Short focal length video color projector employing dichroic mirror block

Apparatus for projecting on a display screen a composite color video image formed from three monochrome raster images respectively produced on the faceplates of three monochrome image display devices;

• the faceplate of each display device being convex on the interior surface thereof and having an interference filter deposited thereon in the form of an internal angularly reflective coating (IARC), said filter narrowing the spectral range and the angular distribution of the light rays from the monochrome raster produced on said faceplate;
• characterized in that said projection apparatus comprises:
• a pair of crossed dichroic mirrors forming a four-sided dichroic block for receiving in three respective entrance sides thereof the light rays from the three monochrome rasters on said faceplates and combining them to provide composite color light rays corresponding to a color video image, such composite color light rays being projected through an exit side of said block;
• a single lens element between the faceplate of each of the respective display devices and the respective entrance sides of said dichroic block;
• and
• an assembly of lens elements for receiving said composite color light rays from said dichroic block and projecting them on said display screen to form said color image thereon, said assembly including at least one optically positive lens element and forming together with said single lens elements a projection lens of which all elements except said single lens elements are located between said exit side of said dichroic block and said display screen.