METHOD AND APPARATUS FOR CALIBRATING VIDEO CAMERA

• US 20100259624A1
• Filed: 04/09/2010
• Published: 10/14/2010
• Est. Priority Date: 10/24/2007
• Status: Active Grant

• Current Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Device Company Limited (Huawei Investment & Holding Co., Ltd.)
• Inventors: LI, Kai, Liu, Yuan, Wang, Jing, Fang, Ping
• Granted Patent: US 8,436,904 B2
• Time in Patent Office: Days
• US Class Current: 348/187
• CPC Class Codes: G06T 2207/30208 Marker matrix
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

A method for calibrating the video camera includes: obtaining the internal and external parameters of the video camera according to a reference template; recording data of a reference object in the scene; obtaining images of the reference object from at least two perspectives; and obtaining the internal and external parameters of the video camera according to the recorded data of the reference object. An apparatus for calibrating the video camera includes: a preliminary calibration unit, configured to obtain the internal and external parameters of the video camera according to a reference template, and record the data of a reference object in the scene; a recalibration unit, configured to obtain images of the reference object from at least two perspectives, and obtain the internal and external parameters of the video camera according to the recorded data of the reference object. The invention is applicable to various scenes and features simple operations.

Claims

1. A method for calibrating a video camera, comprising:

obtaining internal and external parameters of the video camera according to a reference template to calibrate the camera preliminarily, and recording data of a reference object in the same scene with the reference template; and

when the video camera needs recalibration, obtaining images of the reference object from at least two perspectives, obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera.

2. The method for calibrating the video camera according to claim 1, wherein:

the obtaining images of the reference object from at least two perspectives comprises;

obtaining images of the reference object from at least three perspectives.

3. The method for calibrating the video camera according to claim 1, wherein:

the recording of the data of the reference object in the same scene with the reference template comprises;

determining and recording positions of feature points on the reference object in the vicinity of the reference template in the scene based on the obtained internal and external parameters of the video camera according to the reference template.

4. The method for calibrating the video camera according to claim 2, wherein:

the recording of the data of the reference object in the same scene with the reference template comprises;

determining and recording positions of feature points on the reference object in the vicinity of the reference template in the scene based on the obtained internal and external parameters of the video camera according to the reference template.

5. The method for calibrating the video camera according to claim 3, wherein:

the reference template is a rectangle inscribed in a circle; and

the feature points on the reference object comprises;

the feature points on the straight lines and/or arc lines on the reference object.

6. The method for calibrating the video camera according to claim 1, wherein:

the reference object is a nameplate; and

the obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera comprises;

detecting straight lines of the nameplate in the obtained images;

fitting each straight line and establishing a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtaining coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in a world coordinate system; and

calculating the internal and external parameters of the video camera based on coordinates of images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.

7. The method for calibrating the video camera according to claim 2, wherein:

the reference object is a nameplate; and

the obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera comprises;

detecting straight lines of the nameplate in the obtained images;

fitting each straight line and establishing a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtaining coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in a world coordinate system; and

calculating the internal and external parameters of the video camera based on coordinates of images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.

8. The method for calibrating the video camera according to claim 3, wherein:

the reference object is a nameplate; and

the obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera comprises;

detecting straight lines of the nameplate in the obtained images;

fitting each straight line and establishing a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtaining coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in a world coordinate system; and

calculating the internal and external parameters of the video camera based on coordinates of images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.

9. The method for calibrating the video camera according to claim 4, wherein:

the reference object is a nameplate; and

the obtaining the internal and external parameters of the video camera at the time based on the recorded data and the images of the reference object to recalibrate the video camera comprises;

detecting straight lines of the nameplate in the obtained images;

fitting each straight line and establishing a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtaining coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in a world coordinate system; and

calculating the internal and external parameters of the video camera based on coordinates of images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.

