Testing a Full Aperture f/0.4 Solar Dish

Authors : James Johnson, Jim Burge, Roger Angel

A new technique to map surface slope over large diameter, aspheric solar mirrors has been developed. In the test, a moving light source and a camera are located near the center of curvature of the mirror. Images of the mirror taken by the camera are recorded to show reflections from the mirror for different positions of the light source source. As each each point on the mirror is seen to reflect the source. Its surface slope is determined from the relative positions of the camera and the source, using Snell’s law of reflection. In the experimental test illustrated below, a raster of illuminated pixels on a computer LCD screen provides the moving source to measure the surface of a segment of an f/0.5 paraboloid. The technique will shortly be used to test a full aperture 3 m reflector.

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