Apparatus for forming superimposed image patterns having controlled

Abstract

The image forming apparatus includes: an image forming portion having a multiple image forming stations each forming a color separated image; a transfer device for superimposing and transferring color separated images; a pattern image forming device for forming a predetermined pattern image; a pattern image density measuring device for measuring the density of the pattern image. In this configuration, the pattern image is formed so as to be greater than the measuring area of the pattern image density measuring device and is formed of multiple lines having a line width and a line spacing so that any part of the pattern image within the measuring area will produce an approximately constant measured density value. The image forming apparatus further includes a timing control device which performs control in such a sequence that one image forming station to be the reference, in the image forming portion, a pattern image; the image forming station to be adjusted forms another pattern image, which is superimposed over the pattern image formed by the reference image forming station; the pattern image density measuring device measures the density of the superimposed pattern image so as to judge the superimposed state of the pattern image based on the measured density; and the image forming station to be adjusted is controlled so as to perform image forming at a timing so that the measured density will fall within a predetermined permissible density range.