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Proceedings Paper

Determining contrast sensitivity functions for monochromatic light emitted by high-brightness LEDs
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Paper Abstract

Light-emitting diode (LED) technology is becoming the choice for many lighting applications that require monochromatic light. However, one potential problem with LED-based lighting systems is uneven luminance patterns. Having a uniform luminance distribution is more important in some applications. One example where LEDs are becoming a viable alternative and luminance uniformity is an important criterion is backlighted monochromatic signage. The question is how much uniformity is required for these applications. Presently, there is no accepted metric that quantifies luminance uniformity. A recent publication proposed a method based on digital image analysis to quantify beam quality of reflectorized halogen lamps. To be able to employ such a technique to analyze colored beams generated by LED systems, it is necessary to have contrast sensitivity functions (CSFs) for monochromatic light produced by LEDs. Several factors including the luminance, visual field size, and spectral power distribution of the light affect the CSFs. Although CSFs exist for a variety of light sources at visual fields ranging from 2 degrees to 20 degrees, CSFs do not exist for red, green, and blue light produced by high-brightness LEDs at 2-degree and 10-degree visual fields and at luminances typical for backlighted signage. Therefore, the goal of the study was to develop a family of CSFs for 2-degree and 10-degree visual fields illuminated by narrow-band LEDs at typical luminances seen in backlighted signs. The details of the experiment and the results are presented in this manuscript.

Paper Details

Date Published: 26 January 2004
PDF: 7 pages
Proc. SPIE 5187, Third International Conference on Solid State Lighting, (26 January 2004); doi: 10.1117/12.509195
Show Author Affiliations
Vasudha Ramamurthy, Rensselaer Polytechnic Institute (United States)
Nadarajah Narendran, Rensselaer Polytechnic Institute (United States)
Jean Paul Freyssinier, Rensselaer Polytechnic Institute (United States)
Ramesh Raghavan, Rensselaer Polytechnic Institute (United States)
Peter Boyce, Rensselaer Polytechnic Institute (United States)

Published in SPIE Proceedings Vol. 5187:
Third International Conference on Solid State Lighting
Ian T. Ferguson; Nadarajah Narendran; Steven P. DenBaars; John C. Carrano, Editor(s)

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