Geometric calibration of a camera or a stereoscopic vision sensor
Transformation between the camera reference frame and the sensor reference frame (retinal plane)
The second transformation, referred as
on Figure 2 binds the camera reference frame
to the sensor reference frame
(retinal plane). This is a perspective projection (3×4 matrix, referred as
) that transforms a 3D point
into an image point
(in metric units).
(2)
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where
refers to the focal length of the lens used.
Equation (2) that shows the perspective projection is to be written:
These equations are non-linear ones.
The use of homogenous coordinates makes it possible to write the perspective projection (and the complete pinhole camera model) under a linear form (see equation (2)).