Diffusers play an important role in optical and digital holography, because they can improve the quality of the reconstructions. However, the application of diffusers generally suffers from a severe drawback: they introduce a speckle pattern which may disturb the reconstruction. An analysis of the speckle phenomenon reveals the possibility to avoid speckle by the use of special diffusers which can be designed by digital techniques.

The guided-mode resonance properties of planar dielectric waveguide gratings are presented and explained. It is shown that these structures function as filters producing efficient exchange of energy between forward and backward propagating diffracted waves with smooth lineshapes and arbitrary filter linewidths. Simple expressions based on classical slab waveguide theory give a clear view and quantification of the inherent TE/TM polarization separation and the free-spectral ranges of the filters. Furthermore, the resonance regimes, defining the parametric regions of the guided-mode resonances, can be directly visualized. It is shown that the linewidths of the resonances can be controlled by the grating modulation amplitude and by the degree of mode confinement (refractive-index difference at boundaries). Examples presented of potential uses for these elements include a narrow-line polarized laser, tunable polarized laser, photorefractive tunable filter, and an electro-optic switch. The guided-mode resonance filter represents a basic new optical element with significant potential for practical applications.

Different parts of diffractive optics can be stated which differ from each other in the diffraction theory suitable to describe the diffraction phenomenon. Diffractive optics on the basis of scalar diffraction theory deals with thin holograms. The diffraction efficiency of thin holograms is the subject of this paper.

Many optical systems are based on the polarization state of light (e.g., the magneto optical disk). Others may be optimized using polarized light (e.g., the capacity of optical communication systems may be doubled). For such systems polarization depending optical elements are needed. Polarizing computer generated holograms (PCGH) may allow the integration of different functions in one element. They should help to simplify existing systems and open up new applications. We propose the fabrication of PCGHs based on micro structuring of polarizing or birefringent materials. A method of calculation of the PCGH transmission function is described. A simple and useful method for production of binary and grayscale amplitude PCGHs is shown. Experimental results demonstrating the possibilities of our approach are presented. Possible applications are discussed.

The diffraction problem of image reconstruction from volume phase holograms of diffuse objects is stated rigorously in the context of the multiple scattering theory. The diffraction efficiency of transmission and reflection holograms is derived with inclusion of the first and second scattering orders.

The performance of optically mastered holographic fan-out elements is considered, in the limit, as the angular separation between output beams becomes small. This type of element consists of a number of superimposed gratings, each recorded with a common reference and a distinct signal beam. On replay with the reference beam, in addition to the expected zero and first orders, a large number of spurious orders are observed. These are produced by multiple grating diffraction processes and can contain significant power. By considering an infinite set of spurious orders, operator expressions are derived for the power in each of the significant diffraction orders. These expressions are analogous to the two wave solution for a single grating but with the coupling constant replaced by a coupling operator. In the cases of two and three gratings expansion of the operator expressions yields simple and analytical formulae. For the general case a pure recurrence relationship is derived linking all the diffraction orders. The validity of the results is demonstrated by comparison with a direct numerical solution of the coupled wave equations. Excellent agreement is obtained for angular separations of up to 1 degree(s) and for holograms of moderate thickness up to 5 degree(s).

The optical hybrid systems, i.e., systems containing the optical elements of different types (diffractive and gradient-index lenses), are considered. The corrective scope of two- and three-element hybrid objectives are investigated. It is shown that the two-element objective may be corrected for all monochromatic third-order aberrations. It is possible in a wide range of relations between optical powers diffractive and gradient-index lenses. It allows us to reduce the space frequency of the structure of the diffractive lens and to decrease the magnitude of the refractive index change of gradient-index lens. In addition, the correction of various fifth-order aberrations may be achieved in this case too. As a result this objective forms the image with high resolution and a wide linear field in the image space. The three-element hybrid objective consists of one diffractive and two gradient-index lenses. This objective has symmetric configuration and unit magnification. It is shown that in such an objective, which is free from all third-order aberrations, it's possible to eliminate simultaneously three out of the four different even fifth-order aberrations. In particular, the validity of this result is conserved if the optical power of the diffractive element is equal to zero. The design of a three-element hybrid objective is given. The resulting designs are compared with homogeneous objectives.

Progress in the fabrication of diffractive optical elements (DOEs) as 2-dimensional continuous-relief microstructures is described. The elements are fabricated by laser-beam writing in photoresist and have typical microreliefs up to 5 micrometers and periods down to 10 micrometers . Examples include fan-out elements and Fresnel microlens arrays. The design and fabrication of a 9 X 9 fan-out DOE with a diffraction efficiency of 94% and an overall uniformity of +/- 8% is described. High quality replicas are produced by low-cost embossing and casting techniques.

A new pattern generator, initially designed for ASIC fabrication, is employed for writing synthetic holograms and other micro-optical components. The specifications and some limits of this machine have been investigated. Test structures and synthetic holograms are shown. Arbitrary patterns with micron resolution, submicron positioning accuracy, large area (up to 150 X 150 mm² possible), and good quality of the microprofile were demonstrated.

We report on direct-writing EBL manufactured, proximity compensated blazed transmission gratings. The proximity compensation is made using a non-linear iterative process in the spatial domain. The diffraction efficiency for a compensated 8 micron period grating was 84%, almost twice that of an uncompensated grating.

We report on the design, calculation, and fabrication of binary and multilevel synthetic lenses realized in silicon. The diffractive patterns of the lenses are computer generated, direct E-beam written, and dry etched into the surface of silicon wafers. This paper describes the fabrication tools used and the techniques applied for the lens fabrication. The data processing as well as the efforts necessary for the electron beam writing are emphasized. Binary as well as multilevel elements are fabricated. First results are given for the performance of binary lenses in terms of diffraction efficiency, the efficiency of laser diode to fiber coupling, and the image quality of lenses.

