Total Internal Reflection (TIR) Lens Design for Surface Mount Techonology (SMT) LED Application

In this paper, Total Internal Reflection (TIR) lens for a micro optical LED application is proposed. The aim of this paper is to design TIR lens in collimating light emitted from a surface mount technology (SMT) LED. To satisfy current technical needs, it was designed to have both thickness and diameter less than three millimeters with eleven facets where light refracts and reflects. Overall geometry of the TIR lens is numerically calculated and designed in Matlab and the central hyperboloid is designed through Code V. Manufacturability of TIR lens has been obstructing its realistic LED application because of its limitation of size. In this study, we have considered this issue and found the optimized each facet angles in which ultraprecision diamond turning is applicable. Typical blue SMT LED was modeled in LightTools to verify the decrease of solid angle. After designing, the solid angle of a LED was reduced from 120° to 20° while loosing source energy about 52%. The solid angle varies with respect to its distance from the source. The simulation results show collimation efficiency of the designed lens.