Projection screen

Abstract

An improved projection screen includes a projection lens for projecting a light image on a diffusion plate and apparatus for laterally moving the projection lens relative to the diffusion plate to eliminate undesirable polychromatic shimmer of the projected image. The projection lens may be comprised of two cylindrical Fresnel lenses arranged in stacked relation, with one Fresnel lens having parallel grooves which are arranged in perpendicular relation to parallel grooves of the other Fresnel lens. An alternative embodiment of the invention utilizes a projection lens comprised of a single Fresnel lens having a first set of parallel grooves formed in one of its faces and a second perpendicular set of parallel grooves formed in its opposite face. The projection lens may also be comprised of a spherical Fresnel lens or a cylindrical Fresnel lens with a first set of parallel grooves formed in a projection face and a second set of parallel grooves formed in the same projection face at right angles to the first set. The projection lens of the improved screen may also be comprised of a lens having a spherically reproducing honeycomb structure which forms an array of prisms or lenses.

Dependencies are inferred from the claim text.