The first 3D ideal concentrators that were found composed solely of mirrors had the property of transmitting elliptic bundles. These are the flow line concentrator (FLC) and the cone concentrator (CC), designed in the late 1970s. More recently, the Lorentz geometry formalism was applied to the problem of finding elliptic bundles in a medium of homogeneous refractive index. In this approach, the edge rays of the elliptic bundle were identified with lightlike curves in Einstein's gravitational theory. A restrictive condition was imposed in this approach: the edge rays were forced to be geodesics of the Euclidean metric and of the Lorentz metric. This restriction provided a tool for getting results, and new elliptic bundles were found. Later, by application of a series expansion from the bundle defined at a reference surface ,it was proven that other solutions exist, and thus the condition imposed in the Lorentz geometry approach was shown to be too restrictive. However, it was not demonstrated that the reference surface approach is general either. A subset of the reference surface solutions was also recently found using the Poisson Bracket design method in curvilinear coordinates which provided a deeper insight in the properties of these bundles. In this paper we present a new approach that leads to the equations which must be fulfilled by all the possible elliptic bundles in an homogeneous medium. This approach is based on the application of the Poisson Bracket design method in Cartesian coordinates. The already-known elliptic bundles are identified as particular solutions of the general equations. The search of new solutions is open, and the condition that must be fulfilled by them is given.

Conservation of etendue or phase space volume has been a useful tool in nonimaging design and analysis. It is one of the Poincare's invariants associated to any Hamiltonian system. It expresses that the phase space volume of a region representing a bundle of rays do not vary when the rays proceed along the optical system. Another of these invariants is the 2D etendue conservation in 3D optical systems. This invariant can be expressed as the conservation along the ray trajectories of the differential form: dxdp + dydq + dzdr where x, y, z are position coordinates and p, q, r are the conjugate variables in the Hamiltonian formulation. When the optical system is frequency dependent (through the dependence of the refractive index of w) or it is time dependent, then the Hamiltonian formulation must include two new variables: t (time) and its conjugate variable -w. The application of the 2D etendue conservation to this new set of variables allows formulating the conditions for achromatic designs in a simple way. The results are coincident with Conrady's formula and its simplicity permits a direct application to the design of achromatic lenses. We have applied these concepts to the design of achromatic aplanatic aspherical doublets, where the aplanatic condition means free of spherical aberration and circular coma of all orders and the achromatic condition means that the doublet is aplanatic for wavelengths in a neighborhood of the design wavelength. Several examples of these designs are given.

The 30 X DSMTS is a trough-like photovoltaic concentrator, meant to track the sun in one axis, which has a mirror allocating two concentration stages and a secondary lens that increases its acceptance up to +/- 2.3 degrees. Provided that the sun subtends an angle of +/- 0.256 degrees, such acceptance seems excessive. However, thanks to it, we can relax requirements that often demand accuracy in systems of the kind. For instance, the shape of the mirror can be achieved by simply bending an aluminum sheet. To foresee the results we may expect of this strategy, we carried out some mechanical calculations, whose results are the boundary conditions that lead to a minimum standard deviation on the local slope of the elastic mirror with regards to the theoretical value. We checked by ray tracing that such an error actually provoked a small decrease on the acceptance. This fact persuaded us to carry out the manufacture of two elastic prototypes. In the test that have been performed so far with them we achieved an acceptance angle of +/- 1.63 degrees and a collection efficiency of 98 percent at a geometrical concentration of 30 times, results that can be considered as outstanding in the photovoltaics framework.

In this work it is presented a new design of a TIR lens-mushrooms lens device developed with the Simultaneous Multiple Surfaces (SMS) method. In SMS nomenclature, it is named TIR-R. In contrast to previous TIR-mushroom designs, application of the SMS method to this configuration consists in the simultaneous design of both TIR (total internal reflection) and R (refraction) optical surfaces using extended ray-bundles and the edge-ray theorem. In this paper is presented a basic approach to do the design. In this basic approach, first it is considered the TIR lens as a microstructured surface with infinitesimal flat facets. Afterwards, it is generated a TIR lens with finite size facets from the already designed one. In an advanced approach could be considered the TIR lens with finite facet size and designed simultaneously each facet with a portion of the outer surface of the mushroom lens. With respect to others SMS high-gain devices (as the RXI), the TIR-R concentrator has the following advantages: is a mirror-less device, there is not shadowing elements, and the receiver/emitter element's placement is more favorable for encapsulation and electrical connection. As it is common in the SMS devices, the TIR-R concentrator achieves wide acceptance angle and high efficiency with a low aspect ratio (thickness to entry aperture diameter ratio). For example, a 1256X concentration device has a theoretical efficiency of 100 percent (without optical losses) with an acceptance angle of +/- 1.7 decgrees, and an aspect ratio of 0.34.

