| 摘要 |
PURPOSE:To retrieve a track stably in a high speed, by processing outputs of two light receiving parts, whoch are arranged in parallel with the tangential direction of a groove-shaped guide track, to count an accurate number of traversed tracks. CONSTITUTION:Outputs of two photodetectors 13a and 13b arranged in parallel with the tangential direction of a groove-shaped guide rack of an optical disc are applied to pre-differential amplifiers 19, 26, and 28, and difference signals are inputted to an OR circuit and monostable multivibrators 44 through low pass filtes 40 and waveform shaping circuit 41. Outputs from the OR circuit and monostable multivibrators 44 are inputted to a flip flop 100 through AND circuits 45, and a processed output is inputted to a counter 46. The output of the counter 46 indicates a number of traversed tracks. When it is detected by a comparator 48 that this counted value coincides with the set value of a traversed track number set register 47, the operation of a linear motor driving control circuit 49 is stopped. |
