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Tailored freeform optical surfaces for illumination

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... We have shown in several previous papers how tailoring can be used for the design of smooth (non-Fresnel) optical surfaces, both in two dimensions, 8,9 and in three dimensions. 10,11 In this contribution we show how the technique can be applied to determine the global shape of Fresnel optical surfaces. ...
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The key idea of Fresnel optics is to decouple the global slope from the local slope by breaking up the optical surface into small facets. The size of the facets is irrelevant as long as they are larger than the wavelength of light, so that the system behaves according to geometrical optics, and at the same time small compared the overall size of the optical surface. From the point of view of phase-space conservation, Fresnel optics suffer from a basic shortcoming. The phase-spaces of incoming and outgoing radiation beams need not automatically be equal. This results in either a dilution of radiation or losses or both. On the other hand, decoupling local from global slope allows to tailor the overall shape of the Fresnel lens independently from designing the individual facets. We show that it is possible to closely match incoming and outgoing radiation beams with a particular choice of the global shape of the Fresnel surface. This shape imultaneously minimizes dilution and blocking.
... Free surface tailoring method is a design method that partial differential equations are solved using numerical values so as to construct the surface figure [1] of free-form surface in lighting optics, it is very widely applied in the field of lighting design. One of the most important steps in designing tailored free-form surface is to calculate [2] the light intensity after light passes through the optical surface with light wavefront as the carrier. As shape of the light wavefront has changed after passing through the optical surface, therefore, changes [3] of the light wavefront curvature tensor and optical surface tensor must also be considered, so that complexity of the differential equation that is required to be ultimately solved is increased. ...
Article
As a new generation of light source, LED has many advantages that other light sources do not have. However, due to the nonuniform lighting of LED, secondary LED optical system design is particularly important. Freeform surface tailoring method, an important method of lighting design, establishes a light intensity change model after smooth surface refraction (reflection) of the light and simplifies the solution process for more complex issues of solution using the free surface tailoring method. Based on this method, secondary LED optical system is designed, and the light intensity distribution is simulated after LED light passes through the secondary optical system. The results show that the method has not only simplified the calculation process of the free surface tailoring method, but also the designed LED secondary optical system has achieved the purpose of uniform lighting to a certain degree.
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The edge-ray principle can be used to tailor a reflector. However, one set of edge rays already fully determines the reflector profile. We present a design method for tailoring compact compound elliptical concentrator (CEC)-type reflectors to a given source and a desired angular power distribution. Two reflected images of the source, one on each side of the source, contribute together with the direct radiation from the source to produce the desired power distribution. We determine the reflector profile by numerically solving a differential equation. No optimization is required. Beyond the angular region in which the power distribution can be strictly controlled, the power drops to zero in a finite decay range. This decay range becomes narrower as the reflector increases in size. We show a reflector for producing a strictly constant irradiance from −43 to 43 deg from a cylindrical source of constant brightness. The reflector extends to a maximum distance of 8 source diameters. No power is radiated beyond ± 50 deg.
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Since the first volume of this work came out in Germany in 1924, this book, together with its second volume, has remained standard in the field. Courant and Hilbert's treatment restores the historically deep connections between physical intuition and mathematical development, providing the reader with a unified approach to mathematical physics. The present volume represents Richard Courant's second and final revision of 1953. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. All rights reserved.
Article
The problem of designing a reflector to distribute the illumination of a nonisotropic point source on a plane aperture according to a pre-assigned pattern is analyzed. An integral equation and equivalent partial differential equation are derived. The form of the latter reveals this reflector-design problem to be a singular elliptic Monge—Ampère boundary-value problem.
Article
The subject of photometrics, the measurement of radiation and the calculation of amounts of radiant power, is treated by an application of the methods of field theory to concepts in geometrical optics. The basic concepts of pharosage, pharos and helios are introduced, and relations between them are examined. Reflectance holors and pharosage vectors are considered, and the solution of radiation problems by means of field methods, involving primarily the quasi-potential is discussed. Contour integration based in Stoke's theorem is presented as an alternative method of calculating the photic field, and the possibilities of the vector potential in the radiation field are considered. Determinations of the total pharos between two surfaces by the use of the McAllister-sphere, field-mapping and contour-integration methods are examined, as well as calculations for two-dimensional fields. Attention is also given to weighting functions used for various receptors, and to a phenomenological specification of polarization.
Article
For both linear and point-focus Fresnel reflectors, we present a new type of ideal nonimaging secondary concentrator, the tailored edge-ray concentrator, that can closely approach the thermodynamic limit of concentration. For large rim-angle heliostat fields, practical-sized secondaries with shapes that should be relatively easy to fabricate can achieve concentrations substantially above those of compound parabolic concentrators. This superiority stems from designing so as to accommodate the particular flux from the heliostat field. The edge-ray principle used for generating the new secondary dictates a heliostat tracking strategy that is different from the conventional one but is equally easy to implement.
Double-tailored imaging concentrators. in Nonimaging Optics: Maximum Efficiency Light Transfer V
  • H Ries
  • J Gordon
Ries, H. and J. Gordon. Double-tailored imaging concentrators. in Nonimaging Optics: Maximum Efficiency Light Transfer V. 1999. San Diego, Ca.: Proc. SPIE.