| 摘要 |
PROBLEM TO BE SOLVED: To prevent an LD from deteriorating due to excessive emission in the case of monitoring plural LD light with one monitor diode, sampling the monitored voltage for each LD light, and controlling a driving current of each LD. SOLUTION: When a sample hold signal SH1 becomes L, an APC circuit 10-1 becomes to be of a sampling mode, and in this sampling mode, a capacitor C1 is charged or discharged according to an output signal of a comparator 13-1 and a charged potential VM1 is increased or decreased, and a LD driver 15-1 controls light quantity of LD1 to be a predetermined value. Then, when a lighting signal XDATA 2 is made active (L), a select signal SEL 2 is made H after a time T3, and then, an output voltage V1 of a current-to-voltage conversion circuit 12-1 becomes low, and after a time T4, a sample hold signal SH2 is made L.
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