|Title:|| Projection screen|
|Abstract:||Large projection screens, of which planetarium domes are typical, may conveniently be made up of a plural of prefinished panels, at least one edge of at least some of which panels overlaps another panel in a lap joint construction so that edges of the panels have a minimal effect upon light directed upon the screen from any angle. Panel edges overlapping another panel are tapered from a generally uniform thickness to substantially reduced thickness at the edge in a relatively short distance compared to panel dimensions and made to conform to and lay against the other panel. The panels are preferably made by a method which may involve either first shaping or finishing the projection surface of the dome panel. Each edge which will overlap another panel is then chamfered on the surface opposite the finished surface to form the taper. Finally the chamfered edge is deformed so that it will lay against and conform to the panel which it overlaps.|
|Inventor(s):|| Ward, Jr.; Robertson (Chicago, IL) |
1. In a projection screen that includes a plurality of curved interior reflective surfaces arranged to provide at least one generally circularly arranged row of reflective surfaces and
whereby each pair of adjacent surfaces is constructed and arranged to provide minimal effect upon reflection of projected light from the region of adjacency of the pair of surfaces, the improvement in construction comprising, in combination:
at least one of each adjacent pair of the plurality of curved surfaces being provided as part of a prefinished panel that is of a size and shape to have an edge portion thereof overlap an edge portion of the adjacent curved reflective surface;
said prefinished panel including a substrate sheet of metal that is originally of uniform thickness and is deformable and easily set upon deformation beyond the metal's elastic limit, and a continuous uniform reflective finish provided on the
concave side of the substrate metal sheet prior to deformation of the metal sheet;
a portion of the panel adjacent the edge thereof that overlaps the adjacent curved reflective surface being shaped and arranged and deformed, without destroying the continuous character of the uniform reflective finish on the metal substrate, to
have the face of reflective finish at the edge terminus of the panel terminate adjacent the said adjacent reflective surface, with the thickness of the substrate sheet of metal adjacent said edge terminus being lessened, resulting in providing a back
surface, opposite the reflective surface, that will lie adjacent the adjacent curved reflective surface, to cause the reflective finish at the edge terminus of the panel to be located closely adjacent the overlapped curved reflective surface, thereby
minimizing any discontinuity between the reflective finish on the panel and the overlapped reflective surface.
2. A projection screen as in claim 1 wherein the screen has the shape of a hollow dome suitable for a planetarium.
3. A projection screen as in claim 2 wherein the screen includes a plurality of circularly arranged rows of reflective surfaces that are spherically dished.
4. A projection screen as in claim 2 including a support frame conforming to the shape of the dome.