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For a regular RGB camera, reading the wikipedia page for camera resectioning/calibration here, they divide the paramters into two categories:

Intrinsic: - focal length, scale factors in x and y, and principal point

Extrinsic: - the rigid body transform of the camera relative to some origin point

My question is how does camera calibration for a depth camera relate to these parameters, for example a Kinect v2 depth camera.

Edit: For example in the SUN RGB-D dataset, there are two files associated with each png image/ png depth image pair. An intrinsic file, and an extrinsic file.

The intrinsic file is a 3 by 3 matrix, example:

529.500000 0.000000 365.000000

0.000000 529.500000 265.000000

0.000000 0.000000 1.000000

From what I understand, using 1-indexing, entry (1,1) and (2,2) according to the camera resectioning article on wikipedia are the focal length multiplied by scale factors relating "pixels to distance" (any elaboration on this appreciated). Whereas entries (1,3), (2,3) represent the coordinates of a principal point. Is this principal point in 2-D or 3D space and what do these numbers mean?

The extrinsics file/s (for some reason there are multiple files sometimes) are a 4 by 4 matrix, example:

0.979445 0.201365 0.011827 0.000000

-0.201365 0.972640 0.115861 0.000000

0.011827 -0.115861 0.993195 0.000000

Which is a rigid body transform.

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Pretty much the same.

The intrinsic calibration tells you the relationship between stuff "out there" relative to the camera's frame of reference and the image the camera makes. The extrinsic calibration tells you how to get from the camera's frame of reference to whatever your "global" frame of reference may be.

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  • $\begingroup$ I elaborated my question a bit to make it more specific. Thanks for the help. $\endgroup$ – IntegrateThis Sep 13 '20 at 3:37

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