JPS6413265A - Pattern coincidence detection circuit for digital signal - Google Patents

Abstract

PURPOSE:To avoid the false detection of a prescribed pattern by detecting it as the coincidence of a pattern only when the prescribed pattern is detected continuously extending over prescribed time, even if it is detected that the prescribed pattern is contained in a digital signal. CONSTITUTION:A voltage signal 27 to show the reflection quantity of a laser beam is converted to a serial digital signal by a waveform processing circuit 21 by means of, for instance, differential detection, and is given to a shift register 23 to operate as a series./parallel conversion circuit. A clock 25 has twice cycles as speed, at which a regenerative signal 27 is regenerated from an optical disk, i.e., the bit cycle of the digital signal and the shift register 23 fetches and shifts successively the digital signal 22, assuming the clock 25 to be a shift pulse. Feature point signals 24a-24l which are parallel output bits from the shift register 23 are the signals of respective points, at which twelve bits are selected and set as feature points out of thirty five bits at the time of the signalization of the sector mark 1, and these respective feature point signals 24a-24l are given to the reference pattern detection circuit 370 of the twelve outputs.