| 摘要 |
PURPOSE:To detect the position of a pickup accurately without further improvement to the pickup by transmitting a part of a laser beam irradiated from the pickup to a disc through the disc, being incident on the optical sensor and obtaining a different output in response to the photo sensing position of an optical sensor. CONSTITUTION:A part of the irradiated laser beam is transmitted through the disc 11. Then the disc 11 is driven by a disc motor 12 at a prescribed rotating speed. The optical pickup 13 is moved radially in opposition to the information recording and reproducing face of the disc 11 by a pickup feed motor 14. Then the photosensor 15 is provided along the moving path of the pickup 13 on the other side of the pickup. The photosensor 15 senses the incident light and outputs a signal to a signal processing circuit 16. The output is a discrete signal when an amorphous sensor or a CCD element is used as the sensor 15, a scan signal is generated by the circuit 16 and the position is detected based on the signal from the photosensor 15.
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