This PDF file contains the front matter associated with SPIE Proceedings volume 7423, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We propose a design method for single reflectors that takes into account extended sources with any arbitrary luminance distribution. This method is suitable for non-uniform prescribed illuminance distributions with arbitrary shapes. We use the method of supporting ellipsoids developed by Oliker in conjunction with optimization in order to control the effects of the source extent. Design examples related to street illumination and LED illumination are presented.

The Simultaneous Multiple Surface design method (SMS) is applied to the design of free-form V-groove reflectors. The general design problem is to achieve perfect coupling of two wavefronts after two reflections at the groove, no matter which side of the groove the rays hit first. All possible 2D designs are listed and used as a basis for the 3D free-form reflector analysis. The extension to the 3D case is given, and illustrative particular canonical examples are developed. Besides the theory and design work, first prototypes were produced of a mirrorless TIR device using V-grooves that emulates a parabolic reflector. The experimental measurements of the TIR reflector show reflectance up to 98%.

The design equations of freeform two-lens optical systems for redistributing the input radiation in a prescribed manner over a given target set are presented in explicit form. These equations are applied to derive sensitivity measures of the output radiation to figure errors. The general results are applied in several special cases validated against known results for rotationally symmetric lenses.

This past spring a new for-credit course on illumination engineering was offered at the College of Optical Sciences at The University of Arizona. This course was project based such that the students could take a concept to conclusion. The main goal of the course was to learn how to use optical design and analysis software while applying principles of optics to the design of their optical systems. Projects included source modeling, displays, daylighting, light pollution, faceted reflectors, and stray light analysis. In conjunction with the course was a weekly lecture that provided information about various aspects of the field of illumination, including units, étendue, optimization, solid-state lighting, tolerancing, litappearance modeling, and fabrication of optics. These lectures harped on the important points of conservation of étendue, source modeling and tolerancing, and that no optic can be made perfectly. Based on student reviews, future versions of this course will include more hands-on demos of illumination components and assignments.

Aplanatic designs have interested scientists since the days of Galileo, Newton and Descartes. It is remarkable that an onaxis condition which can be simply formulated ensures good off-axis performance. The condition is that rays parallel to the axis intersect rays converging to the focus on the surface of a sphere. In this paper the authors have extended aplanatic designs to refractive media in a non-trivial way, which yields highly compact and fast aplanatic singlets.

We study the analogy between the geometrical vector flux, the light vector introduced by A. Gershun and Pharosage vector introduced by P. Moon. From this analogy we present a treatment of the design of concentrators in terms of field theory. We study first the symmetry of concentrators in different coordinate systems. In particular, we study concentrators in elliptical cylindrical coordinates as asymmetric concentrators linking rotational and translational concentrators. Following that symmetry we study the light field produced by an elliptical disk, and we show that onesheet hyperboloids behave as ideal 3D asymmetric concentrators. This result can be generalized to orthogonal surfaces by using field theory. Finally, we find higher order field lines by the study of the light field produced by a 2-D truncated wedge, which can be used to define a new higher order concentrator, the Hyperparabolic Concentrator (HPC). This concentrator has the profile of a hyperbola continuously joined with a tilted parabola. In the limit of infinite focal length of the hyperbola, the 3D HPC reaches the thermodynamic limit of concentration.

The purpose of a nonimaging concentrator is to transfer maximal flux from the phase space of a source to that of a target. A concentrator's performance can be expressed relative to a thermodynamic reference. We discuss consequences of Fermat's principle of geometrical optics. We review étendue dilution and optical loss mechanisms associated with nonimaging concentrators, especially for the photovoltaic (PV) role. We introduce the concept of optical thermodynamic efficiency which is a performance metric combining the first and second laws of thermodynamics. The optical thermodynamic efficiency is a comprehensive metric that takes into account all loss mechanisms associated with transferring flux from the source to the target phase space, which may include losses due to inadequate design, non-ideal materials, fabrication errors, and less than maximal concentration. As such, this metric is a gold standard for evaluating the performance of nonimaging concentrators. Examples are provided to illustrate the use of this new metric. In particular we discuss concentrating PV systems for solar power applications.

