JPS5589859A - Method and apparatus for forming stable image - Google Patents

Abstract

PURPOSE:To reduce the time for stabilization of copied images by detecting the potential differences of the bright and dark latent images through uniform light radiation of plural stepwise quantities of light and determining a uniform light quantity change-bright-dark potential contrast curve thereby controlling image stabilization. CONSTITUTION:For example, when the latent images of black and white paper corresponding to the brightness and darkness of the original images provided at the leading end part of an original platen 30 are formed on a photosensitive drum 1, the uniform light quantity from a lamp 13 for uniform light is changed to plural steps by a bias power source 15 beforehand so as to be able to cope with environment fluctuations, photoreceptor degradation, etc. and the poetential differences of the bright and dark latent images formed on the drum 1 are detected with a probe 6. If these are processed with a potentiometer 16, arithmetic part 20, etc., the relation of the potential contrast Vc and uniform light quantity change x corresponding to the potential differences of the bright and dark latent images based on formula (Vc=ax<2>+bx+c) is determiened in a short time. Hence, the light quantity change is controlled according to the potential differences of the bright and dark contrasts of the images deteted by the probe 6, whereby the image contrast is stabilized. Because of this, the initial control is completed while the photosensitive drum makes 1 turn.