A new approach for concentrating photovoltaic systems that can easily attain the maximum flux levels commensurate with solar cell technology is proposed. The collection unit is a miniature paraboloidal dish which concentrates sunlight into a short glass rod. The flux distribution of the transported light is homogenized in a miniature glass kaleidoscope that is optically coupled to a small high-efficiency solar cell. The cell resides behind the dish and can be cooled adequately with a passive heat sink. These nominally independent collection units can be assembled into modules and arrays that produce almost any prescribed power level. All system elements are predicated on existing technologies.

We report results of a study our group has undertaken to design a solar concentrator with uniform irradiance on a planar target. This attribute is especially important for photovoltaic concentrators. We find that a variety of optical mixers, some incorporating a moderate level of concentration, can be quite effective in achieving near uniform irradiance.

The optical performance of remote lighting systems and recent innovations in solar fiber-optic concentrators is acutely sensitive to transmission losses in their optical fibers. Typically, these multi-mode fibers are expected to incur small losses over long distances for broad-spectrum light sources. Experimental results reveal substantial light leakage within the nominal numerical aperture of optical fibers that have been deemed suitable for these applications. The same fibers exhibit negligible attenuation in their core. Of particular interest is the dependence of this leakage on: (a) incidence angle, (b) the optical properties of the core and the cladding, and (c) fiber length. We present laboratory measurements of fiber angular transmission, along with a theoretical model.

By using a solid-core fused silica light guide of a large numerical aperture, high power solar energy can be transmitted economically to a convenient place outside the focal area of a primary parabolic concentrator. The light flux distribution at the focal phase was firstly measured and the intercept factors of angle dependence were calculated individually for the light guides of 2, 4, 5.8, 7.3, 10, 12 and 14 mm diameters. By taking into account the influence of the loss dependence η_g(Φ_i) on incident angled, a simple model for the efficiency calculation of the whole system was introduced. The light guides were placed separately at the focus of the primary concentrator and the output powers of 50, 206, 374, 506, 690, 770 and 818W were successfully measured, attaining the transmission efficiency of 65 percent for the light guided of 14mm diameter. In length dependence loss measurement, the attention of -1.87 dB/m was found. The transmission property of a curved light guide was also tested, showing no significant loss in output power. The utilization of high power solar energy inside rooms or other thermally insulated places can therefore be expected. A novel light guide with an angular transformed input end was also put forward at the end. The input rays of large angles were transformed into the output rays of small angles by the angular transformed polished direction on a light guide. Both high transmission efficiency and high output power were achieved.

The component of the optical direction vector along the symmetry axis is conserved for all rays propagated through a translationally symmetric optical device. This quality, referred to herein as the translational skew invariant, is analogous to the conventional skew invariant, which is conserved in rotationally symmetric optical systems. The invariance of both of these quantities is a consequence of Noether's theorem. We show how performance limits for translationally symmetric nonimaging optical devices can be derived from the distributions of the translational skew invariant for the optical source and for the target to which flux is to be transferred. Examples of computed performance limits are provided. In addition, we show that a numerically optimized non-tracking solar concentrator utilizing symmetry-breaking surface microstructure can overcome the performance limits associated with translational symmetry. The optimized design provides a 47.4% increase in efficiency and concentration relative to an ideal translationally symmetric concentrator.

While gradient-index lenses are usually analyzed in terms of image fidelity, they are also capable of high flux concentration. In the first part of this presentation, the simplest class of gradient-index problems is revisited. An alterative way to obtain established solution of the refractive index profiles that produce perfect imaging is derived form the method of Fermat's strings and skewness conservation. The degree to which difference classes of such spherical lenses can realize the thermodynamic limit to flux concentration is explored. An answer is also sought to the intriguing question of the extent to which the spherical gradient-index lens of the fish eye is a modified Luneburg lens optimized subject to material constraints. The second half of this presentation addresses gradient-index rod lense. Both analytic methods and computer raytrace simulations are used for a comprehensive evaluation of their concentration and collection efficiency. They appear to be well suited as concentrators for the distal end of laser fiber-optic surgical units.

