<title>Design of the aplanatic and anastigmatic two-mirror four-reflection system</title>

Abstract

The invention relates to a mirror system with two mirrors and four reflections, comprising a concentrating reflector and a diffusion reflector fitted on the same optical axis, an image field and a detector. The concentrating reflector has a central drilling. The concentrating reflector reflects the light to the outer part of the diffusion reflector, from where the light is reflected on the concentrating reflector again, that reflects the light on the central part of the diffusion reflector, that in turn reflects the light through the central drilling to the image plane. Prior art twin- mirror systems like the Ritchey-Chretien system do not correct astigmatism, curvature of the image field and distortion. According to the invention spherical aberration, coma and astigmatism are corrected by double reflection at both mirrors, whereby the concentrating mirror and the outer part are hyperbolically shaped and whereby the inner part of the diffusion reflector is elliptical, spherical or ellipsoidal shaped. That depends from the axial radius of curvature of the diffusion mirror in relation to the distance between both mirrors. Hence--this shape depends from the overall focal length of the mirror system in relation to the paraxial focal length of the concentrating reflector.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.