Abstract
In light-emitting diode (LED) applications, it is becoming a big issue that how to optimize light intensity distribution curve (LIDC) and design corresponding optical component to achieve uniform illumination when distance-height ratio (DHR) is given. A new reversing design method is proposed to solve this problem, including design and optimization of LIDC to achieve high uniform illumination and a new algorithm of freeform lens to generate the required LIDC by LED light source. According to this method, two new LED modules integrated with freeform lenses are successfully designed for slim direct-lit LED backlighting with thickness of 10mm, and uniformities of illuminance increase from 0.446 to 0.915 and from 0.155 to 0.887 when DHRs are 2 and 3 respectively. Moreover, the number of new LED modules dramatically decreases to 1/9 of the traditional LED modules while achieving similar uniform illumination in backlighting. Therefore, this new method provides a practical and simple way for optical design of LED uniform illumination when DHR is much larger than 1.
Highlights
Light-emitting diodes (LEDs), with increasing luminous efficiency and cost performance in recent years, have greater applications in daily life, such as backlighting for LCD TV, headlamp of vehicle, road lighting, commercial lighting, etc. [1,2,3]
Values of d, z0 and distance-height ratio (DHR) = d/z0 are given by customer design requirements, and our work is to optimize the light intensity distribution curve (LIDC) of LED light source to achieve uniform illumination on the target plane
A new reversing design method is proposed to solve the problem of optimizing LIDC and designing corresponding optical component to achieve LED uniform illumination when the DHR is given
Summary
Light-emitting diodes (LEDs), with increasing luminous efficiency and cost performance in recent years, have greater applications in daily life, such as backlighting for LCD TV, headlamp of vehicle, road lighting, commercial lighting, etc. [1,2,3]. Whang et al proposed a reversing design method for uniform illumination system by integrating surface-tailored lens with configurations of LED arrays [7] They only considered the situation when E(r, θ) = E0(r)cosmθ, which makes the maximum DHR [4/(m + 2)]1/2 less than 1.41 resulting in application limited. A new reversing design method for LED uniform illumination is proposed, including design and optimization of LIDC to achieve high uniform illumination and a new algorithm of freeform lens to generate the required LIDC by LED light source. Since the design processes of these applications are quite similar, we only take the optical design of new slim direct-lit LED backlighting as an example in the following discussion
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