| 摘要 |
PURPOSE:To pulse an analog signal, by a method wherein, a photoelectric conversion circuit which monitors a part of the output beam from laser diodes and feeds it back to the input side is provided, and an image clock pulse for a printer is level-regulated and added to the output side to be superimposed to a monitor signal. CONSTITUTION:When a clock pulse is superimposed to a monitor signal so that the amplitude of the clock pulse may accord to the maximum value of the monitor signal by a level regulating circuit 61, photoelectric conversion circuits 33, 43 and 53 each output a signal Sb by superimposing a clock pulse clk level-regulated to an Sa signal. The level of the signal Sb obtained by superimposing two signals becomes higher than a power-regulated level. Therefore, the signal Sb is fed back to be compared with the analog signal Sa, thereby lowering its level by an excess amount. As a result, a monitor signal to be received from optical sensors 32, 42 and 52 becomes Sb'. Since the monitor signal Sb' is obtained by monitoring a part of the output beam of laser diodes (LD) 31, 41 and 51, the output beam from the LD also results in a beam applied with a pulsing similarly to the Sb'.
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