| 摘要 |
PURPOSE:To prevent the erroneous detection of a peak value in a pulse waveform and to execute the abnormal detection with high reliability by generating a comparing voltage with using a reference voltage value to execute power setting at the time of DC light emission and pulse modulation, latching a comparing output in timing when optical power control is stabilized and executing the abnormal detection. CONSTITUTION:In a DC light emitting mode, an optical power control part 4 drives a current source 8 in correspondence to a reference voltage VR3 which executes the power setting to a third optical power value and controls the optical power value of a semiconductor laser 1. In a pulse modulating mode optical power is controlled according to a first reference voltage VR1 which sets the optical power value of the peak value in the optical pulse waveform and a second reference voltage VR2 which sets the optical power value of a bottom value. The peak power value of the pulse modulating mode is detected by peak power light emission check timing 30, in which the transient response time of peak power control lapses and the peak power value is stabilized, in the rear half part of a peak power sample control block 28. Thus, even in the DC light emitting mode and pulse modulating mode, a normal light emitting level or an abnormal light emitting level can be exactly detected. |
