| 摘要 |
PURPOSE:To simplify a circuit and to reduce its size and cost by driving each of plural semiconductor lasers by a constant current circuit and a constant output circuit one to one and making the quantity of light by controlling the quantities of light of some of the semiconductor lasers. CONSTITUTION:For example, semiconductor lasers 11, 12, and 13 are driven by the constant current circuit 54 while a driving current is set constant. The remaining semiconductor 14 is driven by the constant output circuit 55. The constant output circuit 55 receives a light quantity signal S4 outputted from a photodetector and controls the laser driving current so that the light quantity signal S4 has a specific value. Further, a control circuit 56 which varies the setting output of the semiconductor laser 14 is connected. On the other hand, a light quantity detector 52 which detects the quantity of the spot S of a composite beam 45 is arranged and its light quantity signal is compared with a reference signal which indicates the specific quantity of the composite laser beam and the laser driving current of the constant output circuit is so varied as to eliminate their deviation.
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