Infrared afocal zoom telescope

Details Infrared afocal zoom telescope Infrared afocal zoom telescope

1986-04-21

1989-02-07

Corbin, John K.

350 12, 350427, 350560, G02B 1314, G02B 1516

Patent

active

048027170

ABSTRACT:
An afocal zoom lens system is provided that has particular utility for use in aircraft navigation systems where a unitary (1.0.times.) magnification power is desirable. Two embodiments are disclosed, the first providing an 8:1 magnification ratio with the second embodiment providing a 12:1 ratio. Both embodiments employ four lens groups including a front fixed objective lens (A,E), a second lens group including a negative zooming element (B,F), a third fixed group (C,G) and a fourth rear negative zooming element (D,H). In the highest magnification position, the lenses are arranged so that the front zooming element is positioned adjacent the positive lens of the the third group to form a weak negative doublet. In the minimum magnification position, the front zoom element is widely separated from the third group to create an inverse telephoto Galilean form. The rear zoom element and aperture stop move together to maintain collimation of the output beam and to hold the diameter of the on-axis exit beam to a constant value.

REFERENCES:
patent: 3825315 (1974-07-01), Altman et al.
patent: 3947084 (1976-03-01), Noyes
patent: 4249793 (1981-02-01), Uehara
patent: 4479695 (1984-10-01), Neil
patent: 4486069 (1984-12-01), Neil et al.
patent: 4632498 (1986-12-01), Neil
Roberts, "Compact Infrared Continuous Zoom Telescope", Optical Engineering, vol. 23, No. 2, Mar./Apr., 1984.
Jamieson, "Zoom Lenses for the 8u-13u Waveband", Optica Acta, vol. 18, No. 1 (1971).
Neil, "Zoom Lenses for the Thermal Infrared", Optical Systems Design, Analysis, and Production; vol. 339, Apr. 1983.
Neil, "Use of Chalcogenide Glass in Thermal Infrared Telescopes", SPIE, vol. 237, 1980 International Lens Design Conference (OSA).

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