Patent ID: 7697648
Filing Date: 2010-04-13
Classification: G11B

Abstract:
1. An asymmetric error correction device comprising: an analog-to-digital (A/D) converter which samples analog radio frequency signals reproduced from an optical disc, converts the radio frequency signals into the digital sampling signals, and outputs the digital sampling signals; a signal detector which detects digital sampling signals which vary in polarity after a predetermined number of sampling periods; an operator which selects and adds signals among the digital sampling signals which are detected to provide an asymmetric error value; an error magnitude modifier which multiplies the asymmetric error value by a correcting coefficient to modify a magnitude of the asymmetric error value; a counter which counts the asymmetric error value modified by the error magnitude modifier; and a corrector which corrects a signal level of the digital sampling signals output from the A/D converter if the asymmetric error value counted by the counter is out of a predetermined range, wherein the sampling signals vary in polarity every 4T period, wherein the corrector adjusts a magnitude of a signal level of the digital sampling signals output from the A/D converter if the asymmetric error value counted by the counter is out of the range, wherein the signal detector comprises: a variable frequency oscillator (VFO) detecting part which outputs a VFO detecting signal if a VFO part of the optical disc is reproduced; and a VFO sampling signal output part which outputs a digital sampling signal when the VFO detecting signal is output from the VFO detecting part, and wherein the VFO detecting part comprises: a first header signal detecting part which detects a header_peak signal reproduced from the optical disc; a second header signal detecting part which detects a header_bottom signal reproduced from the optical disc; a pulse output part which outputs a control pulse in a certain magnitude when at least one of the header_peak signal and the header_bottom signal is detected from the first header signal detecting part and the second header signal detecting part; a timer part which counts an elapsed time from a point when the control pulse is output; and a VFO detecting signal output part which outputs a VFO detecting signal for a certain time if the elapsed time exceeds a predetermined setting time.