| 摘要 |
PROBLEM TO BE SOLVED: To enable desired focal signal detection by both the DVD and CD. SOLUTION: A light receiving element 8 for focal detection has two-split light-receiving regions at a central part and two light-receiving regions outside. Among a plurality of light beam fluxes having a different wavelength returned from a recording surface, the return light beam flux of a first wavelength is received by the two-split light-receiving regions at the central part to generate a focal signal. Among the plurality of light beam fluxes having a different wavelength returned from the recording surface, the return light beam flux of a second wavelength is received by the two-split light-receiving regions at the central part and by the two light-receiving regions to generate focal signals. |
