Camera/lens calibration apparatus and method

• US 5,930,740 A
• Filed: 04/04/1997
• Issued: 07/27/1999
• Est. Priority Date: 04/04/1997
• Status: Expired due to Term

• Current Assignee: RT-Set Real Time Synthesized Entertainment Technology Ltd.
• Original Assignee: Evans & Sutherland Computer Corp. (Elevate Entertainment, Inc.)
• Inventors: Mathisen, Allen E.
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): MILLER, CRAIG S
• Application Number:
  US08/835,120
• Time in Patent Office: 844 Days
• Field of Search: 702/92-95, 702/150-155, 396/128, 348/349, 348/350
• US Class Current: 702/152
• CPC Class Codes: H04N 23/633 for displaying additional information relating to control or operation of the camera
• CPC Class Codes: H04N 23/695 Control of camera direction for changing a field of view, e.g. pan, tilt or based on tracking of objects
• CPC Class Codes: H04N 5/222 Studio circuitry; Studio devices; Studio equipment cameras or camera modules comprising electronic image sensors, or control thereof H04N23/00

Abstract

A method and apparatus for generating a viewport definition for a computer generated image using sensor information relating to a video camera'"'"'s pan, tilt, zoom, and focus controls. The method generally comprises the steps of: (a) establishing reference points within an enclosed space which is to be used for recording images with the camera; (b) positioning the camera within the enclosed space relative to the reference points such that the camera position can be determined through triangulation with respect to the reference points; (c) developing position data through triangulation which identifies the camera position in a coordinate system relative to the reference points; (d) recording camera orientation data from sensors disposed to detect camera parameters defining the camera'"'"'s pan, tilt, zoom, and focus settings; and (e) developing a database defining a viewport for the camera defined from a combination of the position data and the camera orientation data. Calculating the viewport (i.e., a nodal point or eyepoint, an orientation, a field of view, a focal plane distance, and a focus of expansion) as the camera moves is the ultimate goal of the camera tracking device.

Claims

1. A method for generating a viewport for a computer generated image using sensor information relating to settings of a video camera'"'"'s pan, tilt, zoom, and focus, the method comprising the steps of:

(a) establishing reference points within an enclosed space which is to be used for recording images with the camera;

(b) positioning the camera within the enclosed space relative to the reference points such that the camera position can be determined through triangulation with respect to the reference points;

(c) developing position data through triangulation which identifies the camera position in a coordinate system relative to the reference points;

(d) recording camera orientation data from sensors disposed to detect camera parameters that define the camera'"'"'s pan, tilt, zoom, and focus settings; and

(e) developing a database defining a viewport for the camera, the database defined from a combination of the position data and the camera orientation data.

2. The method of claim 1 wherein step (a) comprises positioning at least four points viewable by the camera in a planar configuration within the enclosed space.

3. The method of claim 1 wherein step (b) comprises successively positioning the camera within the enclosed space relative to the reference points.

4. The method of claim 1 wherein step (b) comprises positioning the camera on a support such that the reference points are within the view of the camera.

5. The method of claim 4 wherein the support is selected from the group consisting of a tripod and a pedestal.

6. The method of claim 1 wherein step (b) comprises laterally centering the camera on a support.

7. The method of claim 1 wherein step (b) comprises leveling the camera on a head of a support.

8. The method of claim 7 wherein leveling the camera comprises visually ascertaining levelness of the camera and then manually leveling the head on the support to thereby level the camera.

9. The method of claim 1 wherein step (b) comprises developing position data which indicates a tilt offset of the camera.

10. The method of claim 1 wherein step (b) comprises developing position data which indicates an absolute pan angle of the camera.

11. The method of claim 1 wherein step (c) comprises entering the position data into a processor programmed to generate the database defining a viewport for the camera, the position data including a tilt offset, a model space scale, an absolute pan angle, a horizontal distance between reference points, a vertical distance between reference points, a lens characterization, a studio offset and orientation, encoder specifications, and camera angles relative to the reference points.

12. The method of claim 11 wherein the coordinate system is selected from the group consisting of a rectangular coordinate system, a cylindrical coordinate system, a spherical coordinate system, and a polar coordinate system.

