focal plane

noun Optics.

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

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British Dictionary definitions for focal plane

focal plane

noun

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