METHOD FOR DECIDING ERRONEOUS DETECTION OF PRE-PIT SYNCHRONOUS-BIT FOR OPTICAL DISK AND METHOD FOR DECIDING STABILITY, INSTABILITY OF PRE-PIT SYNCHRONOUS-BIT AND THOSE CIRCUITS

摘要

PROBLEM TO BE SOLVED: To precisely decide erroneous detection of pre-pit synchronous-bit and to precisely decide stability/instability of pre-pit synchronous-bit detection based on the decision. SOLUTION: An AND circuit 16 detects whether or not the pre-pit synchronous-bit are obtained in a window set by a timing generator 14 at every synchronous-frame. The detection result is held to a shift register 18 to be shifted at every synchronous-frame. A decoder 22 decides correct/error or the pre-pit synchronous-bit b2 detection based on the parallel outputs of the shift register 18. A counter 26 one counts up whenever the decoder 22 decides as correct, and one counts down whenever the decoder 22 decides as error. A decision part 28 decides the stability/instability of the pre-pit synchronous-bit according to the count value of the counter 26.