Raman spectroscopy, a chemical analysis method with potential use in clinical studies, environmental sensing, and process monitoring, may be revolutionized by the integration of Lippmann volume holographic filters. Holographic filters of this type are being produced by Physical Optics Corporation and are referred to as Raman Holographic Edge (RHE) filters. RHE filters effectively remove the Rayleigh line to within 250 wavenumbers. The addition of the RHE filter will help create a new compact portable Raman spectrometer for university, industrial, and biomedical applications.

A new method to deliver high-quality laser beams through multimode optical fibers, based on the principle of phase conjugation generated by a hologram, is investigated. The delivery process is divided into two steps. In step 1, a hologram, which records the distorted output from the fiber, is made with the aid of a self-pumped phase-conjugating crystal. In step 2 the laser beam is first directed to the hologram, which gives the laser beam a phase precompensation, and is then coupled into the fiber. A clean wave with diffraction-limited quality is obtained at the other end of the fiber. The experimental configuration is almost the same as for an ordinary delivery system, except that the lens which couples the laser beam into the fiber is replaced by a hologram; some energy is lost if the hologram is not very efficient. The beam pattern of the final output could be one of any desired shape such as plane wave, spherical wave or Gaussian beam. Experimental results demonstrating diffraction- limited linearly polarized output are presented, and some limitations are discussed.

Techniques have been developed for the design and fabrication of surface relief holographic optical elements used to split single beams into multiple beams, of either equal or unequal intensities. The designs were fabricated as chrome on glass masters by standard electron beam mask-making techniques. Patterns were transferred using photolithography and reactive ion etching to form the required relief image in quartz. Binary phase holograms have been fabricated with measured efficiencies of around 70% for a range of uniform split arrays up to 20 X 20 with beam intensity ratios within 1% of the design values. Weight matrix holograms, both binary phase inversion symmetric and 4 phase non-inversion symmetric, have been fabricated with a similar measured efficiency.

The diffraction efficiency of interferometrically formed holographic lenses is influenced by the recording geometry and properties of the recording material. Variations in efficiency increase when attempting to make high numerical aperture elements. In this presentation the factors which influence the diffraction efficiency of high numerical aperture holographic lenses are examined.

The use of volume transmission gratings in a wavelength multiplexer can offer significant advantages over surface relief gratings in terms of efficiency and uniformity of response to different polarizations. The authors consider a double pass through the volume transmission grating obtained by placing a mirror behind the grating. This doubles the device dispersion while maintaining good peak diffraction efficiency (>90%) and polarization independence. The authors report the design compromise and fabrication of such volume gratings, produced in dichromated gelatin, targeted to efficiently cover reduced wavelength ranges in either the 1300 or 1500 nm telecommunications window. The experimental performance is described for a range of mirror backed gratings.

Two engineering fabrication techniques are described for single-mode waveguide multiplexed holograms. These techniques include a computer-controlled holographic recording system for fabricating high-density single-mode waveguide multiplexed holograms and an alignment technique for phase matching a waveguide hologram to a channel waveguide.

A new kind of true color rainbow holography--color coding reproduction of a 3D object--is presented. By making use of one wavelength laser to encode three Fresnel holograms in which each of the three primary colors of a 3D object is recorded by three primary color lasers, respectively, this new technique can produce a true color rainbow hologram of a 3D object with one exposure and one type of recording material; an available method to make high quality embossing masters of a true color hologram is thus provided.

Use of Du Pont's OmniDexTM holographic materials in the production of display or graphic arts holograms is discussed. The dry color tuning process that changes the hologram's playback wavelength, for example, from blue-green to gold or red, is described, and experimental results to support a diffusion-based color tuning mechanism are presented. The authors comment on possible uses of dry color tuning to control the playback wavelength of display holograms and holographic optical elements.

