| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly accurate radial contrast signal. SOLUTION: In this recording/reproducing device, irradiated positions by sub-spot lights Psa, Psb are set so as to be in equal distance from a main spot light Pc, by which a groove is irradiated, and to be within the area of a land. The reflected light Pc' of the main spot light Pc is detected by a photodetector 14 and the reflected lights Psa', Psb' of the sub-spot lights Psa, Psb are respectively detected by photodetectors 15,16. An amplification signal Sx' is produced by producing an adding signal Sx based on detected signals S15, S16 of the photodetectors 15, 16 and amplifying it with an amplifier 26 having an amplification factor K/n. An RF signal SRF is produced based on detected signals SA-SD of the photodetector 14. The radial contrast signal DRC is provided by passing the signal (SRF-Sx') of an absolute value of the difference between the RF signal SRF and the amplification signal Sx' through an envelop detecting circuit 27 and a binarization circuit 28. The factor K is set to a ratio of the light intensity of the main spot light Pc and sub-spot lights Psa, Psb, and the factor n is set to the number of photodetectors 15, 16.
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