PC-LED luminance enhancement due to phosphor scattering

Waqidi Falicoff; Julio Chaves; Bill Parkyn

doi:10.1117/12.619517

22 August 2005 PC-LED luminance enhancement due to phosphor scattering

Waqidi Falicoff, Julio Chaves, Bill Parkyn

Proceedings Volume 5942, Nonimaging Optics and Efficient Illumination Systems II; 59420N (2005) https://doi.org/10.1117/12.619517
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

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.

Citation Download Citation

Waqidi Falicoff, Julio Chaves, and Bill Parkyn "PC-LED luminance enhancement due to phosphor scattering", Proc. SPIE 5942, Nonimaging Optics and Efficient Illumination Systems II, 59420N (22 August 2005); https://doi.org/10.1117/12.619517

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