# US 2008/0187335 A1 · Printing apparatus and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2008/0187335 A1 - Document ID: US20080187335A1 - Status: Published application - Kind: A1 - Application number: 11/702,238 - Filed: 2007-02-05 - Published: 2008-08-07 - Earliest claimed: 2007-02-05 - Assignees: Xerox Corporation - Inventors: Joseph M. Wing; Brian R. Conrow; Robert Edward Hildebrand; Brian J. Perry; Alan G. Schlageter; Shawn Updegraff; Moritz P. Wagner; R. Enrique Viturro - Web page: https://patentgrep.com/patent/US20080187335A1 ## CPC - G03G 15/5062: {by measuring the characteristics of an image on the copy material} - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract Disclosed is a printing apparatus and method to correct for image non-uniformities. The printing apparatus comprises a photoreceptor (P/R) belt charging device positioned to charge the P/R belt after an image is transferred to a media sheet. Subsequently, an image sensing device scans the P/R belt residual image or patches to detect image non-uniformities. ## Claims ### Claim 1 A printing apparatus comprising: a P/R (Photoreceptor) belt; one or more image recording stations arranged to transfer one or more images to the P/R belt; an image transfer station arranged to transfer an image from the P/R belt to a media sheet; a P/R belt charging device positioned to charge the P/R belt after an image is transferred to a media sheet; and an image sensing device to sense images associated with the P/R belt, the image sensing device positioned to scan the P/R belt image after the P/R belt is charged by the P/R belt charging device. ### Claim 2 (depends on 1) The printing apparatus according to claim 1, further comprising: a P/R belt cleaner positioned to remove the images associated with the P/R belt after the image sensing device scans images associated with the P/R belt. ### Claim 3 (depends on 1) The printing apparatus according to claim 1, the P/R belt charging device comprising: a dicorotron device to negatively charge the P/R belt. ### Claim 4 (depends on 1) The printing apparatus according to claim 1, the P/R belt charging device comprising: a pre-clean magnet adapted to collect stray carrier beads from the P/R belt; and a pre-clean dicorotron adapted to negatively charge the P/R belt after the pre-clean magnet collects stray carrier beads from the P/R belt. ### Claim 5 (depends on 4) The printing apparatus according to claim 4, further comprising: a P/R belt cleaner positioned to remove the images associated with the P/R belt after the image sensing device scans images associated with the P/R belt. ### Claim 6 (depends on 5) The printing apparatus according to claim 5, wherein the P/R belt cleaner removes the image associated with the P/R belt by attracting the negatively charged image particles with a positive charge. ### Claim 7 (depends on 5) The printing apparatus according to claim 5, the image sensing device comprising a full width array sensor. ### Claim 8 (depends on 1) The printing apparatus according to claim 1, wherein the printing apparatus is configured to apply spatial Tone Reproduction Curves to reduce image non-uniformities detected by the image sensing device. ### Claim 9 (depends on 1) The printing apparatus according to claim 1, further comprising: a controller operatively connected to the image sensing device and the one or more image recording stations, wherein the controller applies spatial Tone Reproduction Curves to reduce image non-uniformities associated with the P/R belt. ### Claim 10 (depends on 1) The printing apparatus according to claim 1, wherein the printing apparatus is configured to transfer one or more patches to the P/R belt and the image sensing device scans the one or more patches to detect non-uniformities associated with the patches. ### Claim 11 (depends on 10) The printing apparatus according to claim 10, wherein the one or more patches includes a plurality of patches where each patch is associated with a different color. ### Claim 12 (depends on 10) The printing apparatus according to claim 10, wherein the one or more patches comprise overlays. ### Claim 13 A method of controlling image non-uniformities associated with a printing apparatus P/R belt, the method comprising: transferring an image from one or more image recording stations to the P/R belt; transferring the image from the P/R belt to a media sheet; negatively charging the P/R belt and residual image associated with the P/R belt; using a full width array sensor to scan the P/R belt residual image; and adjusting one or more image recording stations to reduce image non-uniformities associated with the P/R belt. ### Claim 14 (depends on 13) The method of controlling image non-uniformities according to claim 13, further comprising: pre-cleaning the P/R belt with a magnet after an image is transferred to a media sheet and before the P/R belt is negatively charged. ### Claim 15 (depends on 14) The method of controlling image non-uniformities according to claim 14, wherein the P/R belt is negatively charged with a dicorotron. ### Claim 16 (depends on 15) The method of controlling image non-uniformities according to claim 15, wherein the P/R belt is positively charged prior to the P/R belt being negatively charged. ### Claim 17 (depends on 15) The method of controlling image non-uniformities according to claim 15, further comprising: cleaning the P/R belt of any residual image with a positively charged cleaning device after the full width array sensor scans the P/R belt. ### Claim 18 (depends on 14) The method of controlling image non-uniformities according to claim 14, further comprising: transferring one or more patches from one or more image recording stations to the P/R belt; using a full width array sensor to scan the P/R belt patches; and adjusting one or more image recording stations to reduce image non-uniformities associated with the P/R belt patches. ### Claim 19 (depends on 18) The method of controlling image non-uniformities according to claim 18, wherein the one or more patches comprises overlays. ### Claim 20 (depends on 18) The method of controlling image non-uniformities according to claim 18, further comprising: applying Tone Reduction Curves to adjust the one or more image recording stations to reduce image non-uniformities associated with the P/R belt patches. ### Claim 21 A xerographic apparatus comprising: a P/R belt; one or more image recording stations operatively coupled to the P/R belt; an image transfer station operatively coupled to the P/R belt and adapted to transfer an image from the P/R belt to a media sheet; a P/R belt pre-clean dicorotron adapted to negatively charge the P/R belt after the pre-clean magnet positively charges the P/R belt; and a full width array sensor operatively coupled to the P/R belt image after the P/R belt is negatively charged by the pre-clean dicorotron.