| 摘要 |
PROBLEM TO BE SOLVED: To improve the incident accuracy of each incident spot to each optical sensor when a light from a laser diode is diffracted by a diffraction grating and plural incident spots are generated from plural diffraction of lights, and the incident spots are respectively projected to tracks sequentially arrayed in the radial direction of an optical disk so as to make reflected light incident on corresponding optical sensors. SOLUTION: The position of an optical sensor device 29 is fixed in a direction perpendicular to an optical axis by aligning the center of an optical sensor 40M with the center of an incident spot 47M while a focus servo is operated. A diffraction grating plate holder is adjusted for positions in the direction of an optical axis and in the peripheral direction of the optical axis such that the outputs of optical sensors 40E, F, G and H are in specified levels or higher, and then fixed to a chassis.
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