A method for fabrication of a microlens raster with full filling on photographic plates PFG-01 is proposed. A twodimensional
holographic crossed grating (TDHG) with improved imaging properties is used as an image multiplying
optical element. In order to create the improved TDHG, we have proposed a special technique for photographic emulsion
layer treatment. The light intensity distribution from the display image was projected onto a light-sensitive material using
the TDHG. After the development of the photographic plates, either hardening bleaching or short-wave ultra-violet
illumination is used for relief creation.
Holographic fabrication methods of regular and nonregular relief-phase structures on silver-halide photographic
emulsions are considered. Methods of gelatin photodestruction under short-wave ultra-violet radiation and chemical
hardening with the help of dichromated solutions were used as a technique for surface relief formation. The developed
techniques permitted us to study specimens of holographic diffusers and microlens rasters with small absorption and high
light efficiency.
The results of the synthesis and investigation of two special kinds of thick-layered self-developing glycerol- containing dichromated gelatin are presented. One type was sensitive to blue light while the other type with methylene blue additions was red-sensitive. The thickness of the layers varied from 0.1 to 2 mm. The holographic characteristics are discussed. The method for 3D data storage by means of multiplexing 3D speckle-shift holograms when using counterpropagating beam hologram recording is presented. The method permits hologram multiplexing by shifting a speckle wave by the value equal to its correlation radius. The number of multiplexed holograms and lifetime of holograms are discussed.
A new method of 3-D image projection is considered. The recording of the image includes two steps and is performed with the help of conventional photographic methods. At the first stage of the recording the set of aspects of a 3-D scene is registered. At the second stage the set of aspects is transformed into a set of so-called subaspects. At the stage of projection the subaspects are transilluminated by a laser beam that is focused in spot. The beam scans the screen and as a result the matrix of luminous spots is formed. It is shown that when viewing such a matrix, the spectator sees on the screen a two-dimensional image of the scene. When the point of observation is changed, the configuration of the image represented on the screen is changed, too, simulating the changes of the aspects of the scene which take place when viewing a real 3-D object. As a result, the spectator has got the illusion of the 3-D character of the projected image. It is mentioned that the process of scanning the screen by the set of aspects focused in spots is equivalent to simultaneous scanning of the screen by a set of independent thin beams of light, a special 'own' aspect being projected on the screen by each beam of light. The version of the display that reproduces the horizontal parallax only is considered. It is shown that the viewing zone should be stretched in this case in the vertical direction with a help of a one-dimensional diffusing screen. The case when the scanning beam is controlled by a conventional TV signal is analyzed. It is shown that the display is compatible with existing TV systems. An experiment on modeling the display that reproduces the horizontal parallaxes of a 3-D scene only was carried out. A photograph of a speckle pattern which was formed by a diffusing luminous line was used as a one-dimensional diffusing screen. Some data on the chemical treatment of this photograph are presented. The experiment has shown that while stretching the viewing zone in the vertical direction, such a screen practically does not impair the quality of the image of the aspect projected through the screen. The experiment has also confirmed the possibility of the complete elimination of the speckle structure of the projected image by giving small circular movements to the screen.
KEYWORDS: Holograms, Speckle, Multiplexing, Holography, 3D image reconstruction, Data storage, Wavefronts, Photosensitive materials, Modulation, Signal to noise ratio
THe hologram multiplexing method for the 3D data storage with speckle reference wave is considered. It permits to multiplex holograms by shifting of the speckle wave on the value equal to the its correlation radius. The limit of the number of information units presented by this type of holographics storage exceeds the same value for the spectral or angular multiplexed holograms. However, the system noises reduce it to the regular value. Two different experimental set-ups were tested for the holograms recording: with incident beams and with included beams. It occurred that the number of information units that can be stored in unit volume is larger in the case when both beams possess speckle structures, however the signal-to-noise ratio is also larger in this case, so the spatial modulation of the object beam does not improve the information capacity. Holograms recording was carried out using volume photosensitive medium: newly developed self processing dichromated gelatin of 0.5 mm thickness, and it was compared with the recording in DuPont photopolymer of 100 micron thickness and Fe:LiNbO3 crystal of 2 mm thickness. The method seems to be very suitable for the laser-disk-memory devices.
The thick layered dichromated gelatin synthesis is described and the properties of this light-sensitive material are considered. The schemes of axial speckle-shift hologram and axial 1D hologram are presented. The result of the experiments on recording these types of holograms are discussed. The experiments have confirmed the possibility of multiplexing speckle-shift holograms by shifting the light- sensitive material on the distance equal to the size of the speckle of the reference wave. The experiment has shown that in the case when speckle-shift holograms are multiplexed in a thick-layered gelatin their lifetime decreases as the number of holograms increases. In the case of multiplexing of 1D holograms this decrease of the lifetime is not so pronounced.
