Temperature compensating focusing in infrared zoom lenses
Patent 4148548 Issued on April 10, 1979. Estimated Expiration Date: 
September 19, 1997. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
September 19, 1997. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3825315 3840290 Long-wave infrared afocal zoom telescope Varifocal lens system with macro-photography capabilities Three element varifocal lens systems Focusing mechanism for varifocal objective Lens system capable of wide range zooming and macrophotography Patent #: 4080047 InventorAssigneeApplicationNo. 05/834523 filed on 09/19/1977US Classes:359/354, Including continuously variable magnification or focal length (zoom lens, adjustable lens)359/357, Having four or more components359/676, With variable magnification (e.g., zoom type)359/683, With mechanical compensation359/694Adjusting mechanismExaminersPrimary: Stern, Ronald J.Attorney, Agent or FirmInternational ClassesG02B 13/14 (20060101)G02B 15/14 (20060101) Foreign Application Priority Data1976-10-02 GBAbstractThis invention provides a lens which operates in a waveband in the infra-red region of the electromagnetic spectrum and which has a variable focus or magnification. The invention relates particularly to an infra-red zoom lens. The lens has a front part and a rear part which are adjustable axially towards and away from one another and a middle part whose function is to provide different focal length or magnification settings. The adjustability of the front and rear parts of the lens assists in overcoming the defocussing effect of temperature variations, the front and rear parts being held stationary when a focussed image of an object is formed in a desired image plane. In a zoom lens the middle part is a zoom part with elements movable axially to vary the image size in the image plane, the front and rear parts being adjustable axially relative to each other and to the range of movement of the elements of the zoom part.Other References
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