Low profile episcopic projector and opaque materials therefor

Claim 1

A large copy optical projector capable of imaging a generally horizontal copy sheet on a generally vertical viewing screen spaced from said projector, said copy sheet having an upper face and a lower face, said lower face being reflectorized, said optical projector comprising: a. housing means defining an enclosed chamber, said housing means having a substantially horizontal upper portion, said upper portion having a first opening throughout a major portion of its area; b. a flat Fresnel lens at said opening in said upper portion, said Fresnel lens being substantially coextensive with said opening in said upper portion; c. said copy sheet, when releasably placed on said Fresnel lens, being substantially coextensive therewith and having substantially the entire upper face of said copy sheet accessible visually and manually to an operator; d. said housing means having a second opening, objective lens means at said second opening for receiving imaging light along an imaging path and defining a projection axis that is directed toward said generally vertical viewing screen; e. lamp means in said chamber for directing illuminating light along an illuminating path; f. an oblique plane mirror underlying said Fresnel lens within said chamber, an edge of said mirror being adjacent to an edge of said Fresnel lens; g. said illuminating light diverging in said illuminating path along a first illuminating axis communicating with said oblique plane mirror and then being reflected along a second illuminating axis communicating with said Fresnel lens; h. said imaging light reflected from said copy sheet being converged by said Fresnel lens in said imaging path along a first imaging axis communicating with said oblique plane mirror and then being reflected along a second imaging axis communicating with said objective lens means; i. said lamp means and said objective lens means being disposed at one side of said oblique plane mirror; j. said projection axis being disposed externally of the region directly overlying said Fresnel lens; k. said Fresnel lens directing substantially parallel illuminating light to said bottom face of said copy sheet and receiving substantially parallel imaging light from said bottom face of said copy sheet; and l. said chamber being substantially light tight with respect to stray light therewithin when said copy sheet is superposed on said Fresnel lens.