| 摘要 |
PURPOSE:To make it possible to start a defective light pickup for automatic focusing by exciting a focusing coil by ramp shaped waveform on which high frequency signals are superposed and bringing an objective lens close to a disk face. CONSTITUTION:When a focus search instruction is inputted to input of a ramp waveform generating circuit 11, an electronic switch 12 becomes open, and output of the ramp waveform generating circuit 11 and signals of a high frequency superposition signal generating circuit 13 are composed in an adder 14, and a power amplifier 4 is excited by the signal. Frictional force of focusing direction existing in the movable part including an objective lens is reduced by output signals of the high frequency superposition signal generating signal 13, and the objective lens can be brought close to the disk face smoothly by signals of the ramp waveform generating circuit 11. When the focus search instruction is made off, the electronic switch is shunted, and accordingly, signals in which high frequency signals are superposed on ramp wave are not transmitted to the power amplifier 4. |
