| 摘要 |
PROBLEM TO BE SOLVED: To enhance productivity of a system while eliminating variation in the state evaluation of a laser diode by making possible to self-diagnose deterioration and breakdown state of the laser diode in the system. SOLUTION: An LD modulating section 19 detects the level of a current flowing through a laser diode unit 20, a voltage level at the LD modulating section 19 correlated with the detected current level is compared with a preset reference voltage, and an error signal is outputted when the reference voltage is exceeded. An output selecting section 210 compares the duration of an error signal outputted from the LD modulating section 19 with a preset reference time and outputs a signal notifying abnormality of the laser diode when the reference time is exceeded.
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