Poisson bracket design method is, as yet, one of the few known 3D nonimaging concentrator design methods. In general, this method provides concentrators requiring variable refractive index media, which become quite impractical. Another fruitful 3D-concentrator study was done by application of the Lorentz geometry to the nonimaging theory. In this study some new 3D ideal concentrators (with constant refractive index) were found by the analysis of the certain sets of edge rays with some particular symmetries. These bundles were called elliptic bundles of rays. On the other hand, a new approach based on the concept of reference surface has been recently used to find new bundles of this type. In this paper we review Poisson bracket design method, reformulate it and apply it to the analysis of elliptic bundles. The basic equations have become fully symmetric after reformulation. Moreover, the expression of the Hamiltonian function is of the same type as the expression of the first integral that contains the elliptic bundle. In this way one cannot distinguish, from the mathematical point of view, which is the Hamiltonian function and which is the first integral function. The formulation must be done with some selected coordinates in which one of the coordinate lines are the flow lines of the elliptic bundle and the other two ones are normal to the flow lines and tangent to the symmetry planes of the cone of edge rays. All the elliptic bundles found with the Lorentz geometry method and the reference surface method are again found here excepting those that aren't symmetric with respect the coordinate surfaces. No new elliptic bundle has yet been found. Nevertheless the new analysis procedure is more adapted to arbitrary orthogonal coordinate systems and to variable refractive index, and so it is expected it will provide new bundles.

The Simultaneous Multiple Surfaces of Nonimaging Optics has been used successfully in the past for the synthesis of concentrators in two dimensions. In this paper we present a first approach to extend this design method to 3D geometry. As a first result, an aspheric lens without rotational symmetry that focus sharply two plane wavefronts at two points in 3D geometry is found, feature which cannot be obtained with an axisymmetric optical system with a finite number of optical surfaces.

Two new static nonimaging designs for bifacial solar cells are presented. These concentrators have been obtained with the Simultaneous Multiple Surface design method of Nonimaging Optics. The main characteristics of these concentrators are: (1) high compactness, (2) linear symmetry (in order to be made by low cost extrusion), (3) performance close to the thermodynamic limit, and (4) a non-shading sizable gap between at least one of the cell edges and the optically active surfaces. This last feature is interesting because this gap can be used to allocate the interconnections between cells, with no additional optical losses. As an example of the results, one design for an acceptable angle of +/- 30 degrees gets a geometrical concentration of 5.5X, with an average thickness to entry aperture width ratio of 0.24. The 3D ray-tracing analysis of the concentrators is also presented.

The purpose of this work is to present the measurements of the main characteristics of a series of RXI concentrators developed: angular transmission, acceptable angle, optical efficiency, and optical concentration. The RXI concentrator has been designed with the Simultaneous Multiple Surfaces method developed by Minano et al. at the Instituto de Energia Solar--Universidad Politecnica de Madrid. The design characteristics are: geometric concentration 1256X, acceptance angle 1.8 degree(s).

In this work the variational calculus will be applied to the design with axisymmetric sequential optical surfaces for small sources directly in 3D. This method is proven to be useful even in the case in which the skewness distributions of output bundle and emitter do not fit. The tool provides both the optimum 3D ray bundles at the exit aperture of a rotational collimator and the best 2D assignation of rays allowing the collimation reach its limit. Once this best assignation has been obtained, the optical profiles can be designed easily using only the central ray of the bundles. Afterwards, the actual device is obtained by rotation. As a consequence of the kind of method aforementioned, the angular performance of the collimators can be nearly error- free predicted before ray tracing.

A new approach to the efficient collection and remote delivery of concentrated solar energy is proposed. The system's building block is a miniature (e.g., 0.2 m diameter) dish which concentrates sunlight into a single optical fiber. A number of mini-dishes comprise a module from which the optical fibers transport bundled power to a remote receiver. A second-stage nonimaging concentrator can boost flux levels to those approaching the thermodynamic limit and can be performed either in each individual dish or collectively in one or more larger devices at the entrance to the remote receiver. There are substantial advantages in efficiency, compactness, reduced mechanical loads, and ease of fabrication and installation relative to conventional solar designs. The design exploits the availability of low- attenuation optical fibers of high numerical aperture, as well as the practical advantages of mass producing highly accurate very small parabolic dishes. Designs for maximum efficiency attaining collection efficiencies as high as 80%, and maximum-concentration designs realizing flux levels of 30,000 suns, are achievable.

