The principle of diffusional enhancement has been embodied in the rigid glassy polymer with phenanthrenequinone able to photochemically attach to surrounding macromolecules, thus forming a permanent grating. Owing to material stiffness, it does not suffer from shrinkage and can be made very thick; serving a basis for very stable spectrally selective elements. Replacement of commonly used acrylic glass by polycarbonate ensures further significant improvement of performance and stability of 3D holographic optical elements and memories.
We have developed grisms, designed for astronomical observation with the 8.2m Subaru telescope on Mauna Kea, Hawaii. In order to improve both efficiency and cost, we proposed a new type of grism by sandwiching a volume phase holographic (VPH) grating between two prisms, dubbed 'VPH grism'. Photosensitive materials are required for
fabrication of VPH grating with high groove density. In this paper, we employed the liquid photopolymer with high viscosity. Using the analysis program valid for the refractive index modulation grating of the rigorous coupled wave analysis (RCWA), we were able to design and fabricate a grism prototype with good performance. From the data we
obtained, it was ascertained that the experimental VPH grism had excellent performance. We further aimed to develop a VPH grism with higher dispersion and efficiency by making use of a new photopolymer that has larger refractive index modulation than the present material.
By using volume holography characteristics, optical devices having demultiplexer and/or dispersion compensator capabilities are proposed which can control multiple channel wavelengths in the wavelength division multiplexed (WDM) system. Through a specially designed mask system, multiple volume gratings corresponding to the multi-channel components are recorded in a photorefractive crystal. This mask recording scheme simplifies the conventional sequential multiplexing procedure which requires complex mechanical or laser source system. Recording schemes and device characteristics of the above devices are presented in relation with volume diffraction principle and photorefractive crystal properties.
Holographic data storage (HDS), which makes use of the full volume of the recording medium, possesses high potential by promising fast transfer rates of hundreds of Megabytes/sec and storage densities greater than 200 Gbytes per 120mm disk. The restrictions that are placed on the holographic media, however, are stringent. Described here is a high performance photopolymer based medium that has the properties necessary to enable this technology. Through the use of several different holographic techniques, the material characteristics that are necessary for holographic storage products may be determined. The two different systems that are discussed here include Plane Wave and Digital Holographic Data Storage. These measured characteristics include high dynamic range (M/#), sensitivity, and small recording-induced Bragg detuning. In addition, results of archival and shelf-life environmental testing of the media will be discussed.
There are three modes of operation in a holographic data-storage system: recording, reconstruction and detection. Storage capacity is limited by diffraction, optical systems, interpage cross-talk, storage density and material quality. Wavelet image processing has the potential for reducing noise from optical scattering, lens aberration and crosstalk, as well as being potentially 3D. Wavelet image processing will be applied to holographic data storage to enhance 2D image resolution and potentially increase 3D storage capacity. This effort will apply wavelet image processing to holographic data storage at two levels (a) beam interaction in the photorefractive crystal; and (b) wavelet analysis and synthesis applied to holographic recording, reconstruction and detection.
It is well known that the macroscopic characteristics describing holographic materials are determined by the physical and chemical processes taking place at a microscopic level during and after exposure and during processing. Very well controlled and systematic measurements have been carried out to determine for the first time the 'complex' nonlinear characteristics of a silver halide material (processed to obtain phase holograms), i.e. to measure its Lin-curves (square-root of diffraction efficiency as a function of bias exposure and fringe visibility) in a range of grating spatial ferquencies. In such a way both the MTF and the nonlinearity of the material can be determined. An analytical function was fitted to the measured data, allowing for the use of these characteristics in the assessment of the quality of the reconstructed holographic image using the method (based on the double Fresnel-Kirchhoff integral) developed by the author.
In this work we have studied the characteristics of reflection gratings recorded with BB640 emulsions from Colourholographics Ltd. processed with a set of different developers and bleaching techniques. Overall diffraction efficiencies evaluated with spectral response curves result in values higher than 70% (80% taking into account reflection losses) for conventional fixation free rehalogenating bleaching processes, with very low scattering.
A slightly lower value was obtained with reversal bleaching techniques, but with lower scattering in the recordings.
For the latter, an analytical analysis of the spectral responses based on the Kogelnik's theory has been performed, leading to anomalous results regarding physical thickness of the hologram and the reply wavelength, a performance that points towards holographic profile distortions. We have also used a completely different processing scheme based on Kodak D8, a developer never used in reflection holography, with a direct bleach rendering 40% diffraction efficiency, a broad bandwidth and a reconstruction wavelength longer than the recording one.
