Appearance Degradation and Chromatic Shift in Energy-Efficient Lighting Devices
Abstract:All artificial lighting devices undergo some color shift over the course of their useful lifetime. Unlike incandescent and halogen lamps, which display a gradual shift along the Plankian locus, energy-efficient lamps degrade Color-Correlated Temperature (CCT), in a non-blackbody manner. This exacerbates a generally poor appearance, and can impede public acceptance, especially among residential users. We show the trend of degradation and chromatic shift of the two available incandescent replacements for residential general lighting, Light-Emitting Diode (LED) Compact Fluorescent (CFL). It is found that over the useful lifetime, not only does the efficiency of the lamp decrease, but the CCT and Color Rendering Index (CRI) of these lamps shifts continuously in an unfavorable manner. The majority of the shift is due to differential phosphor aging. In several cases, the shift is alarming in that the lamps start in a part of color space which is tenuous in its color acceptability, and shift into substantially inferior color space, with poor CRI and undesirable CCT. Possible solutions, using current LED and CFL technology, can only be implemented by paying a price in energy efficiency. Some solutions for the future which retain reasonable color and efficiency over lamp lifetime are discussed.
Document Type: Research Article
Publication date: January 1, 2011
CIC is the premier annual technical gathering for scientists, technologists, and engineers working in the areas of color science and systems, and their application to color imaging. Participants represent disciplines ranging from psychophysics, optical physics, image processing, color science to graphic arts, systems engineering, and hardware and software development. While a broad mix of professional interests is the hallmark of these conferences, the focus is color. CICs traditionally offer two days of short courses followed by three days of technical sessions that include three keynotes, an evening lecture, and a vibrant interactive papers session. An endearing symbol of the meeting is the Cactus Award, given each year to the author(s) of the best interactive paper presentation.
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