Cardinal Points

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: a set of points which characterize the function of an optical element or a group of elements in Gaussian optics

Category: article belongs to category general optics general optics

optical properties of devices

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DOI: 10.61835/vhm Cite the article: BibTex BibLaTex plain text HTML Link to this page! LinkedIn

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What are Cardinal Points?

Various types of cardinal points are defined in Gaussian optics for characterizing the optical function of a single optical element or a group of such elements:

There are the front and back focal points at the intersection of the focal planes with the optical axis.
The principal points are at the intersections of the principal planes with the optical axis.
Further, there are the front and back nodal points.

The cardinal points can be calculated from the ABCD matrix (ray matrix), and vice versa. They are useful, for example, when geometrically constructing images of objects.

According to the basic assumptions of Gaussian optics, the rays are considered for the limiting case of small angles relative to the optical axis. If parallel incoming rays are calculated for a wider range of offsets, for example, they will generally not exactly meet in a focal point.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What are cardinal points in optics?

In Gaussian optics, cardinal points are a set of special points on the optical axis used to characterize an optical system. They include the front and back focal points, principal points, and nodal points.

What is the main application of cardinal points?

Cardinal points are primarily used to simplify the analysis of optical systems, for example in the geometrical construction of images formed by an optical element or a system of multiple elements.

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