Recent improvements in the processing of commercially available holographic recording materials for pulsed holography are reviewed. Harmonics of pulsed Nd:YLF/Nd:Phosphate Glass, Nd:YLF, Nd:YAG laser's, and the fundamental wavelength of a pulsed Ruby laser were used as radiation sources for the recording of transmission and reflection holography gratings. It is shown that ultra-fine grain size materials such as PFG-03C and Ultimate-15 can be successfully applied for small and medium format pulsed holography applications. These small grain size emulsions are especially important in the areas of artistic archival portraiture and contact Denisyuk micro-holography of living objects, where noiseless image reconstruction is of a primary concern. It suggests that HOE's, such as full-color image projection screens, may be successfully recorded on PFG-03C holographic emulsions using a pulsed RGB laser. A range of commercial RGB pulsed lasers suitable for these applications are introduced. Visible wavelengths currently produced from these lasers covers the spectrum of 440 - 660nm. Latest developments of a full range of pulsed holographic camera systems manufactured by GEOLA that are suitable for medium and large format portraiture, medical imaging, museum artifact archival recording, and other types of holography are also reviewed with particular reference to new integrated digital mastering features. Finally, the initial commercial production of a new photopolymer film with a sensitivity range of 625-680nm is introduced. Initial CW exposure energies at 633nm were 30 - 50mJ/cm2; with diffraction efficiencies of 75 - 80% observed with this new material.
Lin-curves of plane-wave phase holograms recorded in Agfa-Gevaert 8E75HD emulsions were measured for the combinations of AAC developer and the R9 bleaching agent. Then each holographic grating was studied by phase-contrast microscopy, using both medium-power (40 X) and high-power immersion (100 X) objectives. Thus, besides of the Lin-curves, the modulation of the refractive index as a function of the bias exposure and the visibility of the recording interference pattern can also been determined. This latter characteristics is used in coupled wave theory to calculate the diffraction efficiency of holographic gratings, thus the measured diffraction efficiencies can be compared to those predicted by the theory. Moreover, this direct study of the phase profile of the gratings can be used for optimising processing.
Dichromate gelatins are well known as good holographic materials. Now by doping this material with synthetic vanilla, a change in the spectral amplitude response is obtained. Due that the maximum absorption spectra from the dichromate ammonium is localized in UV region at λ = 390. With vanilla, the maximum spectral response is similar, exception for its optical density, reducing the exposure factor the order of 2 times. An important property with this mixture is the high resistance to humidity of the ambient. We have recorded some diffraciotn gratings, using the argon laser λ = 488 nm, which show good diffraction (grooves). A characteristic of the developed process is its simply, only using solution composed of water and isopropyl alcohol, this process takes approximately one hour.
This report is aimed to review obtained in Institute of Semiconductor Physics of National Academy of Sciences of Ukraine results of investigations of phototechnical performances inherent to layers of chalcogenide vitreous semiconductors with As40S60-xSex composition (x=0...20) as a medium for recording holographic protective masterelements. Such inorganic resists are sensitive to visible and ultraviolet radiation and electron beams, which enable one to produce master optical-digital holographic elements possessing many safety levels. When exposing photoresist, to obtaine interferential 2D/3D patterns, we used He-Cd laser radiation and electron-beam submicrometer technology. The exposure was chosen from the range 20 to 300 mJ/cm2, and spatial frequencies of obtained gratings were 800 to 1600 mm-1. In addition, resist performances were investigated using the Dot-matrix technology. Results of investigations showed that As40S60-xSex (x=0...20) photoresist is characterized by higher light and electron-beam sensitivity and this
enables to get combined optical-digital protective elements: digital hologram; optical and digital hologram; combination of optical and digital holograms with submicrotext image.
Author(s): Gennadi A. Sobolev; Svetlana B. Soboleva; Alla N. Taranova
We discuss different holographic materials for thick holograms recording. For material selection we apply various holographic and technological factors. Chalcogenide glasses have good optical properties, low scattering and high resolution for IR application. Dichromated gelatic film and thick layer-gel of dichromated gelatin may be used in visible green-blue light, but these holograms are unstable. Photo polymer PMMA - for hologram recording in visible light we used as base material, which has high holographic quality and good stability. We discuss the synthesis of material and describe the method of latent image for selection of optimal composition and additives. We use the molding method for production of high quality surfaces. A special recording scheme allows the material to record large size elements with highly reproducible parameters. It is shown that in order to obtain highly uniform elements it is necessary to maintain the very strict control of synthesis process. Application of this technology is discussed.
The solution composed of bromocresol green (BCG) with rosin diluted in isopropyl alcohol. Its present as holographic recording element. Based in diffraction gratings recorded, over two parameter of recording, such as: different concentration BCG and rosin, and to different angle between the object beam and reference beam. This material if photosensitive to the blue light λ = 457 nm employed an Argon laser. Obtain in this gratings diffraction efficiencies the
order of 2.27%.
