| 摘要 |
PURPOSE:To make the record center coincident with the center of rotation of a turntable, by detecting the eccentricity of the record center from the center of rotation of the turntable by using the final groove of the record. CONSTITUTION:To trace the final groove 12 of a record 1, a tone arm 5 has a shutter plate 8 arranged between a light emitting element 61 and a photodetecting element 71. This optical sensor generates an electric signal V which corresponds to the angular displacement of the tone arm 5. Optical sensors 101-104 consisting of light emitting elements 62-65 and photodetecting elements 72- 75 arranged and fixed at 90 deg. rotation angle intervals generate position signals P1-P4 when a reflecting member 9 fitted to the circumferential side surface of a turntable 3 arrives. By detecting electric signals V1-V4 when the position signals P1-P4 are generated, signals V1 and V3 are information on the eccentricity of the record 1 from the rotation center of the turn table 3 in the direction X-X, and signals V2 and V4 is that in the direction Y-Y. |
