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Optics Lab
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The optics lab includes a vacuum evaporation system for coating mirrors up to 0.3 meters in diameter, an actuator and faceplate assembly and testing area, and an 8-meter long optical test tunnel. Optical testing is done using various techniques. A small and a large contact interferometer using Newton rings are used during mirror fabrication. For non-contact evaluation a Zygo interferometer is used. 1-meter diameter mirrors can be evaluated here.
In addition to measuring the optical figure the radius of curvature can be determined accurately even for mirrors having radii of over 100 meters. Since most of the optical path length is virtual, the effect of atmospheric turbulence is minimal. In addition a large Hindle sphere is being completed to measure the optical figure of either concave or convex large mirrors. Convex mirrors are usually needed to form mandrels for concave composite optical transfer mirrors, and are difficult to measure using more common techniques.
We also have a 20 meter long optical tunnel where we use a Michelson Interferometer for dynamic interference monitoring of the performance of adaptive optics actuators operating at frequencies from dc to over one kilohertz, and a Coblenz sphere for measuring the angular dependence of scattered light and the microroughness at any point on a mirror surface down to irregularities of one A rms or one ten billionth of a meter.
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Vacuum coating of mirrors is also done at BOR. The figure above shows a just-coated 0.3-meter aperture composite mirror intended as an adaptive optic useable at lower elevations for applications such as the Space Elevator, which will operate on the equator at sea level.
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