Defect detection in an optical disk data reproduction system

Abstract

A defect detection circuit and method for detecting disk defects in an optical disc data reproduction system allows for correct detection of defects not only during operation in a constant linear velocity mode but also during operation in a constant angular velocity mode using a channel bit clock signal as a reference signal. The circuit includes a comparator for comparing an RF signal with a first compare voltage having a predetermined voltage level and a second compare voltage having a voltage level lower than the first compare voltage, and for generating a first comparison signal activated in response to the RF signal having a level higher than that of the first compare voltage and a second comparison signal activated in response to the RF signal having a voltage level lower than that of the second compare voltage. A defect detector receives the first and the second comparison signals and a channel bit clock signal, and generates a defect detecting signal when both the first and the second comparison signals are deactivated for a period of time less than nT in duration (here, n is a positive integer and T is a period of a channel bit clock signal) and when the first or the second comparison signal is deactivated for a period of time longer than the maximum pit length+mT where m is an integer larger than 0.