Patent ID: 6346958
Filing Date: 2002-02-12
Classification: B41J,H04N

Abstract:
In a laser color image forming method for developing a latent image formed on an electrophotographic photosensitive belt by laser scanning having a fixed scanning frequency and a pixel forming clock frequency within one scanning by toner absorption, and then transferring the developed image to a printing medium, that is, a paper sheet, and in a method using a plurality of laser beams and a plurality of toner colors,a method for detecting the quantity of a laser scanning positional deviation on said photosensitive belt, comprising the steps of: setting a plurality of zonal patterns formed by toner development on said photosensitive belt for optional one among a plurality of colors and arrayed on a fixed cycle as image patterns for detection of a printing positional deviation of a reference color, setting image patterns having shapes similar to those of said image patterns for the detection of the printing positional deviation of the reference color and designed for the detection of the printing positional deviation of other colors as image patterns for the detection of the printing positional deviation of a color to be measured, spatially shifting the image patterns for the detection of the printing positional deviation of the color to be measured from said image patterns for the detection of the printing positional deviation of the reference color, and varying said quantity of spatial shifting for each of said plurality of the image patterns for the detection of the printing positional deviation of the reference color, thus forming the image patterns in a superposed state on said photosensitive belt; measuring reflection densities of the plurality of the image patterns formed in the superposed state for the detection of the printing positional deviation; detecting a group having said minimum reflection densities among the plurality of said image patterns formed in the superposed state for the detection of the printing positional deviation; and detecting the quantity of the deviation between a laser scanning position of the reference color and a laser scanning position of the color to be measured based on the quantity of shifting given when the detected group of the image patterns for the detection of the printing positional deviation is formed by being superposed on the color to be measured.