Recent advances in optical pickup heads using holographic optical elements (HOEs) are reviewed, with emphasis on a practical servo-signal detection system that can realize compact integration of HOE, laser diode, photodetectors, and objective lens. This paper presents a new type of holographic servo method that employs a blazed HOE placed in close proximity to the objective lens so that wide allowance range of the optical system is maintained, thus allowing the lens and HOE to move simultaneously. The blazed HOE and the integrated optical system are analyzed and discussed in detail.

An investigation aimed at reducing chromatic variations in the performance of optical waveguide devices is described. Methods to achromatize the characteristics of integrated optics lenses, input/output couplers, and beam-splitters are presented with the goal of eliminating, or minimizing, any performance variations over a wavelength interval at least on the order of the operating range of presently available laser diode sources. It is shown that an achromatic waveguide lens can be made using a mode-index/diffractive doublet. With this approach, it is possible to cancel the longitudinal chromatic aberrations of the refractive lens with an appropriate diffractive component. Achromatic input/output couplers are described which use an external diffraction grating to correct for the angular dispersion of either prism or grating couplers. It is shown that double grating couplers can be used to obtain an achromatic wavelength range on the order of ten nanometers, and that hybrid prism/grating couplers can yield an achromatic range of several hundred nanometers. It is also shown that the angular chromatic dispersion of waveguide grating beam-splitters can be corrected using a second grating that is appropriately specified. This permits a guided optical beam to be split into two or more separate beams whose directions are independent of wavelength. These achromatic waveguide components can be combined in various configurations to reduce the wavelength sensitivity of devices such as optical disk pickup heads.

The authors consider only hybrid singlet lenses composed of a plano-convex or a plano- concave glass lens and of a volume phase holographic optical element (HOE) in dichromated gelatin, coated on the plane surface of the glass lens. A design method is described which combines usual ray-tracing through a refractive lens and, for the HOE, the method of Hasman and Friesem. This latter method is based on a ray-tracing procedure that uses the minimization of the mean-square difference of the propagation vector components between the actual output wave fronts and the desired output wave fronts. Considering the one-dimensional case and a given spectral bandwidth, the authors determine by simulation the image spot sizes, the distortions at the image plane, and the mean-square difference of the propagation vectors. At the end, the results are compared with the performance of the optimal HOE alone, the spherical HOE, the refractive lens alone, and a diffractive system made of two HOEs. In conclusion, the authors discuss the space bandwidth product of the optimal HOE used in the hybrid systems.

Modern optical instrumentation increasingly requires miniaturization of the devices used, as is the case, e.g., in the field of endoscopy. The combination of such technology with holography offers advantages such as 3-D documentation and display with the possibility of large magnification a posteriori as well as metrology in form of holographic interferometry of objects with difficult optical access. Miniaturized holographic instrumentation requires small illumination and imaging systems, as well as minute recoding devices. As could be demonstrated, these requirements can be met by introduction of micro-optical elements. The use of (single-mode) optical fibers offers easy handling and flexibility. In particular, new single-mode imaging fiber bundles show improved performance data (high lateral resolution, low speckle noise, and low mode interaction) at submillimeter diameters. Assembled gradient- index rod lenses commonly are used for submillimeter imaging systems. In holographic endoscopy, speckle noise caused by these small limiting apertures can be reduced by using such a gradient-index imaging system simultaneously for both imaging and illumination. The use of electro-optical crystals opens the possibility of developing a minute holographic storage device for in-site recording, reconstruction, and erasure with fast repetition rate.

Recent trends in laser application systems such as optical information systems, optical network systems, and optical measurement systems have presented a need for small size, light weight, low cost, and mass productivity. Advantages of a micro grating device in laser beam application systems are high integration capability, design flexibility, and mass productivity. In this paper, recent investigations of the micro gating devices using electron-beam lithography are described, with emphasis on clarifying both their uses and fundamental optical characteristics.

Using local holograms, recording methods on the photothermoplastic (PTP)-carrier with IR- laser heating holographic disk systems with registration of two-dimensional holograms in step- by-step regime and one-dimensional holograms on the moving carrier are developed. Requirements for linear velocity of the PTP-disk are formulated, and an electronic scheme for its stabilization on the whole disk surface is realized. The need for and advantages of one- dimensional microholograms recording with track size d > 200 mkm on the moving PTP- disk are shown. For the first time, qualitative microhologram recording on all surface of moving photothermoplastic disk is obtained. This result supplies PTP-disk capacity of approximately 0,6 Gbit for one-dimensional microhologram recording with disk diameter 133 mm. The use of holographic a PTP-disk as a bank of interconnected weight matrixes in optical implementation of neural networks is suggested.

