| 摘要 |
PURPOSE:To perform optimum control over the light and shade of a copy image easily and excellently according to an original surface by performing the control according to light and shade judgement results based upon reflected light detection outputs of an original image in a prescribed area and its preceding and following areas which are divided from the front end. CONSTITUTION:The reflected light detection output of a photodiode 1 for the original image is applied to a microcomputer 7 to make light and shade judgement by interruption, and the DC component of a development bias voltage passed through a high- voltage transformer 8 is controlled to adjust the light and shade of the copy image. The interruption of the computer 7 is controlled by an operational amplifier 11, transistor 12, etc., which detects the zero crossing of an AC power source 9. Then, the computer 7 judges the light and shade of the original in each area obtained by dividing the time from when reflected light from the front end of the original is detected to when the front end of the image appears on specific basis, and judgement results of an area before or after the divided area is added to obtain a light and shade judgement result. Thus, the optimum control over the copy image corresponding to the original surface is carried out with good reproducibility for a low-density character original and without fogging, etc., for a high-density character original. |