Blazed Fresnel zone lenses for 1.5 micrometers wavelength were fabricated in quartz glass by means of microstructuring technology. The blazed profile in each zone of the lenses was approximated by 2, 4, and 8 discrete levels. The effects of fabrication errors, such as depth and alignment errors, on the diffraction efficiency of the different Fresnel zone lenses were investigated. Further the location and intensity of the parasitic foci appearing due to the discrete level approximation are calculated. Theoretical results along with experimental measurements are presented.

Positive resist was used to record holographic plane gratings. In order to have rectangular groove profiles a nonlinearly acting developer liquid was chosen. When gratings were read, the incidence angle of the reading laser was varied from the Bragg angle to the direction of the plate normal. If the grating profiles were rectangular the diffraction efficiency (DE) at normal incidence should have been low. However, noticeable DE:s were detected. The high efficiencies were due to the rounding of the grating groove edges. Thus by measuring the DE at different angles the rounding of the profile could be estimated.

In this paper we present the experimental results we obtained for the optimization of an acrylamide photopolymer for use in real time holography. The optimum energetic sensitivity is obtained by decreasing inhibition time, which is achieved by including a second sensitizing system, and carrying out a pre-exposure. In this way it is possible to eliminate all the oxygen present in the sample which is a fundamental cause of the inhibition process. We have obtained a sensitivity of 3 mJ/cm² at 633 nm.

Wave aberrations determine the quality of the focal spot and, more generally, the imaging quality of the lens under test. Here we propose the measurement of the wave aberrations with the help of a Twyman-Green interferometer adapted to the special requirements for testing holographic optical lens elements. The evaluation of the interferograms is done with the phase-shifting technique. The resulting wave aberrations are expanded as Zernike polynomials. In addition to this evaluation, the point spread function and the modulation transfer function are calculated from the wave aberrations. The setup, the evaluation method, and some exemplary results of a tested holographic optical element are presented.

High efficiency, deep groove, surface relief diffractive optical elements (DOE) with various optical functions can be recorded in a photoresist using conventional interferometric holographic and computer generated photolithographic recording techniques. While photoresist recording media are satisfactory for recording individual surface relief DOE, a reliable and precise method is needed to replicate these diffractive microstructures to maintain the high aspect ratio in each replicated DOE. The term `high aspect ratio' means that the depth of a groove is substantially greater, i.e., 2, 3, or more times greater, then the width of the groove. A new family of dry photopolymers SURPHEX^TM was developed recently at Du Pont to replicate such highly efficient, deep groove DOEs. SURPHEX^TM photopolymers are being utilized in Du Pont's proprietary dry photopolymer embossing (DPE) technology to replicate with a very high degree of precision almost any type of surface relief DOE. Surfaces relief microstructures with a width/depth aspect ratio of 1:20 (0.1 micrometers /2.0micrometers ) were faithfully replicated by DPE technology. Several types of plastic and glass/quartz optical substrates can be used for economical replication of DOE.

Surface photodeposition is a photon assisted process, by which thin films can be formed on substrates immersed in colloidal solutions. Holographic gratings of various spatial frequencies have been recorded by photodeposition of amorphous selenium colloids. The holographic surface relief grating formation is described in relation to the modulation transfer function of colloidal photodeposition. Spatial frequencies of about 1500 lines/mm can be recorded with amorphous selenium, whose colloidal particle sizes range from 30 to 80 nm.

The processing procedures for surface relief holograms recorded on silver halide emulsions are presented. The most promising methods have been investigated and compared. The aim is to develop and optimize methods for obtaining relief structures on silver halide gelatin emulsions for holography at rather high spatial frequencies. Such a relief pattern can then be used for making a metallic matrix. The main advantage of using a silver halide material, instead of photoresist material, is the favorable sensitivity characteristics over the whole visible spectrum of silver materials.

In the industrial applications of holography as well as in display holography, there is a need to adapt, in order to generate the specifically asked for effect, the type of the recording material or the processing of the emulsion after recording. Therefore, the search for new holographic materials as well as newly adapted processing techniques can lead to easier measurements or to better performances. This paper deals with a description of the techniques used for performance improvement of silver halide photographic emulsions. The study has shown that by the use of a fitted physical developer, the bandwidth of reflection holograms can be increased from 70 nm to 200 nm and diffraction efficiency can reach 14%. Using physical and chemical developments, the color of the hologram can be chosen depending on the composition of the development baths. Values of the efficiency of more than 40% were reported with selected chemical developers.

The mechanism of the recording of a static hologram by a rapidly moving interference pattern in a photorefractive crystal is investigated theoretically and experimentally. The difference between the frequencies of the writing beams strongly exceeds the inverse response time of the hologram and is equal or multiple to the frequency of the external ac field applied to the crystal. The experiment was performed in Bi₁₂TiO₂₀ crystal.

An exact method for the evaluation of the effects of the finite spatial resolution and the nonlinearity of the recording material on the reconstructed holographic image is presented in this paper. This new method is based on substitution of the amplitude transfer function and the amplitude diffraction efficiency vs. bias exposure and beam ratio characteristics of the recording material to the double Fresnel-Kirchoff integral descripting the complex amplitude of the reconstructed image. All the above characteristics have been fitted by analytical functions. The contrast of the reconstructed image as a function of various parameters such as the spatial resolution limit of the recording material, the object position, and the beam ratio has been computed by numerical quadrature of the above mentioned integral. Numerical calculations have been carried out for thin amplitude holograms of microline objects in several different recording geometries, including those with a tilted object plane.

