Apparatus and method for correcting unsymmertry of light disk regenerating system

Abstract

Apparatus and method for correcting asymmetry in an optical disc reproduction system. The device for correcting the asymmetry of the RF signal received from the optical diode and outputting the asymmetry-corrected signal as a digital EFM signal, the device comprising an envelope detector for detecting the upper and lower envelopes of the RF signal, A controller for controlling the level of the sum of the upper and lower envelopes and outputting a signal having the controlled level, and for comparing the level of the signal output from the level controller with the level of the RF signal and serving as A comparator that outputs a comparison result for a digital EFM signal.

Description

technical field [0001] The present invention relates to optical disc reproduction systems, and more particularly to an apparatus and method for correcting the asymmetry of an RF signal output from a photodiode in an optical disc reproduction system. Background technique [0002] In an optical disc reproduction system, an asymmetry correcting device corrects the asymmetry of an RF signal and converts the RF signal into a digital eight to fourteen modulated (EFM) signal. That is, the asymmetry correcting means clips the RF signal output from the optical diode based on the clip reference level at which the asymmetry is corrected, and obtains a digital EFM signal. The 'EFM comparator (CXA12710)' shown on page 89 of "SONY SEMICONDUCTORIC DATABOOK" published by 'SONY' in 1990 (hereinafter referred to as a conventional asymmetry reference device) is an example of such an asymmetry correction device. [0003] The structure and operation of a conventional asymmetry correcting device...

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Problems solved by technology

Here, a hole defect is where the disc material is not good or the disc is drilled so deep that light passes through the disc without being reflected

Thus, the data cannot be detected

[0008] Then, in the portion where there is a scratch or a hole, since the asymmetry of the RF signal may be incorrectly corrected, an error correcting portion (not shown) connected to a conventional asymmetry correcting device cannot correctly correct the error.

[0009] Since the time constants of the resistors R5 and R6 and the capacitors C2 and C3 of the low-pass filter 16 are, for example, 5 ms, it is difficult for the clipping reference level to follow the RF signal much shorter than 5 ms at the portion where there are scratches or holes. mid level

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