PROBLEM TO BE SOLVED: To enable an impairment in a semiconductor laser to be accurately detected independently of a variation in its ambient temperature.;SOLUTION: A laser impairment detection device is equipped with a light volume stabilizing unit which obtains signals corresponding to the light volume of a laser 51 through a light receiving element 71, and performs feedback control on the drive current of the laser 51 on the basis of the signals so as to make the received light volume identical to a target value. Moreover, the laser impairment detection device is equipped with an impairment detecting unit which detects an impairment in the laser 51 comparing a monitoring value corresponding to the drive current of the laser 51 with an impairment judging threshold value, a temperature detecting means for detecting the ambient temperature of the laser 51, and an impairment judging threshold value setting unit which sets up an impairment judging threshold value used by the impairment detecting unit corresponding to the detected temperature detected by the temperature detecting means. The laser impairment detecting device is capable of accurately detecting an impairment in the laser 51 independently of a variation in the drive current of the laser 51 due to a change in its ambient temperature. Furthermore, maintenance operations can be quickly performed.;COPYRIGHT: (C)2007,JPO&INPIT
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