| 摘要 |
PURPOSE:To prevent abnormal operation from occurring by a method wherein an abnormality is detected when it occurs so as to output an emergency signal comparing the monitored signal with a reference signal when the monitored signal varies much as compared with a reference signal. CONSTITUTION:When an abnormality occurs in a laser diode 1a, a photodiode 1b, or an automatic light quantity control mechanism, the voltage of a monitored signal decreases sharply or gradually in level, and a state signal LDREADY is made to turn from a low level to a high level again due to the action of a comparator 25 when the monitored signal becomes lower than the reference voltage. The change of the state signal LDREADY in level is transmitted to the set terminal S of an RS flip-flop 31 through an opened AND gate 30, and an output signal which appears at an output terminal Q is outputted as an abnormality signal LDNG. This abnormality signal informs that an abnormality occurs in a host system or a peripheral equipment and is inputted into the inversion input terminal of an AND gate 24 which constitutes a forced stop circuit, an analog switch 7 becomes electrically conductive, a control circuit and a power circuit are made to stop operating, and the laser diode 1a is forcedly turned off. |
