| 摘要 |
PURPOSE:To accurately recognize a long defect by increasing the reference number of differential defects for determining whether or not an optical disk is normal according to defect length. CONSTITUTION:The quantity of reflected light from the optical disk 1 is detected by an optical pickup 2, led out of an optical pickup control circuit 3 as a regenerative signal, and inputted to a differentiating circuit 4 - an address decision circuit 7. The differential signal from the circuit 4 is compared 9 with the reference voltage from a reference voltage generating circuit 8 to detect whether or not there is a differential defect and then inputted to a counter 11 through a gate circuit 10 together with the gate signal of the circuit 7. Further, the regenerative signal from the circuit 3 is passed through an LPF 6 and a reference voltage generating circuit 12 to generate a reference voltage, which is compared 13 with the output of a buffer circuit 5 and inputted to a counter 15 through a gate circuit 14. Further, the signal from the comparing circuit 13 is inputted to a counter circuit 18 together with the defect length reference signal from a defect length reference generating circuit 16. Then the counted values of the counters 11, 15, and 18 are processed by a microcomputer arithmetic part 19. |