It is well-known that conservation of phase-space volume or optical etendue leads to strict limits to concentration. Less well- known is the connection between entropy and etendue. Entropy has a logarithmic dependence on etendue in addition to the familiar linear dependence on heat. This trade-off permits in principle an exponential boost in concentration. Optical systems that make use of this possibility will be discussed.

Originally developed to ameliorate image quality, aplanatic optics were only recently analyzed as maximumperformance light-transfer systems with concentration approaching the fundamental limit. A basic categorization scheme is presented that appears to cover the full spectrum of aplanatic designs, illustrated for far-field dual-mirror concentrators and motivated by high-irradiance solar applications. Several previously unrecognized classes of concentrators are identified.

In this paper we will discuss an innovative optical system for solar power applications in space. In this system solar radiation is collected by the concentrator array which transfers the concentrated solar radiation to the optical waveguide (OW) transmission line made of low loss optical fibers. The OW transmission line directs the solar radiation to the place of solar power utilization such as: the thermochemical receiver for processing of lunar regolith for oxygen production; or the plant growth facility where the solar light is used for biomass production.

Collimating light is a common task in optical design. The smaller the source, the simpler the optics required for collimation. Small sources cannot emit sufficient power for some demanding applications. Larger sources are required. The physical limits of collimation due to the conservation of ´etendue and skewness are discussed. Two systems are presented:a domed nonimaging Fresnel lens with toroidal primary focus and our "Umbrella" optics consisting of two free-form non-aximsymmetric mirrors.

A point-focus solar concentrator is described for use in high temperature terrestrial and space applications. The system comprises a nonimaging reflective lens in the form of a ring array concentrator coupled to a fiber optic bundle through which the concentrated light is transmitted. Unlike mirror-based systems, the concentrator is a ring array composed of concentrically nested elements focusing energy to the rear of the structure. Energy is transported from the concentrator by optical fibers and directed at a target where high heat flux is needed. The fiber optic bundle is tailored for solar energy transmission and includes a fused end to minimize inter-fiber losses at the injection point. The integrated system is intended to produce concentrated thermal energy without the need for electricity intensive heating elements. Optical efficiency is investigated through a ray trace analysis.

In the work, stages of designing, optimizing, manufacturing and testing the circular flat-plate Fresnel lenses (FLs) for photovoltaic modules with multi-junction solar cells (SCs) are presented. A mathematical model based on ray tracing has been developed for optimizing lenses design parameters and calculating their optical-power characteristics (OPCs). In searching the optimum combination of the lens aperture, its focal distance and refracting profile parameters, the optimization criterion was the maximum of the average sunlight concentration at high optical efficiency in the focal spot of minimum size. Analysis of OPCs of circular Fresnel lenses with conical (the generatrix of surface is a straight line) and curvilinear (the generatrix of surface is a curved line) refracting surfaces has been carried out. Fresnel lens specimens were fabricated and a control of their profile parameters has been done. Experimental lens OPCs have been obtained with use of newly developed optical test bench. A degree of the effect of the light flux and Fresnel lens geometrical imperfections on validity of the experimental data interpretation has been determined. To establish the lens optical efficiency values at standard irradiance conditions, the correction of the calculation model was done. Also, the effect of temperature on the lens optical efficiency is studied.

A central solar plant, based on beam-down optics, is composed of a field of heliostats, a tower reflector and a ground receiver. The tower reflector is an optical system comprises of a quadric surface mirror (hyperboloid), where its upper focal point coincides with the aim point of a heliostat field and its lower focal point is located at a specified height, coinciding with the entrance plane of the ground receiver. The optics of a tower reflector requires the use of ground secondary concentrator, composed of a cluster of CPCs, because the quadric surface mirror always magnifies the sun image. There is an intrinsic correlation between the tower reflector position and its size on one hand, and the geometry, dimensions and reflective area of the secondary concentrator on the other hand; both are related to the heliostat field reflective area. Obviously, when one wishes to have a smaller tower reflector by placing it closer to the upper focal point, the image created at the lower focus will be larger, resulting in a larger secondary ground concentrator. The present work analyses the ways for a substantial decrease of the size of the ground concentrator cluster (and, implicit, the concentrators area) via truncation, without significant sacrifice of the performance, although some increase of the optical losses is inevitable. This offers a method for cost effective design of future central solar plants utilizing the beam down optics.

