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
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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
Tiny robot arms position the ends of 5000 optical fibers to match the locations of galaxies on the telescope’s focal plane, and quickly reposition them when the telescope moves to different part of the sky.
From Science Magazine ● Apr. 4, 2024
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
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.
