Color image forming apparatus

Abstract

A color image forming apparatus of a so-called tandem type which has image forming units in correspondence with colors is provided. In the color image forming apparatus, a color discrepancy amount storage unit stores information of a color discrepancy amount of each of the image forming units, which is measured in advance. A first color discrepancy correcting unit performs color discrepancy correction in a pixel unit by performing coordinate conversion of bitmap data to be printed based on the information of the color discrepancy amount stored in the color discrepancy amount storage unit. A second color discrepancy correcting unit performs color discrepancy correction in less than a pixel unit by performing tone correction of the bitmap data corrected by the first color discrepancy correcting unit based on the information of the color discrepancy amount stored in the color discrepancy amount storage unit.

Description

technical field [0001] The present invention relates to a color image forming apparatus, and more particularly to an electrophotographic color image forming apparatus. Background technique [0002] An electrophotographic color image forming apparatus is known. It forms an image in the following way: a photoreceptor is developed in various colors with multiple developers, and the image of each color is superimposed on a transfer material through repeated exposure-development-transfer process. A color image is formed and fixed to obtain a full-color image. [0003] However, this method has the disadvantage that in order to obtain one printed image, the image forming process needs to be repeated three times (four times in the case of using black), and it takes a lot of time to form an image. [0004] As a method to overcome this disadvantage, there is a so-called tandem method in which a plurality of photoreceptors are used, and images obtained for each color are sequentially...

AI Technical Summary

Problems solved by technology

But on the other hand, there is also such a problem: due to the deviation of the position accuracy or diameter of each photoreceptor, the position accuracy deviation of the optical system, etc., the color registration deviation caused by the position deviation of each color on the transfer material occurs, Difficulty obtaining high-quality full-color images

[0007] However, with the method disclosed in Patent Document 1, problems such as the following arise

[0008] First, in order to correct the optical path of the optical system, it is necessary to mechanically operate the correcting optical system including the light source, the f-θ lens, the reflection mirror in the optical path, etc., to keep the position of the toner image consistent with the test. For this reason, it is necessary to High-precision moving parts, resulting in increased costs

Furthermore, it takes a lot of time until the calibration is completed, so frequent calibration cannot be performed, and sometimes the deviation of the optical path length changes with time due to mechanical temperature rise. In this case, it is very difficult to prevent color registration deviation by correcting the optical path of the optical system.

Second, when correcting the writing start position of the image, the position deviation of the left end and the upper left can be corrected, but the tilt of the optical system and the magnification deviation caused by the deviation of the optical path length cannot be corrected

Therefore, there is a problem that the amount of calculation increases and the configuration of the processing system becomes complicated.

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