Free-form optical surfaces with limited mid-spatial frequency error have many applications in NASA's optical systems. Specific examples of NASA optical systems that are improved by free-form surfaces are x-ray and UV imaging instruments on weather satellites, the IRMOS spectrometer at the Kitt Peak National Observatory, and three mirror telescope systems. Three-mirror telescope systems specifically have found significant improvements with free-form surfaces. In addition, many NASA applications require tight mid-spatial frequency specifications to reduce flare in the optical systems. Specific NASA programs that have tight mid-spatial frequency specifications are the International X-ray Observatory (IXO) and the Javian planet finder. The current budgeted error for the IXO mandrels is 1.4 nm rms over the 2 mm Like with the NASA applications, almost any optical system can have better performance with free-from surfaces with limited mid-spatial frequency errors. High energy laser applications, such as National Ignition Facility (NIF) at Lawrence Livermore National Laboratory are susceptible to mid-spatial frequency errors. The MSF errors are a source of damaging intensity, specifically in the region of interest for high energy laser systems. In EUV lithography, flare is a significant problem, where flare is the optical effect of MSF errors in optical components. The MSF errors cause light to scatter into small angles and reduce image contrast. The MSF errors scales dramatically as lambda is less, which causes a worse problem as the lithography industry heads toward shorter and shorter wavelength systems. Detailed modeling by Youngworth and Stone of MSF errors in diffraction limited imaging systems showed that the variance of the MSF errors strongly affect the imagery of an optical system. Their model was specifically focused on both radial spoke errors induced from ring-tool grinding and rotational polishing marks from CNC deterministic polishing. Similar to X-Ray telescopes, the optics in X-Ray Synchrotron's are grazing incidence also suffer from degraded optical performance from scatter from MSF errors. Several labs around the country have extreme interest in this technology, such as Lawrence Berkeley Laboratory, Brookhaven and Argonne.
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