Afocal refractor telescopes

Details Afocal refractor telescopes Afocal refractor telescopes

1981-02-25

1983-08-09

Henry, Jon W.

350 12, 350481, 350564, G02B 102, G02B 910, G02B 2300

Patent

active

043975208

ABSTRACT:
An afocal refractor telescope (10) is formed by a fixed focus achromatic objective system (11) and a fixed focus eyepiece system (12) aligned on a common optical axis (13), the objective system (11) being formed by two lens elements (C, D) and the eyepiece system (12) being formed by two lens elements (A, B), each of the four lens elements (A, B, C, D) being made of a material which has a useful spectral bandpass in the infrared wavelength region, and having refractive surfaces (1,2,3,4,5,6,7,8) intercepting the optical axis (13) which are substantially spherical, lens element (c), which is proximal the eyepiece system (12) being color corrective, with a V-value not less than 120, negatively powered and having a lower refractive index than lens element (D) which is positively powered. Conveniently lens element (C) is made of Chalcogenide glass and each of lens elements (A, B and D) is made of germanium.

REFERENCES:
patent: 2865253 (1958-12-01), Thielens
patent: 3622218 (1971-11-01), Kruger
patent: 3674330 (1972-07-01), Strong
patent: 3825315 (1974-07-01), Altman et al.
patent: 3947084 (1976-03-01), Noyes
patent: 4199217 (1980-04-01), Rogers
Klee, H. W., & M. W. McDowell, Optical Eng., vol. 19, No. 5, Oct. 1980, pp. 748-752.

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