The
cardinal points and the associated
cardinal planes are a set of special
points and
planes in an
optical system, which help in the analysis of its
paraxial properties. The analysis of an optical system using cardinal points is known as
Gaussian optics, named after
Carl Friedrich Gauss.
The cardinal points and planes of an optical system include
For a lens, there will be two of each of these, identified by "front" and "rear" depending on whether they are on the input or the output side of the lens, respectively.
These points and planes, together with the aperture stop, and the chief and marginal rays of the system, define the locations and sizes of the entrance and exit pupils of the system, as well as its other image-forming properties, such as the focal length and magnification.
