METHOD AND APPARATUS FOR IMAGE ENHANCEMENT AND ABERRATION CORRECTIONS IN A SMALL REAL IMAGE PROJECTION SYSTEM, USING AN OFF-AXIS REFLECTOR, NEUTRAL DENSITY WINDOW, AND AN ASPHERIC CORRECTED SURFACE OF REVOLUTION

摘要

A real image projection system comprises a single curved mirror having two different optical surfaces of revolution, one on the convex surface and one on the concave surface. In one embodiment, the convex surface is a conical curve of spherical or parabolic surface of revolution, coated with a reflective optical coating. The concave surface is much like that of a Mangin mirror, but it has an aspheric surface of revolution, optimized to reduce spherical aberrations over a larger area offset from the optical axis. The system optionally employs a single aspheric surface of revolution on the concave surface for reduction of aberrations, although the Mangin mirror approach, using an aspheric concave surface of revolution, is the preferred embodiment.