METHOD AND SYSTEM FOR CALIBRATING CAMERA WITH RECTIFICATION HOMOGRAPHY OF IMAGED PARALLELOGRAM

• US 20090153669A1
• Filed: 03/04/2008
• Published: 06/18/2009
• Est. Priority Date: 12/17/2007
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: KIM, Jin Ho, KIM, Jae Hean, CHOI, Byoung Tae
• Granted Patent: US 8,208,029 B2
• Time in Patent Office: Days
• US Class Current: 348/187
• CPC Class Codes: G06T 2207/10012 Stereo images
• CPC Class Codes: G06T 7/593 from stereo images
• CPC Class Codes: G06T 7/85 Stereo camera calibration

Abstract

A method for calibrating a camera including (a) obtaining a two-dimensional (2D) homography that maps each of parallelograms projected onto images taken by two arbitrary cameras into a rectangle, wherein the 2D homography is defined as a rectification homography and wherein new cameras that have virtual images are defined as rectified cameras and a new infinite homography is generated between the two rectified cameras, the virtual images being transformed from original images by the rectification homography; (b) obtaining an original infinite homography by using the correlations among the new infinite homography, the rectification homography and the original infinite homography; and (c) obtaining intrinsic camera parameters based on the correlation between the original infinite homography and the intrinsic camera parameters, thereby calibrating the camera.

Claims

1. A method for calibrating a camera comprising:

(a) obtaining a two-dimensional (2D) homography that maps each of parallelograms projected onto images taken by arbitrary two cameras into a rectangle, wherein the 2D homography is defined as a rectification homography and wherein new cameras that have virtual images are defined as rectified cameras and a new infinite homography is generated between the two rectified cameras, the virtual images being transformed from original images using the rectification homography;

(b) obtaining an original infinite homography by using the correlation among the new infinite homography, the rectification homography and the original infinite homography; and

(c) obtaining intrinsic camera parameters based on the correlation between the original infinite homography and the intrinsic camera parameters, thereby calibrating the camera.

2. The method of claim 1, wherein the rectangle has two edges parallel to the horizontal and vertical axes of the images.

3. The method of claim 1, wherein the new infinite homography is obtained under the assumption that all the edges of each parallelogram are on the same planes of 3D space.

4. The method of claim 3, wherein the new infinite homography is represented by only 4 parameters as in the following equation:

$H_{\mathrm{\infty <br><br>}}^{r_k}=\left[\begin{array}{ccc}{\mathrm{\lambda <br><br>}}_k& 0& u_k\\ 0& {\mathrm{\lambda <br><br>}}_k& v_k\\ 0& 0& w_k\end{array}\right]$

wherein the above Equation is subjected to a k-th parallelogram existing in the scenes in the virtual images, and the new infinite homography is obtained for each parallelogram.

5. The method of claim 1, wherein the intrinsic camera parameters are obtained under the assumption that the intrinsic camera parameters are not changed upon capturing each image.

6. A system for calibrating a camera comprising:

a rectification homography generator for obtaining a two-dimensional (2D) homography that maps each of parallelograms projected onto images taken by arbitrary two cameras into a rectangle, wherein the 2D homography is defined as a rectification homography and wherein new cameras that have virtual images are defined as rectified cameras and a new infinite homography is generated between two rectified cameras, the virtual images being transformed from an original images using the rectification homography;

an infinite homography calculator for obtaining an original infinite homography by using the correlations among the new infinite homography, the rectification homography and the original infinite homography; and

a camera calibrator for obtaining intrinsic camera parameters based on the correlation between the original infinite homography and the intrinsic camera parameters of the camera to calibrate the camera.

7. The system of claim 6, wherein the rectangle has two edges parallel to the horizontal and vertical axes of the images.

8. The system of claim 6, wherein the first infinite homography calculator represents the new infinite homography under the assumption that all the edges of each of the parallelograms are on the same planes of 3D space.

9. The system of claim 6, wherein the camera calibrator obtains the intrinsic camera parameters under the assumption that the intrinsic camera parameters are not changed upon capturing each image.