Color image forming apparatus

A color image forming apparatus comprising:

• a plurality of image forming units, each one of said image forming units corresponding to a different color, which form superimposing image of different colors on a recording medium or on an intermediate transfer body;
• a conveyer unit having a conveyer belt which supports the recording medium, conveys the recording medium to the vicinity of each of the image forming units, and dispatches at least one of the recording medium and the intermediate transfer body to outside of said image forming apparatus when the image formation by said image forming units is completed;
• a positional deviation detection mark formation control unit which, when receiving a request, orchestrates said conveyer unit and said image forming units to form a positional deviation detection mark of respective color on either said conveyer belt or said intermediate transfer body;
• an image density regulation mark formation control unit which, when receiving a request, orchestrates said conveyer unit and said image forming units to form an image density regulation mark of respective color on either said conveyer belt or said intermediate transfer body;
• a mark detection unit which detects positions of the positional deviation detection marks or densities of the image regulation marks when the positional deviation detection marks or densities of the image density regulation marks are formed on said conveyer belt or said intermediate transfer body;
• an alignment unit which receives the positions of each of the positional deviation detection marks detected by said mark detection unit, based on the position of a predetermined color calculates a deviation in the positions of the positional deviation detection marks of the other colors, and provides a control so that the positional deviation detection marks of respective colors are formed at specific positions with respect to the positional deviation detection mark of the predetermined color;
• and
• a density regulating unit which receives the densities of the image density regulation marks of different colors detected by said mark detection unit, based on a predetermined density of each color the calculates a deviation in the density of each color, and provides a control so that the image density regulation marks of all the colors having the predetermined densities are formed, wherein when the request for formation of the positional deviation detection marks and the request for the formation of the image density regulation marks is received at the same time or at substantially the same time, said positional deviation detection mark formation control unit and said image density regulation mark formation control unit orchestrate said conveyer unit and said image forming units to form the positional deviation detection marks and the image density regulation marks in continuation.

A color image forming method comprising the steps of:

• forming superimposing image of different colors on a recording medium or on an intermediate transfer body using a plurality of image forming units, each one of said image forming unit corresponding to a different color;
• conveying the recording medium to the vicinity of each of the image forming units using a conveyer belt when forming the image of a respective color;
• forming a positional deviation detection mark of respective color, when receiving a request, using said image forming units, on either said conveyer belt or said intermediate transfer body;
• forming an image density regulation mark of respective color, when receiving a request, using said image forming units, on either said conveyer belt or said intermediate transfer body;
• detecting the positions of the positional deviation detection marks or densities of the image density regulation marks when the positional deviation detection marks or the image density regulation marks are formed on said conveyer belt or said intermediate transfer body;
• calculating, based on the position of a predetermined color, a deviation in the positions of the positional deviation detection marks of the other colors;
• providing a control so that the positional deviation detection marks of respective colors are formed at specific positions with respect to the positional deviation detection mark of the predetermined color;
• calculating, based on a predetermined density of each color, a deviation in the density of each color;
• and
• providing a control so that the image density regulation marks of all the colors having the predetermined densities are formed,
• wherein when the request for formation of the positional deviation detection marks and the request for the formation of the image density regulation marks is received at the same time or at substantially the same time, the steps of formation of the positional deviation detection marks and the image density regulation marks are preformed in continuation.