| 摘要 |
PURPOSE:To detect only a defective place and to obtain the location of defect and length of defect by writing a rectangular wave signal of 50% duty onto an optical disk and comparing adjacent bit data at the measurement of defect so as to write the location of defect and length of defect in a memory circuit. CONSTITUTION:If a defect exists in an optical disk, a data string of '00' or '11' is inputted to a shift register 10 synchronously with a read clock signal 91 at the defective location and the parallel output of the shift register is '11' or '00', and a defect detection output 111 of an exclusive OR 11 is '0'. Thus, in storing a count 141 of a defect location counter 12 when a defect detection output 111 decreases its level, the number of read clocks 91 counted at the occurrence of a reference pulse 71, that is, the distance from the reference position till a location having a defect is stored in the memory circuit 14. Thus, the location of defect and length are measured.
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