Compound parabolic concentrators (CPCs) are good candidates for secondary concentrators in solar applications. Practical considerations, however, sometimes dictate the use of planar as opposed to curved reflectors. In addition polygonal apertures may be desired in order to tile a large area with several smaller secondary concentrators. We analyze in our contribution secondary concentrators which approximate a CPC but consist of plane facets with various numbers of subdivisions in axial and circumferential direction. We found that an `intuitive' axial profile with a constant angle between neighboring facets does not lead to optimal performance. We optimized by ray-tracing the size and orientation of the facets and found concentrators with significantly higher performance as compared to the `intuitively' facetted CPCs. The resulting shapes are usually significantly longer than classical CPCs. The higher the reflectivity of the surfaces, the longer the optimized concentrators get, approaching the infinite cone as an ideal concentrator for perfect reflectivity.

Many attempts were made in the past to convert Solar light to Laser light. To date, only two systems were demonstrated successfully: Photo-Dissociation Lasers and Solid State Solar lasers. The absorption spectrum of many dimmer molecules posses a broad structural spectrum overlapping with the solar spectrum and can be good candidates for direct solar pumping. In the gas phase, the emission spectrum of the active medium offers tunability and high beam quality without significant thermal lensing or thermal induced birefringence. Optical characterization and initial pumping experiments of a few selected systems will be discussed.

Solar light is considered as an efficient source for direct optical excitation of solid state lasers. The high efficiency is achieved through the use of different solar spectral bands to pump simultaneously several lasers. In this way it is possible to convert solar energy into laser light at an efficiency of approximately 30% (this value is calculated relative to the solar spectrum inside the atmosphere, after the short UV and far IR are filtered out). Since solar radiation on the ground is unstable, the thermal lensing and other beam quality parameters are not constant and cannot be compensated by standard methods. In the past, most efforts in the development of solar pumped lasers were devoted to the achievement of maximum power and high efficiency while the beam quality was neglected. However, beam quality is important for power transmission, satellite communication, frequency doubling and other applications of solar pumped lasers. A new approach to improve the beam quality of solar pumped solid state lasers using a phase conjugate mirror will be discussed.

Fresnel lenses have been used for years as solar concentrators in a variety of applications. Several variables effect the final design of these lenses including: lens diameter, image spot distance from the lens, and bandwidth focused in the image spot. Defining the image spot as the geometrical optics circle of least confusion, a set of design equations has been derived to define the groove angles for each groove on the lens. These equations allow the distribution of light by wavelength within the image spot to be calculated. Combining these equations with the blackbody radiation equations power, power distribution, and flux within the image spot can be calculated. In addition, equations have been derived to design a lens to produce maximum flux in a given spot size. Using these equations, a lens may be designed to optimize the spot energy concentration for given energy source.

A computer package, Automated Mirror Design, has been developed by us to automate the design of luminaire reflectors. In this paper, new improvements to the algorithm for Automated Mirror Design are presented. We have previously reported a study on a series of point-light source luminaire problems. We now report on the operation of Automated Mirror Design for non-trivial light sources. In particular, reflector designs are presented for an extended light source, which produce limited Lambertian output and return no radiation to the source. Finally, the operation of differential evolution relies on the use of an appropriate merit function to determine the quality of proposed mirror designs. Merit function specific to the Lambertian output design problem are discussed.

Many commercially available sources can be modeled as collimated, annular sources. We use a tailored central-ray method to concentrate light from such a source onto a cylindrical target. The design method is a straightforward extension of methods previously describing for point sources. The device was developed and is now being used for a commercial application.

A requirement for a uniformly illuminated rectangular aperture is common in optical design, particularly for projection applications. We have previously presented an all-reflective design that provides high flux-transfer efficiency from a cylindrical source to a 1.5:1-aspect-ratio rectangular target, with target etendue equal to that of the source. That design used a numerically optimized nonrotationally symmetric reflector having a star-like cross-section combined with a light tunnel having a constant rectangular cross-section. In this paper we present a more advanced design in which the constant-cross-section light tunnel is replaced with one having a numerically optimized cross-sectional geometry that varies as a function of position along its length.