The coherent intermodulation of the spatial phases of a stationary holographic grating with a separated traveling surface acoustic wave modulates the intensity in the resulting diffracted orders of a probing laser beam. The detected signal in the m equals 0 and higher diffracted orders contains information about both the stationary and traveling grating structures. For the `tuned' condition, where both grating periods are nearly the same, the detected intensity modulation is at the same frequency as the surface acoustic wave. We have analyzed this double grating interaction and discuss its inherent sensitivity and enhanced selectivity.

The advantages of holography for remote optical inspection and mensuration can be greatly reduced by loss of image quality caused by an unoptimized reconstruction geometry. For underwater holography it is essential that image quality is high to ensure mechanical defects, such as cracks, corrosion, or deformities, can be detected. In practical replay systems, a number of physical constraints limit image resolution to a value significantly lower than that theoretically possible in an ideal system. In most cases, even this limited resolution is unobtainable, due to mismatch of the reconstruction wavefronts caused by imprecise relocation of the hologram and inexact conjugation of the reference beam. It is shown how deviations from the optimum reconstruction geometry affect image resolution, both theoretically and experimentally, for a number of in-air and underwater recording geometries.

Digital transforms, such as Walsh or Haar transforms for example, are often used to improve the quality of the picture and obtain a better resolution. The mathematical computer procedure of the transform operation can, however, be lengthy and complicated. We suggest use of coded holography with a mask representing the Walsh or Haar transform as a reference beam. Details of the set up and the construction of the mask are discussed and the results are shown.

The possibility of using the angular selectivity property of a pseudo-deep hologram for a 3-D image formation is investigated. The optical system characterized by the presence of an inclined hologram and a horizontal slit which filters the beams of an object and that of an extended reference source is considered. It is shown that the hologram recorded with the help of such a system is capable of reconstructing 3-D images while being illuminated by an extended source of light which is characterized by a distribution of phases different from that of the reference source. The above-mentioned record is referred to as a selectogram.

A design method of improving imaging quality for infrared holographic optical elements (HOEs) in which a cylindrical lens is added into an object beam to form a hyperbolic wavefront is researched. Here, we temporarily name these HOEs recorded by aberrant wavefront or aspherical wavefront as AWHOEs to discriminate HOEs recorded by spherical wavefront.

In contrast to imaging and interconnect applications, which require fixed diffractive optical elements, applications such as optical image processing and target recognition require diffractive elements that can be altered dynamically in real-time and, therefore, require the use of spatial light modulators (SLMs). Present SLM technology, however, has limited spatial resolution and space-bandwidth which affects system performance. We present techniques for designing diffractive filters for display on SLMs in coherent and incoherent image processing systems. Laboratory results are presented for a coherent matched filter design for display on a binary phase SLM.

A novel coherent optical processor for discriminating between similar patterns is described. A multiplexed hologram of two complex spatial filters (CSF) synthesized with a common reference beam provides the correlation. The two halves of the template pattern are encoded in the two CSFs. The response of the system consists of two sets of reconstructed waves that interfere at the output plane. One set of the waves is made to phase shift with respect to the other. A phase shifting interferometric technique extracts the product of the two correlation signals. Results are shown to demonstrate improved discrimination over a traditional optical correlator.

The biological photochrome bacteriorhodopsin (BR) has attractive photophysical properties which allow its use as the photoactive component for dynamic recording media for optical applications. Purple membrane (PM) patches, which contain BR in a two-dimensional crystalline lattice, are isolated from Halobacterium halobium. Polymeric films with embedded PM are well suited reversible media for holographic recording. In addition, artificial derivatives of BR with improved optical properties can be generated by genetic methods and isolated from the mutated halobacterial strains. The high reversibility (> 10⁶ record/erase cycles), the fast timescale of its photoconversions (fs - ms), and the high resolution (> 5000 lines/mm) make these films suitable media for real-time holographic applications. A dual-axis joint-Fourier-transform correlator is described with two liquid crystal television screens as input devices and a BR-film as active holographic material in the Fourier plane. The experimental data presented demonstrate that this system is capable of processing two independent video signals in real-time with a signal-to-noise ratio of 45 dB. The polarization recording properties of BR-films offer an efficient method to separate the correlation signal from scattered light.

Holographic optical elements (HOEs) in dichromated gelatin (DCG) offer high flexibility in design and packaging, and exhibit high diffraction efficiency even at large deflection angles. HOEs can be used for the efficient coupling of light into the guiding modes of a glass substrate or slab waveguide. Experimental results with multiplex holograms in dichromated gelatin for an optical backplane and a laser Doppler velocimeter system (LDV) are presented.

Permutation elements can reorder and change the spacing of a set of input channels at an output plane. A two-dimensional implementation of these elements is currently of interest as a component in switching networks. The realization of such elements is theoretically and experimentally analyzed. Each grating is individually recorded in a rotated position in respect to the others. In this way arbitrary 2-D interconnections are achieved at the cost of higher design requirements. To produce these elements with high diffraction efficiency at reconstruction with the light of mixed polarization increases the recording complexity. The Fresnel reflection coefficients add further to the difficulty of the theoretical analysis. Experimental and theoretical results are compared. Two demonstration components were implemented.

