit 1, a controller 2, a selector 3, and a high frequency component cutting unit 4. C for scratch detection means 1
The RF signal obtained by reading the information on D is input to a peak poled circuit having different time constants, and the signal of the difference is binarized with a certain threshold value to output a flaw detection signal. If there is a scratch on the CD, the "H" scratch detection signal is output, and if there is no scratch, the "L" scratch detection signal is output. This flaw detection signal is input to the controller 2, and the controller 2 switches the selector 3 at the rise of the flaw detection signal so that the focus error signal is input to the high frequency component cutting means 4 during the flaw section. The high frequency component cutting means 4 is used in the scratched section. The high frequency component cutting means 4 is basically composed of a low pass filter.

When the scratch detecting means 1 determines that there is a scratch on the CD, the high frequency component (scratch component) contained in the servo error signal is removed by passing the servo error signal through the high frequency component cutting means 4. This prevents the servo from being dislocated due to scratches. The high-frequency component cutting means 4 is used only in a scratched section, and its use in a scratch-free section adversely affects the servo control. Therefore, it is necessary to prevent it from being used in a scratch-free section. Although the servo is hardly applied by the high frequency component cutting means 4 during the scratched section, normal servo control based on the servo error signal is performed when the scratched section ends. In this case, since the control once based on the servo error is restarted, the servo error signal immediately after the flawed section is more disturbed as compared with the normal time, which causes servo misalignment. It has been empirically known by experiments that the main cause of the servo deviation due to the scratch is the vertical imbalance of the servo error signal amplitude when the servo returns immediately after the scratch section on the CD. It is also known that the servo error signal balance can be adjusted by adjusting the gain of the high frequency component cutting means 4 used in the flaw section.

FIG. 6 shows signal waveforms of a flaw detection signal and a focus error signal in a flaw section in the conventional example. In this figure, the focus error signal after the end of the flawed section is not balanced above and below the DC component of the error signal, and the positive peak value is above the reference error signal level (the level of the wavy line), so servo deviation occurs. It is an easy situation. As described above, the imbalance of the error signal is the cause of the servo deviation, and the imbalance of the error signal can be eliminated by adjusting the gain of the high frequency component cutting means 4. CD drive has scratches
Playability (how large a scratch can be played without skipping sound) is regarded as an important indicator of performance. Therefore, at the time of developing the CD drive, the high frequency component cutting means 4 is adjusted in order to improve the scratch disk reproducing ability.

[0006]

The high-frequency component cutting means 4 configured to prevent sound skipping in the conventional optical disk reading has a fixed gain setting value,
This gain setting value is fixed at the time of shipment of the optical disc drive, and it does not correspond to the variations in the quality of the hardware and pickups that make up the optical disc drive.
In all optical disk drives, the servo error signal immediately after the scratched section is not balanced with respect to a certain reference voltage. Therefore, there is a problem that an optical disk drive in which the servo error signals are not balanced is more likely to cause servo deviation than other optical disk drives. In other words, it means that the optimum parameter of the high frequency component cutting means 4 in one optical disk drive is not necessarily the optimum parameter in another optical disk drive.

The present invention has been made to solve the above problems, and provides an optical disk reproducing apparatus capable of performing a reliable servo control operation in reproducing an optical disk having a scratch regardless of variations in hardware. To aim.

[0008]

According to the optical disk reproducing apparatus of the present invention, the cutoff frequency of the high frequency component cutting means, namely It is composed of a controller that adjusts the gain. According to the present invention, C which is less likely to cause a servo deviation with respect to a scratch disk
A D drive device is obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a scratch detecting means for detecting a scratch on an optical disk based on an information signal obtained by reading information from the optical disk and outputting a scratch detection signal. When there is a scratch on the optical disk, a servo error signal peak detecting means for holding two positive and negative peaks of the servo error signal with a certain reference voltage, a reference servo error signal and the two peak-held servos. Peak comparison means for respectively comparing error signals, and changing the cutoff frequency to a predetermined value based on the comparison result of the peak comparison means, and the high frequency component of the information signal read from the optical disc by the changed cutoff frequency. It is equipped with a high-frequency component cutting means that removes Scratches cutoff frequency (servo parameter) for countermeasures can be set, it has the effect of realizing a strong outstanding optical disk reproducing apparatus with respect to wound that does not depend on variations in the hardware and the pickup of the optical disc drive.

According to a second aspect of the present invention, in the optical disc drive, the amplitude of the reference error signal in the peak comparing means is determined by detecting the error signal amplitude when the servo is turned on.
There is an effect that the error signals can be compared correctly without being affected by variations in hardware and pickup or the size of the disc wobbling, and a CD drive device that is stronger against a scratched disc can be realized.

