| 摘要 |
PURPOSE:To reduce size and weight by performing the detection of a tracking error and a focus error, and the detection of information, on the basis of the output of a photodetector, attached to a light guide, of a reflected light beam, converged by a converging diffraction grating. CONSTITUTION:The light beam 15 emitted from a seniconductor laser 16 is transmitted through the light guide 29, and is converged by an objective lens 18 so as to focus on the reflecting surface 14 of an optical disk 13. The reflected beam 15' from the disk 13 passes through the lens 18, and is diffracted in FGs 31, 32, and comes incident into the guide 29. The quantity of light of the beam 15', converged by the FG 31, is detected by photodiodes PD1, PD2, and the quantity of light of the beam 15', converged by the FG 32, is detected by the photodiodes PD3, PD4. The outputs of the diodes PD1-PD4 are processed, and the recorded information can be read by a read circuit 40, and besides, the lens 18 can be shifted through a tracking coil drive control circuit 42 and a focus coil drive control circuit 41. |
