| 摘要 |
PURPOSE:To remove an offset error from a tracking servo by expanding and deflecting light by a cylindrical mirror mounted on a rotary sliding table and making the light incident upon a division type photodetector to detect the position of an objective lens in tracking and focusing directions. CONSTITUTION:The cylindrical mirror 9 arranged in the vicinity of the objective lens 3 so as to be driven together with the lens 3 and orientating its cylindrical axis direction rectangularly to the optical axis of the lens 3 deflects light right and left in accordance with the rotation of the lens 3 and in the vertical direction in accordance with the parallel advancement of the lens 3. The deflected light is detected by the division type photodetector 10 to detect the two-dimensional moving distance of the lens 3 fitted to an actuator 4, an offset generation variable at the time of detecting a tracking error due to the movement of the lens 3 is calculated based on the obtained objective lens moving distance and the calculated value is subtracted from a tracking error signal. Consequently, an error at the time of detecting the tracking error can be removed.
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