Results are presented of an on-going experimental program to characterize the effects of processing errors on kinoform performance. Diffraction efficiency and modulation transfer function data are given for various types of processing errors present in staircase kinoforms of a f/10 Fresnel phase lens having two and four levels. Processing errors include etch depth, linewidth, and mask alignment. Processing errors, especially mask alignment, are shown to have the greatest impact on diffraction efficiency and very little effect on image quality.

Techniques for calculation of two types of kinoform optical elements with increased causticdepth are presented: first, the elements that produce an image of the axial point as a straight line without projective transformation (axicons); second, the elements that extend caustic without changes in projecting properties of the optical system (generalized zone plates - GZP). The transmission function of kinoform axicons is determined from the second-order differential equation derived from the integral Kirchhoff-Fresnel approximation with the stationary phase technique for the given intensity distribution along the focal line. It is shown that with the given procedures one can calculate axicons that provide arbitrary desired intensity distribution along the focal line for the given amplitude distribution of the field of the illuminating lightwave. Low concentration of radiation is an important feature of axicon focusing that limits its application. Therefore, modification of lens caustic by introducing controlled aberrations is of particular interest. It is suggested to determine GZP zone topology with the tautochronizm principle and the requirement of concentration of power of the radiant energy flow from a ring zone of small width to a focal line of small length. The produced samples of kinoform axicons and GZPs have ben experimentally studied.

An essential aspect of diffractive optics is the inverse problem of how to proceed from the desired wave field in space to the design of the diffractive element which can be used to form this field. The subject is treated under the consideration of various approximations. This approach defines digital holography as a subset of diffractive optics. Coding theory is a central topic in digital holography. Coding methods and predictions of diffraction efficiency are discussed.

A method is described that uses a frequency analysis to calculate the wavefront of a diffracted light; a hologram is then produced starting from the generated light. If the Fresnel equation for diffraction is applied, one has to consider a 2-D object, or a 3-D set of cross-sections, to be parallel to the hologram plane. By considering the angular spectrum and its properties concerning translation and rotation, it is possible to calculate the light on a plane rotated with respect to the hologram. To this end, a theory on the angular spectrum has been used, and the rotation transformation has been pointed out. This approach can be applied to generate a synthetic hologram of a 3-D object, considering a 3-D object as a collection of planes translated and rotated in the space. The frequency analysis permits evaluation of the wavefront diffracted by the planes, thus obtaining the field on the hologram plane. The analysis is performed via FFT algorithms. Simple but significant holograms have been generated and a computer reconstruction has been carried out, confirming the validity of this frequency approach.

Hologram generation by means of computers has been developed during the last three decades. The most frequently used methodology is the Fourier method. However, these techniques are not completely adequate to obtain holograms for 3-D display. A method of calculating holograms of parametric curves and surfaces is presented. These holograms are well suited to 3-D display although, in practice, their size is small. Holograms are obtained regardless of the position and the size of the object. Furthermore, the effects of the intermodulation noise are theoretically eliminated by cancelling the corresponding terms in the expression of the hologram. Thus, this technique is easily extended to combinations of curves or surfaces. Calculations can be carried out using suitable numerical approximations. Although the method is quite general, results are presented for linear segments. One example of a linear segment hologram has been represented on a computer screen. After photo-reduction, the segment has been successfully reconstructed.

An analysis of the error diffusion method is presented which is based on the terminology of filter theory. The calculation of diffractive elements with the error diffusion method is shown. The stagnation of the iterative Fourier transform algorithm with a bandwidth constraint is overcome by error diffusion.

Computer-generated holograms of a diffused object can be generated as the sum of intensity holograms obtained by interference of each point of the object with the reference beam. Thus the intermodulation noise is avoided. According to this, the authors have obtained computer- generated holograms of a square diffused object, and they were represented in a computer screen. By means of a photo-reduction process, they were stored in an emulsion 8E56 HD. The diffraction effiency (DE) and the signal-to-noise ratio (SNR) was evaluated in the reconstructed real image. A DE of 1% and a SNR of 100 have been obtained.

The fabrication of a range of computer-generated holographic optical elements by means of electron beam lithography is described. These elements can be considered as the combination of two overlapped cylindrical diffractive optical elements of the same focal length. The imaging properties of both orthogonal and non-orthogonal combinations are discussed. These elements produce sets of line foci at different distances and orientations determined by the angle between the two cylindrical elements. The detailed features of the line foci, 'macro- and micro-beading' can be related to the structure of the combined gratings. Equations identifying the locations of the foci are presented, and these suggest a distance measuring technique which might be applicable to machine vision.

