KR980004431A - Focus control circuit - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control circuit that automatically sets focus reference values required for the manufacture of an image disc device. In particular, the present invention projects light onto a disc on which information is recorded and detects reflected light and writes the disc onto a disc. An optical pickup for reproducing the received information, an image signal variation detection circuit for detecting a change amount of the RF signal, that is, a jitter rate or an error rate, after amplifying and waveform-shaping a radio frequency (RF) signal read out from the optical pickup; The servo control means performs focusing by changing the focus zero value according to the change amount of the video signal detected by the change amount detecting circuit. The focus reference value required for manufacturing the video disc device is used to change the change amount of the video signal, in particular, the jitter rate or the error rate. By detecting and automatically adjusting, optimal focusing is achieved.

Description

Focus control circuit

Since this is an open matter, no full text was included.

1 is a block diagram of a focus control circuit according to the present invention;

FIG. 2 is a detailed block diagram of the jitter reading unit of FIG.

Claims (5)

An optical pickup for projecting light onto a disk on which information is recorded and detecting reflected light to reproduce information recorded on the disk; Signal change amount detecting means for detecting a change amount of the video signal read out from the optical pickup; And servo control means for focusing by varying a focus zero value according to the signal change amount detected by the signal change amount detecting means. The focus control circuit according to claim 1, wherein said signal variation detecting means detects the jitter rate of the waveform-shaped RF signal. The focus control circuit according to claim 1, wherein said signal variation detecting means detects an error rate of a waveform-shaped RF signal. An optical pickup for projecting light onto a disk on which information is recorded and detecting reflected light to reproduce information recorded on the disk; Signal processing means for amplifying and waveform shaping a radio frequency (RF) signal read out from the optical pickup; Jitter reading means for detecting a difference between a waveform-lowered RF signal and a reference RF signal having an ideal duty in the signal processing means; And servo control means for performing focusing by varying a focus zero value according to a difference value of the RF signal detected by the jitter reading means. 5. The apparatus of claim 4, wherein the jitter reading means comprises: a counter for counting a high section or a low section of an RF signal at which the waveform is shaped and output by the signal processing unit; A comparison and storage unit for comparing the output of the counter with a high or low interval value of a reference RF waveform having an ideal duty and storing the difference value for a plurality of RF waveforms and the comparison and storage unit And an averaging unit for varying a focus zero value by averaging a plurality of difference values. ※ Note: The disclosure is based on the initial application.