Design of a novel freeform lens for LED uniform illumination and conformal phosphor coating

Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, 430074, China.
Optics Express (Impact Factor: 3.49). 06/2012; 20(13):13727-37. DOI: 10.1364/OE.20.013727
Source: PubMed


A conformal phosphor coating can realize a phosphor layer with uniform thickness, which could enhance the angular color uniformity (ACU) of light-emitting diode (LED) packaging. In this study, a novel freeform lens was designed for simultaneous realization of LED uniform illumination and conformal phosphor coating. The detailed algorithm of the design method, which involves an extended light source and double refractions, was presented. The packaging configuration of the LED modules and the modeling of the light-conversion process were also presented. Monte Carlo ray-tracing simulations were conducted to validate the design method by comparisons with a conventional freeform lens. It is demonstrated that for the LED module with the present freeform lens, the illumination uniformity and ACU was 0.89 and 0.9283, respectively. The present freeform lens can realize equivalent illumination uniformity, but the angular color uniformity can be enhanced by 282.3% when compared with the conventional freeform lens.

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Available from: Xiaobing Luo, Aug 09, 2015
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    • "In recent decades, light-emitting diode (LED) technology has created more turmoil in the lighting industry than anything occurring over the previous century. The conventional incandescent and fluorescent light sources are increasingly being replaced by more energy-efficient, longer-lived, and environmentally friendlier white LEDs [1] [2] [3] [4] [5]. However, white LEDs still suffer from challenges related to brightness, efficiency, reliability, and performance. "
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    • "High power light-emitting diode (LED) has grown explosively in recent years for its extraordinary characteristics, such as high luminous efficiency, low power consumption , high reliability, and long life. Thus, LEDs are considered as the most potential solid-state light source for the next generation lighting and have been widely used in our daily lives123. So far, the most common approach for getting white LEDs is based on mixing blue lights emitted from LED chip with yellow lights reemitted from phosphor material (as shown in Figure 1). "
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    • "To solve this problem, appropriate optics including primary lenses or secondary lenses, are essential for high quality LED illumination. Our group has conducted a lot of research on the freeform lens design method [6] [7] [8] [9] [10] [11] [12] [13]. However, in our previous freeform lens designs, we just consider the outer surface of the freeform lens, while keeping the inner surface as hemispherical for simplicity. "
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