We report on the performance and application of a commercially available 128 X 128 pixel, electrically addressed ferroelectric liquid crystal spatial light modulator (FLCSLM). In combination with appropriate polarization optics the FLCSLM can be configured as a 2-level phase only modulator. The performance of this `programmable phase transformer' (PPT) is demonstrated by using it in conjunction with a positive lens to produce near diffraction limited, reconfigurable, arrays of spots in the Fourier plane of the lens. Near diffraction limited performance is also shown for the PPT with pixels configured to act as a Fresnel zone plate. Finally, the pixel configuration for spot array generation is combined with that for zone plate to produce spot arrays without the aid of a lens. Improved performance with 2-dimensional over 1-dimensional optimization procedures is also demonstrated.

Optical clock signal distribution has widely been discussed to be an attractive way to reduce the clock skew in high speed digital systems. For short interconnection lengths, especially for chip level clock distribution, free space systems using diffractive optical elements (DOEs) have specific advantages. The optoelectronic pathway described in this paper consists of a GaAs laser diode, a microetched silicon mirror, a facetted diffractive element, and silicon photodiodes. The key element of the clock distribution demonstrator is the diffractive element (the mirror), which matches set-up requirements like compactness, an off-axis geometry, and use of an unshaped laser diode beam. The diffractive mirror is computer generated, it is direct E-beam written and its diffraction pattern is dry etched into the surface of a silicon wafer. It is shown that the whole set-up meets the demands of alignment accuracy in an excellent way. This is achieved by the very good imaging characteristic of the DOE and by an alignment technique based on precision mounting of microetched silicon components.

We report the successful design and fabrication of integrated devices that combine optical beam splitting and lensing into a single element. These elements are made by etching a 4-phase level pattern into quartz glass using electron beam lithography and reactive ion etching. They are designed using an algorithm based on simulated annealing to optimize the Fresnel-Kirchhoff integral that transforms the lens pixel pattern, containing up to 4 million pixels, to fit the desired output pattern. The devices can be optimized for any conjugate ratio; we have made examples of both imaging and focusing elements. At a working wavelength of 1.52 micrometers , measured efficiencies have been obtained of 67% for 4-phase level, F/2 single lenses and around 62% for 4-level F/2 and F/5 multiple imaging lenses that produce 16 output spots from a single input. In all cases for both the single and multiple lenses the output spots were diffraction limited.

The design, production, and evaluation of a polychromator with high spectral resolution are discussed. In the example of using it in environmental monitoring some aspects of the designing process are shown. Some useful tools, such as spot diagrams and lineprofiles, to evaluate the performance of a grating are shown. As a part of this designing process the use of surface contouring is discussed. Some results of the performance are presented.

The successful introduction of the Holographic Notch Filter was the critical first step in the development of a new generation of holographic optical components suitable for laser spectroscopy applications. This paper looks at the characteristics, structure, specification, and performance of an improved version of the Holographic Notch Filter and two new components. The Holographic SuperNotch^TM Filter, Holographic Beamsplitter, and the Holographic Laser Bandpass Filter have been designed to support the development of more advanced instruments for use within the field of Raman spectroscopy and Raman microscopy.

Applying photo-lithography technique, a new type of Fresnel zone plates (FZPs) are developed to detect focusing error (FE) signal of the optical head. By radially spread lines, the FZPs are divided into several areas where the zones of the FZPs are straightened. Comparison among conventional FE detective devices and curved patterned FZPs and straight patterned FZPs are numerically and experimentally demonstrated.

We propose a configuration for multiplexed holographic storage that uses different diffracted beams generated from an acousto-optic deflector (AOD). The AOD is driven by amplitude-modulated electrical signals to generate several diffracted beams with different frequencies. These beams produce moving interference fringes. A short exposure time and a moving medium, whose velocity is reduced through an image-reduction optical system, compensate for the reduction in visibility. Angular-multiplexing is achieved by switching the AOD driving frequencies.

The criterion combining the information capacity and the average time of selection is suggested for potential possibilities of various memory devices to be compared with each other. It has been shown that according to this criterion a HMD has some advantages compared to the other memory devices due to two-step addressing. The optimization of HMD because of the right selection of hologram number correlation in a memory device has been noted to be possible.

Holographic associative memory that is able to retrieve complete objects from their partial or rotated and changed in position inputs is presented. Angularly or spatially multiplexed Fourier-transform holograms of an object and of its synthetic discriminant function respectively, recorded with angularly multiplexed reference beams onto thermoplastic tape or disk are used as the memory elements.

The process of local holograms recording on organic photothermoplastic (PTP) materials and the influence of their characteristics on the quality of registration are investigated. The original simultaneous method of the local holographic recording on the PTP materials by IR-laser heating supplying qualitative Fourier-hologram recording of the analog and digital information is described. The usual simultaneous method of PTP-recording is characterized by exponential growth of diffraction efficiency in time. The possibility of a linear case of diffraction efficiency growth in time on the PTPM allowing the increase of both the time of surface relief development and the value of hologram diffraction efficiency is shown. The approach for the holograms recording on the PTP-disk in automatic regime allowing stabilization of their characteristics is suggested. Also, the process of local multiplexed holograms recording on the PTPM by the developed method is studied. Using the developed simultaneous method two-dimensional Fourier-holograms were recorded in step-by-step procedure on the PTP-disk carrier. The possibility of the holographic PTP-disk based data storage realization is discussed.

Recently, a real-time holographic display system has been developed at MIT. The system can generate, transmit, and display holographic images in real-time. Although the display device itself can treat tens of images in a second, computational time to generate holographic fringe pattern takes a second to a few seconds even on a supercomputer. In this paper, holographic stereogram approaches to reduce its computational time are studied. Basic experimental results are also discussed.

