A detrack detecting system in an optical recording/reproducing apparatus.

摘要

A detrack detecting system for detecting deviation of the beam spot from the track in an optical recording/reproducing apparatus in which recording and reproducing of data are performed by irradiating optical beams onto an optical disc. Three beam spots are irradiated at positions on the optical disc which are shifted from each other by a predetermined distance laterally of the track. The reflected lights are respectively detected by three photodetectors whose photosensitive surfaces are divided into two parts and tracking error signals are detected by a push-pull system. A tracking error signal obtained from the centre beam spot of the three beam spots and tracking error signals obtained from other two beam spots are respectively added to obtain the first and second composite tracking error signals. Detracking state is detected based on the polarities of the first and second composite tracking error signals.