| 摘要 |
PURPOSE:To prevent the destruction of a semiconductor laser and to prevent the degradation of S/N by providing a timing circuit which switches a laser driving circuit at a prescribed time after the switching operation of a high frequency superposing circuit. CONSTITUTION:A signal (b) and a signal (e) are generated from a timing circuit 17 and a timing circuit 14 only for prescribed times respectively in accordance with the trailing edge of a sector signal (a) and are generated at a prescribed time after the sector signal (a). A control signal C is generated from a control signal gate circuit 18 in accordance with this generation to stop a high frequency superposing signal (d) and the generation of this signal is started simultaneously with the leading edge of the control signal C and meanwhile, a signal (f) is generated from a write gate circuit 15 to perform recording. By this constitution, the generation of the high frequency is so suppressed that the margin of time for stable oscillation and stop of the high frequency exists on the boundary between high output light emission and low output light emission of a semiconductor laser 9. |
