| 摘要 |
PROBLEM TO BE SOLVED: To stably read a signal of a recording area continuous with an unrecorded area and to suppress the resolution of an AD converter from degrading. SOLUTION: The optical disk drive 1 is provided with an optical pickup unit 10 which irradiates an optical disk 2 with a laser beam, detects the catoptric light from the optical disk 2, and outputs an RF signal introducing an AC component and a DC component from the catoptric light. Then, the RF signal including the AC component and the DC component output from the optical pickup unit 10 is output to an AGC section 20 which is DC coupled to the optical pickup unit 10. Also, a VGA 21 of the AGC section 20 controls the amplitude of the RF signal to prescribed magnitude by using the maximum value of the voltage of the RF signal output from a peak hold circuit 22 and outputs the value to a level shift circuit 30. In the level shift circuit 30, the voltage of the RF signal of 80% in modulation percentage output from the AGC section 20 is shifted so as to have the same voltage level as that of the D range of the AD converter 41 and is then output to the AD converter 41. COPYRIGHT: (C)2008,JPO&INPIT
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