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.

Download full-text


Available from: Xiaobing Luo, Aug 09, 2015
48 Reads
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, genetic algorithm (GA) was utilized to optimize the phosphor distribution to decrease the junction temperature of white phosphor-converted light-emitting diodes (pc-LEDs). The key steps of the GA were introduced, including selection, crossover, and mutation. Both the junction temperature and the entransy dissipation of each evolution were calculated. It was found that with evolutions, the phosphor particles tend to build a "thermal bridge" between the chip and the convective boundary and spread along the convective boundary. The junction temperature decreases from similar to 157.5 degrees C to similar to 150 degrees C and the entransy dissipation decreases from 18 W K to 6 W K. The least entransy dissipation principle was demonstrated to be the rule that governs the optimization processes.
    International Journal of Heat and Mass Transfer 10/2014; 77:891-896. DOI:10.1016/j.ijheatmasstransfer.2014.06.024 · 2.38 Impact Factor
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we demonstrated a double freeform-surface lens to realize uniform illumination and minimum Fresnel losses for light-emitting diode (LED). In the present design, the inner surface and outer surface of the freeform lens were designed simultaneously, thus the light path can be controlled more flexibly. The detailed calculation and design process were presented. Monte Carlo ray-tracing simulation and Fresnel losses calculation were conducted to validate the present freeform lens. The simulation and calculation results indicated that the present freeform lens could enhance the illumination uniformity greatly and realize minimum Fresnel losses as low as 7.67%.
    Optik - International Journal for Light and Electron Optics 10/2013; 124(19):3895-3897. DOI:10.1016/j.ijleo.2012.12.019 · 0.68 Impact Factor
  • Source
    • ", and irradiates at corresponding point R on the target plane. According to the Snell's law [15], we have Fig. 1. Schematic of twice refractions through the freeform lens "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the conventional freeform lens design, people usually assume the inner surface as hemispherical and only the outer surface is designed. An important design degree of freedom on the inner surface is abandoned. In this study, by distributing the deviation angle, we proposed a method to design the inner and outer surfaces of freeform lens simultaneously. Detailed design method was presented and several examples were designed to verify the method. It was found when the distribution ratio is 0.75, the simulated illumination is the most uniform and its Fresnel light loss is the rather smaller than that conventional freeform lens. By overall consideration of the illumination uniformity and the Fresnel loss, the distribution ratio of 0.75 is the optimal extra condition and corresponds to best performance.
    2013 14th International Conference on Electronic Packaging Technology (ICEPT); 08/2013
Show more