Networks for parallel data processing consist of processing stages and permutation stages. The permutation stages provide the interconnection between the processing stages, thereby changing the order of the different data channels. The authors propose a free-space implementation of optical permutation stages with holographic optical elements. The holographic elements used are space-variant prism (or plane grating) arrays. Each light beam (or data channel) is incident on its own grating and gets deflected by a corresponding individual angle. Such space-variant holographic prism arrays can easily be produced with an adequate step-and-repeat recording setup. This technique is flexible in that it allows the realization of arbitrary permutation patterns. And it is light efficient if one uses a high-quality holographic recording material like dichromated gelatin. The authors fabricated holographic permutation elements in dichromated gelatin and show examples for the Butterfly and for the Perfect Shuffle permutation patterns. The data of the elements are related to the signal-to-noise requirements in actual digital systems. These requirements are directly fulfilled for off-axis geometries. But also on-axis permutation elements can be of practical use if one takes additional care to get rid of the zeroth diffraction order noise.

Several strategies in optical pattern recognition are applied to recognize objects which differ only on their color distribution. The two problems studied are the discrimination of a given object among other objects and the recognition of a character contained in an object. High pass matched filters and phase only filters are used to carry out the strategies.

The optimized matched spatial filter recording on the thermoplastic medium in terms of bias exposure and beam balance ratio for a high-frequency band is considered. Real-time recording of synthetic discriminant function based filters on the thermoplastic medium by using CRT that modulates a liquid crystal light valve is presented. An adaptive correlator system with holographic filter memory on the thermoplastic tape recorder is proposed.

Inaccurate positioning and low-quality optics introduce position-dependent phase errors into coherent optical processors. For the inspection of composite objects, these lead to interference effects at the correlation plane and in particular the occurrence of blind spots through destructive interference. This in turn may result in a misinterpretation of the output. The circumstances under which this might occur are experimentally investigated.

A hetero-association neural network using an interpattern association algorithm is presented. By using simple logical rules, hetero-association memory can be constructed based on the association between the input-output reference patterns. For optical implementation, a compact size liquid crystal television neural network is used. Translations between the English letters and the Chinese characters as well as Arabic and Chinese numerics are demonstrated. The authors have shown that the hetero-association model can perform more effectively in comparison to the Hopfield model in retrieving large numbers of similar patterns.

Electromagnetic diffraction theory is applied to the analysis and synthesis of grating devices that generate equal-intensity spot arrays. Types of devices considered include diffractive lenslet arrays and array generators based on the fractional Talbot effect, but the emphasis is on binary and multilevel Fourier-domain grating interconnects. Reconstruction fidelity of all these components is analyzed as a function of the period-to-wavelength ratio, and the domain of validity of the scalar theoretic design algorithms is determined. First results are given on the application of the electromagnetic theory to the synthesis problem of binary resonance domain array generators, and preliminary experimental results are provided using millimeter-range radio waves.

Spatial holographic multiplexing with a photothermoplastic device is an attractive solution for interconnection of high bit rate channels in a telecommunication network. Because the wavelength of the recording beams is largely different from the wavelength of the IR reading beams, a symetrical two-stages optical configuration is required to keep optical aberrations as low as possible. Such a configuration is described here, which enables interconnection of input single-mode fibers to output single-mode fibers. Concerning the material properties, another problem has been solved: by using a self-stabilized thermoplastic molecule, large cyclability (80,000 cycles) is demonstrated with a high diffraction efficiency of the holographic recorded gratings.

The recording of the efficient fan-out elements as volume holograms has been studied using coupled wave theory. The authors have found that the efficiency and uniformity of regular fan- out elements depend strongly on the relative phases of the object waves, if the thickness t of the holographic emulsion is smaller than t<(lambda) /(n tan(theta) 0 (Delta) (alpha) ). High efficiency and uniformity can be achieved by optimized phases of the object beams, thereby requiring a low dynamic range of the holographic recording material.

The coupled multiwave diffraction approach together with an optimization method is applied to design gratings, which diffract one incoming beam into N output beams with a given power distribution. Several gratings have been designed. It is shown that by choosing the material parameters properly, relatively simple continuous grating profiles having better diffraction characteristics than Dammann gratings or kinoforms can be found.

A model is presented in which a recorded and processed volume holographic grating and an 'effective diffraction grating.' The effective grating is determined by the grating vector after processing and has an effective thickness. This effective thickness can then be used to express the relation that exists between the components of the grating vector before and after processing. This thickness determines the direction of the reconstruction beam when Bragg's Law is complied with. Experimental results with holographic gratings are presented.