A holographic 3D printer is a system that produces a direct hologram with full-parallax information using the 3-dimensional data of a subject from a computer. In this paper, we present a proposal for the reproduction of full-color images with the holographic 3D printer.
In order to realize the 3-dimensional color image, we selected the 3 laser wavelength colors of red (λ=633nm), green (λ=533nm), and blue (λ=442nm), and we built a one-step optical system using a projection system and a liquid crystal display. The 3-dimensional color image is obtained by synthesizing in a 2D array the multiple exposure with these 3 wavelengths made on each 250mm elementary hologram, and moving recording medium on a x-y stage. For the natural color reproduction in the holographic 3D printer, we take the approach of the digital processing technique based on the color management technology. The matching between the input and output colors is performed by investigating first, the relation between the gray level transmittance of the LCD and the diffraction efficiency of the hologram and second, by measuring the color displayed by the hologram to establish a correlation. In our first experimental results a non-linear functional relation for single and multiple exposure of the three components were found. These results are the first step in the realization of a natural color 3D image produced by the holographic color 3D printer.
This paper describes a holographic display using liquid crystal panels from which holographic images can be perceived with both eyes. In the display, the hologram plane is composed of two high-resolution liquid crystal panels each with a pixel pitch of 10 microns (both horizontally and vertically) and 3840 (horizontal) × 2048 (vertical) pixels. The horizontal viewing zone is doubled by applying the viewing-zone enlargement method, which uses higher-order diffraction beams, to the high-resolution liquid crystal panels. In addition, obstacles resulting from conjugate beams are eliminated using the modified single-sideband method. As a result, the viewing zone of the display is 6.5 cm, which is equivalent to the distance between pupils, at a viewing distance of 90 cm. Thus, moving three-dimensional holographic images free off conjugate beam obstacles could be perceived with both eyes.
In this paper, a new high-resolution (XGA) SLM is implemented through modification of a commercial TFT-LCD beam projector and its optical modulation characteristics are analyzed as well. The optic module, projection lamp and cooling fans are removed from the beam projector and instead, the electric circuits to compensate their removal are manufactured and inserted into the beam projector, a new high-resolution SLM is finally implemented. Some experiments on the optical modulation characteristics of the implemented SLM have been carried out by using the Mach-Zehnder interferometer. These experimental results show a good optical linearity in amplitude and phase modulation and as a result, the implemented LC-SLM is suggested as a new low-cost, high-resolution input and filter devices for the optical information processing systems.
Accidental abrasion of a specular surface sometimes produces real and virtual images of the abrading object. Investigation of this phenomenon in 1994 led to a simple technique which almost sounds like a joke: a method for creating white light holograms by scribing interference fringes one at a time onto a plastic plate by hand. The optics of these 'abrasion holograms' is similar to Rainbow holography, and the similarities reveal techniques for controlling distortions, for producing images of opaque objects, as well as for producing animation effects and images that extend out through the film plane. As with any rainbow hologram, spatially coherent or 'point-source' illumination is required, both a transmission mode and a reflection mode exist, and conjugate illumination produces pseudoscopic images. This 'abrasion holography' highlights the fact that the zoneplates comprising a Rainbow hologram function independently not only of illumination frequency but also of fringe spacing. Size-independent fringes suggests that truly enormous holograms can be engraved on a wide variety of very crude everyday surfaces.
This study is focused on proposing a creative system that can display 3D hologram on the real-time basis. This method applies 3D display on volume hologram based on CGH. The process of implementing the system consists of two stages of fringe pattern recording for passive component that includes information on hologram, and irradiating object beam. Distinguished from an existing electronic holographic display system, this system is free from the process of a huge calculation that is necessary to compose CGH for a real-time 3D display. Clarifying a theoretical basis on this method, we have proved validity through results of experiments.
In this paper, a photopolymer-based VHOE is optimally manufactured and using this VHOE, an experimental model of the VHOE-based 8-view stereoscopic display system is implemented. That is, the VHOE is optically made by angle-multiplexed recording of 8-view's diffraction gratings in the Dupont's photopolymer(HRF-150-100) using an optimized exposure-time scheduling scheme and then, the VHOE-based 8-view stereoscopic display system is implemented, in which the incident angles of the diffracted reference beams of the VHOE are sequentially synchronized with the respective 8-view stereo images displayed on the LCD panel. From some experimental results using 8-view test images, it is found that 8-view stereo images can be diffracted to the eight different directions corresponding to the incident angles of the reference beams and there is some disparity between the stereo images. From these experimental results, a possibility of implementing the VHOE-based multi-view stereoscopic 3D display system is also suggested.