Our paper discusses geometrical and optical concentration ratios of the optimum nonimaging arched linear Fresnel lens which we designed earlier. This is a fundamental issue, with practical implications for the design of refractive nonimaging concentrators. The deliberations yield a better understanding of the way the refractive index of the thin lens, and the refractive index of the possible dielectricum between lens and receiver, as well as light incident in the plane of the secondary acceptance half angle ψ, influence the performance of the nonimaging concentrator. Theoretical results are compared with tests of the existing prototypes of the nonimaging lens, used for the concentration of solar radiation. The novel nonimaging lens is put into the context of historic research, and is made comparable to other nonimaging concentrators, notably the Compound Parabolic Concentrator. We propose the use of a linear kaleidoskope-based secondary concentrator to achieve a uniform flux distribution and the reproduction of the spectrum of the incoming light.

A new application of design techniques for nonimaging concentrators is presented. Variable Geometry Nonimaging Optics Devices are presented for 2D systems. These devices have a variable acceptance angle allowing for its continuous variation within a range of values. The relation between the sizes of entrance and exit apertures must then vary according to the laws of nonimaging optics. This implies a variation in the size of either the entrance or the exit aperture, resulting in two types of devices. Moveable mirrors are an integral part of the new devices discussed in this paper, with positions depending on the variable acceptance angle. These new combinations of optical and mechanical solutions, although not ideal, may represent approximation ideally.

We present preliminary results of optimizing a T1 LED integral dome lens for efficient and uniform illumination. The automated optimization process is based on a geometrical model of the LED die radiation inside the encapsulant. A commercial nonsequential ray-tracing program is combined with an external global optimization engine to maximize both efficiency and uniformity. The LED model is based on surface radiance images of an LED package sectioned with a diamond saw, and validated by comparison to measured near-field irradiance patterns. The resulting lens design is compared with the original design based on calculated irradiance patterns. The optimized lens substantially improves calculated uniformity, and somewhat improves efficiency, at the expense of a more complex lens profile, including multiple ripples on the surface. Robustness of the new design is evaluated by ray-tracing the lens with the LED displaced by typical manufacturing tolerances for low-cost LED's, resulting in significantly degraded uniformity. The results are still better than the original dome lens, but clearly indicate that manufacturing variabilities may place an upper bound on the uniformity achievable, at least with our preliminary approach.

We demonstrate a remarkable analogy between the measurement of radiance and the well-know van-Cittert-Zernicke Theorem.

Traditionally reflector design has been confined to the use of surfaces defined in terms of conic sections, assuming that all light sources can be considered to be point sources. In the middle of the twentieth century, it was recognized that major improvements could be made if the shape of the reflector was designed to produce a desired distribution of light form an actual light source. Cylindrical reflectors were created which illuminated airport runways using fluorescent lamps in such a way that pilots could make visual landings safely even in fog. These reflector contours were called macrofocal parabolic cylinders. Other new reflector contours introduced were macrofocal elliptic cylinders which confined the light to long rectangles. Surfaces of revolution the fourth degree were also developed which made possible uniform floodlighting of a circular region. These were called horned and peaked quartics. The optimum solution of the automotive head lighting problem has not yet been found. The paper concludes with a discussion of the possibility of developing reflectors which are neither cylindrical nor rotational but will produce the optimum field of view for the automobile driver both in clear weather and in fog.

A unique solar thermal chamber has been designed and fabricated to produce the maximum concentration of solar energy and highest temperature possible. Its primary purpose was for solar plasma propulsion experiments and related material specimen testing above 3000 Kelvin. The design not only maximized solar concentration, but also, minimized infrared heat loss. This paper provides the underlining theory and operation of the chamber and initial optical correlation to the actual fabricated hardware. The chamber is placed at the focal point of an existing primary concentrator with a 2.74-meter (9 foot) focal length. A quartz lens focuses a smaller sun image at the inlet hole of the mirrored cavity. The lens focuses two image planes at prescribed positions; the sun at the cavity's entrance hole, and the primary concentrator at the junction plane of two surfaces that form the cavity chamber. The back half is an ellipsoid reflector that produces a 1.27 cm diameter final sun image. The image is 'suspended in space' 7.1cm away from the nearest cavity surface, to minimize thermal and contaminate damage to the mirror surfaces. A hemisphere mirror makes up the front chamber and has its center of curvature at the target image, where rays leaving the target are reflected back upon themselves, minimizing radiation losses.

