focal plane
Americannoun
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a plane through a focal point and normal to the axis of a lens, mirror, or other optical system.
-
the transverse plane in a telescope where the real image of a distant view is in focus.
noun
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the plane that is perpendicular to the axis of a lens or mirror and passes through the focal point
-
the plane in a telescope, camera, or other optical instrument in which a real image is in focus
Etymology
Origin of focal plane
First recorded in 1890–95
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
The process was time consuming in instances when a worm left the focal plane of the camera, blurring the image, in which case Ran needed to click by hand to record its position.
From Science Daily • Oct. 15, 2025
A four-story tower was built on top of the foundation, and the focal plane, or the height of the light, is 63 feet.
From Washington Post • Sep. 2, 2022
Its traditional 12-megapixel sensor has a larger focal plane than the Ultra.
From The Verge • Mar. 11, 2020
The instrument has 5000 fibers attached to its 0.8-meter-wide focal plane.
From Science Magazine • Sep. 11, 2019
With telescopic sights, a fine hair in the focal plane of the telescope provides a far more accurate guide to the precise alignment of a star.
From "The Scientists" by John Gribbin
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