Progress in a novel wave-optical algorithm for synthesizing object waves of three-dimensional surface objects is reported. The algorithm has been proposed last year and has a feature of wave-optical calculation in diffraction by object surfaces. Numerical simulation of diffraction is implemented by a method based on coordinates rotation in Fourier spectrum. Source fields on a surface of objects are given as complex property functions defined on each object surface. These property functions provide information on each surface, such as the shape and diffusiveness. General formulation of the algorithm has been presented, but its numerical implementation was limited only to the cases of single axis rotation of plane surfaces. In this investigation the limitation is removed, i.e. two-axes rotation of plane surfaces is presented and reconstruction of holograms of 3-D objects composed of rotated planes are demonstrated. Furthermore, compensation of surface brightness is discussed for accurate shading objects.
In this paper, we present a method based on mathematical morphology for digital-hologram synthesis. The principles and operations of mathematical morphology are used for morphologic thansformation of images and for generation of digital image sequence. The sequence of digital images can be used to create kinetic and beatuful hologram which has a good prospect for application in laser anti-counterfeiting field.
A blue white He-Cd laser composed of three R/G/B component beams in place of He-Ne laser is directly applied to fabricate the optical Fourier transform hologram (OFTH) using the red sensitive silver halide material (SO-253 film) for holography. As a result, the red beams play an important role as the coherent beams in the fabrication of OFTH. A green solid state laser is applied to fabricate the OFTH using the same film for holography. The visual appearance of reconstruted color images caused by He-Cd laser is discussed in contrast to that of an ordinary OFTH which can be made using the He-Ne laser and solid state laser. The visual color effect using the He-Cd laser is checked from the viewpoint of the relative real size and its place in the OFTH, and the visual depth sensation of overlapped ghost images called cross-talk in the Fresnel hologram. The purpose using a commercially available software such as HSL color model is to carry out the intuitive modification of overlapped and deteriorated color images in the digital reconstruction of OFTH and Fresnel hologram.
One of the main problems in practical application of digital holography is that the unit cell size of CCD(Charge-Coupled Device) is too large. As a result, the object size of recording of interference pattern to CCD is very limited. The angle of incoming laser light ray is reduced by the ratio of two focal lengths of two confocal lenses. This induces the spatial frequency of interference pattern to be lower. So the higher spatial frequency of interference pattern than the spatial frequency determined by the unit cell size of CCD, can be recorded. By using confocal lenses optical setup, a merit can be achieved like that the area of the 0-th order diffraction light is reduced to the square of the ratio of two focal lengths at numerical reconstruction. As a result, numerical reconstruction for larger object size compared with CCD only case, is calculated by using FFT(Fast Fourier Transform) adapted to the integral came from Huygens-Fresnel principle. The needed diameters of two confocal lenses and the position of CCD camera are calculated for recoding the interference pattern of larger object size.
This paper describes a method of numerical reconstruction for digital holography with changed viewing angles within the Fresnel domain. The proposed algorithm could not only render the real image of the original object with different focal lengths but also with changed viewing angles selected in 3D space. The numerical reconstruction can be implemented by using the Fast Fourier Transform. Some representative simulations are presented to validate the proposed algorithm.
The traditional way of making holograms requires the use of a coherent light source and also a special care on the experimental setup. Usually, the light beam from the source is split into two beams with intensities having a special ratio as the respective lengths of their optical paths. In this work we report a different approach based on the use of synchronized coherent light sources, where the traditional experimental setup is not required. We comment on the advantages of using this scheme over the traditional one.
In this paper, to reduce the Bragg-mismatch problem of the dual-wavelength method, we record the hologram in the Dupont's photopolymer of thickness L=38μm and use a digital image data which has 78×104 bit/page. Also, to compensate the image magnification problem, a pair of cylinder lens consisting of 4F system behind the F2 lens and proposed data matrix image processing technique is used. As a result, the raw BER through Gaussian fitting after extracting binary data is around 3.09×10-6.
