Reactive-ion-beam-sputtering (RIBS) is used to deposit doped vanadium dioxide (V1-xMxO2), where M is a dopant that lowers the transition temperature (Tt) from that of stoichiometric V02. The objective is to synthesize a material that will passively switch between a heat-transmitting-and a heat-reflecting-state at specific design temperatures in the human comfort range. The films are deposited at elevated temperature (>700K) onto glass and sapphire substrates for spectrophotometric evaluation above and below Tt. Then by analyzing the deposited films via EDAX, correlations between film composition and passive solar switching performance are made. Also concepts for synthesizing suitable crystallites of such materials are described. These crystallites could act as switchable pigments for throchromic solar paint. The overall long range goals of this research are to develop these materials for: (1) thin film application to building glazings and (2) pigments for opaque wall coatings. The glazings will transmit and the walls will absorb solar energy when the V1-xMxO2 temperature (T) is low (T<Tt). At T>Tt, both glazings and walls will reflect the solar infrared.

VO2 films were produced by reactive e-beam evaporation followed by annealing post-treatment. Electrical measurements demonstrated a semiconductor-metal transition at Tc ~ 60°C. Spectrophotometry showed that the near-infrared solar transmittance was reduced when Tc was exceeded while the luminous transmittance remained relatively unchanged. This thermochromism may be utilized for regulating the energy throughput of windows. Practical application hinges on improved transmittance and on Tc-depression. These goals can be accomplished to some extent by dielectric overlayers, as verified by measurements on SiO2-coated VO2 films.

The electrochromic phenomenon consists of changing the optical absorption properties of certain materials by an externally applied electric field or current. In the unactivated state, these materials do not absorb in the visible range of the spectrum and hence they are colorless. However, on applying a moderate DC electric field, the material develops an absorption band in the visible region which results in a color change. The coloration remains for various lengths of time even after the external field is removed. The system returns to its original state when the polarity of the external field is reversed. Consequently this basic phenomenon can he utilized for a great variety of technologically important applications such as light modulation, display devices, optical information recording, electrophotography, and the like. The term "electrochromism" can he applied to a broad range of phenomena in which any kind of color change is brought about by an electric field or a current in a solid or semi-solid system. A great deal of interest in this type of phenomenon arose primarily as a result of an observation that large densities of color-centers can be generated in a controlled and reversible manner in thin films of certain transition metal oxides, such as W03, Mo03, etc., which are ordinarily large band gap insulators. In this paper we will present some historical perspectives on this effect and assess, to a limited extent, the current status of this technology.

The electrochemical and optical switching characteristics of a variety of variable transmittance complementary electrochromic windows are presented. The complementary configurations are based on hydrogen insertion in cathodically coloring amorphous WO3 and crystalline KxWO3+(x/2) combined with anodically coloring IrO2. These windows exhibit typical transmittance modulations from 70 to 15% in the visible spectrum and undergo ca. 4000 to 6000 switching cycles without degradation. The optical switching characteristics are discussed in terms of the complementary device structure and the electrochemistry of the individual electrochromic layers.

It is shown that practical spectrally-selective transmittance modulation can be achieved with thin (50-100nm) WO3 films, and therefore such films should be useful for fabricating electrochromic windows. The transmittance and reflectance modulation results are compared with theoretical predictions. The results indicate an excess intraband absorptance, which is attributed to free electron scattering arising from extended defects.

The conversion of solar energy into electrical power is a demonstrated fact. The crucial considerations for this technology are: high conversion efficiency, long-term stability, and lower cost. In order for photovoltaics to make a significant contribution to global energy supply needs, it is essential that this technology be able to provide electricity at a cost that is competitive with the electricity generated by conventional means. The U.S. Department of Energy's (DOE) Photovoltaic Program objective is to develop this technology to a point where it can eventually become a viable energy option. One of the key elements of the program strategy is to carry out research and development on advanced and high risk materials and device concepts. DOE's research and development efforts are focused primarily on applied research for the development of promising new photovoltaic approaches, such as thin film and multijunction concepts, whereas basic research is directed toward gaining scientific knowledge in an effort to meet a recognized need. Further development of photovoltaic technology directs that knowledge towards the production of useful materials, devices, and systems. Despite the potentially high payoff of these research and development activities, they are costly, risky, and lengthy, and private enterprise is unlikely to pursue them for these reasons. The purpose of SERI's Photovoltaic Program is to conduct high risk, potentially high payoff research and development which will result in a scientific and technical knowledge base which private enterprise can use for further concept and product development and, ultimately, competitive application in electrical energy markets. Consistent with this strategy, a multiple research approach that ensures greater probability of success has been developed. In this paper we shall review the current status of research and development in a few leading technologies such as (i) amorphous silicon, (ii) polycrystalline thin films based on CuInSe2 and CdTe, (iii) high efficiency solar cells using III-V compounds and their alloys, and (iv) high efficiency crystalline silicon.

