| 摘要 |
PURPOSE:To stop accurately a shift stage for optical system at a desired address of the track designated on a disk despite the large eccentricity of the disk, by controlling the counting of the clock signals obtained from the tracking error signals by means of the detecting signal. CONSTITUTION:The output of each stage of an up/down counter 30 is used to the address signal of a function generating circuit 32 consisting of a read-only memory and supplied to the circuit 32 via an address decoding circuit 31. The output of the circuit 32 undergoes D/A conversion through a D/A converting circuit 23 and turned into the voltage which controls the actual speed of the shift stage for optical system. The output of a relative phase detecting circuit 34 is supplied to a clock control circuit 35. Thus the control is carried out so that the clock pulse delivered from a waveform shaping circuit 33 is not supplied to the counter 30 for a period when the track on a disk moves back, i.e., while the output of the circuit 34 is kept at a high level. Thus the position shift errors can be decreased. |
