Prepopped film transparency and method of making

Claim 1

IN A FILM TRANSPARENCY MOUNT THE COMBINATION COMPRISING: (A) A PAIR OF SPACED APERTURED MEMBERS ARRANGED IN OVERLYING RELATION IN SUBSTANTIALLY PARALLEL PLANES WITH THEIR APERTURES SUBSTANTIALLY IN REGISTRY; (B) A FILM TRANSPARENCY INCLUDING AN IMAGE AREA BOUNDED BY MARGINAL SURFACES, SAID IMAGE AREA BEING SUBSTANTIALLY IN REGISTRY WITH SAID APERTURES AND SAID MARGINAL SURFACES BEING LOCATED BETWEEN SAID SPACED MEMBERS; AND (C) MEANS LOCATED ON THE ADJACENT INNER SURFACES OF SAID MEMBERS AND AT CORRESPONDING SIDES, AND IN BOUNDING RELATION TO THE APERTURES THEREIN FOR ENGAGING OPPOSITE FACES OF SAID TRANSPARENCY TO PRESTRESS THE TRANSPARENCY TO IMPART A CURVATURE TO THAT PORTION OF THE TRANSPARENCY SPANNING SAID APERTURES AND COMPRISING: (1) PROJECTIONS EXTENDING INWARDLY FROM EACH OF THE INNER SURFACES OF SAID MEMBERS WHICH ARE PARALLEL TO EACH OTHER AND HAVING TIP PORTIONS CONTACTING OPPOSING SURFACES OF SAID TRANSPARENCY ABOUT THE MARGIN THEREOF; (2) SAID PROJECTIONS ON ONE MEMBER BEING SPACED A DIFFERENT DISTANCE FROM THE CENTER OF SAID APERTURES THAN THE CORRESPONDING PROJECTIONS ON THE OTHER OF SAID MEMBERS SO THAT THE TIP PORTIONS OF OPPOSED PROJECTIONS THAT ENGAGE OPPOSITE FACES OF SAID TRANSPARENCY ARE IN THE OFFSET RELATION TO ONE ANOTHER; (3) THE DISTANCE FROM THE TIP PORTION OF EACH OF SAID PROJECTIONS ON ONE SAID MEMBERS TO THE OUTER SURFACE OF THE OPPOSITE MEMBER BEING LESS THAN THE SUM OF THE THICKNESS OF SAID TRANSPARENCY PLUS THE DISTANCE FROM THE TIP PORTION OF THE CORRESPONDING PROJECTION ON SAID OTHER MEMBER TO THE SAME OUTER SURFACE.