The long wavelength quantum efficiency of a-Si solar cells can be greatly enhanced by light scattering at the rough tin oxide front contact. SEM photographs of the textured tin oxide indicate the surface to be composed of pyramidal microcrystallites with diameters ranging from .1 to 1.5 microns. A model is presented which idealizes the pyramid by replacing it with a sphere, a feature with known scattering properties. To account for the variety of microcrystallite sizes, the distribution of spheres is assumed to be Gaussian. Results of the model are compared with the integrated scattered transmission of visible light measured through tin oxide films of various feature size.

This paper reports results of Tin oxide antireflection coating of silicon solar cells made using textured polysilicon substrates by vacuum evaporation process. The results indicated short-circuit current enhancement of 22% for textured and 31% for polished single crystal substrate.

The approach selected is the fabrication of holographic optical elements, which will focus sunlight to either a line or a point. A concentrating mirror is replicated in the hologram which consists of dichromate gelatin exposed to a laser beam. The dichromate gelatin can be processed to produce a nonuniform microstructure, which gives the hologram a significant waveband width. Even so, it becomes necessary to stack at least three holograms, with each hologram reflecting a different region of the solar spectrum, if we are to reflect most of the solar energy. To achieve high efficiency, it is necessary to obtain adjacent quasi-square waves for the efficiency-wavelength profile of each of the holograms in the stack. Profile information was obtained by the use of a monochromator coupled to a computer. An optical efficiency in excess of 50 percent was measured for a three hologram stack. This represents approximately 70 percent of the efficiency achievable within the limited measuring range of the monochromator. A line-focus holographic concentrator model has been built for demonstration purposes. A cost analysis for mass producing holographic concentrators indicates that holographic concentrators become cost effective in relation to mass-produced conventional concentrators when the holographic optical efficiency exceeds 70 percent. To surpass this number, it becomes necessary to produce a five hologram stack and to broaden the monochromator optical sensitivity range.

The growth of greenhouse produce in the northern regions of the country is not economical because large amounts of heat are required during the cold season. It has long been recognized that one solution would be to heavily insulate large areas of a greenhouse to prevent heat loss and then use optical devices on the remaining glazing to distribute the incident light throughout the greenhouse (Figure 1). The design, fabrication and installation of holographic optical elements for this purpose is reported here. The ultimate goal is not necessarily increased yields or an economic superiority over imported produce. Since locally grown produce can be marketed rapidly and since varieties can be chosen which do not sacrifice quality for durability, local produce from holographically illuminated greenhouses will be economically viable so long as there are reasonable yields even if the technique does not result in prices competitive with produce grown in warmer climates and shipped to northern markets. There are varieties of effects here on growing plants that are unique to holographic lighting. For example, different portions of the spectrum are delivered to the plants at different times of the day and diffracted light often arrives at the plant from unusual directions.

In this presentation we report on the experience gained in the past year in the manufacturing of large, dielectric holograms for solar energy application. The experimental investigations were aimed at the solution of problems related to the large size (30 x 30 cm2) of the manufactured holographic optical elements such as the consistency of the film thickness and the mechanical stability of the optical set-up.

Changes in the configuration of an holographic grating have to be anticipated in the fabrication of practical Holographic Diffractive Structures (HDSs) for solar illumination engineering. Because photographic material used in HDSs changes characteristics during processing, there is a change of slant angle (due to shrinkage or swelling, i.e. actual dimensional change of the emulsion) and a change of average refractive index (due to bleaching and fixing). Computer aided analyses of test data have been performed in a way that predicts, under a wide range of conditions and for any given holographic recording material, the exposures required to attain specific intended optimum illumination results. This model has been verified in experiments and has been used to design illumination geometries for HDSs that meet the intended and often site specific target conditions very accurately.