The authors investigate a developing process for volume holograms consisting of poly-N- vinylcarbazole (PVCz), and achieve a new process that enables high diffraction efficiency, large holograms and uniform quality. Conventionally PVCz holograms are developed by two sequential dipping processes: first into good solvent, then into poor solvent. When a swollen PVCz film is dipped into poor solvent, PVCz molecules precipitate into small grains, and micro-gaps between grains are formed corresponding to the degree of swelling. As the result of the difference in swelling between highly exposed and low exposed areas, refractive index modulation appears. In this process, it is difficult to obtain a large hologram, because the upper area dries more than the lower area when the swollen film is carried to poor solvent. Based on the investigation above, the authors found a new process where the holograms are developed by a single dipping process into a mixture of volatile good solvent and nonvolatile poor solvent. The hologram film swells with the mixture, and is then carried out slowly from the tub. The solvent mixture in the film becomes poor solvent, rich and small grains are formed, because a good solvent evaporates more quickly than a poor solvent. With this new process all areas of a hologram plate can be developed under same conditions, so large holograms with uniform quality become possible.

The photopolymer comprising the matrix polymer, polyfunctionalmonomer, radical initiator, and sensitizing dye are sensitive to visible light to give the holographic recording material for an argon ion laser exposure. The radical exposure involves 3, 3', 4, 4'- tetrakis(t-butyloxycarbonyl)benzophenone(BTTB, I) and iron-arene complex (II), and the sensitizing dye is ketocoumarin(III). The photopolymer gave the sensitivity from 0.1-4 mJ/cm2, depending on the holographic recording angle, for 488 nm argon ion laser light. Large-size rainbow holograms, 50 cm X 40 cm, were successfully recorded with this photopolymer with 10 sec exposure.

The increased emphasis on speed of operation, wavelength selectivity, compactness, and ruggedization has focused a great deal of attention on the solutions offered by all-optic devices and by hybrid electro-optic systems. In fact, many photonic devices are being considered for use as partial replacements for electronic systems. Optical components, which include modulators, switches, 3-D memory storage devices, wavelength division multiplexers, holographic optical elements, and others, are examples of such devices. The success or failure of these modern optical devices depends, to a great extent, on the performance and survivability of the optical materials used. This is particularly true for volume holographic filters, organic memory media, second- and third-order nonlinear material-based processors and neural networks. Due to the critical importance of these materials and their lack of availability, Physical Optics Corporation (POC) undertook a global advanced optical materials program which has enabled it to introduce several optical devices, based on the new and improved materials which will be described in this article.

The authors present a nongelatin dichromated (NGD) holographic film which is a new type of holographic recording material with excellent anti-humidity and real-time effects as well as other good performance features. In this paper, the basic process of making an NGD hologram is described briefly, a primary suggestion on the mechanism of forming images is proposed, and some characteristics and experimental results are presented.

An interference microscope is employed to take a photo of the interfering fringes, and its density is analyzed by a computer image system to measure the thickness distribution of a photolithographic hologram (PLH). This method is much more simple than that of SEM. The theory of measuring is presented in the paper. The authors measured the distributions of photolithographic gratings before and after the etching process. Comparing both the thickness distributions of corresponding recording layers, some primary rules of pattern transfer process by etching were identified.

The authors have, on combining holography with photolithography, improved the etching conditions of making binary elements and produced photolithographic holograms which can yield continuous phase modulation. This paper points out that it is most important to strictly control the selection ratio of etching rates, and gives the curves of the etching rates in respect to the flow of etching gas in the case of constant response power. A proper working point has been found. As the applications of the curves, high-quality optical elements can be made.

Reports on current research efforts in the application of holographic techniques to food processing. Through a simple and inexpensive production process, diffractive and holographic effects of color, depth, and motion can be transferred to edible products. Processes are discussed which can provide a competitive advantage to the marketing of a diverse group of sugar and non-sugar-based consumable products, i.e. candies, chocolates, lollipops, snacks, cereals and pharmaceuticals. Techniques, applications, and products are investigated involving the shift from a chemical to a physical basis for the production of food coloring and decorating.

Computer simulations can generate massive quantities of data. One problem for scientists and engineers is to assimilate and place in perspective the information available from the simulation and to communicate this information to other interested parties. The authors have been exploring some novel holographic display formats that provide hardcopy output of the results of computer simulations. These holograms allow rapid survey of graphical data as well as an opportunity to examine specific results. The hologram is more portable than a graphics workstation and is easily reproduced for wide distribution. The authors describe some of the holographic techniques, make some comments on pictorial presentation of data, and illustrate these points with examples from fluid dynamics, fracture mechanics, and architecture.