KEYWORDS: 3D image processing, 3D displays, 3D image reconstruction, Image acquisition, Holography, Photography, Image processing, Transparency, 3D modeling, Mirrors
A new method of 3D image formation is proposed. A 3D image is generated in this case by a matrix of aspects of a 3D scene that are focused in spots. The matrix is formed by a laser scanning beam in which the aspects of the scene are introduced in consecutive order. As a result the observer sees on the screen a 2D image whose configuration changes depending on the position of the eye in such a way as if the observer examines the real 3D object. The optical scheme of AFS Display (Aspect-Focused-in-Spot Display) is presented and the mechanism of 3D image formation is considered. The results of the experiment on modeling a 3D image which is formed by a scanning spot of light that projects the aspects of the scene are given. The experiment has been carried out as applied to the case of projection of a 3D image that reproduces the horizontal parallax only. It is pointed out that the display considered is compatible with existing TV system. It is supposed that it can be used as a 3D computer display, for 3D imaging in educating, medicine, flight and car training and so on.
Thick-layered self-developed glycerol-added dichromated gelatin has been suggested for the recording of volume holograms. The thickness of the layers varied from 0.4 to 0.6 mm. The diffraction efficiency is equal to 30% at the exposure about 5 J/cm2.
A new method of 3D image recording, so-called reference-free selectogram is considered. According to this method, the object wave is split into two parts with the help of a diffraction grating. The pattern originated from the interference of these components must be recorded in a thick-layered light-sensitive material that is positioned just behind the grating. Gel-like thick-layered dichromated gelatin has been suggested for the selectogram recording. In this case, the layer represents a gel of dichromated gelatin that is sealed between two glasses. The thickness of layers varied from 1 to 3 mm. Holograms are recorded in such a material immediately during the process of exposure. The experimental data on the dependence of the diffraction efficiency on the exposure and the data on the dependence of the diffraction efficiency on the spatial frequency of the recorded grating are presented. The angular selectivity of the holograms recorded in the layers was about 10'. The experiments have shown that the lifetime of the hologram recorded in gel-like gelatin is measured by several hours. The experiments on the recording of the reference-free selectogram were carried out. To compensate the low value of the sensitivity of the material, the selectograms were recorded when concentrating the light on a small area of the layer during the exposure.
Results of experiments on synthesis of a thick-layered light-sensitive material on the base of gel-like dichromated gelatin are presented. In these experiments, the coated layer of liquid dichromated was not subjected to drying but it was sealed between two glasses in order to be protected from drying. The recording was performed on moisture-saturated layers after the liquid was transformed into gel. The thickness of the layer varied from 1 to 3 mm. The maximum efficiency of transmission holograms recorded in the layer reached 17%. The sensitivity to the blue light ((lambda) equals 0.44 micrometers ) was about 10 J/cm2.
A special type of 3D holographic imaging is considered. In this case object wave that is filtered by a horizontal slit is split into two identical components with the help of a diffraction grating that is positioned just ahead of a thick-layered light-sensitive material. It is shown that the 3D pattern formed as a result of the recording of the interference of the mentioned components of the object wave reveals the property of reconstructing the 3D image of the object when being illuminated by the light scattered by a diffusing screen. Such a type of the recording is referred to as reference-free selectogram. The results of the experiments on the reference-free selectogram recording are presented. Two types of thick-layered light-sensitive materials were used in the experiments: reoxan and dichromated gelatin. The material reoxan presents a polymer matrix (1 mm thick) in which an anthracene compound sensitizer and oxygen are dissolved. The dichromated gelatin presents a jelly that has been sealed between two glasses. The thickness of the light-sensitive layer varies from 1 mm to 3 mm in this case.
The results on the experiments on recording reference-free selectograms that reconstruct 3D images of objects are given. The selectograms were recorded by splitting the radiation of the object into two identical components with the help of diffraction gratings placed in front of a light-sensitive layer. The recording was performed on thin-layered inclined light-sensitive plates by using the method of pseudodeep holograms. The possibilities of recording reference- free selectograms of such a kind by a coherent radiation as well as by the radiation with a restricted spatial coherence were studied. In the case for which the selectogram was recorded by a coherent radiation, the radiation scattered by the object was split into two components by a diffraction grating placed in front of an inclined light-sensitive plate. The selectograms recorded in such a way reconstructed the volume images of objects whose resolution was sufficient for visual perception. For recording in an incoherent radiation an interferometer was suggested that was composed of two diffraction gratings which shifts the plane of the zero path difference of interfering beams into the center of the inclined photographic plate. The restriction of the coherence of the beam illuminating the object was performed by moving a diffusor that was used for illuminating the object-transparency. The selectogram recorded in such a way reconstructed the image being in a form of a luminous horizontal stripe corresponding to one of the horizontal cross-sections of the object being recorded. The experiment on the multiple recording of selectograms on one photographic plate at the successive displacement of the interferometer along the optical axis of the system has been carried out. In this case, the reconstructed image represented a system of horizontal luminous stripes each of them representing one of the lines of the image of the recorded object.
Some properties of a pseudodeep hologram are considered as applied to the problems of optical computing. It is shown that the diffraction efficiency of this type of hologram can be increased by means of increasing the inclination factor of rays that intersect the light-sensitive layer. The results of the experiments are presented.
