| 摘要 |
PROBLEM TO BE SOLVED: To make obtainable stable servo signals and to make suppressible a T/F cross talk too, even though a magneto-optical disk having a different track pitch is set. SOLUTION: Reflected laser light beams from a disk, on which optical information is recorded, are bisected by a hologram 18 and defocuses in positive and negative directions concerning an optical axis directions are generated. Photodetecting elements 22a and 22b are arranged on an approximately same plane to receive the bisected light beams. Each of the pair of photodetecting elements has at least three photodetecting elements that are divided by dividing lines parallel to a tracking equivalent direction. Based on the outputs of these elements, focus error signals and the signals indicating wavelength fluctuation of the laser beams are detected. |
