Browsing by Author "Ye, Zhi Ting"

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CSP-LEDs Combined With Light Guide Without Reflective Matrix for Antiglare Design
(2020-01-01)
Ye, Zhi Ting
;
Ruan, Moujay
;
Kuo, Hao-Chung
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光電工程學系
;
光電工程研究所
This study proposed a model with different luminous intensity profiles without reflective matrix bar for light fixtures that used asymmetric luminous intensity(ALI) CSP-LEDs (Chip Scale Package-Light emitting diode) combined with light guide as light source module, and analyzed illumination uniformity and unified glare rating (UGR) performance by using a classroom as an example. The study constructed a model of light fixture use in classrooms. Four important parameters affect the comfort of human eye that include UGR, illumination, uniformity of spatial and light distribution of light fixture, in particular, light distribution of light fixture was major affect factor for direct glare. Therefore, light fixture designers previously used many diverse structures to prevent glare, but which will result in a loss of light fixture efficiency about 25%-35% that caused by material absorption and ray loss. This study proposed used ALI CSP-LEDs combined with light guide as light source to optimize different light distribution angles without attached reflective matrix bar or second optical lens on light fixture to simulate a light fixture in a classroom and to evaluate UGR, illumination and uniformity values. We also consider the light fixture tilt angle caused effect of UGR and uniformity. On the basis of the simulation and experimental results, ALI CSP-LEDs beam angle relative to vertical and horizontal axes were 150 degrees and 120 degrees, respectively, the light distribution profile for a beam angle 90 degrees provided the highest illumination uniformity and a UGR of less than 19. Thus, light fixtures with a light distribution angle of beam angle 90 degrees supply human-friendly for anti-glare lighting.
Nanoparticle-Doped Polydimethylsiloxane Fluid Enhances the Optical Performance of AlGaN-Based Deep-Ultraviolet Light-Emitting Diodes
(2019-07-15)
Ye, Zhi Ting
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Pai, Yung-Min
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Lin, Chih-Hao
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Chen, Lung-Chien
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Hong Thai Nguyen
This paper proposes a new encapsulation structure for aluminum nitride-based deep UV light-emitting diodes (DUV-LEDs) and eutectic flip chips containing polydimethylsiloxane (PDMS) fluid doped with SiO2 nanoparticles (NPs) with a UV-transparent quartz hemispherical glass cover. Experimental results reveal that the proposed encapsulation structure has considerably higher light output power than the traditional one. The light extraction efficiency was increased by 66.49% when the forward current of the DUV-LED was 200mA. Doping the PDMS fluid with SiO2 NPs resulted in higher light output power than that of undoped fluid. The maximum efficiency was achieved at a doping concentration of 0.2wt%. The optical output power at 200mA forward current of the encapsulation structure with NP doping of the fluid was 15% higher than that without NP doping. The optical output power of the proposed encapsulation structure was 81.49% higher than that of the traditional encapsulation structure. The enhanced light output power was due to light scattering caused by the SiO2 NPs and the increased average refractive index. The encapsulation temperature can be reduced by 4 degrees C at a driving current of 200mA by using the proposed encapsulation structure.
Optical and thermal design of light emitting diodes omnidirectional bulb
(2015-10-01)
Ye, Zhi Ting
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Kuo, Hao-Chung
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Chen, Cheng-Huan
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光電工程學系
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Department of Photonics
The penetration of LED light bulbs into the lighting market is growing quickly in recent years due to significant increase of LED efficiency and reduction of cost. One major issue to be improved is the overall light bulb efficiency, which can fulfill "Energy Star for Lamps" while keeping sufficiently high efficiency. The efficiency issue results mainly from the high directionality of the LED sources and the corresponding solutions to make the emission more diverse. In this paper, a diffusion white reflection sheet (DWRS) with an array of holes is proposed as a high efficiency solution for modulating a light emission profile with SMD type LED source. The hole size is adjusted with fixed hole pitch to both maximize the efficiency and meet the omnidirectional specification. In addition, the concept of thermal plastic insertion molding metal is proposed for thermal management without fins for cooling. The prototype demonstrates the efficiency (Ef.) of 87.6% and LED pad temperature of 85 degrees C, which shows the feasibility as a total solution for high efficiency LED omnidirectional bulbs. (C) 2015 Optical Society of America
Thin hollow light guide for high-efficiency planar illuminator
(2015-10-01)
Ye, Zhi Ting
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Kuo, Hao-Chung
;
Chen, Cheng-Huan
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光電工程學系
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Department of Photonics
Light guides have been widely used for transforming line sources into planar illuminators for lighting and display applications. Solid light guides provide good uniformity but still have the issues of heavy weight and material absorption, especially for large applications. Hollow light guides solve the problem of weight, but the uniformity is relatively poor or efficiency could be sacrificed for enhancing uniformity. In this paper, a hollow light guide with edge-lit LED sources has been proposed to simultaneously resolve the issues of weight, uniformity, and efficiency. The major approach is to modulate the LED luminous intensity profile by a ring of parabolic surface with continuously varied focal length. The modulated light emitting profile directly makes up sufficient uniformity on the planar surface, and extra components are not required. The prototype is a circular planar illuminator with a diameter of 178 mm and a weight of 240 g. The experiment shows an overall efficiency of 82.37%, with a uniformity of 83.7%. The weight of the whole module is 40% lighter than that of a solid light guide with the same size. (C) 2015 Optical Society of America