| 摘要 |
PROBLEM TO BE SOLVED: To prevent an improper warning from being issued when a synchronization detection abnormality signal is generated with the trouble of a light emitting device. SOLUTION: When a synchronization detection signal is not obtained from a synchronization detection sensor 7a, a pseudo synchronization detection signal from a pseudo synchronization detection signal generation circuit 14 is selected to drive an LD. The value of a current flowing in the LD or the value of a current flowing in a PD detecting the light quantity of the LD is measured and the warning on the synchronization detection abnormality is issued based on the value of current.
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