Author(s): Maurice Stanley; Robert W. Bannister; Colin D. Cameron; Stuart D. Coomber; Ian G. Cresswell; Jonathan R. Hughes; Victor Hui; Peregrine O. Jackson; Keith A. Milham; Richard J. Miller; Douglas A. Payne; John Quarrel; Dave C. Scattergood; Allan P. Smith; Mark A. G. Smith; Denver L. Tipton; Philip J. Watson; Pam J. Webber; Christopher W. Slinger
Giga-pixel scale displays or spatial light modulators are required in order to form directly viewable 3-D images of 0.5m in size using the principles of computer generated holography (CGH). This has been a key bottleneck preventing commercial development of electro-holography. Active Tiling is a modular spatial light modulator system developed by the authors to provide a route to replay images from giga-pixel scale CGHs. This paper will present the latest development of a multi-channel Active Tiling unit and results from this system for the first time. A holographic 3D display system using a 4 channel Active Tiling modulator with a new replay optics system has demonstrated directly viewable 3-D images and animations from 100 Mega-pixel CGH data. This provided viewing of both horizontal parallax only (HPO) and full parallax 3-D images up to 140mm in size. 25 Mega-pixels of CGH data is written by each channel onto a liquid crystal optically addressed spatial light modulator at high resolution. The modular design of Active Tiling permits CGH data to be written seamlessly across multiple channels which can be updated at rates up to 30 Hz. A Fourier Transform optical replay system was developed and integrated with the 4-channel Active Tiling system to form the CGH images.
A new beam steering scheme using computer-generated holograms(CGHs) is proposed. The steering devices in order to control the reference and object wave are necessary in various holographic multiplexing methods. The beam steering device using CGHs can be simultaneously processed the coarse address function controlling the beam up or down so as to select slice and the fine address function adjusting to the particular holographic page within the chosen layer. From the experimental results, we show that the beam steering can be easily implemented and so powerful to generate the electrically addressed reference wave in digital holographic memory system.
The holographic visualization of three-dimensional object geometry still represents a major challenge in computational holography research. Besides the development of suitable holographic display devices, the fast calculation of the hologram's interference pattern for complex-shaped three-dimensional objects is an important pre-requisite of any interactive holographic display system. We
present a fast method for rendering full-parallax holograms using a standard PC with a consumer-market graphics card. To calculate the hologram of a 3D object, scaled and translated versions of the interference pattern of simple primitives, e.g. point sources, are superimposed. The hologram is built up completely on-board the graphics card. To avoid numerical inaccuracies due to limited
frame-buffer resolution, we use a hierarchical approach. Using an NVidia Geforce4 graphics card, the proposed algorithm takes 1.0 second to calculate the 512×512-pixel hologram of 1024 primitives.
Hidden surface removal (HSR) method is a key technique to display realistic 3D images. We propose a new HSR algorithm for CGH in order to be adapted to multi-view. Object-light on a hologram is decomposed into rays arrived from all points of objects. In the assumption of geometrical optics, both a position and a directional angle determine each ray on a hologram. We propose z-buffer for CGH with the two coordinates of position and angle, which represent rays arrived at a hologram. The path length of all rays are calculated and stored in the elements of the z-buffer. In the area of hidden surface, where there are more than one ray at the same element, the shortest ray is stored. By the process, we get a list of rays arrived at the hologram, and the summation of the listed rays represents the object-light. Using the holograms calculated by the method, optical experiments were carried out. They showed us reconstructed 3D images with opaque surfaces. Because a number of objects dose not dominate the calculation time, the method requires shorter time compared with conventional method in case of a large number of objects.
We have reported that viewing angle of the computer-generated hologram can be expanded with lensless Fourier transform hologram. It, however, requires a laser to illuminate the CGH for reconstruction. In the previous paper, we have proposed that making the second hologram for white-light reconstruction. The reconstructed image from the first hologram is used as the object beam of the second hologram. The second hologram can be either transmission or reflection hologram, which depends on the direction of the reference beam. In this report, we extend this method to make multi-color reflection hologram. First, we calculate the master holograms for each elemental color. Then, the transfer hologram can be made from the master CGH with multimple exposure with either changing wavelength or psuedo-color process. In the experimental result, we obtain multi-color full-parallax computer-generated hologram with 20 degrees of viewing angle and 10 mm × 7.6 mm image size.
The most important advantage of holographic stereograms over conventional hologram is that they can produce 3D images at
any desired scale with movement, holographers in many countries involved in the studies towards it. We began our works in
the early 80's and accomplished two research projects automatic system for making synthetic holograms and multiplex
synthetic rainbow holograms, Based on these works, a large scale holographic stereogram of an animated goldfish was made
by us for practical advertisement. In order to meet the needs of the market, a copying system for making multiplex holographic
stereograms, and a special kind of silver halide holographic film developed by us recently. The characteristic of the copying
system and the property of the special silver-halide emulsion are introduced in this paper.
Using holographic microscopy we have been able to visualize submicron-sized. bacteria in-vivo. A simple holographic method enables us to capture as a single data set the trajectories of micron size objects suspended in water. By subtracting consecutive holograms of a particle suspension and then adding these difference holograms, a final data set is constructed that contains the time evolution of the particle trajectories free from spurious background interference effects. Temporal and spatial resolution at the sub-second and sub-micron levels can easily be achieved. The method is illustrated by recording the motion in 3-D of 5μm diameter latex spheres subject to gravity and electrostatic fields to visualize their micro-fluidic flow. Another example is the 3-D motion of a collection of algae, protozoa and bacteria in water.
