| 摘要 |
PURPOSE:To obtain a stable image even when the quantity of charge or the sensitivity of a photosensitive body is changed by measuring a surface potential of a photosensitive body and a image signal pulse width being a cause of image forming so as to control the image forming condition in a laser beam printer. CONSTITUTION:A pulse width control means 30 applies D/A conversion to an input digital binary picture data and compares it with a triangle wave of a prescribed period to convert the input data into a signal subject to pulse width modulation. The signal is supplied to a laser control circuit 46, the photosensitive body 1 is exposed by a semiconductor laser 4 to apply laser beam print. Prior to the exposure, the surface potential of the photosensitive body 1 formed with a latent image by the laser beam having the measured pulse width being a cause to the image forming is measured by an electronic sensor 41 and a potential measuring instrument 42, and the image forming condition such as the laser intensity of the laser 4 and the charging current of the charger 3 is controlled via the laser control circuit 46 and a high voltage control circuit 47 controlled by a control microcomputer 44. Thus, even when the charging quantity and the charge sensitivity of the photosensitive body are changed, a stable image is formed.
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