PURPOSE: To stabilize print starting positions for every scanning by executing a feed-back control so that the rising of the output voltage of a radiation detector is stabilized even when the irradiating quantity to the radiation detector is lowered in an electrophotographic printing device provided with the radiation detector for determining scanning starting positions at the time of scanning a modulated light on a photosensitive drum.
CONSTITUTION: A waveform shaping circuit 110 for transmitting a print starting position signal to a controller and an A/D converter 102 for monitoring the output voltage of a radiation detector 101 are connected to the anode side of the radiation detector 101. Data monitored by the A/D converter 102 are outputted to a microprocessor 108. Besides, a D/A converter 103 and a current- voltage conversion circuit 109 is connected to the cathode side of the radiation detector 101 as a reverse bias generating circuit and the D/A converter 103 is controlled by the microprocessor 108.
YOKOGAWA HIDEHO
AIDA SATOSHI
NEMOTO SHIGEO
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