Holographic Interferometry has been successfully employed to characterize the materials and behavior of diverse types of structures under dynamic stress 1,2,3,4. Specialized variations of this technology have also been applied to define dynamic and vibration related structural behavior 5. Such applications of holographic technique offer some of the most effective methods of modal and dynamic analysis available. Real-time dynamic testing of the modal and mechanical behavior of jet engine turbine, rotor, vane, and compressor structures has always required advanced instrumentation for data collection in either simulated flight operation test or computer-based modeling and simulations. Advanced optical holography techniques are alternate methods which
result in actual full-field behavioral data in a noninvasive, noncontact environment 6. These methods offer significant insight in both the development and subsequent operational test and
modeling of advanced jet engine turbine and compressor rotor structures and their integration with total vehicle system dynamics. Structures and materials can be analyzed with very low amplitude excitation and the resultant data can be used to adjust the accuracy of mathematically derived structural and behavioral models.
Holographic Interferometry offers a powerful tool to aid in the developmental engineering of turbine rotor and compressor structures for high stress applications. Aircraft engine applications
in particular must consider operational environments where extremes in vibration and impulsive as well as continuous mechanical stress can affect both operation and structural stability. These
considerations present ideal requisites for analysis using advanced holographic methods in the initial design and test of turbine rotor components. Holographic techniques are nondestructive, real-time, and definitive in allowing the identification of vibrational modes, displacements, and motion geometries. Such information can be crucial to the determination of mechanical configurations and designs as well as critical operational parameters of turbine structural
components or unit turbine components fabricated from advanced and exotic new materials or using new fabrication methods. Anomalous behavioral characteristics can be directly related to hidden structural or mounting anomalies and defects.
The principle of holographic CT measurement is introduced briefly, and the possibility of measuring 3D variation of the refractive index from the intensity distribution of a real-time holographic interferogram is proven theoretically. Based on this method, simulated study on calculating the variation of refractive index of an axis symmetry media is made by computer and the example of application is also presented in this paper.
In a series of the experiments of real-time holographic interferometry, some dark shadow areas appear among the interference fringes. The appearing of the dark shadow area plays a very important role in the fracture process. We find that the appearing of these dark shadow regions are the phenomena of caustic in Fracture Mechanics. The shadow region is so called shadow spot in Fracture Mechanics and the factor of stress intensity can be calculated by measuring the size of the correosponding length of the shadow spot and the strain field can be calculated by traditional holographic method. Therefore, holographic method and caustic method can be combined together in holographic interferometry and it will lead to a wide application in Experimental Mechanics.
To determine the phase distribution of the under testing object wave from the interferogram is the foundation of holographic interferometry. A digital image processing method for deleting the background noise and obtaining the phase distribution precisely is proposed by the authors and the example is also presented in this paper.
This work deals with Computer-Generated Rainbow Holograms (CGRHs), which can restore the 3D images under white light. They are devoted to include in Diffractive Optically Variable Image Devices (DOVIDs) that are currently widely used for security needs. CGRHs prevent counterfeiting due to the complexity of recreation on the one hand and allow the simple identification at the first (visual) level of verification on the other hand. To record it the Electron Beam Lithography (EBL) is used. The CGRH computation process is conventionally divided on two parts: synthesis and recording. On the synthesis stage, firstly, the geometrical and optical constants of recording scheme are determined, secondly, the basic parameters accounting for discretization of ID in hologram plane are defined and, finally, the calculation of the Interferogram Data (ID) - the array of Bipolar Intensity (BI) values - is carried out. This calculation is performed separately in each independent horizontal slice of object space and hologram plane. On the recording stage a suitable quantization parameters are chosen and transformation of ID into the multilevel rectangle data appropriate for EBL is accomplished. The investigations on optimization of synthesis and recording of the multilevel CGRHs of 3D images integrated in Polygrams are presented here. So the rules for definition of the appropriate discretization parameters were finding out. Advantages of using non-linear quantization that implies condensing of quantization levels near the BI zero were explored. The random deviation of location and direction of elemental hybrid radiating area was applied.
We present a design procedure and atrial fabrication of a new 2D light source module composed of a vertical cavity surface emitting laser (VCSEL) array and a multi-level zone plate (MLZP) array as collimate lens. Furthermore, its application to an optical parallel correlator for facial recognition is also exhibited. The size is reduced by one-fifth and the throughput time of MLCOPaC with twelve parallel channels module is also, improved to record 19 faces which is 3 times faster than the second-generation compact parallel correlaor. By experimentally evaluating the system through one-to-one correlation using 300 database of front facial images, two kinds of error; False Match Rate 1.7% and False Non-Match Rate 1%, were obtained. Consequently, our system proved robust as applications to a security apparatus such as PC log-in entry control for network systems.
