| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical drive device which performs a reliable focus servo operation using an interlayer detection signal. SOLUTION: The optical drive device has a signal processing section that generates an interlayer detection signal based on an output signal of a photodetector, and performs layer determination based on the interlayer detection signal. A light receiving face of the photodetector includes quadrant light receiving faces A1 to D1, and light receiving faces A2 to D2 for interlayer instruction signal output arranged around the quadrant light receiving faces A1 to D1. The signal processing section subtracts the output signals of the light receiving faces A2 to D2 for interlayer instruction signal output from the output signals of the quadrant light receiving faces A1 to D1, to generate the interlayer detection signal. The sizes t<SB>2</SB>and t<SB>3</SB>of the light receiving faces A2 to D2 for interlayer instruction signal output are equal to or less than 5.4 times a diameter of a spot formed by an optical beam on the light receiving faces. COPYRIGHT: (C)2011,JPO&INPIT
|
