JPS60151846A - Optical disc reproducing device - Google Patents

Abstract

PURPOSE:To prevent the disturbance of tracking due to flaws and dirt of a disc by cutting off transmission of a tracking signal for a prescribed time including the time, when the level of the AM detection output of a read information signal exceeds a prescribed level, and holding the level of the tracking signal just before cutting-off. CONSTITUTION:An AM detecting circuit 7 performs AM detection of the output of an information signal amplifying circuit 2 to extract amplitude components of the information signal. A high-pass filter HPF8 permits only signal components having frequencies higher than a prescribed cut-off frequency in the output of the AM detecting circuit 7 to pass through, and thereby, signal components due to flaws and dirt of the disc are taken out. A loop cut-off control signal generating circuit 9 outputs a control signal which turns off the switch of a loop cutting-off circuit 10 while the output level of the high-pass filter 8 exceeds a certain level. The input signal to an actuator driving circuit 5 in the time, when this switch is turned off, is held in the signal level just before turning-off and is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical disc that reproduces information by irradiating a light beam onto a disc on which information such as audio or video is recorded on concentric or spiral tracks. Regarding a playback device.

Conventional configuration and its problems In an optical disc playback device, in order to play back information from a disc, it is necessary for a light spot to accurately trace a concentric or spiral information track. In other words, tracking control is required.

In an optical disc playback device, a relative positional deviation (tracking error) between a light spot for reading information and an information track is detected, and a signal that changes according to the tracking error (size and direction of the error) is obtained. ,
In response to this signal, the position of the light spot is changed to cancel the tracking error, and dragging control is performed so that the light spot accurately traces the page of the information trunk 3.

FIG. 1 shows a part of a conventional optical disc reproducing apparatus that performs the tracking control described above.

In FIG. 1, 1 is a light receiving section in the optical head,
, a, 1. Reference numeral b denotes a tracking error detection light receiving element for detecting a relative positional shift of a light spot on an information track, and lc to 1f are information detection light receiving elements for detecting an information signal from the information track. Reference numeral 2 denotes an information signal amplification circuit that sums and amplifies the information signals from the light receiving elements IC to 1f for information detection, and the output of this information signal amplification circuit 2 is demodulated by a subsequent signal demodulation section (not shown). be done. 3 are light receiving elements la and l for trunking error detection.
A differential amplifier circuit that amplifies the difference between the outputs of b.

4 is the light receiving element la for detecting the tracking error,]
, b, differential amplifier circuit 3. A compensation circuit 5 compensates for gain and phase so that a closed loop composed of an actuator drive circuit 5 and an optical head actuator 6, which will be described later, operates stably. An actuator drive circuit 6 that converts the output into a driveable output is an actuator for an optical head that controls the position of the light spot using the output of the actuator drive circuit 5.

However, in the above conventional example, when the gain of the closed loop is increased in order to particularly improve the vibration resistance performance of the playback device, noise is mixed into the tracking control signal due to scratches and dirt on the surface of the transparent protective layer of the disk. There was a problem in that the tracking control was disturbed and in some cases the track would jump to another track.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional drawbacks, and to provide an optical disc reproducing device that can perform stable tracking control against scratches and dirt on the disc surface.

Structure of the Invention The present invention was read to achieve the above object; [ik
↓ - I 5 of this AM detection output The transmission of the tracking signal is cut off for a predetermined period of time including the period when the page level exceeds a predetermined level, and the tracking signal level immediately before the cutoff is maintained. This may cause scratches on the disc,
This is intended to prevent tracking disturbances caused by dirt.

DESCRIPTION OF EMBODIMENTS In general, the main frequency component of the tracking error signal due to the eccentricity of the disk and disk rotation drive system in an optical disk playback device is several times the disk rotation frequency (for example, several tens of Hz in a compact disk player).
), whereas a tracking error signal due to scratches, dirt, etc. on the disk has many frequency components that are 10 times or more the number of rotations of the disk.

