| 摘要 |
PURPOSE:To attain a precise tracking servo by the fact that a tracking error signal becomes precise since the signal is detected based on the output of the light receiving element of a second photodetector on which no beam outgoing from a LD chip and reflected by a diffraction element is made incident. CONSTITUTION:The reflected beam from an optical recording medium is diffracted by a second diffraction grating 2b, and is made incident to a first photodetector 4 provided in the direction side of a LD chip 1 for the second diffraction grating 2b and a first diffraction grating 2a, and is made incident to a second photodetector 6 provided in the direction side of the recording medium for the first diffraction grating 2a. A focus error signal is generated based on the outputs of the light receiving elements (a), (b) of the first photodetector 4, and on the other hand, the tracking error signal is generated based on the outputs of the light receiving elements (d), (e) of the second photodetector 6. |
