ABNORMALITY DETECTING METHOD FOR SEMICONDUCTOR LASER DEVICE

PURPOSE:To simply determine and set the reference voltage, to be used as the condition for giving a decision for a semiconductor baser diode (LD), based on the characteristics specified in the specification for the semiconductor laser diode by a method wherein a bias current and the reference voltage to be determined as abnormal are compared with each other. CONSTITUTION:The photo output of the LD1 is detected and a stabilized circuit 6, with which the bias current to be supplied to the LD so as to stabilize said photo output will be variably controlled, is provided. The bias current is converted, 1 to voltage and a CMP23, with which the output voltage EX and the reference voltage 22 that was set based on the bias current value at which the LD1 will be determined as abnormal, is provided and the detection of abnormality of the LD1 is conducted based on the results of said comparison of the reference voltage 22 and the CMP23, in other words, the detection of the abnormality of LD1 is performed based on the result wherether or not the actual bias current has become larger than the bias current to be determined as abnormal.