Cardinal point (optics)

In <a href="/facts/Gaussian_optics/Uc9IBe1v">Gaussian optics</a>, the cardinal points consist of three pairs of <a href="/facts/Point_(geometry)/6YPAvX2a">points</a> located on the <a href="/facts/Optical_axis/fKFqnagT">optical axis</a> of a <a href="/facts/Rotational_symmetry/bpvJqcnS">rotationally symmetric</a>, focal, optical system. These are the <a href="/facts/Focus_(optics)/QuRKfhg6">focal points</a>, the principal points, and the nodal points; there are two of each. For ideal systems, the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points. For simple cases where the medium on both sides of an optical system is air or vacuum four cardinal points are sufficient: the two focal points and either the principal points or the nodal points. The only ideal system that has been achieved in practice is a <a href="/facts/Plane_mirror/dLG3UepS">plane mirror</a>, however the cardinal points are widely used to approximate the behavior of real optical systems. Cardinal points provide a way to analytically simplify an optical system with many components, allowing the imaging characteristics of the system to be approximately determined with simple calculations.

Cardinal point (optics) open-in-new

Cardinal point (optics)