afocal system

afocal system

(ay-foh -kăl) An optical system in which both the object and the secondary image are infinitely distant. It is the usual adjustment in a simple refracting telescope and is produced when the objective and eyepiece lenses are separated by the sum of their focal lengths: the lenses are then confocal.

afocal system

[′ā·fō·kəl ′sis·təm]
(optics)
An optical system of zero convergent power, for example, a telescope.
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