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Field Stops

Definition: apertures which limit the field of view of imaging systems

German: Feldblenden

Categories: general optics, vision, displays and imaging

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The field of view of an imaging system, i.e., the angular range in which objects can be imaged, is always limited by some kind of optical aperture, which is called the field stop. Different apertures can play that role:

If an optical system contains multiple apertures, the field stop is that aperture which most severely limits the field of view.

Note that an optical aperture does not lead to sharp edges of the field of view, if it does not lie in a plane conjugate to the object plane. There is then some vignetting effect, i.e., a gradual decrease of image brightness at the edges. In a Keplerian telescope, for example, the field of view is limited by the ratio of the diameter of the ocular lens (essentially the barrel diameter) and the focal length of the objective. The field stop is then the barrel. As the barrel entrance is behind the intermediate image plane, there is some vignetting.

See also: optical apertures, aperture stops, imaging, field lenses, field of view, vignetting
and other articles in the categories general optics, vision, displays and imaging

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