13. The method of claim 11 wherein entering the position data includes successively pointing the camera to each of the reference points and signaling the processor to indicate to the processor that the camera is pointing at one of the reference points.

14. The method of claim 1 wherein step (c) comprises processing with a processor the position data of the camera such that, relative to the coordinate system, the camera position is determined relative to the reference points.

15. The method of claim 1 wherein step (d) comprises dynamically tabulating in a processor the camera orientation data from the sensors disposed to detect camera parameters that define the camera'"'"'s pan, tilt, zoom, and focus settings.

16. The method of claim 1 wherein step (e) comprises processing with a processor the position data and the camera orientation data such that for each setting adjustment in pan, tilt, zoom, and focus, the viewport definition for the camera is dynamically determined in the coordinate system relative to the reference points.

17. Apparatus for generating a viewport for a computer generated image using sensor information relating to settings of a video camera'"'"'s pan, tilt, zoom, and focus, the apparatus comprising:

at least four reference points within an enclosed space which is to be used for recording images with the camera;

a means for positioning the camera within the enclosed space relative to the at least four reference points such that the camera position can be determined through triangulation with the at least four reference points;

a means for developing position data through triangulation which identifies the camera position in a coordinate system relative to the at least four reference points;

a means for recording camera orientation data from at least one sensor disposed to detect camera parameters that define the camera'"'"'s pan, tilt, zoom, and focus settings; and

a means for developing a database defining a viewport for the camera, the database defined from a combination of the position data and the camera orientation data.

18. Apparatus as in claim 17 wherein the at least four points are viewable by the camera and are disposed in a planar configuration within the enclosed space.

19. Apparatus as in claim 17 wherein the means for positioning the camera is a support positioned such that the reference points are within the view of the camera.

20. Apparatus as in claim 19 wherein the support is selected from the group consisting of a tripod and a pedestal.

21. Apparatus as in claim 17 wherein the camera is laterally centered on a support.

22. Apparatus as in claim 17 wherein the camera is level on a head of a support.

23. Apparatus as in claim 17 wherein the means for developing position data comprises a processor programmed to calculate and store data which indicates a tilt offset of the camera.

24. Apparatus as in claim 17 wherein the means for developing position data comprises a processor programmed to calculate and store data which indicates an absolute pan angle of the camera.

25. Apparatus as in claim 17 wherein the means for developing position data comprises a processor having means for entering data into the processor, the processor being programmed to generate position data which identifies the camera position in a coordinate system relative to the at least four reference points.

26. Apparatus as in claim 25 wherein the coordinate system is selected from the group consisting of a rectangular coordinate system, a cylindrical coordinate system, a spherical coordinate system, and a polar coordinate system.

27. Apparatus as in claim 17 wherein the means for recording camera orientation data from at least one sensor comprises a processor having means for entering the camera orientation data into the processor.

28. Apparatus as in claim 17 wherein the means for developing a database defining a viewport for the camera comprises a processor programmed to develop said database, the database defined from a combination of the position data and the camera orientation data.

29. A method for defining a viewport for a computer generated image using information relating to settings of a camera'"'"'s pan, tilt, zoom, and focus, the method comprising the steps of:

(a) establishing reference points in an enclosed space which is to be used for recording images with the camera;

(b) determining the camera position and orientation from a support means in the enclosed space through triangulation in the enclosed space;

(c) measuring a viewport for the camera as a function of zoom and focus settings on the camera;

(d) measuring offsets of the camera that are involved in mounting the camera to the support means;

(e) scaling virtual space relative to space in the enclosed space; and

(f) offsetting virtual space relative to the camera offsets in the enclosed space to thereby generate a viewport for the computer generated image.

30. The method of claim 29 wherein step (b) comprises entering data into a processor when the camera is pointed to each of the reference points in the enclosed space, the processor being programmed to calculate the camera position through triangulation.

31. The method of claim 29 wherein steps (c) through (f) further comprise entering the viewport for the camera into a processor and entering the offsets of the camera into the processor, the processor being programmed to scale virtual space and offset virtual space to thereby generate the viewport for the computer generated image.