| 摘要 |
PROBLEM TO BE SOLVED: To make constitution small and simple and also correctly record and reproduce information on various kinds of optical disks. SOLUTION: A photodetector has a plurality of divided light receiving sections 22, 23, 24 and 25 to receive returned light beams that are separated by an optical separating means 31, from the surface of the disk, when light beams from a light source illuminate the signal recording surface of an optial disk. Relative to the returned light beams, more than three sections of the sections 22 to 25 are arranged in the radial direction of the disk and are bisected by a center line along the radial direction. The returned light beams are separated approximately every one quater circle by the means 31. Two one quater circle returned light beams L1 and L2, which are mutually aligned in diagonal line directions, are made incident on the section 22 or the section 23. The other two one quater circle returned light beams L3 and L4 are made incident on the sections 23 and 24 or the sections 24 and 25. |