The plain white light reconstructed holographic stereogram (PW-HS) is made from the element holograms using photographs of many different viewpoints. It is useful when making a hologram of an object of which a hologram can not be made directly. To see the inside of the human body visually in the 3-D image, the authors apply the technique of holographic stereogram (HS) to the ultrasound B-mode images of the human fetus and display the 3-D image directly. The authors clarify the condition of making HS, then consider the quality of the reconstructed image. This system is applied to medical diagnosis and the effectiveness of this method is made clear.

There are several methods for recording two-dimensional perspective views for a holographic stereogram. Most of these use photographic transparencies recorded with a conventional camera. The subject often is a real object or a graphic image produced by a computer. In both cases the more accurately the recording geometry matches the holographic projection geometry the more realistic the stereogram image will appear. This paper compares several recording techniques. Special emphasis is given to the 'shear lens' technique which uses a moveable camera lens designed to maximize resolution and angle of view. An example is described in detail.

A method for producing holographic stereograms with reduced geometrical constraints is presented. The type of holographic stereogram produced, called the ULTRAGRAM, can offer a combination of large viewing zone, arbitrary viewing distance, minimal image distortion, and high spatial resolution, depending on alterable parameters in the image processing software. Computer-based image processing techniques are used to mimic the effect of optical devices while permitting simple re-configurability. The ULTRAGRAM holographic exposure apparatus can be built with reduced attention to the final viewing geometry. An astigmatic computer graphics camera design greatly simplifies image generation. The techniques described are applicable to both one and multi-step stereograms, optical predistortion methods, and both horizontal and full-parallax systems.

One-step holographic stereograms which can reconstruct large images have been produced by an extremely anamorphic optical system. One of the important lenses is the long and narrow cylindrical lens with small f-number. The lens is designed as a composite dual lens. Reference light is illuminated through this composite lens and the special configuration with cylindrical lenses is considered. But in the one-step holographic stereogram, if the series of conventional perspective original images are used without performing any anamorphic image processing, the reconstructed images are observed behind the hologram plane. In order to enhance the sense of perspective of the reconstructed images and minimize blur of the reconstructed image, an image processing technique is introduced. In this report, the authors describe their optical system and the image processing technique which can display a large and bright 3D image, with about 55 degree(s) viewing zone.

The fidelity of color reproduction achievable in reflection holograms is analyzed by an in- depth theoretical and experimental treatment. A theoretical model is described which incorporates color rendering analysis, effects of bandwidth, signal to noise for color holograms, and wavelength shifting; this analysis considers the effect on color by the holographic process which has been previously neglected. The model compares octagons formed by points on a CIE diagram corresponding to eight Munsell colored chips when reproduced by the holographic image and when lit by a standard light source. The theory is shown to compare well with experimental results obtained using both sandwiched Ilford films and a single panchromatic film. The model is then employed to predict holographic image color reproduction for all possible recording wavelengths. From this analysis optimum wavelength combinations are obtained. It is predicted that the color reproduction obtained by a practical set of recording wavelengths (458, 532, and 633 nm, for example) can actually be more accurate in a holographic image than under laser light, albeit with a reduced gamut area. A brief discussion explains why a short blue component with low diffraction efficiency achieves superior color reproduction.

Holographic moire method was applied to in-plane displacement measurement in the near- and far-field in single-edged notch specimens in plane stress state under static uniform tension. The holographic set-up and the loading rig are shown. Image-plane hologram recording and real-time observation were adopted to obtain optimum fringe visibility. To avoid fringe visibility degradation because of the localization problem the carrier fringe technique was used. Improving the holographic recording characteristics and signal-to-noise ratio were done through selection of the light-sensitive recording medium and its chemical processing. Silver- halide holographic plates HP-650 with hardened carrying matrix combined with optimized physical and chemical processing was used. Two-dimensional finite element calculation was performed to be compared with the experimental values. Agreement between experimental and numerical results was analyzed and discussed.