Recent advances in both the computation and display of holographic images have enabled several firsts. Interactive display of images is now possible using the bipolar intensity computation method and a fast look-up table approach to fringe pattern generation. Full-color images have been generated by computing and displaying three color component images (red, green, and blue). Using parallelism to scale up the first generation system, images as large as 80 mm in all three dimensions have been displayed. The combination of multi-channel acousto-optic modulators and fast horizontal scanning continue to provide the basis of an effective real-time holographic display system.

The optical transfer of a large-scale synthetic holographic master stereogram via Benton rainbow technique is discussed. The limits of this technique when the volume the rainbow hologram fills is increased to 8000 cubic meters are evaluated. Blur and accommodation present the primary difficulties. The choice of imagery plays a crucial role in minimizing these effects.

Three-dimensional image display technique is becoming very important in the field of diagnosis of human fetus by ultrasound B-mode image. We apply the technique of holographic stereogram (HS) to the ultrasound B-mode human fetus images and display a 3-D image which is the real stereoscopic image. In this case each sectional diagram of the human body is measured by the ultrasound B-mode method and the human fetus image is extracted and then a 3-D surface image is reconstructed with the digital image processing. Then the 3-D image is projected to a plane and films which are composed of the various viewpoints are taken. Next, HS is constructed using these films. Then we make clear the condition of making HS. The rainbow hologram is made using the HS as the master hologram and we consider the characteristics of the reconstructed image. Also, the special image reconstructing lamp house is developed for medical application, and we discuss the possibility of this method for the medical diagnosis.

A holographic contact multi-exposure technique to produce a full color hologram is described. Production process of the full color Lippmann hologram could be utilized in commercial mass production.

Holograms made using beam paths separated by a beamsplitter require ultrastable environments if good results are to be obtained at exposure times longer than a fraction of a second. By placing components close together and eliminating the beamsplitter, the optical system can be made almost immune to most causes of instability. A family of such configurations, dubbed bypass holograms, is described, including one which fortuitously produces eight images in various orientations in a single exposure. Methods of maximizing emulsion speed and thus reducing exposure times are also discussed.

Natural full color holographic images can be perceived by the viewer by superimposing red, green, and blue images simultaneously. This is simplest with single stage reflection holograms and has been successfully accomplished by a number of workers using a variety of techniques on single emulsion or by `sandwiching' red and green/blue sensitive emulsions together. Alternatively using `rainbow' techniques has resulted in good natural color holograms and controlled swellings of a single emulsion has produced spectacular pseudo-color holograms. It would be advantageous to have a single emulsion, of broadband sensitivity, capable of recording color holograms. Such an emulsion, from Russia, was used initially at the University of Aberdeen to create color holograms with good results. Investigations were then carried out on emulsions commercially available in the UK to see if any were suitable for color holography, using single layers. It is shown that a near natural color image can be obtained from a single stage reflection hologram recorded on Agfa 8E75HD film, with no preparation, due to it being sensitive to green and blue wavelengths, as well as to red for which it is normally associated.

In order to better understand the nature of holography as a visual medium and in particular to perceive the role and function of holography in contemporary culture, it is useful to look at holograms as they are represented in fiction, where they are depicted in an idealized form, more clearly expressing the human needs and desires which are integrally bound up with the medium, but which are not so clearly discerned in a study of the actual medium itself. This paper constitutes a work-in-progress study of holograms as they have been represented in popular fiction.

Figural holography is often accused of irrelevance to today's art theories and to the medium's future-oriented outlook. This charge is rooted in a highly intellectualized aesthetic sensibility that excludes holography because of its obvious success in provoking sensational and emotional responses from the viewer. The author argues that holography should not be bound by such limited aesthetic parameters.

Recent developments in production techniques of pulsed holograms and holographic stereograms have ameliorated to provide high quality three dimensional illusions that echo the apparently innate need of society to replicate itself through artificial means. A commercial platform has been found for these archetypical illusions through the mass production and distribution of embossed stereograms that depict popular celebrities from the music industry. As pulse recordings of the rich and famous become better known, and as former presidents queue to join the holographic hall of fame, the author asks `is it documentation or entertainment that is shaping the future of holography?'

Due to its unlimited performance of the 3-D space -- and, therefore, thematically coincidental and nowadays decadence in itself -- but also for its physical characteristics, inflection and diffraction of light, holography has become extremely interesting for architecture. Holography has so far hardly found its position -- only as kitsch or, at the most, as decoration.

A new stereogram holographic camera is designed by using the polarization and striped-speckle screen. It can be easily used to record a large scenery stereo-hologram. Furthermore, this hologram is illuminated with a white light, the stereogram can be observed without any appendant spectacles. This camera system consists of three parts: stereoscopic camera attachment, LCLV device, and rainbow holography system.

Photorefractive crystals such as iron-doped lithium niobate can be useful recording materials in holographic interferometry. These crystals are self-developing, erasable and reusable, and sensitive to the recording laser light only. As such they are extremely convenient for routine interferometry applications. In this paper, experiments in interferometry using iron-doped lithium niobate crystals for recording the holograms are discussed. The results presented include double-exposure holographic interferometry with cw and pulsed lasers, holographic subtraction interferometry, and real-time interferometry with photorefractive reference holograms. Example applications such as visualization of aerodynamic flow fields, heat transfer patterns, and acoustic fields are presented.

Dynamic holographic interferometry using polarization preserving optical fibers as light guides and incorporating a photorefractive Bi₁₂SiO₂₀ (BSO) crystal as the recording medium is described. An experimental investigation of the recording of time average holograms through the diffusion process (employing anisotropic self-diffraction) and the drift process (application of dc and ac electric fields across the crystal) is also described. The holographic interferometer was optimized to produce holograms with a high diffraction efficiency and a high signal-to-noise ratio. Results are presented on optimizing parameters such as the writing beam angle and writing beam intensity ratio. The advantages that can be gained by deploying this holographic interferometer in an industrial environment, where the laser light is guided to the location of the object by means of monomode fibers and images are stored within a photorefractive crystal is described. The holographic interferometer is capable of producing time average and double exposure interferograms of vibrating and deformed objects which can be displayed in real time.

