Trasform focal length from pixel to world unit

I done a calibration of my stereo system camera by the toolbox. The output was an object StereoParameters. I seen inside a intrisicMatrix, where the focal length is expressed in pixel. How i can have the focal length in world unit? How i can calculate sx and sy (pixels per world unit in the x and y direction respectively)?

Answer 1

[Dima Lisin]

During camera calibration you can only calculate the ratio of the focal length to the pixel size, i. e. the focal length in pixels. You cannot calculate the focal length in world units and the pixel size separately. The best you can do is look up the pixel size from the manufacturer's spec, and then calculate the focal length in millimeters.

Answer 2

[George Abrahams]

Hi @dix93. Please see the camera calibration documentation on the intrinsic parameters. The intrinsic matrix has the following elements:

where is the focal length in pixels.

Then, to calculate F, the focal length in world units, or , where is the pixel size in world units.

As @Dima Lisin said, the values for should be available in the camera's technical specifications.