| 摘要 |
PURPOSE:To allow the simplification and the low cost of a circuit, by inserting a light-resistance conversion element in series with a semiconductor laser and controlling the resistance according to the output of the semiconductor laser. CONSTITUTION:The light-resistance conversion element 13 constituted of CdS, etc. is inserted in series with the semiconductor laser 11 and connected to a DC source. The output of the semiconductor laser 11 when a transistor 12 is on is detected by a light detecter 14, and the maximum value of the signal voltage thereof is held by a peak hold circuit 15. The output voltage of the circuit 15 is compared with the reference voltage in an error amplifier 16, drive circuit 17 drives a LED 18 by the difference voltage, and accordingly the light is irradiated from the LED 18 onto the element 13. The luminous amount of the LED 18 is varied with the output voltage of the amplifier 16, the resistance of the element 13 is varied with the luminous amount thereof: low when the luminous amount is large and high when it is small. Therefore, the maximum output of the laser 11 is controlled by the value corresponding to the reference voltage. |