Experience from the solar terrestrial glass mirrors can be applied to the design for use in space. In this paper, a brief review of terrestrial experience, space flight tests of glass mirrors, and future design considerations for long-lived mirrors will be treated.

The specular reflection properties of transparent cast polymer sheets and extruded polymer films, silvered and unsilvered, have been characterized with a newly designed specular reflectometer. The results obtained with this instrument are either absolute reflectances or a measure for the Fourier transform of the reflection function of the specimen in one dimension. Cast polymer sheets are investigated before and after silvering, and silvered polymer films are evaluated by mounting them with an adhesive onto aluminum or glass substrates, or by suspending the thin, silvered polymer as a taut membrane. Silvered polymers have attained a specularity such that over 90% of the incident beam is contained in a 1-2 mrad full-cone angle when mounted on a good substrate or suspended as a membrane. This value is well within the current goals for solar concentrators but silvered polymer mirrors are currently less specular than glass mirrors. The image quality of these mirrors does not change significantly over the wavelength range 400 to 1000 nm and angles of incidence between 20 and 60 degrees. A principal limiting factor to the initial specularity of the polymer mirrors was waviness and/or curvature of the surface, hence, the material being used as a substrate plays an important role in the optical performance of the mirror.

This paper will be confined to the effect of optical inhomogeneities in polymer films on the scattering or specular transmittance of light. Potential causes for the presence of scattering entities in the bulk phase of polymers will be discussed. It will be shown that practical transmittance measurements are greatly influenced by the angular width of the instrument receptor aperture. The choice of larger receptor apertures will tend to include some of the scattering at small angles due to large inhomogeneities in the measurement of specular transmittance. As a consequence, the transmittance measured is not necessarily increased by reducing the size of the inhomogeneities in the polymer films, but there is a critical size when the specular transmittance is a minimum.

Solar selective black nickel absorbing films have been deposited on G.I. substrates by a very simple dip and dry method using a mixture of nickel chloride and thiourea solution (0.1M concentration). The films which developed a surface structure with the formation of well-defined globular particles distributed over the entire surface have exhibited better selective properties having αs= 0.81, εTh= 0.10 and S = 8.1.

Coating for energy efficiency is one of functional thin films which is developing vigorously. In this paper requirements of the coatings are analysed wholly while the design of the coatings is discussed and some appropriate layer systems are given. And depositing technique is also discussed from deposited samples. The paper shows the test results of spectral properties, firmness, and reducing and maintaining temperature respectively for summer and winter films, which indicate that the deposited coatings have fulfilled the basic requirements of the coatings for energy efficiency.

The Los Alamos National Laboratory has been involved in supporting, monitoring and conducting exposure testing of solar materials for approximately ten years. The Laboratory has provided technical monitoring of the IITRI1, DSET2, Lockheed3, and Berry4 contracts and has operated the Los Alamos exposure Facility for over five years. This report will outline some of the past exposure testing, the testing still in progress, and describe some of the major findings. While this report will primarily emphasize solar absorber surfaces, some of the significant findings relative to advanced glazing will be discussed .

An emittance meter which utilizes internal standards by Au plated mirror and low temperature blackbody furnace as low and high emittance standards respectively has been developed. The obtained emittance value of which systematic error was compensated had accuracy within ±0.01 and precision within ±0.003. The long term drift of measured emittance value was also checked and confirmed to be within ±0.01 for one year continuous operation.

The absolute reflectance of specular surfaces can be measured with a "V-W" optical system invented by Strong. The most difficult systematic error to eliminate in a V-W measurement is drift of the beam spot on the detector surface with small angular shifts of the beam between the sample-in (W) and sample-out(V) positions. In the infrared, this problem is exacerbated by the nonuniformity and small size of available detectors. Previous researchers have minimized this error with integrating spheres (in the visible) and/or auxiliary optics which desensitize the system to sample tilt errors. In order to verify this sensitivity to beam drift, a set of angular response measurements were performed on a commercial, variable angle V-W accessory and then modelled with a CODE V raytrace. The absolute accuracy of the instrument was estimated by measuring the specular reflectance of silver from 2-20 microns and comparing it to a Hagens-Rubens model. Finally, a nonimaging concentrator and a gold integrating sphere are considered as ways to increase the effective area of the detector and thus further desensitize the optics to misalignment errors.

