Nina M. Ganzherli

Pseudodeep holograms: their properties and applications

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.

Three-dimensional image projection with aspect-focused-in-spots display

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.

Three-dimensional imaging of objects focused on a selectogram surface

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.

On the possibility of the recording and reconstruction of three-dimensional images when using an extended reference source and a pseudo-deep hologram

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.

Pseudodeep hologram and its properties

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 mediums nonlinearities are noted.

Phase recording for formation of holographic optical elements on silver-halide photographic emulsions

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.

Recording of deep three-dimensional holograms in gel-like layers of dichromated gelatin

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.

Thick-layered red- and blue-sensitive dichromated gelatin for hologram multiplexing

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.

Thick-layered gelatin for volume hologram recording

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.

3D imaging by means of a reference-free selectogram recorded in a thick-layered light-sensitive material

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.