| 摘要 |
PURPOSE:To obtain a stable light output from a semiconductor laser by controlling an up/down counter for reproducing power control and an up/down counter for recording and erasing power control according to reproduction, recording and erasure. CONSTITUTION:A circuit is equipped with the semiconductor laser 1, a photodetector 2, a comparator 4, up/down counters 5 and 6 for reproducing power control and recording and erasing power control, digital/analog converters 8 and 10 for reproducing power control and recording and erasing power control, current sources 9 and 11, and a register 12. When reproduction is performed, the counter 6 is turned off to supply a current to the semiconductor laser 1 and when recording is performed, the counter 5 is turned off and the counter 6 is put in operation in none of the recording, reproducing and erasing states to hold its counted value. This counted value is supplied to the digital/analog converter 10 in actual recording, but to the converter 10 in erasure while the counter 5 is turned off and the counter 6 for recording and erasure is put in operation. Consequently, the light output is stably obtained without being affected by temperature. |
