| 摘要 |
PURPOSE:To prevent flow of a current which is not controlled, to eliminate an abnormal light emission and to protect a semiconductor laser against deterioration by providing a quasi-signal input circuit and controlling by ON, OFF of first and second switches at a suitable timing. CONSTITUTION:A power source 7 is turned ON in a state that first and second switches 9, 12 are opened at the initial time of turning ON the power source. Then, when a semiconductor laser 1 actually emits a light, the switch 12 remains opened, and the switch 9 is closed. Thus, a voltage gradually raising through a slow-starter 8 is applied to the anode of the laser 1. In this case, the input of a current controller 5 constitutes a quasi-signal input circuit. A GND level signal is applied to a resistance circuit 11 as a quasi-signal reception signal. When the laser 1 is deenergized, the switch 12 is previously opened to set the input of the controller 5 to a quasi-reception signal, and then the switch 9 is opened. Thus, a current which is not controlled does not flow to prevent emission of an abnormal light. |
