DISCRETE-ZOOM TELESCOPE FOR FAR INFRARED Russian patent published in 2009 - IPC G02B23/00 

FIELD: physics.

SUBSTANCE: invention refers to optical instrument engineering, namely to discrete-zoom telescopic vision arrangements for infrared wavelength spectrum. Telescope contains objective and eyepiece. Objective consists of three positive components. The first component is positive meniscus convex to object. The second component consists of biconcave lens, flat-convex lens and positive meniscus convex to object. The third component is negative meniscus concave to image. The second surface of lens of the first component is aspherical. The second component of objective is introducible and removable from the optical arrangement. The eyepiece consists of three lenses. The first is biconcave, the second and the third are designed as convex to each other. All surfaces of eyepiece lenses are spherical. Herewith the following ratio occurs: 1.1<S'_p'/f'_ok<1.3, where S'_p' is removal of exit telescope pupil, f'_ok is the eyepiece focal length.

EFFECT: higher technological effectiveness ensured with lower number of aspherical surface, higher telescope light-gathering power and reduced narcissus effect with maintained high-quality imaging.

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