focal plane

  1. a plane through a focal point and normal to the axis of a lens, mirror, or other optical system.: Compare principal plane.

  2. the transverse plane in a telescope where the real image of a distant view is in focus.

Origin of focal plane

First recorded in 1890–95

Words Nearby focal plane Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use focal plane in a sentence

British Dictionary definitions for focal plane

focal plane

  1. the plane that is perpendicular to the axis of a lens or mirror and passes through the focal point

  2. the plane in a telescope, camera, or other optical instrument in which a real image is in focus

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012