Paraxial ray

EN: Paraxial ray


A light ray which passes close to the optical axis and is inclined at a very small angle with respect to the optical axis. The point at which paraxial rays converge is called the paraxial focal point. Since the image formed by a monochromatic paraxial ray is in principle free of aberrations, the paraxial ray is an important factor in understanding the basic operation of lens systems.
Canon glossary EU