Quantitative Evaluation of Light Collimating for Commercial UV-LEDs Based on Analytic Collimating Lens

Yong-Sin Syu,Yung-Chun Lee

doi:10.3390/app12020911

Abstract

This paper proposes a lens design method for effectively collimating the light emitting from a light-emitting diode (LED). This collimating lens contains two aspherical lens surfaces which can be mathematically characterized using a few designing parameters, and hence is called an analytic collimating lens. An optical ray-tracing algorithm has been developed for these analytic collimating lenses to analyze their optical performance and to optimize their designs. Six high-power and commercially available ultraviolet (UV) LEDs are chosen as examples for demonstrating the optimal collimating lens design. For each UV-LED, the corresponding optical collimating lens is determined by inputting the ray data file provided by the manufacture over a finite-size emitting area. The divergent angles of the six UV-LEDs have been successfully collimated to a narrow range in between 1.56° to 2.84° from their original radiation angle around 46° to 120°. Furthermore, the proposed analytical collimating lenses are suitable for mass-production using standard mold injection methods, and hence possess great potentials for industry applications of LEDs.

Highlights

Ultraviolet light-emitting diodes (UV-LEDs) have developed rapidly in the past few years with great potentials for many engineering applications
Thøger Kari [14] observed that the total internal reflection (TIR) structure can be employed to construct the purpose of collimating the LED light with compact volume under the point source approximations, but collimation and optical efficiency were still having a scope for improvement
We propose a lens design method and a quantitative evaluation method for light collimating of commercial UV-LEDs

Summary

Introduction

Ultraviolet light-emitting diodes (UV-LEDs) have developed rapidly in the past few years with great potentials for many engineering applications. As the power of a single UV-LED is still very limited so far, one strategy is to deploy an array of UV-LEDs to form a planar UV light source and combine with scanning movement to achieve uniform exposure of UV dose over a larger planar area for contact/proximity photolithography [1]. In this case, it is necessary to collimate the UV light emitted from UV-LEDs, which under the premise of not losing too much light energy, is still a challenging issue. Positive meniscus lenses composed of two spherical surfaces were proposed [15,16] for LED’s light collimating, but the collimation ability is limited near the optical axis and the efficiency is low

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