Quantitative measurements were achieved using different techniques associated with an imaging bundle fiber: (1) the double-reference beam holography method with cw or pulsed laser, (2) TV-holography with cw laser, (3) shearography with cw or pulsed laser, and (4) real-time holographic interferometry with a repetitive frequency-doubled YAG laser working at 25 Hz. Deformations of a loaded aluminum plate or a rubber membrane were calculated using image processings.

An extension of a common electronic speckle pattern interferometry system is presented, which in addition to deformation measurements enables the spatially resolved quantitative determination of image decorrelation. In the absence of other decorrelation effects this quantity is directly related to surface microstructure changes of test specimen. Without principal variations of a typical ESPI setup a speckle correlation formalism is implemented based on the phase-shift method. Feasibility and restrictions are illustrated in measurements of water-induced changes of natural stone surfaces.

The problem of lifetime and durability of reinforced concrete structures has become more important in the last decades, due to different factors the most important being: (1) The exponential growth of building activity after World War II, multiplying the items subjected to deterioration processes. (2) The growing aggressiveness of the environment in areas with a high concentration of industry, but also in urban environment. (3) Developments in design principles and concrete technology, resulting in more slender structural elements. (4) Sometimes a lack of care in execution, promoted by a high building rate and wrongly applied economic considerations. Since the late seventies, all this has led to intensified research about the causes and the nature of degradation processes and to the development of general strategies for handling such situations. General strategies for handling the problem were laid down in European standardization documents, published in 1988.

A multiple exposure immersion method for contour mapping is proposed that improves the accuracy of the measurement by means of interference fringes sharpening. The method is based on recording of the multiple exposure holograms of the object which was put into the immersion chamber with equal changes of a refractive index between the exposures. For the purpose of the full or partial suppression of the side maxima of the interference pattern the change of the object wave amplitude from one exposure to another is proposed. It is shown that this is equal to the change of the exposure time of the object and reference waves. This method is confirmed by experimental data.

The principles of the polychromatic holographic interferometry (PHI) with line spectra have been developed. This method allows us to investigate simultaneously spatial and spectral characteristics of various objects. The general theory of the formation of interference fringes in the PHI, which takes into account the dependence of the object refractive index on wavelength and the experimental conditions, has been constructed and the quantitative criteria for the necessity of this general theory application have been determined. Optical schemes and light source equipment for the PHI have been developed and the possibility of the PHI with the use of a `comb-like' laser generation and gas-discharge light sources is shown. The PHI have been applied for plasma diagnostics and new diagnostic possibilities appearing due to the PHI application have been demonstrated.

The use of holographic interferometry to determine large deformations of opaque bodies by compensating modifications when reconstructing has been treated previously in several publications. The present contribution concerns a similar investigation in the case of a domain with a strong spatial change of the index of refraction as for instance in a gas with a high temperature gradient. Firstly, the general theory about the analogy between both fields as well as the image aberration and the fringe modification is outlined. Secondly, a development of the fringe vector in the case of a moderate index gradient is performed, leading to an approach for measuring the integral of the lateral gradient of the index along the curved ray.

The application of holographic interferometry to phase object analysis is described. Emphasis has been given to a method of extracting quantitative information automatically from the interferometric fringe data. To achieve this a carrier frequency has been added to the holographic data. This has made it possible, firstly to form a phase map using a fast Fourier transform (FFT) algorithm. Then to `solve,' or unwrap, this image to give a contiguous density map using a minimum weight spanning tree (MST) noise immune algorithm, known as fringe analysis (FRAN). Applications of this work to a burner flame and a compressible flow are presented. In both cases the spatial frequency of the fringes exceed the resolvable limit of conventional digital framestores. Therefore, a flatbed scanner with a resolution of 3200 X 2400 pixels has been used to produce very high resolution digital images from photographs. This approach has allowed the processing of data despite the presence of caustics, generated by strong thermal gradients at the edge of the combustion field. A similar example is presented from the analysis of a compressible transonic flow in the shock wave and trailing edge regions.

The technique of heterodyne holographic interferometry for the accurate measurement of small displacements is well established. In this paper a new detection method is employed which allows the direct measurement of strain components. This potentially offers an optical, non-contact replacement for the strain gauge, with a resolution of better than one microstrain. In double exposure heterodyne holographic interferometry, a separate reference beam is used for each exposure, and during reconstruction a phase shift (10 kHz in this case) is applied to one of the reference beams. The phase of the beats between the two images is proportional to the displacement between the images. In the technique described in this paper, light from a small region on the two superimposed images is focused onto closely spaced photodetectors. The phase difference between the two signals is directly proportional to a component of the strain at that point. The instrument is insensitive to small translational movements of the surface in any direction. The method has been applied to both double exposure and real-time holographic interferometry, and it has been tested against a strain gauge. The results obtained so far show that the technique is a reliable method for measuring strain, with several advantages over alternative methods.

The work done in order to perform a vibrational analysis of an aircraft winglet is presented. The analysis was intended to acquire general purpose structural information, and to define the best location for accelerometers to be used in subsequent vibration fatigue tests. The winglet was mounted on a platform driven by an electromagnetic shaker and thus excited in order to simulate on-flight stressing; induced deformations were detected by pulsed holographic interferometry. Different stress conditions were tested while the shaker was vibrating at frequencies in the 30 - 1500 Hz range and with accelerations in the 0.5 - 2.0 g range.

