We propose two energy-mapping methods to produce a uniformly illuminated area for a nontilted (straight) and a tilted light source toward a target plane. These energy-mapping methods define the positions of the desired points (the destination points of the refracted rays of a light source) on an illuminated area. The surface of the lenses can then be formed through the position of the desired points. Based on these design methods, two freeform lenses, (i) a symmetric lens and (ii) an asymmetric lens, were designed to provide uniformity within a rectangular illumination footprint for a nontilted and a tilted light source, respectively. This method can produce uniformity for a tilted light source within 0 deg to 45 deg toward the normal vector on the target plane. Two freeform lenses for 0 deg and 20 deg tilted toward a target plane were designed. The illumination footprint of the symmetric and asymmetric freeform lenses was evaluated through ray-tracing simulations and experiments. Both models produce over 90% uniformity within an illuminated area.
The Dielectric Totally Internally Reflecting Concentrator (DTIRC) has been developed in the past for wireless infrared communications and solar energy applications. This paper proposes a novel non-imaging optic design based on the DTIRC family of concentrators for use in illumination applications. The novel optic can be integrated with a light emitting diode (LED) and can be tailored to meet specific requirements. The proposed optic can be used as a first or secondary optic to provide uniform illumination within a circular footprint with a desired radius. The results from this work show that, with the optimised DTIRC, it is possible to achieve a uniformity of illuminance of over 95%.
This paper presents the performance analysis of a freeform lens that can be used as a first or secondary optic when combined with a point or an extended light source. The light source can be an LED. The purpose of the optic is to increase uniformity of illumination within the footprint. The analysis is performed on the freeform lens when combined with: (i) an isotopic or a Lambertian point light source (ii) an isotropic or a Lambertian extended light source. This paper shows that through a design based on energy mapping between a light source and a target plane it is possible to achieve uniform illumination. The ZEMAX ray tracing simulation shows that the uniformity reduces gradually when the size of the light source increases. The results indicate that a freeform lens combined with a point source can generate over 95% uniformity.
The Dielectric Total Internal Reflecting Concentrator (DTIRC) is a type of non-imaging optic that has been used in the past to increase the collection efficiency of photovoltaic (PV) cells and photodetectors. It does this by redirecting energy impinging on its largest aperture to a smaller aperture to which the absorber is attached. This paper explores the use of non-imaging optics for light emission control when combined with a Light Emitting Diode (LED). In this case, the smallest aperture of the concentrator acts as its input and the largest aperture as the output. This allows control of the angular characteristics of the emitted light beam and an increase of the illuminance at the target plane, which is of particular relevance in applications such as illumination and optical wireless communications. Its compact size and design characteristics make the DTIRC a more desirable geometry compared to other non-imaging optics when used as a first or secondary optic to control the emission characteristics of a light source. This paper reports the correlation between simulation and experimental results that validate the ability of DTIRCs to collimate the output beam of extended light sources.
Optical fibres as sunlight harvesting waveguides for use in concentrating photovoltaic (CPV) systems are proposed.
Results of ray tracing simulations and experimental measurements in feasible optical fibre configurations are presented
in this paper. The configurations incorporate spherical as well as aspheric lenses, a simpler precursor of the Fresnel lens.
Step index fibres with SiO2 as core material and preferably high numerical apertures and high incidence angles are
utilised initially. Scenarios with sources of monochromatic and 1000 W/m2 irradiance are considered on simulations.
Although high concentrations can be achieved in practice, for CPV applications uniformity at the end receiver is also
considered as a key factor to realise acceptable cell performance. We obtained more than 99% uniformity at the end
receiver of the proposed configurations for flux concentration of 2000 suns.