Apparatus for showing microdocuments

Details Apparatus for showing microdocuments Apparatus for showing microdocuments

1977-11-25

1979-06-05

Stephan, Steven L.

Optics: image projectors

Distortion compensation

For projection axis inclined to screen

350 9, 350122, 350211, 352104, 353 75, G03B 2130, G03B 2156, G02B 308

Patent

active

041572149

ABSTRACT:
A compact microimage viewing apparatus is disclosed which utilizes a low intensity light source with wide-angle projection optics to provide a clear and highly illuminated image to the viewer. To achieve compactness, the high brightness light-distributive screen of the viewing apparatus is located at an acute angle to the axis of projection of the projection lens. Keystone distortion of the projected image is substantially eliminated by employing a correcting lens, preferably a Fresnel lens, between the screen and the viewer at a predetermined angle to the screen such that the image portion projected onto the edge of the screen nearest to the projection lens, which would otherwise appear smaller to the viewer than would the image portion projected onto the farthermost edge of the screen, is magnified to an extent that a rectangular and substantially non-distorted image is presented to the viewer.

REFERENCES:
patent: 2891444 (1959-06-01), Ewald
patent: 3253505 (1966-05-01), Miller
patent: 3658415 (1972-04-01), Miles
patent: 3930723 (1976-01-01), Holt

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