Abstract
In this paper, progresses of color maintenance, also known as color shift, in solid-state lighting (SSL) systems are thoroughly reviewed. First, color shift is introduced and a few examples are given from different real-life industrial conditions. Different degradation mechanisms in different parts of the system are also explained. Different materials used as lenses/encapsulants in light-emitting diode (LED)-based products are introduced and their contributions to color shift are discussed. Efforts put into standardization, characterizing, and predicting lumen maintenance are also briefly reviewed in this paper.
Highlights
Solid-state lighting (SSL) technologies and products are gradually penetrating daily life
Different materials used as lenses/encapsulants in light-emitting diode (LED)based products are introduced and their contributions to color shift are discussed
Efforts put into standardization, characterizing, and predicting lumen maintenance are briefly reviewed in this paper
Summary
1.1 Introduction Solid-state lighting (SSL) technologies and products are gradually penetrating daily life. 1.2 Terms and definitions “Color maintenance” is analogous to lumen maintenance and is defined as the change in chromaticity of a light source with respect to the chromaticity at the beginning of the lamp’s life. The chromaticity coordinates of a source provide a numerical representation of the color of the light. Based on Eq (1), the coordinates ∆u’v’, which define the color shift at any two positions (0 and 1), can be calculated using the following formula:. A product may be made from LEDs that are binned to fall within three MacAdam steps of a target chromaticity. These LEDs have a color consistency of three steps. The term “color maintenance” will be used in this paper
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