| 摘要 |
PURPOSE:To promptly detect the center position simplifying a device, by integrally moving two sensors in a direction of passing through a concentric circular groove and detecting each position from a start point of the sensor, when it passes through the groove, so as to obtain the rotary center of the groove on the basis of said position of the sensor and an already known groove radius. CONSTITUTION:Since a moving distance a' from a home position is known by detecting a position of an optical pickup 6 as a sensor, when it passes through a groove 4, in a point A, a device reads coordinates of the point A for a virtual original point P to be A (O, a) because the home position of the optical pickup 6 for the virtual original point P is already known. While a moving distance b' from a home position is known by detecting in a point B a position of an optical pickup 8 when it passes through the groove 4, and the device reads coordinates of the point B for the virtual original point P to be B (L1, b) because the home position of the optical pickup 8 for the virtual original point P is known. Next a center position Q is obtained because a radius of the groove 4 is known. In this way, the device, using the two optical pickup, enables the two points of the innermost or outermost peripheral groove to be detected, promoting the promptness of detection.
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