Selectogram characteristics are analyzed. The term selectogram stands for the structure obtained by recording the interference pattern of the radiation of an object and that of an extended reference source of light on an inclined photographic plate. Unlike a hologram, the selectogram reproduces 3-D images of objects by selecting definite components out of the radiation of an extended source whose phase distribution is not correlated with that of the reference source used at the recording stage. A case for which the image of the object being recorded is focused near the surface of the selectogram is described. It is shown that in this case, the angular size of an element determining the resolving power of the image reconstructed by the selectogram is equal to the double-angular width of a horizontal slit that filters the radiation of the object. The general structure of the radiation reconstructed by the selectogram is considered. It is shown that apart from the main image being observed through an output filtering slit, the selectogram reconstructs the multiplicity of distorted images of the object, which can be observed through horizontal stripes parallel to the filtering slit. It is pointed out that the total diffraction efficiency of all images reconstructed by the selectogram does not differ from that of a hologram. At the same time, the diffraction efficiency of the main image being observed through the output filtering slit is essentially decreased because of the presence of additional images. Ways to increase the diffraction efficiency of the selectogram are studied. Experimental data that prove these regularities are presented. Possible development of this method is discussed.
The analysis of selectogram characteristics is carried out. The term selectogram stands for the structure obtained by recording the interference pattern of the radiation of an object and that of an extended reference source of light on an inclined photographic plate. The current presentation describes a case for which the image of the object being recorded is focused near the surface of the selectogram. It is shown that in this case the angular size of an element determining the resolving power of the image reconstructed by the selectogram is approximately equal to the angular width of a horizontal slit which filters the radiation of the object. The general structure of the radiation reconstructed by the selectogram is also considered.
A number of points concerning display holography and a method of so-called pseudo-deep holograms are reviewed. The possibility of using the angular selectivity property of pseudo-deep holograms for 3-D image formation is investigated. The optical system characterized by the presence of an inclined hologram and a horizontal slit that filters the beams from an object and those from an extended reference source is considered. It is shown that the hologram recorded with the help of such a system is capable of reconstructing 3-D images while illuminated by an extended light source characterized by a distribution of phases different from those of the reference source. This record is referred to as a selectogram. The resolution of the image reconstructed by the selectogram is analyzed. The results of the recording and reconstruction of selectograms of a special 3-D arbitrary diffuse object are considered. It is noted that it is possible to record a selectogram using the radiation scattered by the object as the reference wave.
The possibility of using the angular selectivity property of a pseudo-deep hologram for a 3-D image formation is investigated. The optical system characterized by the presence of an inclined hologram and a horizontal slit which filters the beams of an object and that of an extended reference source is considered. It is shown that the hologram recorded with the help of such a system is capable of reconstructing 3-D images while being illuminated by an extended source of light which is characterized by a distribution of phases different from that of the reference source. The above-mentioned record is referred to as a selectogram.
The properties of a pseudodeep hologram are studied. This new term refers here to an inclined thin hologram on which a one-dimensional line object is recorded by a sagittal system of beams. In this case the reconstructed image is read out only within the line corresponding to the object. It is shown that, similar to a deep 3-D hologram, the pseudodeep hologram has high angular and spectral selectivity. A simple graphic method for the construction of the images restored by the pseudodeep hologram is presented. A reference-free hologram has been recorded with the help of such a system. When reading out such a hologram for a part of the object recorded on it, the associative image of the object as a whole was reconstructed. The possibilities of using the pseudodeep hologram for performing different operations are considered, including heteroassociative readout of information by the keys associated with it, recognition of pages of information when illuminating the hologram by the objective wave, and multiple recording of information in the same region of the photographic material. In conclusion, the associative memory scheme in which the information pages are recorded on separate stripes of the pseudodeep hologram with the use of different reference sources as the keys associated with these pages has been considered. The retrieval of the pages is performed by illuminating the entire surface of the hologram with one of the reference sources.
A pseudodeep hologram is a thin, inclined hologram on which a one-dimensional line object is recorded by a sagittal beam system; at reconstruction, the object is read within the limits of the narrow line which corresponds to it. High angular and spectral selectivities have been obtained by these means. Attention is presently given to the possibility of recording and associative reading, in view of results from experiments in which the associative reading of a pseudodeep hologram was performed on the bases of fragments of the object in question by a simple graphic-reconstruction method. Components of images caused by the recording medium's nonlinearities are noted.
One of the main directions in the development ot present-day
systems Of information processing is the creation of neural net-
works. In holography neural networks are amply long known: as
early as in 1963 P.I.Van Heerden showed that the coupling by means
of 3-D gratings which are recorded in a deep 3-D hologram is purely
unambiguous In particular, the grating recorded in the hologram
by the radiation of two arbitrary points interacts only
with the radiation of its 'own' points and ignores that of all
other ones during the reconstruction. But most unfortunately, a
deep 3-D hologram is not a convenient element when used in practice. In particular, in this case it is very difficult to choose
a suitable light-sensitive material and to control each separate
grating among a great number of similar gratings which are superimposed
in the hologram volume.
The report is devoted to the consideration of so-called
pseududeep holograms the properties of which are similar to those
of 3-D deep holograms, and which are free of the above-mentioned
dxbacks.
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