| 摘要 |
PURPOSE:To irradiate vertically an optical beam on an information disc at all times, by detecting a reflected light from an information disc by a split photodetector, and applying the difference between respective detector outputs to a driver tilting the optical axis of an optical pickup. CONSTITUTION:The phtodetector 18 is split into four and a focus error signal is extracted. Further, the two sections among the four split sections are used and the difference in outputs between them is formed at a differential amplifier 19 to obtain a tracking signal. A DC component of a tracking error signal is extracted by an LPF112, a driving circuit 113 operates a driver 115 fitted to an optical pickup 114 to drive the pickup around a fulcrum 116 in an orthogonal direction. In the driver 115, a coil 117 is wound around the optical pickup 114, and the left and right parts are inserted in a magnetic pole 118 to form a magnetic field in the same direction. Since opposite currents flow mutually in the left and right magnetic poles, a torque around the fulcrum 116 is generated. |
