| 摘要 |
PURPOSE:To effectively prevent a semiconductor laser from damaging owing to a runaway even if a monitoring light is interrupted, by controlling the output of the laser based on a front light monitor according to the control characteristics determined by the monitor of the rear light output before switching to always maintain the output constant even if the monitor light of the front light is varied. CONSTITUTION:A light 3 from the prism 21 of the front light 16 of a semiconductor laser 15 is received by the second photodetector 1, converted by a resistor R1 to a voltage signal, and he rear light 4 of the laser 15 is received by the first photodetector 2. The detecting voltage of the light 4 generated at a resistor R2 is applied to the (-) input of an operational amplifier 11, and a reference power 12 for setting the lower output is connected with the (+) input of the amplifier 11. The output of the amplifier 11 is connected with the base of a transistor 13 to form a feedback control loop by the monitor of the light 4. The output of the resistor R1 for generating the detecting voltage of the light 3 is applied to an operational amplifier 5. The amplifier 5 forms an AGC circuit with an FET 6 and a resistor R provided in the feedback circuit. |
