Patent ID: 9310705
Filing Date: 2016-04-12
CPC Classification: G03G,H04N

Claim Text:
1. A color image forming apparatus, which comprises a plurality of image forming units, corresponding to respective colors, for forming images on an intermediate transfer member or a conveyed printing material, in a tandem system, comprising: a control unit configured to control the plurality of image forming units to form misregistration detection patterns on the intermediate transfer member, the printing material, or a conveyance member which conveys the printing material; a first detection unit and a second detection unit configured to detect the formed misregistration detection patterns, said first detection unit and said second detection unit being arranged to be juxtaposed in a direction perpendicular to a moving direction of the intermediate transfer member or in a direction perpendicular to a conveyance direction of the printing material; a calculation unit configured to calculate misregistration values from detection results of the misregistration detection patterns by said first detection unit and said second detection unit; and a correction unit configured to correct image forming conditions by the plurality of image forming units using the calculated misregistration values, wherein the misregistration detection patterns include: a linear first reference mark and a first detection mark to be detected by said first detection unit; and a linear second reference mark and a second detection mark to be detected by said second detection unit, the linear first reference mark and the linear second reference mark make substantially 90° as an angle with the moving direction of the intermediate transfer member or the conveyance direction of the printing material, an angle the second detection mark makes with the moving direction of the intermediate transfer member or the conveyance direction of the printing material is smaller than the angle made by the linear first reference mark, an angle the first detection mark makes with the moving direction of the intermediate transfer member or the conveyance direction of the printing material is smaller than the angle made by the linear second reference mark, the linear first reference mark and the second detection mark are arranged so that a detection timing of the linear first reference mark by said first detection unit and a detection timing of the second detection mark by said second detection unit are concurrent timings when no misregistration occurs on the intermediate transfer member, the printing material, or the conveyance member, and the linear second reference mark and the first detection mark are arranged so that a detection timing of the first detection mark by said first detection unit and a detection timing of the linear second reference mark by said second detection unit are concurrent timings when no misregistration occurs on the intermediate transfer member, the printing material, or the conveyance member.