Known designs of reflectors for cylindrical absorbers with gaps either suffer from radiation losses or from dilution which is equivalent to losing maximum concentration. In order to avoid both kinds of losses the global shape of a micro-structured reflector must be such that the gap and the real absorber occupy equal projected angles as seen from all locations. This condition is used to tailor the global shape. We show ideal reflectors for different gap positions. There is no upper limit for the gap size imposed by physical laws.

Microstructures can be viewed as nonimaging devices where all edge rays involved do not change direction over the aperture(s) of the device. This is equivalent to saying that the distance to source and target is much larger than the dimension of the device, which justifies the name microstructure for these devices. Consequently the shape of a microstructure device is independent of its size in this limit. The condition that the etendue of source and target must be equal, generally implies that the projected angle and not the angle itself under which source and target are seen must be equal. This requires at least two surfaces (reflective or refractive). We show how the shape of these two surfaces can be simultaneously tailored to the desired 4 directions delimiting a finite source and target.

We present a new approach in optical design whereby two- stage axisymmetric reflectors are tailored with a completely imaging strategy, and can closely approach the thermodynamic limit to radiation concentration at near-maximum collection efficiency. Practical virtues include: (1) an inherent large gap between the receiver and the second-stage mirror; (2) an upward-facing receiver; (3) the possibility of compact units (large rim angles), i.e., low ratios of total depth to total width; and (4) no chromatic aberration. We describe how one can tailor both the primary and secondary mirrors so as to insure that spherical aberration is eliminated in all orders, and circular coma is canceled up to first order in the angle subtended by the radiation source. An illustrative solution that attains about 93% of the thermodynamic limit to concentration is presented for a far-field source, as is common in solar energy and infrared detection applications. Double-tailored imaging concentrators are similar in principle to complementary Cassegrain concentrators that comprise a paraboloidal primary mirror and the inner concave surface of a hyperboloid secondary reflector, but have monotonic contours that are substantially different with far superior flux concentration.

The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.

The notion of transporting concentrated solar energy radiation by flexible optical fibers or fiber bundles has been developed for a variety of uses. With the aim of CW pumping a laser crystal outside the focusing area of a primary parabolic mirror, an optical fiber bundle with a frustum-type output end was used to transmit and concentrate solar energy to a flux level high enough to pump a solid state laser. The transmission properties of a fiber optic frustum-type concentrator was first analyzed with the help of a ray-tracing program, which revealed strong influences of both output diameter and length on the transmission efficiency of a frustum concentrator. The idea of achieving an ideal angular transformer with fiber optic technology in the area of nonimaging optics was also proposed. The output section of each optical fiber was polished to form a hexagonal frustum. When seven of these polished frusta from the optical fibers were joined together, a novel solar energy concentrator was obtained. The output power from the concentrator end was 67 W, corresponding to the solar flux of 23 W/mm². The experimental results of transporting and concentrating the solar radiation by using four fiber bundle with a square frustum output end was also reported. The maximum solar flux of 28 W/mm² was obtained with a single optical fiber of conical output end.

Flexible optical fibers and fiber bundles can be used to transfer concentrated sunlight to a desirable place where it could be used to pump a solid state laser. One flexible fiber bundle was built. It consisted of seven optical fibers. The output section of optical fibers were polished to an hexagonal form. The bundle was placed at the focus of a primary parabolic mirror to capture the solar energy in the core-region of the focal spot. The radiation exiting the fibers was concentrated with a DCPC or with a long conical concentrator. An optical adhesive was utilized to bond the fiber bundle and the concentrator together. For non-contact type concentration, a DCPC was utilized and no index compensating liquid was necessary. A moderate optical flux of 13 W/mm² was measured, with a large angular divergence as expected together with a non-homogeneous light distribution from the output end of the DCPC concentrator; both were certainly responsible for the unsuccessful attempts at pumping the laser. Hence a long conical concentrator was designed and built. Experimental results shown that both the incident ray acceptance capability and the output light quality are better than the DCPC. A solar flux of about 20 W/mm² was obtained. Success at pumping the crystal laser can now be expected and will be reported elsewhere.

New ideas for the production of optical devices capable of concentrating solar radiation to a degree useful for an application like solar frying of food, but still retaining the ability to remain stationary for extended periods, are presented and discussed.