For some years, theoretical models have been worked out to describe the interaction between electromagnetic waves and a thick dielectric grating. Those models were developed for sinusoidal phase gratings illuminated with a plane wavefront. A method is proposed here to calculate the diffraction efficiencies of spherical and cylindrical holographic lenses and of spherical to cylindrical wavefront converters. Those calculations are based on the coupled wave theory of Kogelnik and on the work of Nishihara.

One of the techniques for fiber-to-fiber connection is based on a basic interferometric method to obtain a holographic grating acting as a holocoupler. Holographic couplers can be used as memory systems storing information to achieve single or multiple fiber connections using a multiplexed hologram. This device works with high efficiency in short intervals of space and time. Applications can be extended, as well, to codify the stored information in a reflection configuration as a switcher system with a laser diode. The flexibility of this technique allows coupling of alternative focusing elements such as two GRIN lenses and other configurations. In order to develop this application in optoelectronic devices, the recording process must by carefully analyzed. The recording of the holograms has been already resolved for planar and spherical waves. Nevertheless, recordings with Gaussian waves require some conditions to be accounted for due to the width waist and divergence of the output beam of the laser source.

The unsymmetrical diffraction spectrum of a reflective hologram grating was observed. Sub- peaks appeared at only one side of the main peak. In this paper, the experimental results and the rule are reported. Also, the principle which results in the unsymmetrical spectrum is analyzed, and the physics picture is described.

A thin oil film on a glass substrate has been subjected to thermal stimulation by means of incident infrared (10.6 micrometers ) laser beams, which were mostly absorbed in the substrate, in order to develop an appropriate real-time recording medium for holography and interferometry. A study of the behavior of this film has led to the development of a theoretical model involving surface tension, viscosity, and other effects such as the Marangoni effect. This model was further verified experimentally and the recording medium used for a variety of experiments in infrared holography and interferometry that are summarized in this presentation. The theoretical model will be discussed in order to stress its possible application to other experimental situations involving thin films.

Many experimental investigations are performed to produce new optical recording materials for holography. They intend to improve applications such as the construction of holographic optical elements (HOEs), filters, aberration correctors, and nondestructive testing as well as optical data storage. All of these applications require materials with high optical performances. Because of their excellent ability to record high spatial frequency gratings, photopolymers are seen as promising holographic recording media. Indeed, one of the greatest photopolymers advantages is their high theoretical molecular resolving power. The addition of dichromate salts to a variety of water-soluble polymers such as gelatin, albumin and poly (-vinyl alcohol) (PVA) generally results in photosensitive materials which become insoluble in water after exposure to the action of light. This paper presents investigations on dichromated poly (-vinyl alcohol) emulsions (DC-PVA).

Dichromated gelatin layers facilitate the design and fabrication of holographic optical elements of high optical quality and diffraction efficiency. The research efforts are aimed at the development and evaluation of layer deposition techniques for the manufacturing of large- format holograms in dichromated gelatin. The emphasis is placed on the realization of DCG films that exhibit low scattering losses, high thickness constancy over the entire aperture, and especially high modulation capacity. Such properties ensure the attainment of the desired diffraction efficiency, bandwidth, and Bragg-shift. These objectives are achieved by means of precise control of the thickness of the holographic layer while maintaining the capability to modify the refractive index modulation over a wide range. The diffraction efficiency is a nonlinear function of the grating strength, i.e., of the layer thickness, of the wavelength and of the refractive index modulation. The phase of the transmitted light depends upon the spatial distribution of these parameters. The desired thickness of 10 micrometers is achieved by means of nozzle deposition and shows a thickness variation of +/- 1 micrometers over the 1 m2 aperture. The high capacity for index of refraction variation is realized by means of precise control of the flow velocity and of the water evaporation rate during the drying of the film. The exposure duration, the development process, and the subsequent thermal after-treatment of the film facilitate the attainment of the desired modulation characteristics. At present, we have achieved 90% diffraction efficiency at 900 nm for transmissive holographic gratings recorded at 514 nm. This technique permitted the attainment of 96% diffraction efficiency at 650 nm (maximum of the solar spectrum) and a band-width of 400 nm. Holographic solar concentrators are fabricated at present in sizes up to 0.5 by 0.5 m. Current developments will facilitate the fabrication of 1 m2 holographic solar concentrators. The results of the theoretical analysis are compared with the experimental data.

Experimental results are described concerning the influence of processing parameters on the spectral selectivity of reflection holograms recorded in dichromated gelatin. The aim of this investigation was to produce holographic gratings with well-defined filter properties and to shift the central wavelength toward the red spectral region and to broaden their bandwidth.

