Hologram Image Research Articles

Computer-generated three-dimensional image holograms

A synthetic generation of three-dimensional image holograms is suggested. The complex amplitude in the hologram is calculated by using the spectrum of plane waves. Specifically, three-dimensional images are composed of planar and inclined two-dimensional distributions. In display applications, large hologram apertures can be achieved by introducing a remote exit pupil. A synthetic three-dimensional image is optically reconstructed.

Electron holograms for subångström point resolution

Using the Möllenstedt-type electron biprism [Möllenstedt and Düker, Z. Phys. 145 (1956) 377] in a Philips EM 420/ST with field emission gun we succeed in taking image holograms with a fringe spacing of 0.032 nm. This is the finest fringe spacing hitherto reported allowing the transfer of periods smaller than 0.1 nm by means of electron holography hence giving a point resolution below 0.1 nm after correction of aberration.

Magnification effect and color blur behavior in holography

This paper describes the spatial behavior of the hologram image as a function of the geometric setup used in the recording and reconstruction steps. Given the equation of the holographic image and using paraxial theory and the synthetic division method, values of the longitudinal and lateral magnification are obtained. The location and magnification of the holographic image are found when the distance between the holographic plate and the object is changed. For white light reconstruction and 3-D scenes the effect of color blur can be expressed in terms of the parameters associated with the optical system that forms the image on the hologram and the recording geometry.

Holographic pseudocolor encoding of filtered images

In this work we propose a pseudocolor coding technique which allows the simultaneous observation of pseudocolored images corresponding to different type of spatial frequency structure in a scene. The method is based on recording three image holograms on the same photographic plate using a HeNe laser of a single wavelength. Each image hologram codes one filtered image with a primary color. In the reconstruction step a wide range of pseudocolor images can be observed corresponding to different spatial frequency structures.

Holographic technique for correcting aberrations in a telescope

A holographic technique for correcting aberrations in a telescope objective is presented. An image hologram of the aberrations is used as a correction plate to cancel out all the aberrations of the objective. Experimental results demonstrate diffraction-limited performance of the corrected telescope, as well as practical fields of view and a useful bandwidth ( approximately 100 nm) for an objective with 10lambda aberrations.

Holographic Techniques In The Color Reproduction Of Two-Dimensional Images

Using the rainbow effect, produced by using a white light source in the reconstruction process of an image hologram, it is possible to obtain normal color two-dimensional images. The technique described in this work requires the recording of three holograms on the same plate, using laser light of a single wavelength (He-Ne laser, A = 632.8 nm) with three reference beams, each at a different angle. The color separation technique of Gale and Knop [Appl. Opt. 15(19), 2189-2198 (1976)] was used to obtain three black-and-white transparencies from one color transparency. The holographic image can be observed when the hologram is illuminated with a white light source. The experimental setup and the conditions for obtaining original color objects are discussed.

Astigmatic holographic processor for local pattern recognition

A coherent processor for local correlation is described. This device can be used to unmask local resemblances between object transparencies and a stored matched filter, which would be hidden in global correlation, as that of a classical Vander Lugt filter. This is achieved by means of a holographic filter that is an image hologram in one direction and a lensless Fourier transform hologram in the other. The hologram is registered with a line reference beam in the conjugate plane of a cylindrical lens and is reconstructed by means of a spherocylindrical optical system.

Electro-Optic Holography System For Vibration Analysis And Nondestructive Testing

A TV system has been developed for detecting and displaying a two-dimensional hologram image that permits concomitant (real-time) hologram interferometry. The optics employed are the same as for electronic speckle pattern interferometry (ESPI), wherein a uniform reference field interferes at zero offset angle with a speckled image of an object. Rather than detecting spatial modulation to indicate interference, as in ESPI, this system modulates the phase of the reference beam by 120° between picture frames to vary speckle irradiance. Each incoming frame is compared with the two previous frames, and only pixels that vary in brightness are passed as white pixels in the video output. The use of binary-valued pixels allows inexpensive data processing at standard video rates.

Ultrasonic Intensity and Phase Imaging at 3.6 MHz Using Liquid Crystal Conversion

Absfracf-A new development of the ultrasonic holography technique, using a nematic liquid crystal convertor, is presented, where an image hologram is formed on the convertor with an acoustic lens. It is shown that digital image processing of the fringed pattern, taking a few tens of seconds by an SOSq microcomputer, can provide high-resolution intensity or phase images of various internal material structures, demonstrating applications to nondestructive testing. Highquality intensity images can be made using only an economical analog processing technique if phase images are not required. Imaging delaminations smaller than 1 mm in graphite-epoxy composites is achieved at 3.6 MHz. With this new system a particular form of phase imaging and ultrasonic interferometric holography may become a practical technique.

Optical processing of acoustical holograms in a liquid crystal convertor

Acoustical image holograms have been recorded at 3.6 MHz using a specially designed nematic liquid crystal convertor. These holograms are reconstructed with He-Ne laser light. The figures presented illustrate the practicability of the system, particularly in the field of nondestructive testing.

In-Line Electron Holography in a Stem Instrument

It was suggested earlier that the idea of in-line electron holography, as proposed by Gabor in 1949 could now be implemented by use of a STEM instrument having a cold field emission gun. Reconstruction from holograms by computer methods, in place of the optical techniques suggested by Gabor, was shown to be effective for one-dimensional theoretically derived holograms. We have now applied the method of computerized reconstruction to digitized shadow image holograms recorded in our HB5 STEM instrument which has been modified to facilitate the process.The shadow image is formed on a phosphor screen in the detector plane. The light produced is amplified by means of an electrostatic image intensifier and viewed with a low-light-level TV camera. The output is digitized and stored by use of a TV-rate frame store and a PDP11/34 computer.