According to a third aspect of the present invention, when the cutoff frequency of the high frequency component cutting means is determined by the peak comparing means to be unbalanced between the positive servo error and the negative servo error, , Are determined so that the positive and negative servo errors can be balanced.

According to a fourth aspect of the present invention, the scratch on the optical disc is detected based on the information signal read from the optical disc, and the size of the scratch on the optical disc is determined based on the information signal. The servo control variable in the servo control operation for reading information is changed according to the degree of the size of the scratch on the optical disc determined above.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4 by taking an optical disk reproducing device of a CD drive as an example.

(Embodiment 1) FIG. 1 is a block diagram of an optical disk reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, an optical disk reproducing apparatus includes a scratch detecting means 1 for detecting a scratch on a CD from an RF signal, a controller 2 for controlling the entire apparatus, and a selector for switching a focus error (FE) signal under control by the controller 2. 3 and F output by switching the selector 3
High frequency component cutting means 4 for removing high frequency components of the E signal
And a focus error signal peak detecting means 5 for detecting the peak value of the FE signal from which the high frequency component is removed, and a peak comparing means 6 for comparing the positive and negative peak values under the control of the controller 2. Is.

The block configuration diagram configured as described above will be described below. Inputs to the block diagram of this embodiment are the FE signal and the RF signal output from the CD drive main circuit (not shown), and the FE signal is output to the drive circuit (not shown). In this CD drive main circuit, feedback control is performed so as to minimize the servo error signal read from the track on the CD, the FE signal indicating the shift in the focus direction with respect to the disc, and the TE signal indicating the shift in the tracking direction. The pickup (not shown) follows the track on the CD,
An RF signal, which is an information signal, is output by reading the upper pit. The flaw detection means 1 detects a flaw on the CD by inputting an RF signal, which is an information signal output from the CD drive main circuit, to peak-hold the RF signal and binarizing it. When there is a scratch on the CD, an "H" scratch detection signal is output, and when there is no scratch, an "L" scratch detection signal is output. This flaw detection signal is input to the controller 2, and the controller 2 switches the selector 3 to determine whether or not the FE signal passes through the high frequency cutting means 4. That is, the scratch detection signal is "L"
When, the focus error signal is output as it is, and when the flaw detection signal is "H", the FE signal is input to the high frequency component cutting means 4 and its output is used. The focus error signal peak detection means 5 records the peak of the focus error for a certain period from the time when the scratch detection signal changes from “H” to “L” (falling edge of the scratch detection signal). Specifically, a peak hold circuit (not shown) is used to hold the positive peak value and the negative peak value of the FE signal (based on the DC component of the FE signal). Subsequently, the peak value comparison means 6 compares the positive peak value and the negative peak value of the focus error, which are the results of the peak detection means 5 of the focus error signal, with the FE signal reference value. The reference value is a signal level which is empirically determined and is considered not to cause servo deviation. The controller 2 determines whether to operate the parameter that determines the gain of the high frequency component cutting means 4 based on the result of the peak value comparing means 6, and when operating the parameter, a new parameter is set to the high frequency component cutting means. Output to 4. This peak value comparison means 6
The specific operation of will be described with reference to the flowchart of FIG.

First, a peak maximum circuit is used to find the maximum positive voltage value of the focus error signal with respect to the reference voltage (step 1). Further, the peak hold circuit is used to obtain the maximum negative voltage value of the focus error signal with respect to the reference voltage (step 2). Further, the sum of the positive maximum voltage value obtained in step 1 and the negative maximum voltage value obtained in step 2 is obtained by using an adder circuit (step 3). Further, the comparison circuit compares the sum of the positive and negative maximum voltages obtained in step 3 with the servo deviation limit voltage of the focus signal obtained empirically (step 4).

When the sum of the positive and negative maximum voltages is larger in the comparison in step 4, the comparator is used to compare the positive maximum voltage and the negative maximum voltage (step 5). When the positive maximum voltage is higher in the comparison in step 5, the gain of the hold filter is adjusted so that the positive maximum voltage becomes smaller so that the servo error signal is balanced between positive and negative (step 6). When the negative maximum voltage is higher in the comparison in step 5, the gain of the high frequency component cutting means 4 is adjusted so that the negative maximum voltage becomes smaller so that the positive and negative servo error signals are balanced (step 7).

