An apparatus for counting a number of record tracks applicable to an access control system of a optical disc

摘要

An apparatus for counting a number of record tracks which an optical head (2) traverses on a basis of a periodical track transverse information INFTR representing the traverse of the head across the record tracks. The periodical track transverse information INFTR is derived by sampling a track information of the record tracks preformed discretely on record tracks TR. In the track counting apparatus (6), a tracking signal generating circuit is installed for generating tracking signals VOP and VOQ which vary their frequencies and phases so as to follow those of the track transverse information INFTR. The number of record tracks which the optical head (2) has traversed are counted on the basis of the tracking signals VOP and VOQ. The tracking signals VOP and VOQ have continous waveforms so that the number of the tracks can accurately be counted even if only a discrete information is derived as the track transverse information INFTR.