Powerful new LEDs provide enough luminosity for a single one to illuminate a transparent EXIT sign, but efficient injection means are required, with luminance-uniformity a prime goal. We present a totally-internally-reflecting `Black Hole' indentation on the waveguide surface. This cuspated configuration deflects the light from an immersed LED, aimed perpendicular to the plane of the waveguide, into guided light trapped within the slab, to be extracted by the sign's alphabetic features. In spherical coordinates, a +/- 60 degree(s) output cone (for example) is deflected into the 360 degree(s)-azimuth guided range of +/- 47 degree(s). That is, this reflector transforms a polar cone into an equatorial swath, a symmetry that is useful whenever the total horizon must be dealt with, just as a lighthouse, or better yet a marker buoy, must send warning light to all the quarters of the compass. In its circularly symmetric configurations, this device offers a removable disc, optically bonded to the LED source, that completely hides the source from view above the indentation. Non-waveguide, stand-alone illumination applications include aircraft-warning beacons, alarm flashers, and near-field illuminators.

In this paper we will introduce a new light distribution technique we term `Constructive Occlusion'. Using the geometry of Constructive Occlusion, diffuse surfaces can be used to tailor the distribution of a light source, eliminating the need for refractors or reflectors. The use of diffuse materials alone does not enable the tailoring of the distribution because lambertian materials distributed light as a cosine distribution. This cosine distribution is largely independent of the specific shape of the surface. Constructive Occlusion overcomes this limitation by the use of its patented geometry. Through application of the geometry, an integrating cavity is formed using a highly reflective diffuse material (>95% reflectivity). A mask is placed over the cavity, such that the light source and major portion of the cavity is occluded, enabling an interaction between the cavity and the mask. The arrangement and dimensions of the cavity opening, the mask, and the distance of the mask from the cavity, as well as several other geometric relationships, combine to control the light distribution of the optic. Contrary to expectations, we have been able to demonstrate our ability to shape the light distribution while maintaining high optical efficiencies, as high as 87% dependent upon the distribution. The specific techniques of constructive occlusion and example applications will be discussed in this paper.

An investigation to enhance the efficiency of Raman- scattered light showed that cylindrical light pipes can significantly increase light collection from a Gaussian beam. Further, the enhanced signal from the light pipe retains the image of the laser beam, permitting the use of smaller detectors and resulting in a favorable signal-to- noise ratios. This investigation focussed on real-time measurements of gaseous media in a laser buildup cavity; however, the imaging properties of the light pipe apply to all measurements of molecular scattering. The light pipe matched the constraints of our measurement system: spectral separation and detection with an optical spectrograph, the need to reduce background light, the need to minimize cost, and stimulation by a laser beam in an optical cavity. After initial experiments collecting light from the ends of light pipes, we developed light pipes with a window on the cylindrical surface. Light emitted from these windows is much more intense than the direct image of the laser beam (typically 10X for light pipes 50 - 100 mm long), and the signal retains the image of the beam. Computer ray tracing modeled this side collection using Monte Carlo techniques, which are discussed in detail. We fabricated and tested light pipes using several different coatings.

The effects of conical optical channel parameters on divergence of the rays radiated from an emitter plate are investigated. The optical channel is used to maximize the radiant power (flux) in a given solid angle at the exit aperture of the channel. A simulation method is presented for optimizing the channel layout, using channel gain (efficiency) as a measure of the output radiant power. Monte Carlo method is employed to generate emitted rays, and ray tracing is performed in a 3D fashion using each of the three reflection models, i.e., specular, diffuse, and Gaussian. The simulation results indicate that, for a given solid angle of output radiation, the channel gain attains a maximum for certain values of length, cone angle and two radii of the semi-conical channel. Moreover, the channel length has only a scaling effect on channel gain, when the cone angle and ratio of two radii are constant.

This subject is the class of high sensitive fiber optical vibrated sensors. It could be classified as a micromachining principle application to a fiber optics. The principle of operation is the resonance frequency change of the micromechanical vibrated fiber optical sections by depending on the environment. Bragg-gratings were considered to measure the amplitudes of vibrations of this small fiber cantilevers.

At every conference since 1995 we have reported on work in- progress to find a consistent formalism connecting the radiance concept with measurement of radiance, even under conditions where wave effects are important. In such circumstances, classical radiometry no longer provides an adequate description. In this conference we report on measurements of radiance that are well modeled by our theory, but would not be adequately described by classical radiometry.