The holographic center high mounted stoplight achieves the required performance of a conventional center high mounted stoplight, but without the obstruction to the driver's view through the rear window. A lamp located in the roof illuminates a transmission image hologram mounted on the inner surface of the automobile rear window. The hologram strongly diffracts the incident light rearward but is transparent to the driver looking in his rearview mirror.

A new method of creating three-dimensional images with a grating pattern which consists of many small diffraction gratings is presented. The grating image gives its holographic display a very interesting feature, showing brilliant multi-color and moving effects. Conventional grating images are two-dimensional (2-D) patterns, but by this method a three-dimensional (3- D) image is generated. The basic principle of this method is parallax panoramagram, and the composed image is similar to the holographic stereogram. This type of image looks much brighter and clearer than the current holographic stereogram, because it consists of very simple gratings. The grating pattern is made by using an electron beam writing system. The system has the capability to change the direction and spatial frequency of the grating. In this paper, the principle and the development of the system for the new 3-D image is described.

The authors describe their experience using holography to gain better resolution than is possible with the conventional optics of the Fermilab 15-foot bubble chamber. In a physics run where the chamber was exposed to a high energy neutrino beam, approximately 293,000 conventional 3-view photographs and 218,000 holograms, of which approximately 110,000 are useful for physics, were recorded simultaneously. Over 1000 interactions from the bubble chamber with at least a 2X improvement in resolution were holographically reconstructed.

The edge-lit display format has been successfully applied to holographic stereograms. Taking advantage of the discrete nature of the information content of stereograms, the three-step production process of edge-lit rainbow holograms has been reduced to a two-step process for edge-lit holographic stereograms. Design improvements have been made to the edge-lit hologram's recording tank. The image distortion resulting from refraction as the object beam transits the air-tank interface in the final recording stage has been investigated and compensation techniques developed.

Three-dimensional image display has become so common that the public expects the realization of real-time display for three-dimensional images. The device which can construct various wavefronts is also important as a device for optical computing. The authors suggest a method to display 3-D moving images or construct wavefronts and consider an application of the technique of fiber optics to the display. The system that displays 3-D images is shown and the results of simulation are reported.

In this paper a theory of a new holographic contouring method based on application of absorption medium is proposed, allowing definition of absolute surface relief.

Since evaporation of cellular water leads to shrinkage and motion, holography of human tissue specimens is generally possible only with pulsed lasers. Plastination is a preservation technique in which cellular water is removed and replaced with a curable polymer. This preserves the tissue, including even the cellular anatomy, and renders the specimen rigid enough for holography with continuous beam lasers.

Underwater holography is attracting attention in the offshore oil and gas industries as a potential technique for high-resolution inspection and measurement of subsea structures and components. Real image reconstruction in the laboratory is employed to produce a high- fidelity image of the underwater scene upon which direct dimensional measurement may be performed. The refractive index change between recording in water and replaying in air introduces aberrations, like those observed by viewing an object from air at the bottom of a swimming pool, into the replayed image. The authors discuss the influence of such aberrations on the fidelity of underwater holograms and report experimental verification of a simple and effective method of minimizing their effect, by replaying in-air at a wavelength reduced in proportion to the refractive index of water.

Any practical holographic display device relying on the MIT synthetic aperture approach will require time-bandwidth products far exceeding those available with single channel acousto- optic modulators (AOMs). A solution to this problem is to use a multichannel AOM, thus making use of the parallelism inherent in optical systems. It is now technically feasible to accommodate a large number of acoustic channels on a single crystal with a corresponding improvement in image characteristics. The vertical view zone also becomes a significant problem for any large size display since each horizontal scan line is visible only from a narrow angle in the vertical direction. Using holographic optical elements (HOEs) alleviates this limitation in two ways: First, the interline spacing can be adjusted easily with HOEs. Second, it is possible to manufacture an HOE which will act as a one-dimensional diffuser. Placing such an HOE in the vertical focus plane of the display increases the view zone by diffusing each line in the vertical direction, but leaves the horizontal image content unaltered.

