| 摘要 |
PURPOSE:To improve a semiconductor laser in safety and to prevent it from excessively emitting light by a method wherein an abnormality signal is outputted and sent to a host system or a subordinate system when troubles occur in an automatic light quantity control mechanism to induce an over light emission. CONSTITUTION:When a laser diode excessively emits laser light due to the malfunction of an automatic light quantity control mechanism, the voltage of the monitored signal is made to increase in level exceeding an upper voltage limit, an inverted signal appearing at the output terminal of a comparator 33 is made to turn high in level, a flip-flop is inverted, and an abnormality signal LDOVER is made to turn high in level. In result, the change of the abnormality signal in level is transmitted to the outside, and when the abnormality signal LDOVER is made to change from a low level to a high level, an AND gate 24 is forcedly closed and an analog switch is put in an ON-state independent of a lighting signal LDON, the automatic light quantity mechanism stops operating, and a laser diode 1a is forcedly turned off. |