On the other hand, in the information signal read by a compact disc player, the tracking error signal component is present as an amplitude modulation signal, and at the same time, the information reading light spot is exposed to scratches on the disc.

There is also amplitude fluctuation due to passing through dirt, and the main frequency component of this amplitude fluctuation (amplitude modulation) is also 10 times or more the disk rotation frequency, as in the tracking error signal described on page 6 above.

In view of the above points, the present invention extracts a signal having a frequency component 10 times or more of the disk rotation frequency from the amplitude component of the information signal, and when this level exceeds a predetermined level, it is detected as a scratch on the disk. Stable tracking control is achieved by interrupting the tracking loop for a predetermined period of time including this period to prevent dirt from forming, and maintaining the actuator drive signal level, that is, the light spot position, at the value immediately before the tracking loop was interrupted. This is what we do.

An embodiment of the present invention will be described below with reference to FIG. Note that in FIG. 2, the same parts as in FIG. 1 are given the same numbers.

In FIG. 2, 7 indicates the output of the information signal amplification circuit 2.
An AM detection circuit 8 detects and extracts the amplitude component in the information signal, and mainly detects scratches on the disk by passing only signal components having a predetermined cutoff frequency or higher from the output of the AM detection circuit 7.

7 High-pass filter (HP) that extracts signal components due to page dirt
F), 9 is a control signal that turns off the switch of the loop cutoff circuit 10, which will be described later, while the output level of the high-pass filter 8 is above a certain level and until a certain period of time has elapsed after the output level of the high-pass filter 8 becomes below a certain level. 10 is a loop interrupting circuit provided between the compensation circuit 4 and the actuator drive circuit 50, and outputs the output signal of the compensation circuit 4 with the output of the loop interrupting control signal generating circuit 9. Transmission to actuator drive circuit 5 to 0N10F
During the OFF period, the input signal to the actuator drive circuit 5 is maintained at the signal level immediately before the actuator drive circuit 5 was turned OFF.

The present embodiment has the above-described configuration, and detects the presence of scratches and dirt on the disk from the level of frequency components that are 10 times or more the disk rotation frequency.

By keeping the position of the disc at the position just before the loop is cut off, it is possible to prevent scratches and dirt on the disc.
151846 (3) It is possible to increase the stability of knocking control.

Effects of the Invention According to the present invention, while the optical spot signal is likely to be disturbed by a tracking error signal due to scratches or dirt on the disk, the optical spot signal is held at the position immediately before that signal, which has the advantage of eliminating significant tracking disturbances. It is something that you have.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a part of a conventional optical disc reproducing apparatus, and FIG. 2 is a block diagram of a part of an optical disc reproducing apparatus according to an embodiment of the present invention. 1. Light receiving section, 1. a, 11], IC, ld, l
e, 1f-... Light receiving element, 2... Information signal amplification circuit, 3 - Differential amplifier circuit, 4... Compensation circuit, 5... Actuator drive circuit, 6... Actuator for optical head, 7 ...AM detection circuit, 8...High-pass filter, 9...Loop cutoff control signal generation circuit, 1o...
・Loop breaking circuit.

Claims (1)

[Scope of Claims] Optical head means for reading information by focusing a light spot on an information track of an optical disk, detecting a relative positional error of the light spot with respect to the information trunk, and generating an error signal. , tracking signal generating means for generating a tracking signal based on the error signal;
tracking control means for controlling the position of the optical spot according to the tracking signal and canceling the relative position error; AM detection means for performing AM detection on the information signal read by the optical head means; a high-pass filter for extracting a signal component having a predetermined frequency or higher from the output of the means; and a high-pass filter for transmitting the tracking signal for a predetermined period of time including the period when the output level of the high-pass filter exceeds the predetermined level. An optical two-page disc reproducing device comprising: control means for shutting off the tracking signal and maintaining the level of the tracking signal immediately before the cut-off during the shut-off.