| 摘要 |
PURPOSE:To realize a driving device, which is simple and highly reliable and also superior in safety, for a semiconductor laser, by a method wherein a limited signal generating circuit capable of generating continuously a dummy photoelectric signal for a constant time since a point when a power source has been turned-ON is added in between the photo output detector and the current control circuit of the semiconductor laser. CONSTITUTION:Parts 3 of laser lights are incided in a photo output detector 4, the parts 3 are amplified in an amplifier 5 and an optical intensity signal 6 is obtained. A limited signal generating circuit 7 has been provided in between the amplifier 5 and a current control circuit 2. A signal 9 obtained by adding the optical intensity signal 6 to the output voltage 8 of this limited signal generating circuit 7 is compared with an optical intensity set value 10, and after that, the signal 9 is turned into an error signal 11 and the error signal 11 controls the output current of the current control circuit 2. Here, it is assumed that (to) is a non-control time, which is decided by the rise characteristics of the amplifier 5 and so forth, and Vo is an optical intensity set value. Under this condition, when a dummy photoelectric signal of a larger optical intensity value than the Vo is made to generate at least for a longer time than the (to), the output current of the current control circuit 2 dwindles into zero during the time. Accordingly, there is no possibility that a semiconductor laser 1 is broken even for a momentary turning-ON of a power source. |