In this paper, we demonstrate the holographic smart card system using digital holographic memory technique that uses reference beam encrypted by the random phase mask to prevent unauthorized users from accessing the stored digital page. The input data that include document data, a picture of face, and a fingerprint for identification is encoded digitally and then coupled with the reference beam modulated by a random phase mask. Therefore, this proposed system can execute recording in the order of MB~GB and readout all personal information from just one card without any additional database system. Also, recorded digital holograms can't be reconstructed without a phase key and can't be copied by using computers, scanners, or photography.
In this study, it is newly attempted to combine digital holography method to get the holography fringe data using the CCD with the pulsed electro-holographic system for real-time display. Owing to the one-dimensional characteristic of the Bragg regime AOSLM that the fringe data propagating in parallel with the laser incident plane in the crystal cannot diffract the incident reference beam vertically by the momentum conservation, the diffraction of vertical direction from the AOSLM is impossible and the vertical parallax is not generated. Therefore the confocal lens system with a horizontal slit is introduced to obtain proper interference pattern. When the display of pulsed laser electro-holographic system is made by the fringe data of which bandwidth is reduced, the image clearness and quality is more improved than the recorded data without the confocal system with a horizontal slit since the fringe is formed to give mainly the horizontal parallax and the bandwidth of vertical direction is reduced so that the one line of object is projected onto only one line pixels of the CCD at same height.
We have previously described a holographic laser apparatus that 'cleans up' a laser beam by discarding off-axis rays. The device uses two matched holograms carefully oriented with respect
to one another so that the Bragg effect from the first hologram cleans up first one direction and then the second hologram cleans up the orthogonal direction. The device works well and reduces
the beam divergence to 0.8 mrad with a 3.0 mm thick hologram. However, there are practical difficulties with this configuration including sensitivity to the mutual alignment of the holograms
and a cleaned-up beam which is inconveniently not in the same horizontal plane as the input laser beam. We describe here a much simpler design using a single hologram that improves performance and avoids these difficulties.
We describe the experimental setup of the image domain joint transform correlator intended for holographic security application. The security verification routine demands two channels. The first one corresponds to the reference hologram stored in the security device. The other is a security holographic mark with several test sub-holograms, applied to a carrier: ID-card, paper seal etc. Each of the holograms stores a part of entire image, stored in the reference hologram. Image domain JTC is used to match the images retrieved from the holograms. The images are recorded by a light addressed spatial light modulator (LASLM). Being recorded and retrieved, the images provides correlation peaks with special positions, with a strict dependence on the tested and reference holograms mutual shifts.
We prove experimentally that the image domain recognizing provides as more effective usage of the LASLM work pupil and resolution as a less device size. The system also has a good tolerance to shift and rotation of the security holographic mark. Few correlation peaks respected to test holograms enhances the device recognizing probability. We provide computer simulations based on the mathematical analysis of the optical signal transforming. The real-time experimental results corresponded with computer simulations are presented.
This paper introduced one method of physics education in universities and colleges to make use of making holograms in classroom. The procedures, we proposed in this paper, are so simple that it is realized easily to make holograms. To construct holography accessible to universities and colleges, cost, safety, simplicity, scientific content, and usefulness are primary requirements.
A method of changing in size of a three-dimensional (3D) image using a Fourier transform hologram (FTH) or a periodic FTH is described. Here, the periodic FTH is made for information reduction in hologram by superimposing a number of identical FTHs. The second hologram for reconstruction of magnified 3D images is reproduced by connecting a number of small holograms clipped from the original FTH or from the periodic FTH. Numerical calculations and experiments using the computer-generated hologram (CGH) have show that numbers of rays of light illuminated from the second hologram produce a magnified similar 3D image. Distortion of the image owing to the magnification can be avoided by reconstructing the image from a number of small holograms. Resolution, which depends on the magnifying power of the image and on the size of small holograms, is estimated by the numerical calculation.
A new method of information reduction in hologram is described. Loss of resolution due to the information reduction is improved by superimposing spatial frequency bands of a Fourier transform hologram. Superposition of a number of identical Fourier transform holograms, which deviate each other with a small distance, forms a continuous periodic Fourier transform hologram. The second hologram for the reconstruction of an image is reproduced by repetition of a small area of the continuous periodic Fourier transform hologram. Experiments have been carried out to examine the reconstruction of 3-D images by using computer-generated holograms (CGHs). Results of the experiments show that a high-resolution image is reconstructed from the second hologram produced by superimposing spatial frequency bands. The information reduction effects on the imaging, so that the reconstructed image is spatially sampled with a constant pitch.