A novel copying technique specially developed for the batch reproduction and manufacturing of large format holographic optical elements (HOEs) which are used in the manufacturing of solar concentrators is presented. The HOEs are designed by means of computer programs that facilitate the optimization of the recording geometry for on-axis or off-axis operation. The HOEs are recorded in dichromated gelatin layers (DCG) and are subsequently subjected to chemical and thermal after-treatment processes in order to promote the desired characteristics and suppress the undesired properties. These 'master' holograms are used for the manufacturing of the copies. In this report, the technique developed for the reproduction of transmissive holograms, i.e. holographic lenses is discussed. the copying procedure requires that the master hologram generates an object wave that carries the information and a reference wave needed for the recording of this information. Since the master is placed in front of the copy during the reproduction process, the master must have 50% diffraction efficiency across the entire aperture. This requirement restrains the permissible variation of the exposure energy during the reproduction process to very narrow bounds. Usually, dichromated gelatin films exhibit a steep dependence of the diffraction efficiency with the exposure energy. Hence, a small variation of the intensity at a given point of the hologram may produce a very large change in the diffraction efficiency. The authors have developed a new method based on film properties control that facilitates the manufacturing of master holograms with 50% diffraction efficiency. The industrial fabrication of large-format

A holographic system formed by two holographic lenses that, when working with white light, allow selection of a particular wavelength is presented. If adequate spatial and temporal coherence conditions are obtained, it is possible to copy holographic optical elements (HOEs) with partially coherent light by using optical systems formed by holographic optical elements.

This paper suggests a new method of active stabilization of interferometers that permits stabilization not only of a majority of interferometer types, but also of holographic interferometers directly during hologram recording without affecting the diffraction efficiency and the quality of holograms.

Holographic mirrors within laminated windshields are used to increase the reflectivity of a windshield or parts of it for a defined spectral wavelength band and for specific angular directions, while its transmissivity in the remaining spectral region is nearly unchanged. A narrow-band, highly reflective holographic mirror serves as a combiner for a car head-up display. Large-sized, broadband holographic mirrors are used to realize a solar protective glazing with direction-dependent transmissivity in the visible spectral range. The holograms are mass-producible and withstand the lamination process for safety glass windshields.

This paper presents a set of design rules for pseudocolor transmission holographic stereo grams illuminated by a point white light source. The three design equations allow calculation of the correct holographic mastering geometry to correct for the chromatic dispersion in the white light-illuminated hologram (H2) and to create the desired color balance in a chosen viewing plane for a multicolor image. The critical design parameters are the tipping of the master hologram (H1) at an angle that is in the plane defined by the final point source and the image plane normal, alteration in the width of the slit images depending on the vertical displacement on H1, and the vertical displacement of the color separations. The practical result of using these design rules is that accurate color composition and true perspective can be achieved along one horizontal viewing line, and precise alignment of the images from color separations of a multicolor image is maintained over an extended vertical viewing range.

Using the rainbow effect produced by employing a white light source in the reconstruction step of an image hologram, it is possible to obtain colored two-dimensional images. In this work a holographic technique to obtain pseudocolored schlieren images is proposed. The method is based on recording three image holograms consecutively on the same photographic plate using a He-Ne laser and three different reference beams, each one with a different angle with respect to the axis of the optical system. Each image hologram is recorded with a different position of the knife-edge into a conventional schlieren system. The multiplexed image hologram thus obtained gives different color information which is associated with the phase variations of the object under test, when it is illuminated by a conventional white light source, in the reconstruction step. Comparing this work with the conventional color schlieren system, color filters are not necessary and the images obtained can have good contrast and bright colors. Experimental results are shown.

Techniques specifically developed for the design and manufacturing of specialized holographic optical elements (HOEs) that are used in the fabrication of integrated optical systems for laser- Doppler velocimetry (LDV) applications are presented. The specialized HOEs needed for the construction of an integrated LDV-optics are: beam-splitters, lenses and/or lens arrays, phase correction plates and the corresponding waveguide structures. The HOEs are designed by means of computer programs that facilitate the optimization of the recording geometry and provide information for the correction procedures needed for optimized performance. The HOEs are recorded in dichromated gelatin films and are subsequently subjected to chemical and thermal after-treatment. These procedures guarantee the realization of HOEs with high diffraction efficiency and low scattering losses. The optimized holographic process has been previously described. In this report we discuss the following specialized HOEs and their specific characteristics as required by the LDV applications.