The ability to measure high reflectance coatings accurately in the visible and near infrared portions of the spectrum is essential in the production of modern building components, lighting components and solar energy conversion systems. This paper describes two computer controlled spectral reflectance measurement syste s which, with different optical inputs, share the ability to measure actual coated parts rather than relying on witness samples from a coating run. Details of the instrumentation, calibration standards, calibration and measurement process and typical results will be given.

By using the emittance meter based on rapid-scan FT-IR spectrometer and the thermo visualized apparatus for the determination of the sample surface temperature and the black body temperature, the accuracy of normal spectral emittance (NSE) was significantly improved. For an example, the accuracy of NSE of the sintered Si3N4 ceramics at about 483°C was assured to be better than ±2% in emittance unit between 3,950 and 400 cm-1 in wave-numbers, while that of measured NSE of the sintered β-SiC ceramics at about 82°C being assured again to be better than ±2% in emittance unit between 2,500 and 400 cm-1 in wave-numbers.

Current efforts at the Lawrence Berkeley Laboratory to improve the operational efficiency of fluorescent lamps are based upon novel techniques intended to reduce internal resonance radiative transport losses. Such losses have been associated with "entrapment" of resonance radiation in the optically thick positive column of the mercury vapor discharge. Two promising techniques for entrapment reduction are provided respectively to selective mercury isotope enrichment and by the broadening of the hyper-fine structure (hfs) of the resonance line X2537 via the Zeeman effect. These techniques have, thus far, led to fluorescent lamp UV production efficiency enhancements, respectively of about 6.8% and 7%. Additional efforts to improve HID sources are in progress. Interesting metallic halides have been combined with electrodeless arc technology to produce a laboratory discharge system operating with an efficacy exceeding 170 lumens per watt, and a color rendering index (CRI) of 52.

The characteristics of medium arc metal halide light sources are defined and discussed. The medium arc is A.C. operated with about 100 watts/mm dissipated in the arc giving arc luminances generally around 12,000 cd/cm2 but, with design compromise, three times this being achievable. The use of metal halides results in very high conversion efficiency into radiation, up to forty percent in some cases, and can provide tailored spectra throughout the near UV and visible wavelengths. The arc's double-ended construction, unjacketed design provides a mechanically precise component suitable for system use.

This paper deals with the characteristics of short-arc (10mm or less)high pressure lamps using xenon and/or an additive metal fill. Metal reflectors produced by the electro-forming process are also described. The combination of short arc lamp and deep-dish electroformed reflector is compared to other collection methods, and applications are explored.

Recent developments in metal halide technology have lead to the introduction of AC Short Arc Metal Halide lamps suitable for a wide range of illumination applications. The advantages of such sources are as follows; high brightness, small source size, high correlated color temperature, and good color quality. In addition, the efficacy of these lamps are two to three times greater than other light sources. In order to apply the AC short arc metal halide lamps properly, their physical, optical and electrical characteristics must be considered comprehensively. The metal halide arc itself is especially complex and requires careful investigation in order to make optimum optical designs. This paper will review the basics of metal halide technology and its application to lamps. Spectral and optical characteristics are discussed and optical design considerations for different applications will be reviewed. Operational requirements, including power supply characteristics and cooling will be presented. In addition, this paper will discuss present and future applications for currently available sources and possibilities for new types of metal halide lamps. Particular attention will be paid to UV radiating types.

The purpose of this paper is to discuss a novel approach to the illumination of large areas such as stadiums, sports arenas, outdoor storage and warehousing, etc.

Two applications of the use of non-absorbing optical coatings in the construction of new light sources are presented. The lamps are utilized for daylight (5600K) film and stage lighting and for infrared security and perimeter lighting. Both lamps are sealed beam construction. Coating designs, fabrication methods and materials are discussed. Alterations to the spectral content of the source due to the coating and reflector substrate are described. The performance of the coatings offer a significant improvement in terms of efficiency and thermal characteristics.

