Abstract
The invention relates to a mirror system with two mirrors and four reflections, comprising a concentrating reflector and a diffusing 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 diffusing reflector, from where the light is reflected on the concentrating reflector again, that reflects the light on the central part of the diffusing reflector, that in turn reflects the light through the central drilling to the image plane. Prior art two-mirror systems like the Ritchey-Chretien system do not correct astigmatism, image field curvature and distortion. According to the invention, spherical aberration, coma, and astigmatism are corrected by double reflection at both mirrors, whereby the inner part of the diffusing reflector is elliptical, spherical or ellipsoidal shaped. That depends from the axial radius of curvature of the diffusing mirror in relation to the distance between both mirrors. Hence -- this shape depends from the overall focal length of the mirror system about the paraxial focal length of the concentrating reflector.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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