# US 5,949,922 A · Image reading apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,949,922 A - Document ID: US5949922A - Status: Granted - Kind: A - Application number: 08/948,084 - Filed: 1997-10-09 - Granted: 1999-09-07 - Earliest claimed: 1996-10-14 - Assignees: Ricoh Company, Ltd. - Inventors: Shinichiro Wada; Koichi Noguchi; Masayoshi Watanuki - Web page: https://patentgrep.com/patent/US5949922A ## CPC - H04N 1/047: Detection, control or error compensation of scanning velocity or position ({H04N1/0402 and } H04N1/17 take precedence) - G06V 10/245: {by locating a pattern; Special marks for positioning} - H04N 1/1013: {with sub-scanning by translatory movement of at least a part of the main-scanning components (H04N1/107 takes precedence)} - H04N 1/193: using electrically scanned linear arrays {, e.g. linear CCD arrays} - H04N 2201/02425: Self-adjusting arrangements, e.g. compensating for temperature fluctuations - H04N 2201/02439: Positioning method - H04N 2201/03162: Original guide plate - H04N 2201/04708: which remain outside the scanned image area - H04N 2201/0472: on or adjacent the sheet support - H04N 2201/04729: in the main-scan direction - H04N 2201/04731: in the sub-scan direction - H04N 2201/04734: Detecting at frequent intervals, e.g. once per line for sub-scan control - H04N 2201/04749: Detecting position relative to a gradient, e.g. using triangular-shaped masks, marks or gratings - 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 - H04N 2201/04791: in the sub-scan direction - H04N 2201/04794: Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING ## Abstract First and second patterns are located outside of an image reading area. A first pattern comprises a plurality of lines each extending at a fixed angle with respect to a sub-scan direction. A second pattern comprises a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction. An image reading portion reads the first and second patterns. A position error measuring portion measures first and second image reading position errors corresponding to different angle oblique lines of the first and second patterns of image data obtained as a result of reading the first and second patterns, respectively. The position error measuring portion compensates for position deviations of the first and second patterns using the first and second image reading position errors, and obtains position-deviation-compensated image reading position errors. A position error correcting portion corrects image data read by the reading means using the position-deviation-compensated image reading position errors. ## Claims ### Claim 1 An image reading apparatus which reads an original image by scanning said original image, main scan line by main scan line, with a fixed time interval, said apparatus comprising: first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a sub-scan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction; reading means for reading said first and second patterns; measuring means for measuring first and second image reading position errors corresponding to different angle oblique lines of said first and second patterns of image data obtained as a result of reading said first and second patterns, respectively; compensating means for compensating for position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-compensated image reading position errors; and correction means for correcting image data read by said reading means using said position-deviation-compensated image reading position errors. ### Claim 2 (depends on 1) The image reading apparatus according to claim 1, further comprising: means for obtaining said first image reading position errors from said first pattern; means for obtaining said second image reading position errors from said second pattern; means for obtaining a difference between said first and second image reading position errors; and means for storing said difference between said first and second image reading position errors; wherein, in ordinary image reading, one of said first and second patterns is used for measuring the image reading position errors, and, based on said difference between said first and second image reading position errors which was stored in said storing means, position deviation of said first and second patterns is compensated for. ### Claim 3 (depends on 1) The image reading apparatus according to claim 1, further comprising: means for obtaining said first image reading position errors from said first pattern; means for obtaining said second image reading position errors from said second pattern; means for setting a window at a position so that said window includes a first pattern portion on a bit-map of image data obtained from reading said first pattern, when image reading position error measurement is started from said first pattern; means for moving said window by an integer number of pixels in sequence along said first pattern portion so as to newly set said window; means for newly setting said window at a position so that said window includes a second pattern portion on the bit-map of image data obtained from reading said second pattern, as a result of moving said window in a main scan direction when said window has reached a predetermined position; means for calculating the position of the pattern portion in said window each time when said window is newly set; and means for obtaining said first and second image reading position errors by calculating a change of the position of the pattern portion in said window through each movement of said window. ### Claim 4 (depends on 1) The image reading apparatus according to claim 1, further comprising; means for obtaining said first image reading position errors from said first pattern; means for obtaining said second image reading position errors from said second pattern; means for comparing said first and second image reading position errors with one another and obtaining a difference between said first and second image reading position errors; and means for determining that a noise is present when said difference between said first and second image reading position errors is significantly large locally, and removing said noise. ### Claim 5 An image reading apparatus which reads an original image by scanning said original image, main scan line by main scan line, with a fixed time interval, said apparatus comprising: first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a sub-scan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction; an image reading portion which reads said first and second patterns as well as said original image; a position error measuring portion which measures first and second image reading position errors corresponding to different angle oblique lines of image data obtained as a result of reading said first and second patterns, respectively, said position error measuring portion compensating for position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-compensated image reading position errors; and a position error correcting portion which corrects image data obtained as a result of said image reading portion reading said original image, using said position-deviation-compensated image reading position errors. ### Claim 6 A computer program product for measuring image reading position errors in image data which is obtained as a result of scanning an original image, main scan line by main scan line, with a fixed time interval, and correcting said image data using said image reading position errors, said measuring of said image reading errors using first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a sub-scan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the sub-scan direction, said computer program product comprising a computer usable medium having computer readable program code means embodied in said medium, said computer program code means comprising: program code means for causing a computer to measure first and second image reading position errors corresponding to different angle oblique lines of image data obtained from reading said first and second patterns, respectively; program code means for causing said computer to correct position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-corrected image reading position errors; and program code means for causing said computer to correct image data read by said image reading apparatus, using said position-deviation-corrected image reading position errors. ### Claim 7 A computer-implemented method for measuring image reading position errors in image data which is obtained as a result of scanning an original image, main scan line by main scan line, with a fixed time interval, and correcting said image data using said image reading position errors, said measuring of said image reading errors using first and second patterns which are located outside of an image reading area, a first pattern comprising a plurality of lines each extending at a fixed angle with respect to a subscan direction, a second pattern comprising a plurality of lines each extending at a fixed angle but having a reverse direction with respect to the subscan direction, said computer-implemented method comprising the steps of; a) measuring first and second image reading position errors corresponding to different angle oblique lines of image data obtained from reading said first and second patterns, respectively; b) compensating for position deviations of said first and second patterns using said first and second image reading position errors, and obtaining position-deviation-compensated image reading position errors; and c) correcting image data read by said image reading apparatus, using said position-deviation-compensated image reading position errors.