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 are generated. Photodetecting elements 22a and 22b are arranged on an a 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. Focus error signals are detected based on the outputs of these elements. |