Method and system for determining camera parameters from a long range gradient based on alignment differences in non-point image landmarks

Patent metadata

Field	Value
Publication number	US-9883163-B2
Application number	US-201313737627-A
Country	US
Kind code	B2
Filing date	Jan 9, 2013
Priority date	Jan 9, 2012
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

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.

First claim

What is claimed is:

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.

2. 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.

3. The method of claim 2 , wherein steps (a)-(c) are repeated until a predetermined, terminating criterion is reached.

4. The method of claim 1 , further comprising:
filtering the camera image to identify pixels that correspond to the planar template pattern.

5. The method of claim 1 , wherein the 3D geometry is a planar surface.

6. The method of claim 1 , wherein the set of parameters values includes intrinsic property values and extrinsic property values of the camera.

7. The method of claim 1 , wherein the set of parameter values includes properties of a lens.

8. The method of claim 7 , wherein the properties of the lens are functions of a focal length.

9. 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.

10. 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.

11. 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.

12. The method of claim 1 , further comprising:
calibrating the camera generating the camera image as a function of the adjusted parameter values.

13. 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.

14. 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.

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.

16. 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.

17. 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.

18. The system of claim 15 , wherein the set of parameter values includes intrinsic property values and extrinsic property values of the image capturing device.

19. 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.

20. 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.

Assignees

• Disney Entpr Inc

Inventors

• Carr G Peter K
• Matthews Iain

Classifications

• H04N13/0207 Primary

  Electricity · mapped topic

• G06T7/85 Primary

  Stereo camera calibration · CPC title

• H04N13/207 Primary

  using a single two-dimensional [2D] image sensor · CPC title