New Optical Systems For The Measurement Of Diffuse Reflectance

Keith A. Snail

doi:10.1117/12.975520

13 October 1986 New Optical Systems For The Measurement Of Diffuse Reflectance

Keith A. Snail

Proceedings Volume 0643, Infrared, Adaptive, and Synthetic Aperture Optical Systems; (1986) https://doi.org/10.1117/12.975520
Event: 1986 Technical Symposium Southeast, 1986, Orlando, United States

Abstract

A new class of two-stage optical systems are proposed for the measurement of diffuse reflectance. The proposed systems consist of a single ellipsoidal or dual paraboloidal primary mirror and a nonimaging compound parabolic concentrator (CPC) as the secondary mirror. When operated in the direct mode, the CPC's larger aperture is occupied by the reflectometer's detector, the CPC's smaller aperture resides at the focus of the primary mirror, and the CPC half-angle is chosen so as to minimize the angular dependence of the detector's response. The resultant uniformity of the detector/CPC response over the hemisphere overcomes a major disadvantage of using ellipsoid and paraboloid-type reflectometers in the direct mode, at the expense of a slightly larger detector area. In the reciprocal mode, the CPC's larger aperture is occupied by a high temperature source, with the CPC's field of view chosen so as limit the variation in the source's directional emissivity to less than one percent. This source design offers less stray radiation than a cavity-type source with comparable Lambertian properties. The emissivity and wavelength dependence of the CPC source is determined by the high temperature surface. An analysis of the design tradeoffs for CPC/conic section reflectometers is given including ray tracing.

Citation Download Citation

Keith A. Snail "New Optical Systems For The Measurement Of Diffuse Reflectance", Proc. SPIE 0643, Infrared, Adaptive, and Synthetic Aperture Optical Systems, (13 October 1986); https://doi.org/10.1117/12.975520

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