| 摘要 |
PROBLEM TO BE SOLVED: To evaluate a reproducing signal with high accuracy even when the recording density of a digital signal is increased in an optical disk. SOLUTION: A computer 20 stores amplitude values HSW and LSW and amplitude value reaching periods HST and LST each time a reproducing signal crosses trigger levels TRu and TRd set on a polarity side opposed to an amplitude value to be extracted. The computer 20 also stores amplitude values HLW and LLW and amplitude value reaching periods HLT and LLT corresponding to an evaluation target pulse width 11T each time the reproducing signal crosses slice levels SLu and SLd. Then, frequency distributions are calculated for amplitude values HSW and LSW corresponding to the amplitude value reaching periods HST and LST belonging to a predetermined time range, and extraction amplitude values HSW1 and LSW2 corresponding to an evaluation target pulse width 2T are extracted. Then, the reproducing signal is evaluated by using the extracted amplitude values HSW2 and LSW2 and the stored amplitude values HLW and LLW. COPYRIGHT: (C)2007,JPO&INPIT
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