Color image forming apparatus

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 misregistration detection patterns formed on the intermediate transfer member, the printing material, or the conveyance member which conveys the printing material, 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 from the calculated misregistration values,
• wherein the misregistration detection patterns include:
• a linear first reference mark, a first detection mark, and a linear third reference mark to be detected by said first detection unit;
• and
• a linear second reference mark, a second detection mark, and a third detection mark to be detected by said second detection unit,
• the linear first reference mark, the second reference mark, and the linear third 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,
• an angle the third detection mark makes with the moving direction of the intermediate transfer member or the conveyance direction of the printing material has a sign different from the angle the second detection mark makes with the moving direction of the intermediate transfer member or the conveyance direction of the printing material,
• 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,
• 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, and
• the linear third reference mark and the third detection mark are arranged so that a detection timing of the linear third reference mark by said first detection unit and a detection timing of the third 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.

A color image forming apparatus comprising:

• an image forming unit configured to form misregistration detection patterns;
• a transfer member on which the misregistration detection patterns are transferred;
• a first detection unit and a second detection unit arranged to be juxtaposed in a direction perpendicular to a moving direction of said transfer member;
• and
• a control unit configured to control an image forming condition by said image forming unit based on a result of detecting the misregistration detection patterns,
• 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, the linear second reference mark, the first detection mark and the second detection mark are formed with toner of the same color, and are marks for detecting misregistration in a main-scanning direction, and
• said first detection unit detects the linear first reference mark and then detects the first detection mark subsequent to the linear first reference mark, and said second detection unit detects the second detection mark and then detects the linear second reference mark subsequent to the second detection mark.

A color image forming apparatus, comprising:

• an image forming unit that forms a misregistration detection pattern;
• a transfer member to which the misregistration detection pattern is transferred;
• a detector that detects the misregistration detection pattern;
• and
• a controller that controls a condition for image forming by said image forming unit according to a result of detecting the misregistration detection pattern,
• wherein the misregistration detection pattern includes a linear reference mark and a detection mark, the linear reference mark and the detection mark, which are formed with toner of the same color, are marks for detecting misregistration in a main-scanning direction, and
• wherein in view of a direction perpendicular to a moving direction of said transfer member and a direction along a surface of said transfer member, at least a portion of each of the linear reference mark and the detection mark are overlapped.

A color image forming apparatus, comprising:

• an image forming unit that forms a misregistration detection pattern;
• a transfer member to which the misregistration detection pattern is transferred;
• a detector that detects the misregistration detection pattern;
• and
• a controller that controls a condition for image forming by said image forming unit according to a result of detecting the misregistration detection pattern,
• wherein said controller causes said image forming unit to form a misregistration detection pattern for a sub-scanning direction in a case of detecting a misregistration value in the sub-scanning direction, and said controller causes said image forming unit to form a misregistration detection pattern for a main-scanning direction in a case of detecting a misregistration value in the main-scanning direction, and
• wherein the misregistration detection pattern for the main-scanning direction is formed after the transfer member is rotated one or more revolutions after starting of forming the misregistration detection pattern for the sub-scanning direction, or the misregistration detection pattern for the sub-scanning direction is formed after the transfer member is rotated one or more revolutions after starting of forming the misregistration direction pattern for the main-scanning direction.

A color image forming apparatus comprising:

• an image forming unit configured to form misregistration detection patterns;
• a transfer member on which the misregistration detection patterns are transferred;
• a first detection unit and a second detection unit arranged to be juxtaposed in a direction perpendicular to a moving direction of said transfer member;
• and
• a control unit configured to control an image forming condition by said image forming unit based on a result of detecting the misregistration detection patterns,
• wherein the misregistration detection patterns include a first mark and a second mark to be detected by said first detection unit, and a third mark and a fourth mark to be detected by said second detection unit,
• wherein the first mark, the second mark, the third mark, and the fourth mark are formed with toner of the same color, and are marks for detecting misregistration in a main-scanning direction,
• wherein in view of the direction perpendicular to the moving direction of said transfer member and the direction along a surface of said transfer member, at least a portion of each of the first mark and the third mark are overlapped and at least a portion of each of the second mark and the fourth mark are overlapped, and
• wherein the third mark is slanted with respect to the first mark, and the second mark is slanted with respect to the first mark and the fourth mark.