1979-08-28
1981-05-26
Henry, Jon W.
350453, G02B 702
Patent
active
042694744
ABSTRACT:
This invention provides an improvement of a wide-angle optical door viewer having a wide-angle optical system for bringing into view more than 190 degrees of vision, which is set through a wall, a door or the like to enable viewing of an object located outside the door from the inside of the door. The system is composed of an assembly of a first objective having surfaces with different curvatures on opposite sides, a second objective having a concave surface with a special curvature on one side and a flat surface on the opposite side, a third objective having concave surfaces of different curvature on both sides, and an eyepiece. A cylindrical sleeve for maintaining the focal length is placed between the third objective and the eyepiece, and a colored filter is placed at an appropriate location with the lenses assembled in parallel into an inner tube from one end thereof, the inner tube being screwed and set into an outer tube.
REFERENCES:
patent: 3514188 (1970-05-01), Blosse et al.
patent: 4116529 (1978-09-01), Yamaguchi
patent: 4172636 (1979-10-01), Yanagimachi
patent: 4175824 (1979-11-01), Daley
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