Wollaston's prism applied to recording holographic optical elements is proposed, and the experimental result in dichromated gelatin is given.

A method of producing large viewing angle rainbow holograms without any special or expensive optical elements by means of holographic phase conjugation is presented. A rainbow hologram with a viewing angle of more than 150 degree(s) has been produced.

The authors consider the quantization and sampling effects of computer-generated holograms (CGH) for optical interconnection of very large scale integrated circuits. Increasing the quantization level can greatly increase the diffraction efficiency of CGH, although there is some difficulty in technique for realizing CGH with more than two levels of quantization. Two kinds of sampling methods, Nyquist sampling and Whittaker-Shannon sampling, are analyzed and compared in the condition where diffractive-reflective optical interconnections are employed.

An automated analysis system is described with subsequent image processing enabling one to analyze complete interferograms. Digital image processing techniques are used to obtain high quality phase maps. Some applications in deformations determination and nondestructive testing (NDT) are given. Phase errors are discussed in some detail.

The influence of illuminating mode on the recordable depth of field in in-line holography of particle fields is discussed theoretically. The results show that the recordable depth of field can be increased using the divergent illumination.

The real-time holography system with a liquid-crystal television spatial light modular (LCTV- SLM) is presented. In the system, the LCTV-SLM is used as a phase hologram device. On the recording, the in-line holography method is used to reduce the spatial frequency of the fringe pattern of the hologram. The CCD camera detects the fringe pattern, and the fringe-pattern signal is transferred to the LCTV-SLM through the video-signal line. On the reconstruction process, the LCTV-SLM is illuminated by an He-Ne laser (633nm) and the spatial filtering technique is used to remove the zero and the higher-order diffracted light. Thus the holographic image of the real object can be observed continuously in real-time.

Left to right channel differences of the transmission factors in a 3DTV system result in asymmetric multiplicative luminance deviations, which can impair picture quality and/or can reduce the visual comfort. Twenty non-expert observers assessed the impairment of overall as well as localized asymmetric deviations (as it may happen, e.g., with lenticular screen displays) in terms of the CCIR impairment scale. The luminance asymmetries were produced by processing the digitized stereo image pair of two natural scenes, according to a reduction of the transfer function of only one channel. Results show that (1) overall and localized luminance asymmetries are perceptible if the transmission factors differ by 3-6 dB, depending on the spatial extension and gradient of the deviation; and (2) if a pattern of a sharply localized luminance deviation is moving (as it may happen, e.g., when an observer moves his head in front of a lenticular screen display), it is perceptible if the transmission factor differs by only 0.2 dB.

New dry photopolymer embossing (DPE) technology was developed recently at Du Pont to replicate highly efficient, deep groove surface relief holographic optical elements (HOEs). DPE technology utilizes Du Pont proprietary materials and processes to replicate with very high degree of precision almost any kind of surface relief or embossed holograms. Very sophisticated embossed HOEs with the width/depth aspect ratio of 1:20 were faithfully replicated by this technology. Dimensions of the replicated grooves or other structures vary from 0.1 micrometers to 3.5 micrometers . Such HOEs can be produced in different geometrical configurations and sizes, which are actually dictated by the master hologram. Embossed HOEs can be fabricated on a plastic film or sheet substrate of different types, thicknesses and shapes. Also glass and other inorganic materials can be used as substrates for these deep groove HOEs. To replicate high quality HOEs the master hologram must be recorded in metal, glass, or other hard surface material. DPE technology may provide substantial technological and economical advantage over existing conventional replication processes, such as injection molding, thermo-embossing, reaction molding or 2P (photo-polymerization) process, in replication of different types of embossed holograms and surface relief HOEs.

The holographic scientist has a long experience of developing and bleaching methods for the silver halides. There is however an underlying asymmetry of the chemical armoury. Whilst numerous developers have evolved throughout the history of photography, there is a paucity of organic bleach compounds that mimic their developing counterparts. This paper discusses the synthesis of novel bleaches starting with a range of developing agents. The door is opened to relatively safe long-keeping organic bleach agents with improved toxic hazard levels.