CIRCUIT FOR DETECTING OFFTRACK OF OPTICAL DISC

摘要

PROBLEM TO BE SOLVED: To provide a circuit for detecting an offtrack of optical disc that is certain to detect ontracks and offtracks at the time of starting access. SOLUTION: An offtrack detecting signal 105 is outputted by comparing a sum light amount sum signal 101 that converts an output signal of a photodetector 9 that is divided into several output signals in an optical head 3 into a digital signal in an AD converter 11 and sums it up in an arithmetic circuit 12 with the output signal through a low-pass filter 13 with a comparator 15, at the time of access to drive an optical head and a recording medium relatively so that an optical spot crosses over the track of the optical disc by a driving means. At the time of starting the access, an offtrack detecting signal 105 is certain to be obtained from the time of starting the access, while eliminating the delay of response of the low-pass filter 13 by adding prescribed offset value to the low-pass filter 13 for a prescribed time from an offset setting circuit 14.