By the above procedure, the error signals are compared, the result is output to the controller, the servo parameter is operated by the controller, and the value is fed back to the high frequency component cutting means 4. By repeating the above-described operation every time a flaw is generated, the parameters of the high frequency component cutting means 4 are optimized, and the focus signal becomes below the reference as shown in FIG. in this way,
According to the present invention, the FE signal can be suppressed below the reference even when reproducing a damaged CD regardless of the hardware of the CD drive and variations in the pickup, so that a CD drive in which servo deviation is unlikely to occur can be realized. Although the focus servo control operation has been described so far, the same method can be applied to the tracking servo control operation.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram of a flaw correction focus servo unit according to the second embodiment of the present invention. The optical disk reproducing apparatus according to the present embodiment has the configuration of the optical disk reproducing apparatus according to the embodiment shown in FIG. 1 with an A / D conversion means 7 added before the selector means. The A / D conversion means 7 detects the amplitude of the FE signal by reading the FE signal at the time of servo-on and performing A / D conversion, and the controller 2 responds to this signal to detect the reference and becomes a reference by the peak comparison means 6. The amplitude of the error signal can be made variable. With such a configuration, it is possible to more strongly cope with variations in drives. That is, the amplitude of the focus error varies depending on the drive, and in a drive with a large original error signal as shown in FIG. 7, the amplitude of the reference error signal which becomes a reference by the peak comparing means 6 is proportional to the magnitude of this error signal. If the parameter is not increased, it is judged that the peak comparison means exceeds the reference error and the parameter value is changed even if the setting of the scratch countermeasure servo parameter is correct, that is, even if the error signal is positively and negatively balanced. Therefore, the balance of the error signal may be lost and the servo may be deviated. According to the magnitude of the original error signal, by setting the magnitude of the amplitude of the reference error signal serving as the reference by the peak comparing means 6 to an appropriate value, it is possible to further cope with the variation of the CD drive and thus the CD drive is resistant to scratches. Can be realized.

In each of the above embodiments, the CD drive has been described by taking the optical disc as a CD.
It is possible to target an optical disk drive that reproduces other optical disks such as an LD in addition to the CD.

[0021]

As described above, according to the present invention, by providing the scratch detecting means for detecting scratches on the optical disk, the peak detecting means, the comparing means, and the control means for controlling them, it is possible to control each optical disk drive. Thus, it is possible to set an optimum servo parameter for scratch prevention, and to realize an excellent optical disk drive device that is strong against scratches due to variations in the optical disk drive hardware and pickup.

[Brief description of drawings]

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

FIG. 2 is a signal waveform diagram of a flaw detection signal and a focus error signal when the optical disk reproducing device according to the first embodiment of the present invention is used.

FIG. 3 is a block configuration diagram of a focus servo unit according to the second embodiment of the present invention.

FIG. 4 is a flowchart showing a procedure of servo parameter operation according to the first embodiment of the present invention.

FIG. 5 is a configuration block diagram of a conventional flaw correction servo device.

FIG. 6 is a signal waveform diagram of a flaw detection signal and a focus error signal when used for focus servo control in a conventional flaw correction servo device.

FIG. 7 is a signal waveform diagram of a flaw detection signal and a focus error signal when a disc with a large flaw is reproduced in a conventional flaw correction servo device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 flaw detection means 2 controller 3 selector 4 high frequency component cutting means 5 focus error signal peak detection means 6 peak value comparison means 7 A / D conversion means

Claims (4)

[Claims] 1. A scratch detecting means for detecting a scratch on an optical disk based on an information signal obtained by reading information from the optical disk and outputting a scratch detection signal, and a servo error signal for detecting a scratch on the optical disk. Servo error signal peak detecting means for holding two positive and negative peaks with a certain reference voltage, peak comparing means for respectively comparing the reference servo error signal with the two peak-held servo error signals, and the peak High frequency component cutting means for changing the cutoff frequency to a predetermined value based on the comparison result of the comparison means, and for removing the high frequency component of the information signal read from the optical disc by the changed cutoff frequency is provided. Optical disk reproducing device. 2. The optical disk reproducing apparatus according to claim 1, wherein the amplitude of the reference error signal in said peak comparing means is determined by detecting the error signal amplitude during servo control operation. 3. The positive and negative servo errors when the cutoff frequency of the high frequency component cutting means is judged by the peak comparing means to be unbalanced between a positive servo error and a negative servo error. The optical disc reproducing apparatus according to claim 1 or 2, wherein the balance is determined so that 4. The size of the scratch on the optical disk is detected based on the information signal read from the optical disk, the size of the scratch on the optical disk is determined based on the information signal, and the size of the scratch on the judged optical disk is detected. An optical disk reproducing method, characterized in that a servo control variable in a servo control operation for reading information is changed according to the degree of.