Through the combination with digital diagram image processing evaluation, completely new application techniques are created for already known optical procedures. In deformation and vibration analysis with holographic and speckle interferometry, fringe patterns, diagrams which represent very exact deformations or vibration amplitudes are evaluated. However, the projection or Moire systems, the micro- and macrostructures of the surfaces, as for example the 3-dimensional shape, can also be recorded. By means of a suitable evaluation, a partial frequency analysis of deformation shapes generated during operation is possible. The applications are described using concrete examples from the automotive industry which are partly obtained under difficult circumstances, such as with rotating components.

It is shown that a three-dimensional analysis of the deformation of a planar surface can be performed utilizing holographic interferometry and by simple and relatively inexpensive means. In order to obtain the in-plane deformations in addition to the out-of-plane deformation, a single interferogram resulting from the double exposure of two states with different mechanical loads has been viewed from at least three noncoplanar directions. The image distortion due to the perspective projection has been taken into account and a simple algorithm found to decompose the three deformations along the orthogonal coordinate axes. For the electronic recording, the fringe interpolation, and the demodulation of the two (pi) ambiguity, commercially available software has been used. This system has been applied to the investigation of a model drill tip under different compressive loads.

A new multisource contouring method is presented. Holographic setup for recording uses single-beam reflection holography. Between exposures the system of object and holographic plate is rotated at a small angle (Delta) i, and an M-fold exposed hologram of the object is recorded on the same plate. After development of the plate contour fringes are generated on a reconstructed object image by multipath interference. It is possible to rotate a source of irradiation or illuminate the object through the plate simultaneously by M collimated beams instead of rotation of object-plate system. The obtained contour fringes have less FWHM in M/2 times than in the two-source contouring method.

During the last few years, the number of intraocular lenses that have been implanted has grown considerably, thereby creating the need for an exhaustive study of the characteristics of such lenses as image-forming systems. In this paper, the spheric aberration of flat-convex intraocular lenses as measured by a holographic interferometer is discusses, and the results are compared with the technical data on the aberration that such a lens presents. The match between theory and experimentation is good.

This paper describes a carrier fringe technique for measuring surface deformation. In contrast to conventional holography and fringe analysis, this holographic system is based on the fiber optics and automatic spatial carrier fringe pattern analysis techniques. Carrier fringes are generated by simply translating the object beam between two exposures. Single-mode optical fibers are used to transfer both the object and reference beams. The use of optical fibers offers advantages in the field of optical holography. The fast Fourier transform (FFT) method is used to process the interferograms. This method of fringe pattern analysis is a successful technique for extracting phase information from fringe patterns which result from the interference of tilted wavefronts. The paper also introduces the tile level, minimum spanning tree and phase unwrapping techniques. The method is illustrated by measuring the centrally loaded disk. A correction is made for the nonuniform spacing of the carrier fringes, which was introduced by a slight inclination of the object. The results are given for disk, including the perspective plot of the out-of-plane deformation field, the maps of wrapped and unwrapped phase, and a contour map of the unwrapped phase.

Holographic interferometry provides certain advantages in the fabrication of interferograms for multidirectional observation of transparent media. This turns out to be useful, if inhomogeneous phase objects such as plasmas of technical interest are to be analyzed. The serious problem of a comparatively small fringe shift being caused by neutral or charged particles in a plasma can be reduced using the technique of spatial optical heterodyning. The corresponding highly resolved phase profiles are well suited for the application of sensitive tomographic reconstruction algorithms, as they are known from x-ray compute tomography in medicine. For the case of rotationally symmetric phase objects a new reconstruction technique is presented. The combination of resonant holographic interferometry with tomography allows the determination of the particle density of distinct atoms and ions and their spatial distribution in an inhomogeneous plasma. Finally, the consideration of saturation effects in the use of resonant holographic interferometry, the degree of ray-bending because of refractive index gradients due to inhomogeneities, and ways of suppression of the troubling strong self radiation of a plasma are discussed.

The authors suggest and discuss a new two-step method of wavefront measurement which eliminates self-aberrations of the interferometer.

Dyes fixed in polymer matrices can generate a phase-conjugate (PC) wave through several different mechanisms such as saturable absorption, trans-cis photoisomerism and photochemical irreversible changes in absorption coefficient and/or refractive index. PC waves generated in dye-doped films have optical properties which are not found in photorefractive materials, and their proper use allows one to perform three types of real-time PC interferometry. Real-time PC interferometries for (1) detecting the phase difference between two objects. (2) subtraction in amplitude of two objects, and (3) detecting a moving object in a scene were demonstrated in a standard backward degenerate four-wave mixing (BDFWM) arrangement. An erythrosin-B- doped polyvinyl alcohol (PVA) film was used in (1) and (2), and a methyl- orange-doped PVA film was used in (3).