For saving energy and healthy lighting, many researches focus on the sunlight illumination system. A Natural Light Guiding System can be separated into collecting, transmitting, and lighting parts. With a cascadable concentrator in the collecting part, the transmitting part will use large number of fibers. It means the most of cost is on the transmitting part. With an N to 1 coupler, the number of lightpipe can be reduced quickly. In general, the optical coupler is tapered structure. According to the Etendue principle, however, the product of beam angle and area is contact. The beam angle of coupled sunlight will increase that isn't easy coupled again and transmitted with long distance. The total energy of the exit beam from the N to 1 coupler should be bigger than the energy of one incident beam. In this paper, we use stepped structure to design an optical coupler for coupling N to 1. In the research, the Natural Light Guiding System with the optical coupler is simulated, and we evaluate the parameters of the stepped structure. Finally, we analyze the coupled efficiency of the coupler.

Due to the energy crisis, the principle of green energy gains popularity. This leads the increasing interest in renewable energy such as solar energy. How to collect sunlight for indoor illumination is our ultimate target. A Natural Light Guiding System includes collecting, transmitting, and lighting parts. To date, most studies of collecting part have delicate in dynamic concentrators which include sun tracking systems. They are powered by small electric motors and require some type of control module to follow sun path, so it requires maintenance and adds a good bit of complexity to the system. The application area of dynamic concentrator is limited. In order to create a low cost, easily set up, and applied on large area structure, we design a unit of static concentrator to collect sunlight for indoor illumination which is prismatic and cascadable. The unit is made up of prismatic structure and can collect the nature light, sunlight, for indoor illumination. For offer more saving energy and more stable illumination, we consider the total collected energy in the whole day and the relationship between the efficiency of the static concentrator and time. We change the size of prism to be different and add the BEF structure to improve the unit. According to the simulation, the prismatic structure with different right-angle prism could advance the total collected energy and the BEF could advance the stabilization of efficiency in the whole day.

Making daylight more available in buildings is highly desirable for reasons of energy efficiency, visual comfort, occupant well-being and health. The Anidolic Integrated Ceiling (AIC) is a highly efficient daylighting system, designed to gather and redirect daylight from the outside of a building into its interior with minimal losses. The reflective coating materials used within AICs have a major impact on the optical efficiency of such systems. The first part of our article presents a new computer model of an AIC consisting of more than 30 distinct components. We discuss on which of them the use of expensive, highly reflective coatings makes the most sense. We conclude that coating the component "Anidolic element 1" is always a good choice and that considerable financial savings can be obtained by following an appropriate optimization sequence.The second part of our article discusses chronobiological properties of Anidolic Daylighting Systems (ADS). We recorded daytime irradiance values for several weeks from March to May 2009 in an experimental office setup in our laboratory using a portable digital spectroradiometer. Our results showed to which extent different sky conditions influenced daylight exposure of office workers in an ADS-equipped office room. We conclude that for the tested ADS-equipped office room, daylight supply can be considered largely sufficient during long periods on most working days. However, complementary artificial lighting with blue-enriched polychromatic fluorescent tubes might be useful on days with predominantly overcast skies as well as before 09:00 and after 16:30 on all days.

We have explored the use of a low-cost, rugged optical system to collect and distribute natural sunlight for daytime lighting purposes. The sunlight collection and delivery is performed using a simple lens system in combination with a plastic optical fiber bundle. Based on such a system, we have demonstrated the ability to provide diffuse lighting over a 100 sq. ft. area. The work included the optimization of the lens and the fiber bundle according to data collected on the spatial distribution of focused sunlight. A key aspect of our work is the use of mirrors which could be easily maneuvered to maintain optimum coupling of light in the fiber throughout the day. An important issue that we addressed in our work is the devising of a low cost tracking mechanism to ensure nearuniform lighting throughout a day. The tracking system is an open loop system that is based on apriori data on the sun's movement and an initial alignment procedure. We have collected such data by tracking a beam of light reflected from a stationary mirror. Our data shows that the mirror needs to be rotated at the rate of 0.25 degrees/minute to maintain a fixed position at the collection plane. We expect to achieve a scalable, modular low cost lighting solution that works in conjunction with a LED array to illuminate common areas of commercial buildings during the daytime.

