Patent ID: 7035178

Claim:
An apparatus for producing a push-pull tracking error signal in an optical disc system using a photo detector with four light-receiving sections A, B, C, and D arranged in a radial direction of the optical disc and producing signals P A , P B , P C and P D , respectively, according to respective intensities of received light, the apparatus comprising: a first operation unit which performs a differential operation on the signals P B and P C to output a signal (P B –P C ); a second operation unit which performs a differential operation on the signals P A and P D to output a signal (P A –P D ); a low-pass filter having a predetermined first bandwidth which filters the signal (P B–P C ); a second low-pass filter having a predetermined second bandwidth which filters the signal (P A –P D ), the predetermined second bandwidth being larger than the predetermined first bandwidth; an amplifier which amplifies the filtered signal (P B –P C ); and a third operation unit which performs a differential operation on the filtered signal (P A –P D ) and the amplified filtered signal (P B –P C ) to output the tracking error signal.