Method and apparatus for calibrating video camera

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, recalibrating the video camera base on the images of the reference object from at least two perspectives and the internal and external parameters of the video camera at the time.

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, adapted 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, adapted 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, calibrate the video camera base on the images of the reference object from at least two perspectives and the internal and external parameters of the video camera at the time.

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

a parameter obtaining unit, adapted to: obtain the internal and external parameters of the video camera according to the reference template; and

a recording unit, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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, adapted 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.