We designed a compact illumination system based on a linear array of single package RGB LEDs which creates a tailored light distribution. Realistic optical simulations in Advanced Systems Analysis Program (ASAP ®) and a statistical approach in Matlab ® , are used to investigate the color uniformity. A clear trade-off between the capability to tailor the obtained light distribution and the color uniformity is found. Two methods to improve the color uniformity while maintaining the light tailoring capabilities of the optical design, are investigated: mixing the LED orientations and using anisotropic scattering properties. The aimed application is an illumination module for Ambilight ® television sets, although the investigated methods can be applied to other LED based illumination systems.

Ecological traffic tunnel means that the manner can deal with tunnel project environmental problem of surrounding area and it is most close to the green environment. In general, we always use artificial light sources, such as traditional light sources and LED, to be the light source of illumination in the traffic tunnel. However, the best light source for the health of the human body is the natural light. If we can guide the sunlight into the tunnel to be lighting source, it would have a great benefit to the health of the human body. In this paper, we use Natural Light Guiding System to provide ecological illumination in traffic tunnel. The system has collecting, transmitting, and lighting parts. In the collecting part, we utilize a static concentrator to collect sunlight which is made up of a prismatic and cascadable unit. In the transmitting part, the collected sunlight is guided by optical fiber or lightpipe efficiently. In the lighting part, we design a lighting module of road lamp for lighting the inside the tunnel. The lighting module redistributes light to conform the traffic regulation. Finally, we build a model of traffic tunnel in optical software with Natural Light Guiding System to simulate the performance.

Wall washers are applications that provide illumination effects onto a wall, generated by light sources located close to that wall. Traditionally, incandescent and fluorescent lamps are used to generate a uniform color or a simple pattern. Solid-state-lighting opens up the possibility to generate more complex patterns of light. In this paper, we discuss the design and results of two different prototypes of wall washers that are able to generate a number of rows and columns of individually addressable spots ('pixels') of light onto a wall. Our conclusions focus on the optical performance of the chosen solutions versus the size of the optical system.

Light guide rods based on multiple total internal reflections provide some powerful design opportunities. Therefore, they are very suitable for producing arbitrary light distributions. Especially for LEDs they work highly efficient due to the use of the whole emitted light flux and the theoretical lossless light propagation by total internal reflection. Frequent applications are color mixing and the creation of a homogeneous luminance distribution at the output surface. However, the capabilities of common light guide rods are under-utilized. Therefore, we demonstrate a new design approach that enhances the performance of light guiding systems and is applicable to illumination problems.

We present a wideband and high pumping-efficiency L-band erbium-doped fiber (EDF) amplified spontaneous emission (ASE) source using a two-stage double pass backward (DPB) pumping configuration.DPB configuration has been proved to have a high pumping-efficiency. In this paper we use a two-stage DPB pumping configuration to generate a stable L-band ASE source for the first time. The source consists of two sections of EDF, a 1480nm pumping laser diode (LD) which is divided into two portions to pump two sections of EDF separately. By using a power splitter, the pumping power of two stages can be adjusted proportionally. The effects of EDF length and pump power arrangement on the output characteristics of L-band ASE spectrum, output power and mean wavelength are theoretically investigated. The results show that the pumping-conversion efficiency and the linewidth can be improved significantly by optimizing the fiber length ratio and pump ratio of the two-stage DPB configuration. Based on former work, the total fiber length is chosen at 19m in this paper. With the total fiber length fixed, the proposed source has a high pumping efficiency of 53%, an output power of 111mW, and a broadening linewidth of 49nm with the mean wavelength at 1580.18nm under the optimizing fiber ratio of 0.842 and pump power ratio of 0.5.

Many applications involve the use of a compound parabolic concentrator (CPC) like, natural lighting, thermal applications, optics for illuminators, optical fibre coupling and solar energy. The use of a CPC in reverse mode for natural lighting gives the chance to use it as a lighting skylight in ceilings because light output is controlled inside the design angle, on the contrary having a low flux transfer ratio because of the reduced area of the entrance pupil regarding exit pupil. The authors propose an innovative 3D hollow prismatic CPC (HPCPC) made of a dielectric material, which has a high efficiency comparing it with aluminium CPC. The basic idea is to use a hollow prismatic light guide with CPC shape. This paper reports 2D, 3D design and numerical analysis by raytracing software, also experimental results are shown. The system works almost like a true CPC when light enters through standard entrance pupil and also collect light that enters outside entrance pupil. Performance and efficiency of the prismatic CPC is in average 300% higher than standard aluminium CPC for collimated light in a range from 0º to 85º. A prototype has been developed and tested.

