| 摘要 |
PURPOSE:To lead a pickup through the arcuate motion of a swing arm by detecting the position relation between a spot sequence formed of a converged beam and tracks on a disk, and adjusting the angle of a turntable which supports the pickup. CONSTITUTION:Reflected light beam from three spots which are reflected by a disk surface strike a photodetector 24 provided in the pickup 1 through a half- mirror 21. The photodetector 24 includes three photodetectors 24a, 24b, and 24c for detecting the reflected light beams of the respective spots, and the outputs of the photodetectors 24b and 24c arranged, specially, at both sides are used to correct the angular deflection of the pickup 1. The output of an amplifier 25 is further inputted to one input of an arithmetic circuit 27 for angle error calculation and processed on the basis of the other input, i.e. a signal level set by a variable resistor 26, so that the output signal of the angle error detected on the basis of the reflected light beams of side spots 22b and 22c appears at the output terminal 28. |
