# US 9,883,163 B2 · Method and system for determining camera parameters from a long range gradient based on alignment differences in non-point image landmarks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,883,163 B2 - Document ID: US9883163B2 - Status: Granted - Kind: B2 - Application number: 13/737,627 - Filed: 2013-01-09 - Published: 2013-07-11 - Granted: 2018-01-30 - Earliest claimed: 2012-01-09 - Assignees: Disney Enterprises, Inc. - Applicants: Disney Enterprises, Inc. - Inventors: G. Peter K. Carr; Iain Matthews - Web page: https://patentgrep.com/patent/US9883163B2 ## CPC - H04N 13/207: using a single two-dimensional [2D] image sensor - G06T 7/85: {Stereo camera calibration} - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL ## Abstract A system and method improves a camera calibration. The method includes receiving a camera image, a planar template pattern, a 3D geometry of a surface on which the planar template pattern is embedded, and a set of parameter values. The method includes rendering the planar template pattern into a camera perspective based on the parameter values to generate a warped template image. The method includes generating an error image including at least one non-zero difference between the camera image and the warped template image. The method includes adjusting the parameter values to reduce an error between the camera image and the warped template image. ## Claims ### Claim 1 A method, comprising: receiving a camera image captured by a camera and a set of parameter values that models a perspective of the camera; receiving a synthetically generated planar template pattern embedded on a surface and a 3D geometry of the surface, wherein the planar template pattern is a representation of a sporting field; calculating a long range gradient of the planar template pattern, wherein the long range gradient of the planar template pattern is based on a calculation within a gradient window; warping the planar template pattern into the perspective of the camera based on the set of the parameter values to generate a warped template image; generating an error image based on a comparison between the camera image and the warped template image; and computing an adjusted set of parameter values to reduce an error associated with the error image, wherein the computing is based on the long range gradient. ### Claim 2 (depends on 1) The method of claim 1, further comprising: (a) warping the planar template pattern into the perspective of the camera based on the adjusted set of parameter values to generate a further warped template image; (b) generating a further error image based on a comparison between the camera image and the further warped template image; and (c) computing a further adjusted set of parameter values to further reduce an error associated with the further error image, wherein the computing is based on a further long range gradient. ### Claim 3 (depends on 2) The method of claim 2, wherein steps (a)-(c) are repeated until a predetermined, terminating criterion is reached. ### Claim 4 (depends on 1) The method of claim 1, further comprising: filtering the camera image to identify pixels that correspond to the planar template pattern. ### Claim 5 (depends on 1) The method of claim 1, wherein the 3D geometry is a planar surface. ### Claim 6 (depends on 1) The method of claim 1, wherein the set of parameters values includes intrinsic property values and extrinsic property values of the camera. ### Claim 7 (depends on 1) The method of claim 1, wherein the set of parameter values includes properties of a lens. ### Claim 8 (depends on 7) The method of claim 7, wherein the properties of the lens are functions of a focal length. ### Claim 9 (depends on 1) The method of claim 1, wherein the set of parameter values includes auxiliary parameter values that represent correlated properties between the camera and at least one other camera. ### Claim 10 (depends on 1) The method of claim 1, wherein the set of parameter values describes a limited configuration, the limited configuration comprising one or more properties of the camera or the camera and at least one other camera having predetermined values. ### Claim 11 (depends on 1) The method of claim 1, wherein the camera image is a temporal sequence of images, the set of parameter values are a temporal sequence of values, and the adjusting minimizes the rate of change of the temporal sequence of values over time. ### Claim 12 (depends on 1) The method of claim 1, further comprising: calibrating the camera generating the camera image as a function of the adjusted parameter values. ### Claim 13 (depends on 1) The method of claim 1, wherein the calculation of the measure of the gradient window includes: a selection of an initial window size, and a performance of a coarse to fine alignment on the initial window size. ### Claim 14 (depends on 1) The method of claim 1, wherein the error image includes displacement data corresponding to at least one difference between the camera image and the warped template image and wherein the long range gradient of the planar template pattern is calculated at a location based on the displacement data. ### Claim 15 A system, comprising: an image capturing device configured to generate a camera image; a memory arrangement configured to store the camera image, a synthetically generated planar template pattern that is a representation of a sporting field embedded on a surface, a 3D geometry of the surface, and a set of parameter values that models a perspective of the image capturing device; and a processor configured to warp the planar template pattern into the perspective of the image capturing device based on the set of parameter values to generate a warped template image, the processor configured to calculate a long range gradient of the planar template pattern, wherein the long range gradient of the planar template pattern is based on a calculation within a gradient window, the processor configured to generate an error image based on a comparison between the camera image and the warped template image, the processor configured to compute an adjusted set of parameter values to reduce an error associated with the error image, wherein the computing is based on the long range gradient. ### Claim 16 (depends on 15) The system of claim 15, wherein, the processor is configured to warp the planar template pattern into the perspective of the image capturing device based on the adjusted set of parameter values to generate a further warped template image, the processor is configured to generate a further error image based on a comparison between the camera image and the further warped template image, the processor is configured to compute a further set of adjusted parameter values to further reduce an error associated with the further error image, wherein the computing is based on a further long range gradient. ### Claim 17 (depends on 15) The system of claim 15, wherein the processor is further configured to filter the camera image to identify pixels which correspond to the planar template pattern. ### Claim 18 (depends on 15) The system of claim 15, wherein the set of parameter values includes intrinsic property values and extrinsic property values of the image capturing device. ### Claim 19 (depends on 15) The system of claim 15, wherein the set of parameter values includes auxiliary parameters that describe correlated properties between the image capturing device and at least one other image capturing device. ### Claim 20 (depends on 15) The system of claim 15, wherein the set of parameter values describes a limited configuration, the limited configuration comprising one or more properties of the image capturing device or the image capturing device and at least one other image capturing device having predetermined values.