Apparatus for uniformly illuminating a light valve

DETAILED DESCRIPTION The present invention meets the need for a simple, low cost light uniformizing or homogenizing transmission system which is cost effective, can efficiently operate using light from sources having a wide variety of sizes and shapes and can function properly within the spatial restrictions usually associated with projection or display systems.
A first aspect of the invention is an apparatus for uniformly illuminating a light valve.
Light from a light source is focused into a light tunnel.
In one embodiment of the invention the light tunnel is shaped as a right parallelepiped.
The focusing means may be one or more lenses or mirrors.
For example, the source may be located at one focus of a truncated ellipsoid mirror.
An additional mirror, in the shape of an annulus taken from the surface of a sphere, may be positioned adjacent the opening in the truncated ellipsoid.
The concave surface of the annulus reflects light back into the ellipsoid mirror, thereby capturing additional light from the source for delivery into the tunnel.
The focus of the spherical segment is coincident with the one focus of the ellipsoidal mirror.
A preferred mirror system includes a first annular paraboloid mirror positioned in edge to edge contact with the ellipsoidal mirror, the reflective surface of the paraboloid mirror forming a continuation of the reflective surface of the ellipsoid.
The focus of the paraboloid annulus coincides with the one ellipsoidal focus.
A second annular paraboloid mirror, having its reflective surface facing the reflective ellipsoid surface and having its focus coincident with the first paraboloid focus, is positioned in edge to edge contact with the first paraboloid mirror annulus.
The final mirror element is the spherical element formed as described above and positioned in space apart and symetrical relation to the second annular paraboloid mirror.
The annular openings in the paraboloid and spherical mirrors is chosen to permit passage of the cone of light reflected from the ellipsoidal mirror to the target