Chromatic Dispersion Compensation in a Fresnel Lens by Means of a Diffraction Grating

Date Published
08/1989
Publication Type
Conference Paper
Author
LBL Report Number
LBL-27950
Abstract

A Fresnel lens imaging performance can be seriously impaired by chromatic dispersion which typically doubles the diameter of the focused sun image in a solar concentrator. This problem can be alleviated by means of a molded diffraction grating whose diffraction-induced dispersion offsets and substantially cancels the lens intrinsic refractive index dispersion. The grating lines would comprise a second tier of small-scale, Fresnel-type facets superimposed on the lens facets, with a typical grating facet height of about 40 micro-inches and a facet width ranging from about 1 milli-inch at the edge of the lens to around 5 or 10 milli-inches near the center. In its primary intended application the grating would function in a core daylighting system to improve the optical performance of a collector which focuses direct sunlight into fiber optic couplers. For this application chromatic dispersion would be reduced by an order of magnitude with only a 2% loss in optical efficiency.

Conference Name
SPIE Optical Materials Technology for Energy Efficiency and Solar Conversion Conf. XIII
Year of Publication
1989
Conference Location
San Diego, CA
Custom 1
<p>Windows and Daylighting Group</p>
Organizations
Research Areas
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