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US 4,339,188 AGranted
Bright screen optical viewer apparatus and method
AssigneeBeattie Systems, Inc.
InventorHarry L. O. Smith
Life of this patent
Estimating the term…
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AssigneeBeattie Systems, Inc.
InventorHarry L. O. Smith
Estimating the term…
A twin lens reflex camera has a viewing system including a ground glass screen having the viewing surface coated with a thin layer of a clear optical grade epoxy and has the coated surface mounted behind and in contact with a Fresnel lens. A pair of magnifying lenses are positioned behind the ground glass screen in front of the viewing station. The coating is applied while in solution with solvents that thereafter evaporate. A final thickness of approximately 0.0001 inch is obtained by further processing. An improvement of received image brightness of approximately 8 to 25 fold uniformly over the image screen has been measured. The magnifying lenses are adjustably mounted within the interior of the viewer to improve eye relief. A flexible hood readily adjustable on the viewer housing cooperates with adjustable flaps secured to the viewer housing to provide good contrast to the image formed on the screen.
A bright screen optical viewer for an optical device having a viewing lens projecting a received image rearwardly to a viewing station, said viewer comprising, a Fresnel lens disposed intermediate said viewing lens and said viewing station, and a ground glass viewing screen, said screen being coated on one surface with a thin layer of optically clear material having an index of refraction of about 1.55 to 1.65 and at least a 95% transmission of visible spectrum light, and means for mounting said coated surface in abutting contact with said Fresnel lens without integrally uniting said surface and said Fresnel lens intermediate said Fresnel lens and said viewing station.
A bright screen optical viewer for a twin lens camera, one of said lenses being a viewing lens, said camera including a viewer housing, means for mounting said viewer lens at one end of said housing, a viewing station disposed in optical alignment with said viewer lens defined at an opposite end of the housing from said one end, said viewer comprising, a Fresnel lens disposed intermediate said viewing lens and said viewing station, and a ground glass viewing screen, said screen being coated on one surface with a thin layer of optically clear material having an index of refraction of about 1.55 to 1.65 and at least a 95% transmission of visible spectrum light, and means for mounting said coated surface in abutting contact with said Fresnel lens without uniting said surface and said Fresnel lens intermediate said Fresnel lens and said viewing station.
The method of increasing the brightness of a ground glass optical viewing screen uniformly over the surface of the screen, said method comprising,
Dependencies are inferred from the claim text.