This paper describes a novel and cost-effective way of guiding natural sunlight to the dark areas of multi-storey buildings. In this hybrid system, two-axis tracking concentrator collects sunlight radiation by focusing it through Fresnel lenses onto solar cells which act as the valves of the optical fibers and transform the solar radiation into electricity. When needed the sunlight can be directly distributed through optical fibers and combined with LED lighting module in specially designed luminaires. This hybrid lighting system guides the sunlight into the building, and also efficiently incorporate DC LED light sources so that they can provide supplemental lighting as necessary.

Light-emitting diodes (LEDs) are very popular light sources in the market currently because of their numerous advantages such as high efficiency, long life time, wide color gamut and cheap production costs [1]. For many applications, such as illumination tasks, backlight modules and projector light sources, a homogeneous illumination of the entrance pupil is desired. Because of LED's high brightness, we can combine the homogeneous illuminance areas in the target plane together as a backlight module for LCD display to solve unreadable problems in the portable devices under the sun. Mostly, the typical light distribution of a LED shows distinct Lambertian profile which is not suitable for the applications. To achieve a better adapted beam profile, an optical system with beam shaping qualities can be used. We design an optical system consisting of refractive microlens arrays and reflection-tubes that collimates and homogenizes LED's beam [2]. The smaller angle of beams, the higher contrast ratio we will get. And the design is less than 10mm in thickness, we can use it in many ways, such as backlight module of cell phones and head-up displays (HUDs). We believe this technology has advantages and provides us a high-brightness display to read information easily.

High concentration photovoltaic (HCPV) utilizes point-focus cost-effective plastic Fresnel lens. And a millimeter-sized Ill-V compound multi-junction solar cell is placed underneath focusing optics which can achieve cell efficiency potential of up to 40.7 %. The advantage of HCPV makes less solar cell area and higher efficiency; however, the acceptance angle of HCPV is about ±1°, which is very small and the mechanical tracking of the sun is necessary. In order to reduce the power consumption and the angle tracking error of tracking systems, a light collector model with larger acceptance angle is designed with ZEMAX®. In this model, the original radially symmetric Fresnel lens of HCPV is replaced by cylindrically symmetric Fresnel lens and a parabolic reflective surface. Light is collected in two dimensions separately. And a couple of lenses and a light pipe are added before the solar cell chip in order to collect more light when sun light deviates from incident angle of 0⁰. An acceptance angle of ±10° is achieved with GCR 400.

Light concentrator is a non-imaging optics whose design can seriously affect the performance of a concentrating photovoltaic module. For effectively increasing the incoming light flux, a new combo system designed by the edge-ray theorem was proposed for solar concentration optics. This system is composed of three zones of total internal reflection (TIR) lens, Fresnel lens, and aspherical lens. In this system, the TIR lens is responsible for large bending angle, while the Fresnel lens and aspherical lens are responsible for small bending angle due to their suffering for total internal reflection at large bending angle. For the requirement of compactness, the TIR lens is located at the outmost zone from optical axis of the lens aperture to shorten the depth of the lens system. The aspherical lens is located at the central zone while the Fresnel zone is then aligned between them. On this design example, the size of solar cell is assumed to be a square with a length of 5.5 mm. The diameter of the lens aperture is 120 mm and the depth of the lens is considered to be lain between 60 and 65 mm. Through design analysis, the full acceptance angle is set at 1.0 degree. Design data shows that this new combo system can meet the requirements of solar concentration optics under considerations and its optical efficiency of the whole system can approach to 81%.

Faceted reflectors are widely used for providing uniform illumination in many commercial lighting products. In this paper, some approaches of constructing faceted reflectors in commercial software are discussed. Two new methods for generating non-rotationally symmetric patterns such as square/rectangular illumination patterns using curved-faceted reflectors are proposed and also explored in commercial software. The performances of various reflectors are compared using Monte Carlo ray-tracing.