Holographic interferometry in conjunction with fiber optics is specially useful for the measurements of a small area deformation, a micromovement, or an intracavity deformation. A single-mode imaging fiber bundle can give higher resolution, better coherency, and less sensitivity if it is used as an image guide system in holographic interferometry. Time-average hologram and stroboscopic double-exposure hologram of a vibrating surface with acceptable signal to noise ratio is presented.

Residual deformations induced in nitrogen implanted steel specimens by a plasma focus device are investigated by means of holographic interferometry. A numerical model is presented to interpret the experimental results.

The recording of holographic short focal length lens is reported. The results of the measuring of the diffraction efficiency dependence on the exposure and the object beam/reference beam intensity ratio are represented. Theoretical analysis of the recorded gratings is made.

Nongelatin dichromated film (designated as NGD) is a kind of new holographic recording material. To get the eternal hologram with efficient diffraction, low noise, and damp resistance is to seek the optimum technology and conditions at their best of the NGD after exposure. This essay, through a great number of experiments and research, has found a proper optimum technology and conditions after exposure: the pre-processing of the cross-linking accelerant solution, infrared light hardening, swelling colorfast of the basic solution, development of acid solution, water washing, isopropanol dehydrate, and drying with a hot blast. The processing time and PH value of the liquid must be strictly controlled. The NGD hologram through the processing of the optimum technology, has possessed the result of relief and volume hologram. The diffraction (eta) is > 30%, it will not degenerate at the relative humidity of 90%, and can be kept forever at indoor temperatures.

Nongelatin dichromated holographic film (NGD) is a new holographic recording material. The holograms recorded on this material have better environmental stability, higher diffraction efficiency, stronger real time effect, etc. In this paper, an experimental study to ascertain the influence of two electron donors, namely N,N--dimethylformamide (DMF) and dimethylsulfoxide (DMSO), on the real time diffraction efficiency (RTDE) of NGD holograms is carried out. The presence of electron donors not only improves the sensitivity but also enhances the real time effect greatly. The RTDE of above 60% at +/- 1 orders of NGD plane transmission gratings is achieved by introducing electron donors.

To extend the sensitivity of photorefractive BSO crystals into the red and near-infrared part of the spectrum, they are doped with transition metals (Fe, Ni, Cr, Mn). These crystals are investigated in terms of their absorption spectra, optical activity spectra, gain coefficient in two-wave mixing, energy of holographic recording with a wavelength of He-Ne laser in diffusion, and drift recording regime.

The paper proposes a method of measuring relief depth and refractive index variation which distribute in a holographic phase grating. By this method an interference microscope and a microcomputer with a CCD camera are used in measuring and can obtain highly precise data. In the paper, an example of measuring DCG grating is presented, the errors of these data are analyzed and optimum conditions which make a measurement system keep its highest accuracy are given.

The paper is dedicated to the analysis of holographic content-addressable memory (HCAM) on the basis of photothermoplastic (PTP) SLM as a storing unit. The joint transform correlator (JTC) scheme with electronic nonlinear feedback is considered, paying attention to the PTP SLM features, problem of negative value optical realization, and computational paradigm choice. Theoretical models, the results of experiments, and computer simulation are presented.

The results of theoretical analysis of viscoelastic SLM with electrically controlled deformable surface characteristics are presented. The new effective technique was elaborated for electric field and surface relief calculation in SLM. The characteristics, which are useful for SLM's application in holographic systems, have been obtained with this technique.

The trend of the increase of the output energy is obviously as good for UV lasers as for IR lasers. This requires radiation resistant elements, for instance lenses, mirrors, or gratings. Monochromatic radiation can be focused by diffractive optical elements to a diffraction limited focal spot with nearly 100% efficiency. Therefore, diffractive optical elements are well suited for application to industrial laser cutting and welding technology. However, usual holographic gratings are destroyed by an irradiation of a few watts per cm². To overcome this difficulty electroforming and etching techniques have been developed. We report on the production, calculation, and measurements of efficiency of gratings in copper with grating constants between 0, 5, and 200 micrometers .

A scheme capable of demonstrating shift- and rotational-invariant associative memory is presented. The scheme can be implemented both digitally and optically. In optical implementation, we use one holographic spatial frequency filter and one ordinary hologram of the reference pattern. A BaTiO₃ crystal is also employed in the experiment. In the digital implementation of the scheme, in addition to the rotational invariance it is shift invariant too. However, the optical implementation exhibits shift invariance only when the BaTiO₃ crystal is sufficiently large.

A shock wave produced by laser pulse interaction with a metallic target immersed in water was studied by methods of holographic interferometry and shadowgraphy. The wave parameters -- velocity, pressure in front, compressed layer thickness -- were determined, the pressure profile was constructed. The dependence of shock wave parameters on incident laser radiation energy was used to develop a method for determination of energy threshold of material damage. As a result of the action of pulsed laser radiation on a metal target a shock wave is generated in surrounding media due to the different processes which take place in a thin surface layer of the target. These processes -- thermal expansion, explosive evaporation, optical breakdown -- become valid step-by-step with the laser radiation energy increase. This paper presents the results of experimental study of such waves produced in water via laser pulse action on the metallic target immersed into it.

A substrate-mode holographic structure for wavelength-division-demultiplexing application is introduced. This type of substrate-mode hologram diffracts normally incident beams into a dielectric substrate with total internal reflection condition. The diffracted beams then propagate through the substrate and are separated for different wavelengths. Normally incident coupling and output on-axis imaging with this structure provide easier alignment with optical fibers.

