Transparency overhead projector

Details Transparency overhead projector Transparency overhead projector

1988-08-22

1990-08-28

Cuchlinski, Jr., William A.

Optics: image projectors

Episcope

G03B 211

Patent

active

049520539

ABSTRACT:
The invention concerns a transparency overhead projector having an illumination unit of which the height has been extremely reduced. The main component of the illumination unit is a specular surface comprising mutually parallel, mirrorized prismatic shoulders either on its top or on its lower side, which reflect the light from at least one lateral source toward the Fresnel lens, the platen and the projecting lens. The specular surface may be plane, however it may also be curved in circular, hyperbolic etc. manner in the longitudinal direction of the prismatic shoulders. This curvature may be constant or it may vary. Further, the specular surface also may be twisted, that is, it may also be curved in a direction orthogonal to the prismatic shoulders, and this curvature also may be constant or variable. However the prism angles of the individual prismatic shoulders are always individually determined so that the light shall appear to come from a source which seems to be mounted centrally along the optical axis underneath the Fresnel lens.

REFERENCES:
patent: 2529664 (1950-11-01), Roysher
patent: 2660087 (1953-11-01), Domeshek
patent: 3523721 (1970-08-01), Hofmann
patent: 3752574 (1973-08-01), Kato et al.
patent: 3752575 (1973-08-01), Ataka
patent: 3877802 (1975-04-01), Greenspan
patent: 4652101 (1987-03-01), Grunwald
patent: 4674850 (1987-06-01), Blom
patent: 4741613 (1988-05-01), Vanderwerf

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