| 摘要 |
PURPOSE:To improve the S/N and to realize the stable tracking servo or focusing servo. CONSTITUTION:One piece of light beam is divided into three pieces in the horizontal direction by a diffraction grating, and moreover, divided into three pieces in the vertical direction by a Wollaston prism, and total nine pieces of light beams are generated. A photodetector 22 is arrayed so that all of these nine pieces of light beams L1, L2, L3, L1L, L2L, L3L, L1R, L2R and L3R can be detected. Outputs of each area A to H of the photodetector 22 are calculated by an arithmetic circuit 31, and a focus error signal Sf, a tracking error signal St, and a signal Si corresponding to recording information are generated, respectively. |
