| 摘要 |
PURPOSE:To stably hold two light quantity independently of a temperature change by controlling with a current the light quantity of a semiconductor laser with a laser driving circuit having two kinds of respective independent feed back loops. CONSTITUTION:The output signal of a level holding circuit 7a is compared with a reference voltage 9a by a comparator circuit 8a to output a difference voltage. This output constitutes a loop so as to pass through only a low band component by a low-pass filter 10a and controls a driving current sent from a driving current source 4a, and keeps the light quantity Pa constant. The output signal of the level holding circuit 7b is compared with the reference voltage 9b by the comparator circuit 8b to output the difference voltage. This output constitutes the feedback loop passing through only the low band component by the low-pass filter 10b and controls the driving current sent from the driving current source 4b, and keep the light quantity Pb of the semiconductor laser 1 constant. |