The design and optimization of the TOPHAT feed horn is presented. This horn is a nonimaging antenna with a few modes. Diffraction effects are approximated using ray-trace techniques with the addition of phase information.

We consider the illumination and the strong illumination properties for closed bounded regions of Euclidean spaces. These properties are intimately connected with a problem of chaoticity of the corresponding billiards. It is shown that there are only two mechanisms of chaoticity in billiard systems, which are called the mechanism of dispersing and the mechanism of defocusing. Our results show how the regions with different illumination properties should be designed. Especially each focusing mirror in the boundary of a region must be an absolutely focusing one. The notion of absolutely focusing mirrors is a new one in the geometric optic and it plays a key role for the illumination problem.

We experimentally tested the operator formalism of radiative transfer on the response of an instrument to partially coherent wavefield produced by radiation emitted by distant and extended blackbody sources. The predictions of the formalism are found to agree well with the experiments. Phase space parameters are identified that characterize a measurement as well as indicating when the formalism will be useful, when we are not in the regime of geometrical optics or plane wave diffraction.

Negative luminescent (NL) devices, which to an IR observer appear colder than they actually are, have a wide range of possible applications, including for use as thermal radiation shields in IR cameras, and as IR sources in gas sensing systems. For many of these applications a large area (>1cm²) device is required, together with as large as possible apparent temperature range. However, under reverse bias significant currents are required to reduce the carrier concentrations to the levels needed for maximum possible absorption. These may lead to current heating of the device, which in turn reduces the apparent temperature range. We have therefore used a novel micromachining technique to fabricate integrated optical concentrators in InSb/InAlSb and HgCdTe NL devices. Smaller area diodes can then be used to achieve the same absorption (e.g. for InSb an area reduction of 16 is possible) and the required currents are thus reduced. To fabricate the concentrators parabolic resist masks are first produced, which are approximately 10 μm high and approximately 53 μm wide, by resist reflow at 120 degrees C. Inductively coupled plasma (ICP) etching is then used to alternately etch the resist mask and the semiconductor, with oxygen and methane/hydrogen respectively, producing concentrators with almost parabolic profiles. Currently, the concentrators are typically 30 μm high, with a top diameter of approximately 15 μm. Continuing optimization of the process to reach the theoretical limits of optical gain is described.

Fusion Lighting, Inc. has been developing an RF-powered electrodless light source known as the ByteLight. This source is spectrally stable, has a high luminous efficiency and exceptional spatial and angular uniformity. In this paper we describe a nonimaging projection lens designed to efficiently collect and transfer flux from the circular aperture of a ByteLight lamp into a rectangular aperture of an optical train of an InFocus Model LP0335-V single-panel DMD-based front projector. The source was experimentally characterized by Radiation Imaging, Inc. using a technique that captures its full 4D phase space behavior. The lens was then designed by implementing a global optimization procedure over a parameterization search space with variables that determine the positional and aspheric geometrical properties of the lines. The optimization was performed subject o constraints arising from packaging and fabrication considerations. The resulting lens employs a combination of refraction and total-internal reflection mechanisms to achieve a total flux-transfer efficiency of 75.6 % which compares favorably to a baseline design that employs a UHP arc lamp.

Fluorescent sensing of oxygen is an optical method for determining the concentration of dissolved or gaseous oxygen in a medium based on flourescent quenching. In the literature, papers on fluorescent quenching oxygen sensor have highlighted certain key problems that limit the sensitivity an disability of these devices. In this paper, we describe a novel optical collection scheme using planar waveguide that overcomes these key issues. The light collection scheme incorporates multiple alterations over the original simple planar waveguide design. These alterations included shearing the end-face of the waveguide, adding reflective coatings, increasing the refractive index of the waveguide material, and finally, tapering one end of the waveguide. The design is modeled and tested using a computer-simulation program. The end result is a light collection scheme that can have a large fluorescing surface are while maintain in a high light collection efficiency. The optimized waveguide is found to guide 7.0% of the total emitted fluorescent power to the detector for an arbitrary surface area of fluorescence material. This design should greatly help to combat a key problem with fluorescent sensing: photo-bleaching.

