| 摘要 |
PURPOSE:To always set the recording light output of a semiconductor laser to an optimum value by detecting the light emission level of the semiconductor laser due to a synchronizing signal and using the detection output as the next control voltage to control a recording signal current value. CONSTITUTION:If the characteristic of a semiconductor laser LD 1 is changed in accordance with the secular degradation of the external differential quantum efficiency of the LD 1 or the like at the time of recording operation, the detection output of the light emission level due to the synchronizing signal pattern at the time of recording operation is compared with a reference voltage ref2 by an error amplifier 13, and the comparison result is outputted to a holding amplifier 14. The control voltage of the output of the error amplifier 13 is held in the holding amplifier 14 and is superposed on the reproduced light output to set the recording signal current valve of a driving amplifier 15 which drives the recording signal current, thus obtaining an optimum recording light output. |
