Uniform variable light sources for instrument calibration.
This paper describes light sources that were developed for use in calibrating cameras for space exploration. The design produces a nearly uniform luminance field whose correlated color temperature ranges from 4000 K to 5000 K in the visible. Luminance of the source may be continuously varied by as much as 500:1 without affecting the uniformity of the field. The sources, consisting basically of two integrating cavities with an iris diaphragm interposed, use xenon light. Luminances as high as 25,000 cd m(-2) are possible. Such sources are used for light-transfer calibration, as well as spectral response of camera systems. After a brief theoretical treatment, the design variations are discussed. Measurement data on these sources indicates that the angular luminance distribution approximates a uniform diffuser within a 50-deg cone.
Squyres
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Rennilson
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