CODEWITHSUNDEEP
matrixcameracomputer-visionrobotics3d-reconstruction
C graphics
C graphics

Reputation: 7458

principle point in camera matrix ( programming issue)

In a 3x3 camera matrix what does the principle point do? how its location is formed? can we visualize that? It is told that the principle point is the intersection of optical axis with the image plane. but why it is not always in the center of image? we use opencv

Upvotes: 4

Views: 8989

Answers (2)

rfabbri
rfabbri

Reputation: 253

The principal point in the 3x3 camera calibration matrix might also, more usefully, represent image cropping. If the image has been cropped around an object, then mapping the pixel coordinates to word coordinates requires a translation vector which appears as a non-centralized principal point in the matrix.

Upvotes: 1

cwadding
cwadding

Reputation: 870

The 3x3 camera intrinsics matrix is used to map between the coordinates in the image to the physical world coordinates. Similarly, the role of the principle point in this matrix is the mapping of "the intersection of optical axis with the image plane", between the coordinates in the image to the physical world coordinates. Ideally the principle point is in the center of the image, for most cameras, but this is not always the case in practice. The principle point may be slightly off center due to tangential distortion or imperfect centering of the lens components and other manufacturing defects. The 3x3 camera intrinsics matrix tries to correct this distortion.

I have found this site to be helpful to me when when learning about camera calibration. Although it is in MATLAB, it is based on the same camera calibration used in OpenCV.

Upvotes: 6

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