Appearance Degradation and Chromatic Shift in Energy- Efficient Lighting Devices

摘要

All artificial lighting devices undergo some color shift overrnthe course of their useful lifetime. Unlike incandescent andrnhalogen lamps, which display a gradual shift along the Plankianrnlocus, energy-efficient lamps degrade Color-CorrelatedrnTemperature (CCT), in a non-blackbody manner. Thisrnexacerbates a generally poor appearance, and can impede publicrnacceptance, especially among residential users. We show therntrend of degradation and chromatic shift of the two availablernincandescent replacements for residential general lighting, Light-rnEmitting Diode (LED) Compact Fluorescent (CFL). It is foundrnthat over the useful lifetime, not only does the efficiency of thernlamp decrease, but the CCT and Color Rendering Index (CRI) ofrnthese lamps shifts continuously in an unfavorable manner. Thernmajority of the shift is due to differential phosphor aging. Inrnseveral cases, the shift is alarming in that the lamps start in a partrnof color space which is tenuous in its color acceptability, and shiftrninto substantially inferior color space, with poor CRI andrnundesirable CCT. Possible solutions, using current LED and CFLrntechnology, can only be implemented by paying a price in energyrnefficiency. Some solutions for the future which retain reasonablerncolor and efficiency over lamp lifetime are discussed.