We present an efficient and effective collimating lens system for LEDs. It consists of two lenses: an immersive ball lens within which an LED die is optically bonded, and an adjacent collimating lens that produces uniform illumination at its output plane. The three surfaces of the system are numerically tailored in accordance with the angular distribution of light emitted by the die. When the immersion lens is surface-tailored, the resultant shapes are sufficiently close to a spherical surface that the manufacturing convenience and low cost of an exact sphere make it the preferred shape. The immersion ball-lens reduces the angular spread of the LED's light from +/- 90 degrees to +/- 60 degrees in air. The bottom surface of the collimating lens redirects each light ray to its proper place (axial radius) in the output beam, at which point the top surface redirects the ray to become parallel to the optical axis. Uniformity of output illuminance occurs when a ray's proper place is determined by its place in the cumulative angular distribution near the immersed source. Three surfaces suffice to give highly efficient collimation as well as spatial uniformity of the output beam.

The strongest known material, carbon nanotube, has inspired designs of spinning space habitats reaching radii of 1000 km. Known as the Space Ring, a cylinder of such radius, with a 'short' 500 km length, has an 'open sky' geometry that only self-occludes a third of the view of the stars, as they spin around twice per hour. Sunlight is unsuitable for illuminating the Ring interior because it cannot be turned off. Instead, the Ring axis is sideways to the sun, and solar-cell concentrator troughs cover its exterior to provide power for a central illuminator. Because the inside living space is p times the projected cell area, illumination effectiveness is at a premium, even if the electrical efficiency of the cells is 50 percent, and enormous storage capacity accounts for 'night-time' sunlight. Only a quarter of the light output of a central isotropic emitter would fall on the Ring, so that nonimaging optics is called for. Overall luminaire size (and cost) is reduced by increased emitter luminance, but considerations of eye safety oppose this. An ideal CPC of revolution would produce a rectangular 'sun' with 4:1 aspect ratio, fixed overhead in a blue sky, unable to generate rainbows, sunrises, or sunsets.

We describe a novel optical architecture for a LCoS binocular virtual display which, for the first time, meets or exceeds market leading pSi headset performance. A key component of the optical system is the frontlight illumination, which affords system specifications such a 36 degree field of view, a contrast of 80:1, and no IPD adjustment necessary (12 mm pupil). We detail the frontlight design and development, and its interaction with the complete electro-optical module.

The book by Jolley, Waldram and Wilson, 'The Theory and Design of Illumination Engineering Equipment', published in 1930, contains methods of designing symmetrical and asymmetrical reflectors that are of historical significance for the field of illumination engineering and nonimaging optics. This paper describes the methods that appear to be first revealed in the book, and the legacy of the work for modern day researchers in the fields of illumination engineering and nonimaging optics. This paper concludes that Jolley, Waldram and Wilson (with, perhaps, some help from the insights of Halberstma) were most likely the first to derive a method of reflector design based on the mapping of an input angle of a source into the prescribed output angle of the reflector based on the concept of integrated flux and energy conservation of flux.

Advances in Photovoltaic technology using multijunction cells allow sunlight-to-electrical energy conversion efficiencies of 25 percent with the potential of reaching 30 percent. The main drawback with these cells is their high cost. By using a concentrating Photovoltaic (CPV) solar collector, the area/cost of the cells relative to the total system area/cost can be reduced substantially. The design of CPV systems has one constraint not found in standard thermal solar concentrators, namely the target is square and the irradiance uniformity goal is very tight. A novel two-stage solar collector system designed for the National Renewable Energy Laboratory (NREL) is presented here. By tailoring the radial profile of the primary mirror that is slightly non-parabolic and using a straight square tube secondary, designs for concentrations between 100-2,000 suns can achieve uniformity under 3 percent and greater than 95 percent efficiencies. A design using a non-rotationally symmetric primary design is also presented, which reduces the problems with shading by spiders that attach the secondary to the primary mirror.