| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce a circuit scale of an RFDC system and current consumption, and to improve accuracy of OPC (Optimum Power Control) by suppressing variation in a result of measuring a modulation degree resulting from in plane fluctuation of an optical disk reflectance. Ž<P>SOLUTION: An RFDC system signal processing circuit of which circuit scale and power consumption are large, is eliminated. A switch 113 is switched depending on on-track mode and off-track mode, to output an RFAC signal in on-track mode, carry out balanced modulation and output an RFDC signal in off-track mode; demodulate a signal output from the switch 113, and obtain a modulation degree or an off-track signal from the demodulated data. Accuracy of the OPC is increased by suppressing variation in the measurement result of the modulation degree. AGC (RFAGC) of an RFAC system is applied to the DSB signal by carrying out balanced modulation and converting the RFDC signal into a DSB signal of both polarity. The RFDC signal which is demodulated by the RFAGC is normalized with a reflectance. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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