| 摘要 |
PURPOSE:To reduce the sticking area of one isolated dot and to improve the picture quality of a laser printer which performs positive/negative development by detecting one isolated dot signal of an image signal and switching it to a dot signal of constant time. CONSTITUTION:When a dot signal from a shift register SR 2 is isolated, an output signal is outputted from a shift register SR 4 to close an AND gate G2 and a monostable multivibrator M/M operates to output a dot signal through an OR circuit OR. The time of the dot signal is set to a constant time shorter than the period of clock pulses CLK so that the toner sticking area of the isolated dot on a photosensitive body is optimized to a small value. Therefore, an unisolated dot signal is delayed by two periods of clock pulses CLK and outputted from an OR circuit as it is as an image signal DATA, and the isolated dot signal is switched to a dot signal shorter than the period of clock pulses CLK, delayed by two periods of clock pulses CLK, and outputted from the OR circuit OR.
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