Variable aperture for infra-red cameras
First Claim
1. A variable aperture assembly for an infrared camera, said infrared camera for use with optics comprising at least two f-numbers, a radiation shield, cooling means, a central axis, a focal plane array mounted substantially coaxial and substantially perpendicular to said central axis, said radiation shield and said focal plane array being thermally connected to said cooling means, said radiation shield having an optical entrance end accepting infrared radiation passing through said optics and a thermal connection end proximal to said focal plane array providing said thermal connection to said cooling means, said radiation shield being positioned to block stray radiation from an inside surface of said infrared camera, and an optical path substantially along said central axis, infrared radiation being admitted through said optics along said optical path, passing through said optical entrance end of said radiation shield and arriving at said focal plane array, said variable aperture assembly comprising:
- a variable iris disposed substantially along said central axis;
said variable iris having an infrared radiation admitting central opening coaxial to said central axis;
said variable iris being located substantially at a same position along said central axis as an exit pupil of said optics, forming an aperture stop;
said variable iris thermally connected to said cooling means;
said variable iris capable of causing said infrared radiation admitting central opening to vary in size;
mounting means for mounting said variable iris;
said mounting means allowing said thermal connection to said cooling means;
said mounting means positioning said variable iris proximal to said optical entrance end of said radiation shield;
said mounting means being designed to minimize deflection of said variable iris,causing said variable iris to remain substantially parallel to a plane of said exit pupil;
actuation means for controlling said size of said infrared radiation admitting central opening of said variable iris;
thermal isolation means for connecting said variable iris to said actuation means;
said thermal isolation means comprising a sufficiently rigid structure designed to reduce conductive heat transfer from said actuation means to said variable iris;
said sufficiently rigid structure being sufficiently strong to minimize flexion of said thermal isolation means caused by said actuation means;
wherein said variable aperture assembly provides f-number matching by adjusting said infrared radiation admitting central opening at least small enough to effectively match a highest f-number of said optics and large enough to effectively match a lowest f-number of said optics.
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Accused Products
Abstract
A variable aperture assembly for an infrared camera for use with optics having two or more f-numbers. The variable aperture assembly includes a variable iris disposed substantially along an axis of the infrared camera and is thermally connected to a cooling assembly. The variable iris is capable of causing an infrared radiation admitting opening to vary in size. The infrared radiation admitting openings of the variable aperture assembly can be circular or non-circular, including generally rectangular or racetrack shaped openings. The variable aperture assembly provides f-number matching by adjusting the infrared radiation admitting opening to the size necessary to effectively match the numerous f-numbers of the optics, or by adjusting to a size so that a fixed aperture on the radiation shield becomes the effective aperture stop, providing the f-number matching.
29 Citations
28 Claims
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1. A variable aperture assembly for an infrared camera, said infrared camera for use with optics comprising at least two f-numbers, a radiation shield, cooling means, a central axis, a focal plane array mounted substantially coaxial and substantially perpendicular to said central axis, said radiation shield and said focal plane array being thermally connected to said cooling means, said radiation shield having an optical entrance end accepting infrared radiation passing through said optics and a thermal connection end proximal to said focal plane array providing said thermal connection to said cooling means, said radiation shield being positioned to block stray radiation from an inside surface of said infrared camera, and an optical path substantially along said central axis, infrared radiation being admitted through said optics along said optical path, passing through said optical entrance end of said radiation shield and arriving at said focal plane array, said variable aperture assembly comprising:
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a variable iris disposed substantially along said central axis; said variable iris having an infrared radiation admitting central opening coaxial to said central axis; said variable iris being located substantially at a same position along said central axis as an exit pupil of said optics, forming an aperture stop; said variable iris thermally connected to said cooling means; said variable iris capable of causing said infrared radiation admitting central opening to vary in size; mounting means for mounting said variable iris; said mounting means allowing said thermal connection to said cooling means; said mounting means positioning said variable iris proximal to said optical entrance end of said radiation shield; said mounting means being designed to minimize deflection of said variable iris, causing said variable iris to remain substantially parallel to a plane of said exit pupil; actuation means for controlling said size of said infrared radiation admitting central opening of said variable iris; thermal isolation means for connecting said variable iris to said actuation means; said thermal isolation means comprising a sufficiently rigid structure designed to reduce conductive heat transfer from said actuation means to said variable iris; said sufficiently rigid structure being sufficiently strong to minimize flexion of said thermal isolation means caused by said actuation means; wherein said variable aperture assembly provides f-number matching by adjusting said infrared radiation admitting central opening at least small enough to effectively match a highest f-number of said optics and large enough to effectively match a lowest f-number of said optics. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A multiple discrete f-number variable aperture assembly for an infrared camera for use with optics comprising multiple discrete f-numbers, said infrared camera comprising a radiation shield, cooling mechanism, a central axis, a focal plane array mounted substantially coaxial and substantially perpendicular to said central axis, said radiation shield and said focal plane array being thermally connected to said cooling mechanism, said radiation shield having an optical entrance end accepting infrared radiation passing through said optics and a thermal connection end proximal to said focal plane array providing said thermal connection to said cooling mechanism, said radiation shield being positioned to block stray radiation from an inside surface of said infrared camera, and an optical path substantially along said central axis, infrared radiation being admitted through said optics along said optical path, passing through said optical entrance end of said radiation shield and arriving at said focal plane array, said multiple discrete f-number variable aperture assembly comprising:
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at least two discrete apertures disposed substantially along said central axis; said at least two discrete apertures having infrared radiation admitting central openings coaxial to said central axis; said at least two discrete apertures being located substantially along said central axis proximal to a plane of an exit pupil of said optics, forming an aperture stop; said at least two discrete apertures thermally connected to said cooling mechanism; said at least two discrete apertures capable of causing said infrared radiation admitting central opening to vary in size between sizes of said at least two discrete apertures; mounting apparatus for mounting said at least two discrete apertures; said mounting apparatus allowing said thermal connection to said cooling mechanism; said mounting apparatus positioning said at least two discrete apertures proximal to said optical entrance end of said radiation shield; said mounting apparatus being designed to minimize deflection of said at least two discrete apertures, causing said at least two discrete apertures to remain perpendicular to said central axis; a selection mechanism configured to cause one of said at least two discrete apertures to provide said infrared radiation admitting central opening;
said selection mechanism configured for thermal isolation;said selection mechanism comprising a substantially rigid structure designed for high thermal isolation, to reduce conductive heat transfer from said selection mechanism to said at least two discrete apertures; said substantially rigid structure to minimize flexion; wherein said variable aperture assembly provides f-number matching by selecting said infrared radiation admitting central opening from said at least two discrete apertures, selecting one of said at least two discrete apertures to effectively match a highest f-number of said optics or one of said at least two discrete apertures to effectively match a lowest f-number of said optics. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28)
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Specification