# US 8,150,283 B2 · Method and system for minimizing non-uniformities in output images using halftone correction patches > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,150,283 B2 - Document ID: US8150283B2 - Status: Granted - Kind: B2 - Application number: 12/706,327 - Filed: 2010-02-16 - Published: 2011-08-18 - Granted: 2012-04-03 - Earliest claimed: 2010-02-16 - Assignees: Xerox Corporation - Inventors: Paul A. Hosier - Web page: https://patentgrep.com/patent/US8150283B2 ## CPC - H04N 1/4058: {with details for producing a halftone screen at an oblique angle (H04N1/4056 takes precedence)} - G03G 15/5041: {Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence)} - H04N 1/58: Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction (H04N1/62 takes precedence) - H04N 1/6033: {using test pattern analysis (H04N1/6055 takes precedence)} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract Disclosed herein are a method and a printing apparatus implementing the method to minimize cross-process direction non-uniformities of color images in printed documents. When printing images on a photoreceptor, halftone test patches are generated for each color. A first halftone cell orientation (of dots) of the test patches and their corresponding color image data is determined. The halftone cells of test patches may be provided or rotated to a second orientation (or angle or degrees) for printing in an inter-document zone of the photoreceptor, while the first orientation of the color image data in the document image area of the photoreceptor remains the same. Errors or non-uniformities (e.g., with TRC correction) caused by sensor misreading of test patches at specific orientations in the cross-process direction are substantially eliminated, thereby providing output images without streaks or visible errors. ## Claims ### Claim 1 A processor-implemented method for minimizing cross-process direction non-uniformities of images in printed documents using a printing apparatus, the printing apparatus comprising a processor for processing documents containing image data, an image bearing surface with a monitoring area and an image area for movement in a process direction, and one or more sensors for monitoring the image bearing surface in a cross-process direction, the processor implementing the method comprising: receiving color image data of a document, the image data comprising a plurality of color pixels and the document comprising at least one page of image data; generating a halftone test patch for each color in the image data to be provided in the monitoring area on the image bearing surface; determining profile data of each test patch, the profile data including a first orientation of halftone dots of the test patch representing a halftone orientation of its associated halftone color image data for output in the image area of the image bearing surface; determining a second orientation for the halftone dots of at least one test patch; and providing the halftone dots of the at least one test patch at a second orientation in the monitoring area, wherein the halftone orientation of its associated halftone color image data in the image area is unaffected for output. ### Claim 2 (depends on 1) The processor-implemented method of claim 1, further comprising: determining if the first orientation of the halftone dots of the at least one test patch causes non-uniformities in a printed document, and if the first orientation causes non-uniformities, providing the halftone dots of the test patch at a second orientation for printing in the monitoring area; else, if the first orientation does not cause non-uniformities, providing the halftone dots of the test patch in the first orientation for printing in the monitoring area. ### Claim 3 (depends on 2) The processor-implemented method of claim 2, wherein the first orientation of the halftone dots of the at least one test patch is determined to cause non-uniformities if the first orientation of the test patch is approximately 0 or 90 degrees with respect to the cross-process direction. ### Claim 4 (depends on 1) The processor-implemented method of claim 1, wherein determining a second orientation for the halftone dots of the at least one test patch comprises: comparing the first orientations of the halftone dots of each of the generated test patches for each color to be marked in the monitoring area; choosing the second orientation from each first orientation based on the comparison. ### Claim 5 (depends on 4) The processor-implemented method of claim 4, further comprising: rotating the halftone dots of each test patch to the second orientation. ### Claim 6 (depends on 1) The processor-implemented method of claim 1, wherein determining a second orientation for the halftone dots of the at least one test patch comprises: determining an adjusted, second orientation based on each of the first orientations of the test patches. ### Claim 7 (depends on 6) The processor-implemented method of claim 6, further comprising: rotating the halftone dots of each test patch to the second orientation. ### Claim 8 (depends on 6) The processor-implemented method of claim 6, further comprising: providing the halftone dots of each test patch at the second orientation. ### Claim 9 (depends on 1) The processor-implemented method of claim 1, wherein the providing the halftone dots of the at least one test patch at the second orientation comprises: rotating the halftone dots of the at least one test patch to the second orientation, the second orientation being at an angle from the first orientation. ### Claim 10 (depends on 1) The processor-implemented method of claim 1, wherein the providing the halftone dots of the at least one test patch at the second orientation comprises: generating at least one new test patch representing the at least one test patch with halftone dots at a second orientation. ### Claim 11 (depends on 1) The processor-implemented method of claim 1, wherein the providing the halftone dots of the at least one test patch at the second orientation comprises: generating a rotated version of the halftone dots of the at least one test patch in the second orientation, wherein the second orientation comprises the halftone dots of the test patch that are at an angle rotated from the first