| 摘要 |
PURPOSE:To enable a comparator to perform high speed control and correct errors because of noises as well by making the comparator cetect a repetition of fine variations at a set point of a constant current with an integrating circuit, thereby confirming according to the designated calculation that the above set point comes to a prescribed level. CONSTITUTION:Once a flip-flop circuit 8 is set with the fall of a signal c and signal d comes to a level H after completing a printing of one line, an integrating circuit 12 starts integrating output signals of a comparator 10. At the same time, its circuit causes a laser diode 2 to be driven continuously with a setting current of a constant current circuit 4 without regard to a video signal e. A photodiode 3 detects a light output of the laser diode 2 and; for example, a light output level signal f rises. When the light output level signal f exceeds a reference level Vr, the comparator 10 exhibits the level H and a counter 11 calculates its rise. While at the integrating circuit 12 its integrating value increases, an output of the laser diode 2 decreases and as a result, the light output level signal f is converted to decrese in number. Repetition of these procedures permits the light output of the laser diode 2 to have a constant temperature of the laser diode with the fluctuation of the light output level f that is centered in the reference level Vr. |
