1987-03-19
1989-05-02
Corbin, John K.
350557, 350569, 350145, 350173, G02B 2300, G02B 2302, G02B 2714
Patent
active
048263028
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Electronic nightvision devices, where a scene is projected by a fast objective lens on the photo-cathode of an image intensifier and where a phosphorous screen of the same intensifier is viewed through a magnifier or a microscope, are used in the dark, with the night sky and the stars as the only illumination.
Such an instrument may have one eyepiece or it may be binocular, whereby the light from the phosporous screen is divided by a beam splitter to two eyepieces so that the observer may watch the phosphorous screen with both eyes. The device may be designed for handheld use--usually with several times magnification--or it may be fitted to the head like spectacles or attached to a helmet. In this latter application the device is called night visiion goggles, usually with unit magnification so that the observer is viewing the night scene in natural scale.
Since the observer in many applications must carry the night vision goggles for extended time periods, it is particularly important that they be as light as possible and that they not protrude unnecessarily in front of the observer, because the associated downward torque would cause neck strain. However, the components of the goggles objective lens, image intensifier tube, microscope unit, batteries etc.--are by necessity comparatively heavy and are according to prevailing design principles, so oriented that the whole device protrudes about 12-20 cm in front of the eyes of the observer. The experience with such an instrument is often that the front weight is embarrassing: Furthest away from the observer is a fast and thus comparatively heavy objective lens, followed by an image intensifier and finally a binocular microscope system with a beam splitter closest to the observer. The optical axis through the objective lens and the image intensifier are thus parallel with the line of sight against the scene being viewed.
SUMMARY OF THE INVENTION
According to the invention, the optical axis of the image intensifier and possibly also the optical axis of the objective lens are oriented at right angles relative to the line of sight. Through this simple measure, the length of the device in front of the observer is significantly reduced to about 6 cm, i.e., less than half of a conventional design. The center of gravity is moved correspondingly closer to the observer, which makes it considerably easier to carry the night vision goggles without observer fatigue, this being the main purpose of the invention.
The invention furthermore enables significant simplification of the design of the binocular microscope system through which the phosphorous screen is being viewed: The orientation of the image intensifier in a horizontal plane and at right angles relative to the line of sight makes the entrance of rays into the microscope asymmetric in relation to the observer, i.e., from the side of the instrument. This fact makes it feasible to arrange a more efficient beam splitter system with very few optical components.
Conventional nightvision goggles have symmetric microscope systems such that the rays from the image intensifier enter the microscope viewing system at the center. Such an arrangement necessitates the use of a larger number of optical components than is the case according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The single FIGURE shows an exemplary embodiment of the invention. The instrument has the approximate shape of a horizontal bar having a substantially rectangular profile in front of the eyes of the observer. The instrument lacks such delicate protruding details as the objective lens. The binocular microscope system, including the eyepieces 13A and 13B, is located in the same horizontal plane as the eyes of the observer. The objective lens 1 and the image intensifier 2 are located in a plane immediately above. The largest dimension of the instrument is along a horizontal direction from side to side, where it however does not collide with an eventual helmet (in a vertical direction), nor creates any annoying t
REFERENCES:
patent: 3195404 (1965-07-01), Bouwers
patent: 4467190 (1984-08-01), Hadani
patent: 4653879 (1987-03-01), Filipovich
patent: 4737023 (1988-04-01), Kastendieck et al.
Corbin John K.
Kachmarik Ronald M.
Simrad Optronics A/S
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