White-light Fourier holography

This paper describes a technique for generating broad spectral band Fourier holograms with an encoded white light source. Since this technique utilizes primary white-light construction and reconstruction process, it is quite suitable for color Fourier hologram image reconstruction. Experimental results are also given.

Waveguide holograms in thin dichromated gelatin films

Thin dichromated gelatin films were used to record waveguide holograms directly inside the film. Information was stored and retrieved by light of the same wavelength. The waveguides were characterized by optical attenuation < 1 dB/cm and this value was retained after the film sensitization, exposure, and development cycle, so that holograms could be recorded. Sinusoidal gratings were formed and these were used to couple radiation into thin-film waveguides and also as waveguide Fourier holograms of two-dimensional images. The efficiency of a sinusoidal grating as a coupling component was 60%. A Fourier hologram reconstructed by the waveguide method with a diffraction efficiency of 11% was characterized by a recorded data density of ~ 105 bit/ mm2 over an area of 1 mm2.

Density Pseudocolor Encoding By Holographic Techniques With Three Primary Colors

A new optical method to generate a family of color-coded images using holographic techniques is presented. This method involves the introduction of three primary colors. Thus, this technique overcomes an important limitation of previous holographic techniques. An image hologram of a black-and-white transparency is first registered. This hologram is put in contact with a beam splitter, and the sandwich is illuminated by three partially coherent waves. One wave produces a positive image, a second wave pro-duces an image with reversed contrast, the negative, and the third image corresponds to the product of the positive and the negative. Coding these waves in three primary colors and adding them at the final image plane results in a color-coded image. The principle of the method, theory, and some experimental color results are presented.

Holographic reciprocity law failure

Previous authors have reported a falloff in diffraction efficiency of reconstructed images in multiple-exposure holograms. We call this phenomenon holographic reciprocity law failure. We propose an explanation for this phenomenon based on latent image formation in photographic materials and discuss a method for superimposing holograms that reconstruct images of equal brightness.

27 衝撃波と液滴および液泡の干渉・分裂に関する研究

In the present study, the interaction of liquid droplets and liquid bubbles in a high speed gas flow is re-examined by using a shock tube equipped with a pulsed laser pholographic interferometer. Constructing double exposure image holograms, we have, in the same experiment.both a hologram equivalent to the shadowgraph and its reconstraction, i.e interferogram.By comparing these photographs it is revealed that the shadowgraph can not show the detailed structure of the wake flowbehind the disintegrating droplets and overestimates the droplet diameter.

White-Light Holography With A Slide Projector

A simple technique of producing two-dimensional hologram images with a slide projector is presented. The technique offers considerable flexibility, adaptability, and less stringent requirements for hologram construction as compared with the conventional two-dimensional laser holography. With this technique it may be possible to record three-dimensional objects of limited depth. Simple experimental demonstrations are given. We note that color hologram images can also be produced by this technique. By proper design, high quality hologram images may be obtained by this technique.

Volume‐type multiple hologram memory using PMMA thick films

AbstractPhotosensitive polymers such as PMMA (polymethyl methacrylate) are favorable materials for volume‐type hologram; properties of PMMA thick films not studied as yet, will be described in the present report. the validity of a dynamic coupled‐wave theory (in which a saturation effect is considered) is shown. the maximum hologram memory density of a photosensitive particle model is discussed; a differential scattering cross section 0.33 mm2 and maximum photosensitive particle density 3 × 1011/cm3 are obtained. These figures predict a maximum memory density which is an order of magnitude larger than that of a Kodak 649F plate. With a PMMA film several hundreds μm thick the possibility of 100‐fold multiple hologram recording and image reconstruction is confirmed.

An arrangement of transmitter and receiver arrays for synthesizing acoustical holograms

AbstractA method is discussed for synthesizing acoustic holograms consisting of MN pieces of data with M transmitters and N receivers in an acoustic hologram imaging system. Several methods similar to the approach presented here for reducing the total number of transmitters and receivers are examined. the distinctive feature of the proposed method lies in the arrangement of transmitter and receiver arrays on separate planes. the point‐spread function of the synthesized holographic imaging system is computed and the arrangement of transmitter and receiver arrays is restricted so that the grating lobe providing narrower separation is eliminated. the arrangement obtained is a generalization of the well‐known multibeam method in that the transmitter and receiver surfaces are separated. Hence it is applicable not only to reflection holograms but also to transmission holograms. It is also shown that under these conditions the numerical image reconstructed from a hologram can be realized by a single application of the discrete Fourier transform of the MN data. Finally, the results of experimental and numerical simulations are shown and the validity of the proposed method is confirmed.

Rainbow holographic aberrations and the bandwidth requirements

Rainbow holographic image resolution, primary aberrations, and bandwidth requirements are presented. The results obtained for the rainbow holographic process are rather general, for which the conventional holographic image resolution, aberrations, and bandwidth requirements, can be derived. The conditions for the elimination of the five primary rainbow holographic aberrations are also given. These conditions may be useful for the application of obtaining a high-quality rainbow hologram image. In terms of bandwidth requirements, we have shown that the bandwidth requirement for a rainbow holographic construction is usually several orders lower than that of a conventional holographic process. Therefore, a lower-resolution recording medium can generally be used for most of the rainbow holographic constructions.