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US 6,295,435 B1Granted
Image forming apparatus which corrects deviations between images of different colors
AssigneeRicoh Company, Ltd.
InventorsTadashi Shinohara, Kiyoshi Ohshima, Yasushi Nakazato, Mitsugu Sugiyama
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Abstract
An image forming apparatus, particularly a color image forming apparatus, of the present invention distinguishes a register mark and the background of a conveying member on the basis of the level of a signal representative of the background and the peak value or the bottom value of the signal. The apparatus can therefore accurately detect deviation between images of different colors and correct it.
Claims18
A color image forming apparatus comprising:
- a conveying member for conveying a recording medium in a preselected direction;
- a plurality of image forming sections arranged side by side along said conveying member, each image forming section forming a toner image of a particular color by an electrophotographic process;
- a plurality of image transfer units respectively assigned to said plurality of image forming sections for sequentially transferring toner images to the recording medium one upon another;
- mark forming means for causing said plurality of image forming sections to form respective register marks with toner and transferring said register marks to the recording medium, whereby deviations in a position of said register marks allows deviations of the toner images on said recording medium to be detected;
- mark sensing means for sensing the position of the register marks;
- correcting means for correcting the deviations of the toner images on said recording medium on the basis of a signal output from said mark sensing means, including,
- mark identifying means for specifying from said signal output from said mark sensing means a background level Vs of said conveying member, and determining a point on said signal in excess of a first level Vs+α or Vs−α, where α denotes a preselected value, having a peak or a bottom value Vp, respectively, within a preselected section of said signal where a part of the register marks has been sensed,
- center identifying means for determining a first pair of points coinciding with a second level (Vp−(Vs+α))×β or (Vp−(Vs−α))×β, where β denotes a preselected ratio, said second level lying between the peak or the bottom value Vp and the first level Vs+α or Vs−α, executing smoothing of said signal to produce a smoothed signal about the first pair of points or about points in proximity to said first pair points, redetermining using the smoothed signal a second pair of points at said second level (Vp−(Vs+α))×β or (Vp−(Vs−α))×β, or a third pair of points in proximity to said second pair of points, and determining a center point between said second or third pair of points to be a center position of one of the register marks,
- deviation calculation means for calculating the deviation of the register marks based on said center position, and
- write control means for adjusting a timing of a transfer of the toner image in such a manner as to correct for said deviation.
7 more elements
A color image forming apparatus comprising:
- a conveying member configured to convey a recording medium in a preselected direction;
- a plurality of image forming sections arranged side by side along said conveying member, each image forming section configured to form a toner image of a particular color by an electrophotographic process;
- a plurality of image transfer units respectively assigned to said plurality of image forming sections and configured to sequentially transfer toner images to the recording medium one upon another;
- a mark forming device configured to cause said plurality of image forming sections to form respective register marks with toner and to transfer said register marks to the recording medium, said register marks allowing deviations of the toner images on said recording medium to be detected;
- a mark sensor configured to sense the register marks;
- a correcting device configured to correct the deviations of the toner images on said recording medium on the basis of a signal output from said mark sensor, including,
- a mark identifying device configured to specify from said signal output from said mark sensor a background level Vs of said conveying member, and to determine a point on said signal in excess of a value Vs+α or Vs−α, where α denotes a preselected value, having a peak or a bottom value Vp, respectively, within a preselected section of said signal where a part of the register marks has been sensed,
- a center identifying device configured to determine a first pair of points coinciding with a second level (Vp−(Vs+α))×β or (Vp−(Vs−α))×β, where β denotes a preselected ratio, said second level lying between the peak or the bottom value Vp and the first level Vs+α or Vs−α, to execute smoothing of said signal to produce a smoothed signal about the first pair of points or about points in proximity to said first pair points, to redetermine using the smoothed signal a second pair of points at said second level (Vp−(Vs+α))×β or (Vp−(Vs−α))×β, or a third pair of points in proximity to said second pair of points, and to determine a center point between said second or third pair of points to be a center position of one of the register marks,
- a deviation calculation device to calculate the deviation of the register marks based on said center position, and
- a write control device configured to adjust a timing of a transfer of the toner image in such a manner as to correct for said deviation.
7 more elements
Dependencies are inferred from the claim text.