| 摘要 |
PURPOSE:To obtain the position and the rotating velocity signal with high accuracy by using a main beam of an optical pickup for controlling a focus and two sub beams thereof for detecting the rotating phase difference. CONSTITUTION:A rotary encoder apparatus 50 is comprised of an encoder plate 53 and an optical pickup 55. The encoder plate 53 is fixed to a rotary part 52 having a hollow part 51 which can be directly coupled to a shaft of a motor, with a plurality of micro pit arrays (pits) 54 formed on an end face 53a thereof. The optical pickup 55 can radiate light beams to the plurality of pits 54 on the end face 53a of the encoder plate 53. When the encoder plate 53 is rotated at a constant speed by the motor, laser beams output from a semiconductor laser device of the optical pickup 55 are divided into three by a grating plate, so that a main beam 55a and sub beams 55e, 55f are applied to the end face 53a of the encoder plate 53. At this time, the main beam 55a is used to control a focus, while the sub beams 55e, 55f are used to detect the rotating phase difference. |
