Patent ID: 7236712

Claim:
An image forming apparatus comprising: a plurality of image forming means for forming color images of mutually different colors on a medium which is moving in a predetermined direction; test image forming means for causing each of said plurality of image forming means to form a test image on said medium; irradiating means for irradiating light to the test image formed on said medium; detecting means for detecting regular reflection light and irregular reflection light of the light irradiated to the test image by said irradiating means; and adjusting means for adjusting, based on detection results of said detecting means, a position of forming a color image on said medium by each of said image forming means so that the color images formed by said respective image forming means are exactly superimposed on each other, wherein said test image forming means causes each of said image forming means to form a color test image composed of a plurality of partial images arranged at predetermined intervals in the moving direction of said medium, at a position on said medium separated from relative positions on said medium where the respective color images are formed by distances according to the respective colors, and said adjusting means includes: partial image distance calculating means for calculating, based on detection results of said detecting means, a partial image distance that is a distance between mutually corresponding partial images in the respective color test images formed on said medium; color image distance calculating means for calculating, based on the calculation result of said partial image distance calculating means, a color image distance that is a distance between the respective color test images formed on said medium; and adjustment amount calculating means for calculating, based on the color image distance calculated by said color image distance calculating means, an adjustment amount for adjusting a position of forming a color image on said medium by each of said image forming means so that the color images formed by said respective color image forming means are exactly superimposed on each other.