Spectral hole burning media — photochemically i9stable dye molecules in low—temperature polymers hibit very narrow (10 Hz) optical resonances distributed over a wide (10 Hz) band along the frequency axis. Exposure of the medium to recording light field burns a 4—D grating pattern into the dielectric permittivity tensor c(x,y,z,), which in turn determines the temporal behaviour of the linear pulse response of the sample. Based on this phenomenon the common holography has been generalized resulting in a 4—D holography where restored light field is completely identical to the stored one and plays back ultrafast temporal behaviour of the object light as pulsed vector field. In the paper, the approach is extended for applications listed in the title and corresponding experimental results of streak —camera measurements on octaethyl—porphin —doped polystyrene plates are briefly discussed.

A theory of phase-modulated beams mixing in photosensitive media is developed in the paper. Application of theoretical results for real-time measurements of vibrating parameters, linear microdisplacements, and small movement velocities of a reflecting surface as well as for experimental study of holographic processes is discussed. High sensitivity of these measurements is caused by interferometers operating point adaptive stabilization due to dynamic holograms used as beam couplers.

Peculiarities of the holographic recording in PMBR and problems connected with these media applications for real-time interferometry are discussed. A sensitive holographic interferometer with phase-modulated recording beams was used for dynamic hologram amplitude measurements. It was determined that the steady-state hologram amplitudes are saturated or reduced if the beam intensities increase. Moreover, the kinetics of a hologram recording with high-intensity beams differed from the exponential law. The nondegenerate two- wave mixing in PMBR demonstrated the amplitude grating existence which promoted hologram amplitude temporal oscillations.

A near diffraction limited kinoform tele-apochromat-anastigmats was designed for broadband spectral range images. By use of kinoform elements, the apochromatic correction of the aberration is achieved without the load- dispersion glasses or crystals both for infinity and for the finite distance. Design and results of the testing are presented.

The basic problem in holographic interferometry, in the case of a deformed opaque body, concerns the determination of displacements, rotations, and especially surface strains from the fringes that can be observed when reconstructing the image. However, in industrial application, large deformations often occur, so that fringes would not be visible. Several approaches were proposed previously to overcome this problem by a sort of compensation. In most cases, fringes can be recovered and analyzed by such a modification. The same problem of recovering fringes can also come up in the case of a strong spatial change of index of refraction, for instance, in a gas with a high temperature gradient. After the process of modification, three conditions must be fulfilled: (a) small areas around each pair of aberrated image points of the undeformed and the deformed object surface must overlap; (b) the expected fringes must become sufficiently spaced; and (c) they must have a sufficient contrast. The authors establish here the basic concept of aberrated images and modified fringe formation leading to two fundamental equations by means of a differential form of the relevant optical path difference. In order to show how to use these equations, a development, in combination with image processing, is given in the case of moderate rotation of the order (mu) << 1 and small strains of the order (mu) 2.

A vision sensor system composed of a CO2 laser. EOM modulator, holographic scanner, infrared detector, and image processor has been developed. The holographic grating disk scanner is composed of ten facets, and each hologram is made of Ge. The maximum diffraction efficiency of 62.9% is achieved. By rotating the holographic grating disk with the number of revolutions (3000 rpm), it is possible to get images in which the resolution is 10 cm within the distance region of 3-30 m.

A rigorous three-dimensional vector characteristic wave arbitrarily slanted anisotropic grating diffraction analysis is presented. The most persuasive argument for the characteristic wave approach use is the ease with which solutions may be obtained. The characteristic wave method applies to any anisotropic volume reflection or transmission sinusoidal or nonsinusoidal amplitude and/or phase grating with slanted fringes, any plane-wave angle of incidence, and any linear polarization. The same analysis applies to the limiting cases of isotropic materials, a grating vector lying in the plane of incidence, Bragg or Raman-Nath diffraction, etc. For pure reflection gratings when the grating fringes (surfaces of constant permittivity) are parallel to the grating boundaries, the permittivity is no longer periodic along the boundary. However, this case can be simply analyzed without approximation by using a rigorous characteristic wave method of analysis. In this paper, diffraction characteristics for holographic volume slanted gratings are presented for various linear polarizations of the incident waves as a functions of the slant angle.

