| 摘要 |
PROBLEM TO BE SOLVED: To perform correct servo control by allowing an arithmetic means to almost cancel offset to be generated by the misalignment of light receiving means or a light splitting means in forming a focus error signal based on signals from two light receiving means to make the characteristic of a servo signal satisfactory. SOLUTION: The return light rays made incident on a beam splitting means 9 become light rays including diffracted light rays by the track groove of a recording surface and the balance of light quantities of these diffracted light rays 142a, 142b changes by the positional relation of the return lights of an outward path with respect to the track groove. Distributions of light quantities of the diffracted light rays 142a, 142b are respectively guided to different light receiving parts and when the difference between outputs of respective light receiving parts is calculated, it becomes a push-pull signal. That is, when, in the beam splitting means 9, the area is splitted into beam-split areas 141a, 141b by a splitting line roughly parallel with a T direction, the diffracted light rays 142a and 142b are respectively made incident on the area 141a and the area 141b and the push-pull signal is obtained by respectively guiding the diffracted light rays to different light receiving parts. |