The diffraction efficiency was analyzed in reflection type Hologram by use of Kogelnik's two coupled wave theory. The relationship among the diffraction efficiency, objective and reference light angles was investigated in consideration of the influence of the surrounding medium of hologram. As the result, it turns out that the surrounding medium and reference light angle have an effect on the diffraction efficiency. For example, we prepare the hologram sample that attached to glass substrate. Reference light is incident toward hologram through glass. Although the diffraction efficiency of hologram (n= 1.63) with 8 micron thickness is less than 40% on the reference light incident condition from perpendicular direction, the diffraction efficiency become more than 80% on the reference light incident condition from glass edge. This means that we can realize hologram having high diffraction efficiency even if the hologram film is thin. This suggests that edge illumination is effective in using reflective hologram and have merit on manufacturing process, even if the hologram film is thin.
To meet the requirements of DWDM spectral filters at 1550nm, we suggest a new design for holographic Bragg gratings in photopolymers. The design is based on an edge-illuminated hologram configuration. Using this configuration, it is not difficult to make a very long grating and to apply apodization to the grating profile. A larger range of filter functions can be realized by cascading several gratings with different properties or by combining the gratings with other planar optical elements. Here, we show both simulated and experimental results using this arrangement. Rouard's method is used to examine the properties of apodized grating, and the results indicate the potential for narrow spectral bandwidths and high side lobe suppression. Experimental results with two types of photopolymer, Aprillis ULSH-500-7A and Phenanthrenequinone-doped PMMA, provide evidence of the effectiveness of this arrangement.
I reflect on the various paths that led to holography, along with various other paths that could have led to holography. Also discussed is how holography, while maintaining a central core, exemplified by display holography, has expanded in scope and has diffused into vast areas of modern technology; in the process, the boundaries between holography and non holography have been blurred.
Holography records not a 3D image but an encrypted wavefront. To determine what object must have caused that wavefront, we must solve the inverse problem. Most of the time, inverse problems are singular, but in certain very simple cases they are not and an optical computer does that very well. In others, it is disastrous. So, optical computing has been part of holography from its beginning in 1947. It was not until 1962 with VanderLugt's work on Fourier Optical pattern recognitiion that holography became part of optical computing. In this paper, I review both directions of that continuing intercourse between hologrpahy and optical computing. Neither requires the other, and both are sometimes best without the other. But there remain a few cases where the fit seems ideal. The processing and recording and modification of spectral-temporal patterns is the test case I will use to illustrate their constructive relationships. Here are some examples: Spectral recognition is best done in the optical domain by holography. Temporal pulse shaping is best done in the optical domain by holography. Temporal pulses are best recorded by holography.
Our interest in this paper is the future of the holography industry. As a commercial entity, that industry has a 20-year history and has consistently grown. But the past year has seen that growth falter for the first time. There are several factors influencing this
slowdown in growth, some of them external. But the industry is at a crossroads and it can continue along its established path, which is unlikely to see growth return to past levels; or it can look for new challenges, new products and new markets, seeking a return to
major growth in new directions. We recognise that most of the participants in Practical Holography may perceive themselves to be distant from the hologram industry, or protected from its fortunes. Many of those here are researchers in academe, or specialist research organisations; others are from the research labs of large companies, for which holography is only a small part of a large business; some of you are artists or independent holographers. But no-one in the
holography community is isolated -- it is a community, and like any community its members are interdependent or co-dependent. So what happens in the industry is likely to affect, directly or indirectly, many of you here.
This paper discusses large-scale but gradual changes in the subject of holography that have only recently become readily observable. Presenting an analysis of publications in holography over the past half century, the paper illustrates and discusses the evolving shape of the subject. Over 40,000 international information sources have been recorded, including some 20,000 papers, 10,000 books, nearly as many of these and at least 500 exhibitions. This statistical and sociological approach is combined with the identification of specific factors - notably the role of individuals, conferences, proof-of-concept demonstrations and exhibitions - to suggest that the development of holography has been unusually contingent on a variety of intellectual and social influences. The paper situates these observations about holography and holographers in the context of a wider discussion about the styles, purposes and difficulties of historical writing on technological subjects. It further suggests that this ongoing process of both recording and reconstructing technological history can be aided by identification of sources sometimes overlooked or undervalued by practitioners: unpublished archival materials such as private file collections; business records; or undervalued by practitioners: unpublished archival material such as private file collections; business records; accounts of unsuccessful activities; and, by no means least, anecdotal accounts inter-linked between participants.