A review of original theoretical and experimental investigations of volume holographic recording on liquid photopolymerizable layers is presented. The experimental results that confirm the thermodynamic model of hologram formation in the layers of question are summarized. Also considered are the actions of intensity gradient of interference field on

Light scattering elements formation are studied in the liquid photopolymerizable layers. Under recording, two of different photopolymerizable layers were replaced one by one, the first layer providing the scattering structure formation and the second one the noise hologram recording with its amplification. The recorded efficiency was found to depend on the delay value in the second layer exposure beginning as it related to the first. The effects of scattering indicate tuning under scattering wave formation and wave formation suppression--both by composition content changes. The light scattering elements obtained were found to provide the light scattering in the range of about 25 degree(s) with the efficiency not less than 90%.

In this work the problems of the design of the testing canal of adaptive optical system on the basis of the hologram optical element (HOE) coated on the active element is considered. The paraxial analysis of the HOE recording and the test ing canal working are presented. As wel 1 as the analys is of holographic testing canal working with respect up to the fourth-order wave aberrat ions . On the bas is of this analysis the tolerances for the hologram construction optical parameters are determined. The results of modeling of the aberration being arisen both in the main canal and in the testing one for the various deformations and the displacements of the active surface are presented.

In studying the imaging quality of holographic lenses, many studies confine their scope to the examination of the third-order aberration theory and pay special attention to the possibility of coma correction. By a suitable choice of the recording geometry of the holo-lens it is possible to obtain aplanatic correction. However, the analysis of imaging quality based on numerical modeling of imaging which enables calculation of the aberration spot shape suggests that such correction does not necessarily give satisfactory results. Better imaging quality can be obtained for the other (nonaplanatic) holo-lens of the same spherical aberration and astigmatism, in spite of some non-zero coma. Further improvement can be achieved by slight compensation of coma obtained by curving of the holo-lens substrate and simultaneous correction of astigmatism following from the input pupil shift. The conclusions are confirmed by calculated aberration spots and incoherent transfer functions.

This paper presents a feasibility study of the use of coherent optical pattern recognition devices as machine vision systems. The fast holographic correlator carrying out real-time data input in the processing channel, coherent holographic filter recording, and correlation image processing is investigated. A detailed analysis is given of the basic components of the coherent optical processor, considering specific requirements to the equipment, and the prospects are outlined for the use of the pulsed solid- state laser, the input unit based on the liquid crystal spatial-temporal light modulator, and FTIROS reversible registering medium for the high-speed filter- hologram synthesis. A schematic diagram of the fast holographic correlator, performance of its basic elements, and the results of the experimental tests on pattern recognition are presented.

Novel photoreplication technology for deep groove surface relief holographic optical elements (HOE) was developed recently at Du Pont. Dry photopolymer embossing (DPE) technology utilizes Du Pont proprietary materials and processes to replicate precisely almost any kind of surface relief or embossed holograms. Very sophisticated surface relief holograms with the high width/depth aspect ratio of 1:20 can be faithfully replicated by this technology. Dimensions of the replicated grooves or other surface relief 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. Glass and other inorganic materials can be also used as substrates in some applications. To replicate such deep groove surface relief HOEs, the master hologram should be recorded in metal, glass, or other hard surface material. DPE technology may provide substantial technological and economical advantages over existing conventional replication processes, such as thermo-embossing, injection molding, wet photopolymerization (2P-process), and injection-reaction molding, in replication of different types of surface relief HOEs.

Distributed optical fiber sensing (DOFS) is a technique which utilizes the very special properties of the optical fiber to make simultaneous measurements of both the spatial and temporal behavior of a measurand field. As such, it provides an extra dimension in the measurement process, leading to finer monitoring and control, and to a new level of understanding, especially in regard to the behavior of large structures. Measurement of spatial distributions with a resolution 0.1 - 1 m over a distance 100m, to an accuracy approximately 1%, may be expected. This paper summarizes the principles of DOFS, gives examples of systems which have been studied, and gives some indication as to what is in store for the future.

The objective of this paper is to motivate a new class of digital logic. OptiComp has focused on a digital optical logic family in order to capitalize on the inherent benefits of optical computing, which include: (1) high FAN-IN and FAN-OUT, (2) low power consumption, (3) high noise margin, (4) high algorithmic efficiency using 'smart' interconnects, (5) free space leverage of GIBP (gate interconnect bandwidth product). Other well-known secondary advantages of optical logic include (but are not limited to): zero capacitive loading of signals at a detector, zero cross-talk between signals, zero signal dispersion, and minimal clock skew (a few picoseconds or less in an imaging system). The primary focus of this paper is on demonstrating how each of the five advantages can be used to leverage other logic family performance such as GaAs; the secondary attributes will be discussed only in the context of introducing the DOC III architecture.