Complex 3D-tailored facets for optimal lighting of facades and public places

Abstract

Due to antiquated technologies (calculation methods, regulations, lighting and luminaire concepts, production techniques) current outdoor lighting causes a lot of problems like light pollution, glare, energy waste etc.New types of luminaires, and in consequence new outdoor lighting concepts, can be created by combining advanced calculation methods for optical surfaces with recent production technologies and novel light sources such as short arc metal halide lamps. Light emitted from this small Etendue light sources can precisely be redirected by 3D-curved surfaces manufactured with injection molding, milling and aluminium metallization. The required optical design may use techniques like complex surface calculations and 3D-Tailoring.An innovative concept based on the latest findings in visual perception research is to focus the light of such short arc light sources onto a facetted secondary mirror which provides the desired illuminance distribution on a facade or a public place. These systems are designed to fulfill lighting requirements as well as providing visual comfort. Thus lamps with improved color rendering, luminous efficacy and increased lifetime are used and glare is minimized by splitting the reflector into many facets (light spot decomposition).A few examples of realized projects are presented where such complex facetted surfaces are used to reach a special quality of light. Using novel techniques like 3D-Tailoring, each facet can be designed to individually create the desired (e.g. uniform) illuminance distribution on the target surface -in this case, a large facade. For this particular application, we chose to impose a square boundary for each facet, in order to tile the rectangular aperture of the secondary mirror without compromising efficiency.

The Design of Freeform Surface Fresnel Lens Used for LED Uniform Illumination

“…In past years, much research on how to make the LED to better serve the people was done and methods were developed, such as the "Trial and Error Based on Experience Method" [2] , "Uniform B-Spline Surfaces Method" [3] and the "The Solution of Partial Differential Equation Method". Some research was developed using freeform surface reflectors [4][5][6], but it is impossible to cover the whole emergence spatial angle of the LED without any absorption loss with this method, thus the efficiency of reflective surface cannot be very high. And a compound parabolic concentrator (CPC) [7] is a selectable solution of forming a uniform illumination only when there is no limitation on the axial length of the device.…”

Construction Method of Tailored Facets for Use in Freeform Reflectors Design

“…The facets are treated as singulars and are defined individually though under global conditions, thus describing freeform facets by means of quadratic Bézier surfaces that can be modified by a global optimization process (Doyle, Corcoran, and Connell 1999). Those conditions are derived from a previous segmentation and mapping process (Oliker and Newman 1993;Pohl et al 2003;Fournier, Cassarly, and Rolland 2010a).Althought the mapping proces is outside the scope of the present papers, it might be taken into account that the success of the proposed method directly depends on the choice of mapping.…”

Estratègia 2D per al disseny de reflectors amb facetes de forma lliure

“…Per assolir solucions viables amb reflectors d'una sola superfície, és necessari introduir elements que donin flexibilitat al disseny i permetin ajustar els resultats a l'objectiu final (Baeuerle et al 2012;Cassarly et al 2000;Rolland 2010a, 2010b;Leutz and Ries 2003;Pohl et al 2003). Així doncs s'ha optat per partir del disseny en facetes on cada faceta correspon a una superficie de Bézier i és necessari, per al seu disseny, descriure la geometria dels seus contorns i la seva orientació en relació a la font i a l'objectiu d'il•luminació.…”