SYSTEM AND METHOD FOR AUTOMATED TEST-PATTERN-FREE PROJECTION CALIBRATION

• US 20150160539A1
• Filed: 12/09/2013
• Published: 06/11/2015
• Est. Priority Date: 12/09/2013
• Status: Active Grant

• Current Assignee: Geo Semiconductor Incorporated
• Original Assignee: Geo Semiconductor Incorporated
• Inventors: Bassi, Zorawar S., Jegatheswaran, Thushyanthan
• Granted Patent: US 9,915,857 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G03B 21/147 Optical correction of image distortions, e.g. keystone
• CPC Class Codes: G06T 3/60 Rotation of whole images or parts thereof
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: H04N 9/3185 Geometric adjustment, e.g. keystone or convergence optical or mechanical adjustment of convergence H04N9/317; using scanning means H04N3/22; optical or mechanical adjustments of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/14
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

Systems and methods for calibrating an image projection system, using image capture devices are disclosed. In particular, Wide-Angle (WA) and Ultra Wide-Angle (UWA) lenses can be utilized to eliminate need for traditional test patterns and tedious alignment settings. That is particularly useful for automatic calibration of projection sources that may require frequent adjustments on the field. Geometric mapping techniques combined with image analytics allow identifying parallel lines in an image captured from a scene. Coordinates of vanishing points corresponding to pairs of parallel lines provide sufficient information to determine orientation of the image projection system in space.

Claims

1. A method to correct for rotational distortions of an image projected from a projection source on a viewing surface, said method comprising:

acquiring an image of a scene containing the viewing surface, using at least one image capture device with a known orientation relative to the projection source;

identifying at least a first pair of parallel lines in the image;

identifying at least a second pair of parallel lines, orthogonal to the at least first pair of parallel lines, in the image;

obtaining coordinates of vanishing points corresponding to the at least first and the at least second pair of parallel lines;

computing angles of rotation of the at least one capture device with respect to a frame of reference, using the coordinates of the vanishing points; and

constructing a correction transformation using the rotational angles and the orientation of the at least one capture device relative to the projection source.

2. The method of claim 1, wherein the at least one capture devices is equipped with a Wide-Angle (WA) or an Ultra Wide-Angle (UWA) lens.

3. The method of claim 2, wherein a portion of the image containing the identified lines are mapped to a projective plane to facilitate obtaining the vanishing points.

4. The method of claim 1, wherein the angles of rotation are represented as a rotation matrix.

5. The method of claim 1, wherein the correction transformation is applied to an output image in a forward direction.

6. The method of claim 1, wherein inverse of the correction transformation is determined and applied to pre-distort an input image, such that projected output image appear substantially rotation free.

7. The method of claim 1, wherein spatial orientation of the projection source changes in time and the correction is dynamically performed.

8. The method of claim 1, wherein the viewing surface is virtual.

9. The method of claim 1, wherein one or more of the at least one capture device is integrated with the projection source.

10. The method of claim 1, wherein one or more of the at least one capture device is physically attached to the projection source.

11. The method of claim 1, wherein the projection source is part of a Heads-Up-Display (HUD) assembly.

12. The method of claim 1, wherein the projection source is used in a front projection configuration.

13. The method of claim 1, wherein the projection source is used in a rear projection configuration.

14. The method of claim 1, wherein said correction transformation is concatenated with correction components associated with at least one of optical distortions and geometry of the viewing surface.

15. A calibration system for use with an image projection set-up having a source and a viewing surface, said system comprising:

at least one image capture device with a known orientation relative to the projection source, to acquire an image of a scene;

means to identify at least a first pair of parallel lines, and least a second pair of parallel lines orthogonal to the at least first pair of parallel lines, in the image;

means to obtain coordinates of vanishing points corresponding to the at least first and the at least second pair of parallel lines;

means to compute rotational angles of the capture device using the coordinates of the vanishing points; and

means to construct a correction transformation using the rotational angles and the orientation of the at least one capture device relative to the projection source.

16. The calibration system of claim 15, wherein the at least one capture devices is equipped with a Wide-Angle (WA) or an Ultra Wide-Angle (UWA) lens.

17. The calibration system of claim 16, further comprising means to map a portion of the image containing the identified parallel lines to a projective plane to facilitate obtaining the vanishing points.

18. The calibration system of claim 15, wherein the viewing surface is virtual.

19. The calibration system of claim 15, wherein one or more of the at least one capture device is integrated with the projection source.

20. The method of claim 15, wherein one or more of the at least one capture device is attached to the projection source.

21. The calibration system of claim 15, wherein the image projection set-up is used in a Heads-Up-Display (HUD) assembly.

22. The calibration system of claim 15, wherein the image projection set-up is used in a front projection configuration.

23. The calibration system of claim 15, wherein the image projection set-up is used in a rear projection configuration.

24. A calibration method for use with an image projection set-up having a source and a viewing surface, said method being carried out by at least one electronic processor configured to:

receive input image data acquired, from a scene containing the viewing surface, by at least one capture device;

receive input data representing orientation of the at least one capture device relative to the projection source;

identify at least a first pair of parallel lines in the image;

identify at least a second pair of parallel lines, orthogonal to the at least first pair of parallel lines, in the image;

compute coordinates of vanishing points corresponding to the at least first and the at least second pair of parallel lines;

compute angles of rotation of the at least one capture device with respect to a frame of reference, using the coordinates of the vanishing points; and

construct a correction transformation using the computed angles of rotation and the orientation of the at least one capture device relative to the projection source.