| 摘要 |
PURPOSE:To control light pulse intensity stably and to perform optical information recording of high quality by controlling the quantity of laser light through an up/down counter according to the monitor output of a laser pulse is lower or higher than two different prescribed levels. CONSTITUTION:Some of laser pulses from a semiconductor laser 10 are detected by a photodetector 14 and applied to the 1st comparator 23 and a comparator 24 having a higher comparison reference voltage than the comparator 23. When the photodetection output is lower than the reference voltage of the comparator 23, an FF25 is not set and a counter 27 counts up; when the photodetection output exceeds the reference value of the comparator 24, an FF26 is set and the counter 27 counts down. Then, the count contents of the counter 27 are D/A-converted to control the laser 10 through the current control circuit 22 of a modulation driving circuit 21, etc., and the quantity of laser pulse light is controlled to specified intensity without disturbance such as temperature fluctuations, etc. performing optical information recording of high quality. |
