Design Method for a Total Internal Reflection LED Lens with Double Freeform Surfaces for Narrow and Uniform Illumination

Abstract

In this paper, we propose a novel differential equation method for designing a total internal reflection (TIR) LED lens with double freeform surfaces. A complete set of simultaneous differential equations for the method is derived from the condition for minimizing the Fresnel loss, illumination models, Snell's Law of ray propagation, and a new constraint on the incident angle of a ray on the light-exiting surface of the lens. The last constraint is essential to complete the set of simultaneous differential equations. By adopting the TIR structure and applying the condition for minimizing the Fresnel loss, it is expected that the proposed TIR LED lens can have a high luminous flux efficiency, even though its beam-spread angle is narrow. To validate the proposed method, three TIR LED lenses with beam-spread angles of less than 22.6° have been designed, and their performances evaluated by ray tracing. Their luminous flux efficiencies could be obviously increased by at least 35% and 5%, compared to conventional LED lenses with a single freeform surface and with double freeform surfaces, respectively.

A Review of Critical Issues in High-Speed Vat Photopolymerization

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A compact wide-spectrum imaging spectrometer using freeform surface

“…Therefore, the realization of miniature prism-based spectrometer is of considerable value. The advantages of freeform surface in optical systems are well known, freeform surfaces have been successfully used in the fields of illumination and imaging field [11][12][13][14][15]. In the characterization of a freeform surface, multiple parameters can offer more degrees of freedom to the system design, which means that correcting non-symmetric aberrations would be easier.…”

A Practical Method to Design Reflector-Based Light-Emitting Diode Luminaire for General Lighting

“…Thus, a secondary optical element is generally needed to redistribute the light energy emitted from LED to meet the specific illumination requirements. Over the past decade, the freeform lenses and the freeform reflectors have been widely used in the design of LED secondary optics in illumination designs [5][6][7][8][9][10]. In real applications, especially in outdoor lighting, the reflector is considered as an important optical component which can not only be used to modulate the light energy emitted from the light source to achieve specific lighting, but also be employed as the protector of the lighting equipment.…”