US Patent 7604354 Three-dimensional projection apparatus using coaxial optical alignment

A projection apparatus comprising a three-dimensional screen, a convex mirror, two or more projectors, and an assemblage of flat mirrored surfaces that share at least one common edge or apex that faces the convex mirror. The flat mirrored surfaces fold the images from separate projectors into a common image that has single optical axis aligned with principal axis of the convex mirror so that the combined image is reflected from the convex mirror onto the three dimensional screen.