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Proceedings Paper

PC-LED luminance enhancement due to phosphor scattering
Author(s): Waqidi Falicoff; Julio Chaves; Bill Parkyn
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Paper Abstract

Nonimaging optics needs to address the interesting effects upon white-LED luminance of scattering within a photoluminescent phosphor, and how strong scattering leads to luminance recycling of TIR-trapped phosphor-emission. This paper analyzes LED optical systems that extract light by multiple internal reflections and varying degrees of bulk scattering. The luminance values of such devices can greatly exceed those predicted by the luminance-conservation law of etendue, formulated for non-scattering, non-recycling optical architectures. To illustrate this, the results of extensive modeling of LED architectures via a commercial raytracing package are described and analyzed. The analysis includes the effects of bulk scattering within the phosphor, and reveals the crucial role of diffuse reflectance, within the LED itself below its emitting layer. The study shows how it is possible to achieve an increase luminance in an LED via use of flat-windows over an LED as opposed to the traditional approach of dome-covers, albeit with some loss of overall luminosity extraction. The paper includes a discussion of luminance-luminosity tradeoffs and a summary of analytical and numerical methods for modeling optical systems involving bulk scattering.

Paper Details

Date Published: 22 August 2005
PDF: 15 pages
Proc. SPIE 5942, Nonimaging Optics and Efficient Illumination Systems II, 59420N (22 August 2005); doi: 10.1117/12.619517
Show Author Affiliations
Waqidi Falicoff, Light Prescriptions Innovators LLC (United States)
Julio Chaves, Light Prescriptions Innovators LLC (United States)
Bill Parkyn, Light Prescriptions Innovators LLC (United States)


Published in SPIE Proceedings Vol. 5942:
Nonimaging Optics and Efficient Illumination Systems II
Roland Winston; R. John Koshel, Editor(s)

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