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focal plane

noun, Optics.
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
1890-1895
1890-95
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for focal-plane

focal plane

noun
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
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10
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