orientation. ### Claim 12 (depends on 1) The processor-implemented method of claim 1, further comprising: printing the halftone dots of the at least one test patch at the second orientation on the monitoring area of the image bearing surface for reading by the one or more sensors, and printing the halftone color image data of the document at the halftone orientation in the image area, the halftone orientation of the image data being at the first orientation. ### Claim 13 (depends on 12) The processor-implemented method of claim 12, wherein the printing of the halftone dots of the at least one test patch comprises printing the at least one test patch on an inter-document zone of the image bearing surface, the inter-document zone comprising at least one area on the image bearing surface between image areas used for printing the document. ### Claim 14 A printing apparatus for processing documents containing image data comprising: a photoreceptor comprising one or more image areas and an inter-document zone for movement in a process direction, the inter-document zone comprising at least one area on the photoreceptor between the one or more image areas used for output; a plurality of color marking stations for applying color in a process direction to the photoreceptor in the one or more image areas and the inter-document zone; one or more array sensors for sensing the color applied to the photoreceptor in a cross-process direction; a processor for receiving color image data of a document, the image data comprising a plurality of color pixels and the document comprising at least one page of image data, the processor performing the following operations: generating a halftone test patch for each color in the image data to be provided in the inter-document zone; determining profile data of each test patch, the profile data including an first orientation of halftone dots of the test patch representing a halftone orientation of its associated color for output in the one or more image areas; determining a second orientation for the halftone dots of the at least one test patch; and providing the halftone dots of the at least one test patch at a second orientation in the inter-document zone, wherein the halftone orientation of its associated color in the one or more image areas is unaffected for output. ### Claim 15 (depends on 14) The printing apparatus of claim 14, wherein the processor further performs the following operations: determining if the first orientation of the halftone dots of the at least one test patch causes non-uniformities in a printed document, and if the first orientation causes non-uniformities, rotating the halftone dots of the test patch to a second orientation for printing in the inter-document zone; else, if the first orientation does not cause non-uniformities, providing the halftone dots of the test patch in the first orientation for printing in the inter-document zone. ### Claim 16 (depends on 15) The printing apparatus of claim 15, wherein the first orientation of the halftone dots of the at least one test patch is determined to cause non-uniformities if the first orientation of the test patch is approximately 0 or 90 degrees with respect to the cross-process direction of the photoreceptor. ### Claim 17 (depends on 14) The printing apparatus of claim 14, wherein determining a second orientation for the halftone dots of the at least one test patch by the processor comprises: comparing the first orientations of the halftone dots of each of the generated test patches for each color to be marked in the inter-document zone; choosing the second orientation from each first orientation based on the comparison. ### Claim 18 (depends on 17) The printing apparatus of claim 17, further comprising: the processor rotating the halftone dots of each test patch to the second orientation. ### Claim 19 (depends on 14) The printing apparatus of claim 14, wherein determining a second orientation for the halftone dots of the at least one test patch by the processor comprises: determining an adjusted, second orientation based on each of the first orientations of the test patches. ### Claim 20 (depends on 19) The printing apparatus of claim 19, further comprising: the processor rotating the halftone dots of each test patch to the second orientation. ### Claim 21 (depends on 14) The printing apparatus of claim 14, further comprising: the processor providing the halftone dots of each test patch at the second orientation. ### Claim 22 (depends on 14) The printing apparatus of claim 14, wherein the providing the halftone dots of the at least one test patch at the second orientation by the processor comprises: rotating the halftone dots of the at least one test patch to the second orientation, the second orientation being at an angle from the first orientation. ### Claim 23 (depends on 14) The printing apparatus of claim 14, wherein the providing the halftone dots of the at least one test patch at the second orientation by the processor comprises: generating at least one new test patch representing the halftone dots of the at least one test patch at a second orientation. ### Claim 24 (depends on 14) The printing apparatus of claim 14, wherein the providing the halftone dots of the at least one test patch at the second orientation by the processor comprises: generating a rotated version of at least one test patch in the second orientation, wherein the second orientation comprises the halftone dots of the test patch that are at an angle rotated from the first orientation. ### Claim 25 (depends on 14) The printing apparatus of claim 14, wherein the plurality of color marking stations print the halftone dots of the at least one test patch at the second orientation on the photoreceptor for sensing by the one or more sensors and wherein the plurality of color marking stations print the halftone color image data of the document at the halftone orientation in the one or more image areas for output, the halftone orientation of the image data being at the first orientation. ### Claim 26 (depends on 25) The printing apparatus of claim 25, wherein the halftone dots of the at least one test patch is printed on the inter-document zone of the photoreceptor and wherein the halftone color image data is printed in the one or more image areas on photoreceptor.