| 摘要 |
PROBLEM TO BE SOLVED: To detect a defect on an optical disk more accurately. SOLUTION: A defect detection device is provided with; an amplifying section which amplifies a reflective signal corresponding to the intensity of light reflected from the optical disk in accordance with a control signal which shows recording or reproducing and outputs it; an envelope detection section which outputs an envelope of output of the amplifying section; a first pulse generation section which outputs a pulse of a predetermined length when the control signal is changed; an integration section which integrates the output of the envelope detection section and outputs it; a differential signal generation section which receives output of the envelope detection section as a first input signal, and output of the integration section as a second input signal, and outputs a differential signal according to the difference of the both; and a comparison section which compares the output of the differential signal generation section with a predetermined value and outputs the results as a defect detection signal which indicates existence of a defect. In a period of the pulse, the second input signal is changed so as to make possibility that the defect detection signal shows the presence of a defect become small. COPYRIGHT: (C)2005,JPO&NCIPI
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