Method and apparatus for calibration of camera system, and method of manufacturing camera system

• US 20070005293A1
• Filed: 08/28/2006
• Published: 01/04/2007
• Est. Priority Date: 11/29/2002
• Status: Active Grant

• Current Assignee: Toshiba Digital Solutions Corporation (Toshiba Corporation), Toshiba Electronic Devices & Storage Corporation (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Nakai, Hiroaki, Maeda, Kenichi, Kubota, Susumu, Taniguchi, Yasuhiro
• Granted Patent: US 7,321,839 B2
• Time in Patent Office: Days
• US Class Current: 702/152
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: H04N 13/246 Calibration of cameras

Abstract

A first mirror and a second mirror are disposed in such a manner that their reflective surfaces are parallel and face toward each other. A mark is drawn between the first mirror and the second mirror. An image of the reflections of the mark in the first mirror and the second mirror is captured with a camera. Calibration of the camera system is performed based on the image.

Claims

1. A method for calibration of a stereo camera system that uses a plurality of cameras, comprising;

disposing a first mirror and a second mirror in such a manner that reflective surfaces of the first mirror and the second mirror face toward each other;

placing at least two marks on a reference plane between the reflective surface of the first mirror and the reflective surface of the second mirror so that a plurality of reflected figures of the each mark are generated by the first mirror and the second mirror, the reference plane used in processes performed by the stereo camera system;

capturing with the cameras an image including the plurality of the reflected figures of the each mark;

determining position of the reflected figures in each of the images, wherein the position of each of the reflected figures is represented by a pair of coordinates; and

calculating projective transformation parameters for planar projection stereopsis method by using the position of the reflected figures.

2. The method according to claim 1, wherein the first mirror is a half mirror.

3. The method according to claim 1, further comprising:

positioning the marks at the same height as that of the reference plane.

4. The method according to claim 1, wherein the first mirror has a portion that passes light.

5. The method according to claim 1, wherein the marks includes two marks that are disposed on a line parallel to the reflective surfaces of the first mirror and the second mirror.

6. The method according to claim 1, wherein each of the marks is a line that is normal to the reflective surfaces of the first mirror and the second mirror.

7. The method according to claim 1, further comprising:

disposing a third mirror in such a manner that the marks reflected in the first mirror and the second mirror are also reflected in the third mirror, wherein images reflected in the third mirror are captured with the camera.

8. An apparatus for calibration of a stereo camera system that uses a plurality of cameras, comprising;

a first mirror having a reflective surface;

a second mirror having a reflective surface, wherein the reflective surfaces of the first mirror and the second mirror face toward each other;

a plurality of marks that are disposed on a reference plane between the reflective surface of the first mirror and the reflective surface of the second mirror so that a plurality of reflected figures of the each mark are generated by the first mirror and the second mirror, the reference plane used in processes performed by the stereo camera system; and

an image processor that calculates projective transformation parameters for planar projection stereopsis method by using position of reflected figures of the marks in images captured by the cameras, wherein the position of each of the marks is represented by a pair of coordinates.

9. The apparatus according to claim 8, wherein the first mirror is a half mirror.

10. The apparatus according to claim 8, further comprising:

a level adjustor that positions the marks at the same height as that of the reference plane.

11. The apparatus according to claim 8, wherein the first mirror has a portion that passes light.

12. The apparatus according to claim 8, wherein the marks includes two marks that are disposed on a line parallel to the reflective surfaces of the first mirror and the second mirror.

13. The apparatus according to claim 8, wherein each of the marks is a line that is normal to the reflective surfaces of the first mirror and the second mirror.

14. The apparatus according to claim 8, further comprising:

a third mirror disposed in such a manner that the marks reflected in the first mirror and the second mirror are also reflected in the third mirror;

wherein images reflected in the third mirror are captured, with the camera.

15. A method of manufacturing a stereo camera system that uses a plurality of cameras and a memory, comprising:

installing the cameras in a predetermined position;

disposing a first mirror and a second mirror in such a manner that reflective surfaces of the first mirror and the second mirror face toward each other;

placing at least two marks on a reference plane between the reflective surface of the first mirror and the reflective surface of the second mirror so that a plurality of reflected figures of the each mark are generated by the first mirror and the second mirror, the reference plane used in processes performed by the stereo camera system;

capturing with the cameras an image including the plurality of the reflected figures of the each mark;

determining position of the reflected figures in each of the images, wherein the position of each of the reflected figures is represented by a pair of coordinates;

calculating projective transformation parameters for planar projection stereopsis method by using the position of reflected figures; and

storing the projective transformation parameters in the memory.

16. The method according to claim 15, wherein the first mirror is a half mirror.

17. The method according to claim 15, further comprising:

positioning the marks at the same height as that of the reference plane.

18. The method according to claim 15, wherein the first mirror has a portion that passes light.

19. The method according to claim 15, wherein the marks includes two marks that are disposed on a line parallel to the reflective surfaces of the first mirror and the second mirror.

20. The method according to claim 15, wherein each of the marks is a line that is normal to the reflective surfaces of the first mirror and the second mirror.

21. The method according to claim 15, further comprising;

disposing a third mirror in such a manner that the marks reflected in the first mirror and the second mirror are also reflected in the third mirror, wherein images reflected in the third mirror are captured with the camera.