# US 8,520,260 B2 · Image forming apparatus and image forming method for correcting registration deviation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,520,260 B2 - Document ID: US8520260B2 - Status: Granted - Kind: B2 - Application number: 12/938,169 - Filed: 2010-11-02 - Published: 2011-05-19 - Granted: 2013-08-27 - Earliest claimed: 2009-11-13 - Assignees: Canon Kabushiki Kaisha - Applicants: Hirokazu Tamura - Inventors: Hirokazu Tamura - Web page: https://patentgrep.com/patent/US8520260B2 ## CPC - G03G 15/50: {Machine control of apparatus for electrographic processes using a charge pattern, e.g. regulating differents parts of the machine, multimode copiers, microprocessor control (sequencing control G03G21/14)} - H04N 1/40037: {the reproducing element being a laser} - H04N 1/4015: {of the reproducing head} - H04N 1/4055: {producing a clustered dots or a size modulated halftone pattern} - H04N 2201/0082: Image hardcopy reproducer (H04N2201/0091 - H04N2201/0094 take precedence) - H04N 2201/03162: Original guide plate - H04N 2201/04787: by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation - H04N 2201/04789: in the main-scan direction - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract There exists a problem that, for registration correction, carrying out less-than-one-pixel-basis correction and one-pixel-basis correction for an image after half toning using screen processing causes unevenness in density when it is hard for linearity of image density against a PWM to come out. Processing of interpolation is carried out so that the way how a halfdot is formed may always becomes the same after the interpolation processing. By applying a matrix in consideration of a dot direction which may be broken by the interpolation processing at the time of the screen processing, conversion in which a way of locating the half dot maintains relation of vertical inversion in a subscanning direction is carried out, and less-than-one-pixel-basis correction is carried out. ## Claims ### Claim 1 An image forming apparatus comprising: an interpolation processing component configured to carry out less-than-one-pixel-basis correction of image data by correcting density of each pixel of the image data so that, with respect to a change point that defines a location where one-pixel-basis correction is carried out for the image data, a sequence of pulse width according to the density of the pixel in a subscanning direction comes into an inverted relationship before and after the change point , wherein a sequence pattern of pulse width having the inverted relationship is limited to a two-sequence pattern; and an image forming component configured to form an image based on a signal acquired by carrying out a pulse width modulation according to the corrected density of the image data. ### Claim 2 (depends on 1) The image forming apparatus according to claim 1 further comprising a half toning component configured to convert inputted image data of M-value into the image data of N-value (M>N) using a dither method, and output the converted image data to the interpolation processing component. ### Claim 3 (depends on 2) The image forming apparatus according to claim 2 wherein the half toning component uses the dither method in which order of lighting of dots lights up in a vertical symmetry in the subscanning direction. ### Claim 4 (depends on 2) The image forming apparatus according to claim 2, wherein the half toning component converts inputted image data of M-value into the image data having high resolution at least in the subscanning direction, and converts the converted image data into the image data of N-value using the dither method, and the interpolation processing component carries out the less-than-one-pixel-basis correction by carrying out conversion into the image data having lower resolution than the high resolution by shifting a phase. ### Claim 5 (depends on 3) The image forming apparatus according to claim 3, wherein the half toning component converts inputted image data of M-value into the image data having high resolution at least in the subscanning direction, and converts the converted image data into the image data of N-value using the dither method, and the interpolation processing component carries out the less-than-one-pixel-basis correction by carrying out conversion into the image data having lower resolution than the high resolution by shifting a phase. ### Claim 6 (depends on 2) The image forming apparatus according to claim 2, wherein the half toning component further outputs a flag indicating a deviation amount related to the image data in the subscanning direction to the interpolation processing component, and the interpolation processing component carries out the less-than-one-pixel-basis correction by converting the image data based on the flag. ### Claim 7 (depends on 3) The image forming apparatus according to claim 3, wherein the half toning component further outputs a flag indicating a deviation amount related to the image data in the subscanning direction to the interpolation processing component, and the interpolation processing component carries out the less-than-one-pixel-basis correction by converting the image data based on the flag. ### Claim 8 An image forming method, comprising the steps of: carrying out interpolation processing of less-than-one-pixel-basis correction of image data by correcting density of each pixel of the image data so that, with respect to a change point that defines a location where one-pixel-basis correction is carried out for the image data, a sequence of pulse width according to the density of the pixel in a subscanning direction comes into inverted relationship before and after the change point, wherein a sequence pattern of pulse width having the inverted relationship is limited to a two-sequence pattern; and carrying out image formation of forming an image based on a signal acquired by carrying out a pulse width modulation according to the corrected density of the image data. ### Claim 9 A non-transitory computer-readable recording medium with a program making a computer execute an image forming method recorded therein, the image forming method comprising the steps of: carrying out interpolation processing of less-than-one-pixel-basis correction of image data by correcting density of each pixel of the image data so that, with respect to a change point that defines a location where one-pixel-basis correction is carried out for the image data, a sequence of pulse width according to the density of the pixel in a subscanning direction comes into inverted relationship before and after the change point, wherein a sequence pattern of pulse width having the inverted relationship is limited to a two-sequence pattern; and carrying out image formation of forming an image based on a signal acquired by carrying out a pulse width modulation according to the corrected density of the image data.