10. An apparatus for calibrating a video camera, comprising:

a preliminary calibration unit, configured to;

obtain internal and external parameters of the video camera according to a reference template, and record data of a reference object in the same scene with the reference template; and

a recalibration unit, configured to;

when the video camera needs recalibration, obtain images of the reference object from at least two perspectives, obtain the internal and external parameters of the video camera at the time according to the recorded data of the reference object to calibrate the video camera.

11. The apparatus for calibrating the video camera according to claim 10, wherein the preliminary calibration unit comprises:

a parameter obtaining unit, configured to;

obtain the internal and external parameters of the video camera according to the reference template; and

a recording unit, configured to;

record the data of the reference object in the scene.

12. The apparatus for calibrating the video camera according to claim 11, wherein:

the reference template is a tessellation; and

the recording unit comprises a first recording unit, configured to;

according to the obtained internal and external parameters of the video camera based on the reference template, determine and record positions of feature points on the reference object in the vicinity of the tessellation in the scene.

13. The apparatus for calibrating the video camera according to claim 11, wherein:

the reference template is a rectangle inscribed in a circle; and

the recording unit comprises a second recording unit, configured to;

when detecting straight lines of the rectangle inscribed in the circle, detect straight lines and/or arc lines on the reference object, and record positions of feature points on the reference object.

14. The apparatus for calibrating the video camera according to claim 10, wherein the recalibration unit comprises:

an image obtaining unit, configured to;

obtain the images of the reference object from at least two perspectives when the video camera is to be recalibrated; and

a computing unit, configured to;

detect features of the reference object to obtain positions of images of the feature points and lines;

obtain coordinates of the images of the feature points and lines and corresponding coordinates of the reference object in a world coordinate system; and

calculate the internal and external parameters of the video camera according to the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and parameter equations.

15. The apparatus for calibrating the video camera according to claim 11, wherein the recalibration unit comprises:

an image obtaining unit, configured to;

obtain the images of the reference object from at least two perspectives when the video camera is to be recalibrated; and

a computing unit, configured to;

detect features of the reference object to obtain positions of images of the feature points and lines;

obtain coordinates of the images of the feature points and lines and corresponding coordinates of the reference object in a world coordinate system; and

calculate the internal and external parameters of the video camera according to the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and parameter equations.

16. The apparatus for calibrating the video camera according to claim 12, wherein the recalibration unit comprises:

an image obtaining unit, configured to;

obtain the images of the reference object from at least two perspectives when the video camera is to be recalibrated; and

a computing unit, configured to;

detect features of the reference object to obtain positions of images of the feature points and lines;

obtain coordinates of the images of the feature points and lines and corresponding coordinates of the reference object in a world coordinate system; and

calculate the internal and external parameters of the video camera according to the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and parameter equations.

17. The apparatus for calibrating the video camera according to claim 13, wherein the recalibration unit comprises:

an image obtaining unit, configured to;

obtain the images of the reference object from at least two perspectives when the video camera is to be recalibrated; and

a computing unit, configured to;

detect features of the reference object to obtain positions of images of the feature points and lines;

obtain coordinates of the images of the feature points and lines and corresponding coordinates of the reference object in a world coordinate system; and

calculate the internal and external parameters of the video camera according to the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and parameter equations.

18. The apparatus for calibrating the video camera according to claim 14, wherein:

the reference object is a nameplate; and

the computing unit comprises a nameplate computing unit, configured to;

detect straight lines of the nameplate;

fit each straight line and establish a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtain coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in the world coordinate system; and

calculate the internal and external parameters of the video camera based on the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.

19. The apparatus for calibrating the video camera according to claim 15, wherein:

the reference object is a nameplate; and

the computing unit comprises a nameplate computing unit, configured to;

detect straight lines of the nameplate;

fit each straight line and establish a coordinate equation to obtain positions of each vertex and point where diagonals intersect;

obtain coordinates of image points of characters on the nameplate and corresponding coordinates of the nameplate in the world coordinate system; and

calculate the internal and external parameters of the video camera based on the coordinates of the images of the feature points, the corresponding coordinates in the world coordinate system, and linear equations.