In this paper we present a theoretical model describing the real images replayed from finite aperture Fraunhofer holograms of two identical co-planar objects. We have solved numerically the resulting image equations for the case of two circular disc objects, and compare our predictions with experimental measurements from in-line Fraunhofer holograms recorded on silver-halide emulsions. Three measurement criteria for calculating the disc diameters and separation are described, and their errors discussed. It is found experimentally that a criterion based on average intensity results in the smallest errors due to its insensitivity to the effects of coherent noise.

We propose a new metrologic application of zone plates, using interferometric techniques, in order to detect changes in the refraction index of a dielectric parallel plate under the influence of the environmental parameters. The key of this kind of interferometer is a couple of circular zone plates produced with the proper combination of initial phase shift, in order to suppress the constant phase factors introduced with the system in the equilibrium state. In this way we are in quadratic condition and then we can measure the variation parameters with great accuracy and with the advantage of knowing the sign of it produced under external actions. The influence of the several fabrications parameters are discussed.

The principles of a new holographic method for the recording of the state of polarization of an optical wave have been proposed. The method is based on the simultaneous recording of two spatially separated holograms corresponding to the orthogonal components of the electric field vectors of object and reference beams. The polarization real-time and two-exposure holographic interferometry have been used for determination of phase relations between these two orthogonal components of the electric field vector, and the possibility of reconstruction of polarization ellipse parameters have been shown. The measurements of the polarization plane rotation by sugar solutions and quartz crystals have been carried out. The tensed state of smelted quartz plate under load was investigated by this holographic method and spatial distributions of the polarization ellipse parameters have been obtained for this sample. Some new experimental possibilities of this holographic technique have been discussed.

In holographic interferometry an object must be irritated in order to make material defects or displacements of the object visible. In solids an elastic wave is a reliable source of this irritation for holographic interferometry purposes. The nature of the elastic wave is quite essential when studying crack-like defects in metal plates. A high quality CO₂-pistol can establish an impact velocity of over 100 m/s and adequate stability in a long series of impacts can be generated by the pistol's bullet. In this paper a new instrumentation for external impact on the object in holographic interferometry is described. Interferograms are recorded by a double-pulsed ruby laser synchronized with the external impact. Some interferograms of a 10 mm thick iron plate are studied. In these interferograms the crack-like defects are clearly observable.

Holographic interferometry and thermography are compared, and conclusions of their applicability in industrial environments are drawn.

Spatial-carrier fringe pattern analysis is a wide-spread technique and has found a lot of applications to optical metrology. Introducing a spatial-carrier into a holographic moire pattern is also a well-known technique to obtain observable moire fringes. Preprocessing of the holographic moire pattern includes optical or digital Fourier filtering to remove the carrier. The fringe pattern is then processed by using time-consuming fringe-counting algorithms. The current work presents a new application of the Fourier transform method to automated analysis of holographic moire fringe patterns. The method owns the advantage of instantaneous determination of both phase functions in the pattern. Investigations are carried out on the frequency restrictions imposed on the phase functions. The technique is demonstrated on computer generated noisy holographic moire patterns. The technique does not complicate the conventional experimental holographic moire arrangement.

The polyvinyl alcohol and several other organic materials are mixed into the aqueous gelatin while the film is coated. This thin solid film is sensitized by aqueous ammonium dichromate, so it is called a dichromated gelatin polyvinyl alcohol (DC-GPVA) holographic recording material. DC-GPVA not only possesses the same excellent holographic properties as the conventional dichromated gelatin (DCG) but also obviously improves its environmental stability. Experimental results have shown that the reconstruction wavelength of a Lippman hologram recorded in DC-GPVA can be shifted to longer or shorter wavelengths and freely controlled to a certain extent by varying the ratio of the gelatin and the polyvinyl alcohol and relative organic materials, or hardeners and its quantity, or heated temperature and heated time exerted on the drying films, or thickness of them. After the films are sensitized, they can be exposed by He-Cd or Ar⁺ laser (441.6 nm or 488.0 nm) and developed by the regular post processed method. Initial discussions are also presented about the functions and mechanisms of the polyvinyl alcohol and relative organic materials added into DC-GPVA.

A new method in the field of holographic interferometry used for plasma diagnostics is presented which allows us to reduce the irradiation onto the interferogram caused by the plasma. The advantages of this new technique are demonstrated in two examples: determination of the electron densities in a high-radiation Xe-lamp applying non-resonant two-wavelength interferometry, and investigation of the degree of population inversion in a He-Ne laser discharge by heterodyne resonant holographic interferometry.

This paper reviews the historical reasons why so few neodymium:yttrium aluminum garnet (Nd:YAG) lasers are dedicated to display holography in comparison to ruby lasers, why positive light holographics (PLH) decided to use an Nd:YAG/Nd:Glass laser and what kind of configuration is used. A practical overview on how to use an Nd:YAG/Nd:Glass laser for deep-image holography is discussed, and an evaluation of the transmission holograms recorded with an Nd:YAG/Nd:Glass laser is made in particular from an image planing point of view.

Holographic interferometry is a widely used tool for nondestructive testing of mechanical deformations. In connection with microscopy, it is also possible to investigate very small objects. However, due to the imaging system used to magnify the object, the visibility of the interference pattern is disturbed. This disturbance still remains even if the conjugated reconstruction is applied. To decrease the influence of the imaging system, the aperture must be of small size. To suppress the speckle effect, the hologram should be made as an image plane hologram.

In the present experimental study it is shown that high quality volume holograms may be recorded and photographically processed in the presence of incoherent light. Experimental data was obtained permitting us to choose optimal recording and processing parameters at given incoherent light intensity.