The wonder of the projected image in the entertainment industry has remained unique throughout most of history. Sunlight, campfires and torches surely illuminated the first storytellers and no doubt cast the first mysterious shadows on cave walls adding to the drama. Historically the sun may be considered to be the light source used in the first projection device. This was a somewhat primative optical device called the camera obscura. It was a device which used pinholes, lenses and sometimes mirrors to focus an image, usually of buildings or landscapes, on a drawing surface. We are not sure if we can credit any one individual with the invention of the camera obscura, but it is directly linked to the work of many artists and scientists. It was used extensively by many in the study of architecture and illustration. It marks a beginning in the creation of optical equipment for projection and photography.

The design techniques of nonimaging optics may have a useful role in illumination systems for buildings; specifically, in the areas of light capture, light transport and light pro-jection at the location of end use. General design methods for various applications are described.

Efficient daylighting systems have recently attracted increasing interest due to their potential for saving a condiderable amount of electrical energy used for lighting purposes. In this paper we discuss the properties of daylighting systems based on either fluorescent planar concentrators (FPC's) and transparent light guiding plates or light pipes coated with a highly reflective silver coated plastic film (3M Silverlux film). First results on daylighting systems in the students' living quarters in Stuttgart-Hohenheim will be presented. This is a demonstration project which is supported by the Commission of the European Communities.

Prism light guides are hollow structures which pipe light by means of total internal reflection (TIR). These devices are unique in their ability to combine the efficiency of TIR with the relatively low cost of a hollow structure. An important application stems from their ability to transform a point source of light such as an incandescent or discharge lamp into a linear or area source of light or illumination. We report the development of an economical, flexible prismatic film for fabricating the light guide wall. This film is adaptable to a wide variety of applications, some of which are described. Other guide geometries and films are currently under development.

After reviewing the main properties of a tapered dielectric guide for collecting and transmitting high energy fluxes, we discuss the problem of the losses and its influence on the optimum design of these devices.

A formula is derived for the flux density associated with each ray traced through an optical system. The formula involves the ratio of the products of the principal curvatures of the wave front as it approaches and leaves each refracting surface. As input to the flux equation, a new and simplified derivation of the general lens equations is given. The general lens equations yield the normal curvatures and torsion of normal curves in the refracted wave front at each surface; these in turn, are related to the corresponding quantities for the incident wave front and the refracting surface. As an application, the flux equation and the generalized lens equations are specialized to meridional rays. The flux density and the caustic surfaces, that is, the loci of wave front principal curvatures, are then computed for a singlet lens. In a second application the flux density for skew rays is calculated over a receiver plane perpendicular to the symmetry axis when light from an off axis point source is reflected from a paraboloid.

The speed of a machine vision system can be dramatically improved by judicious choices of electro-optical components. This is of great importance in agriculture and the consumer products industry where inspections are complex and high volumes the norm. Recent advances in video camera technology allow imaging in discrete portions of the visible spectrum. When these devices are applied based on spectral knowledge of illumination, sample, as well as the transfer functions of filters and sensors, then "optical thresholding" can be effected. The lump transfer function of the system can be predicted since the individual transfer functions for each of the components is known. This can result in a concommitant reduction in the amount of computer processing necessary per image. The work presented here demonstrates the use of a spectroreflectometer in conjunction with spectral knowldege of each of the other components of the system to calculate optical lump responses. The goal is to optimize the optical gain to yield a maximum signal to noise ratio for the entire system. A spectroreflectometer is first used to define the optimum illumination characteristics and filter bandpass for a particular application. A knowledgeable choice of test samples is important. The system is then tested and the range of variation established using experimentally-defined optical components and a video camera with a programmable filter wheel. Spectral reflectance curves, optical transfer functions, and actual video images obtained using this approach with application to the food industry will be shown.

The purpose of this paper is to present a brief overview of the current art in projected optical effects, with emphasis on recent trends and developments that have applications beyond the entertainment industry.

I am the Marketing Manager for a fairly good-sized company in a very small industry which is dependent on the efforts of the kind of people attending this conference. Strand Lighting and other companies like mine supply the lighting needs of the entertainment industry. We listen to people like Dan Flannery and Bran Ferrren as well as thousands of other creative, artistic designers, manufacturing the tools they need to bring you everything from Hamlet to Dynasty, from Masterpiece Theatre to The Price is Right. We design and manufacture dimmers, computerized control equipment for the dimmers, and lighting fixtures.It it the issue of lighting fixtures for our industry that brings me here today. The total yearly volume of the entire entertainment lighting industry is estimated at only $70 million. Compare that to the billions of the defense or medical industries.