Hologram Image Research Articles

ホログラフィー電子顕微鏡(超と匠の世界)

PURPOSE:To obtain a contour map of a sample under observation instantly by calculating for display on a CRT the output of a television camera picking up a hologram image and the output of a linear stripe image generator capable of optionally selecting the direction and distance of a linear stripe pattern. CONSTITUTION:The output signal S2 from a television camera 9 is compared with a certain threshold value by means of a threshold value discriminator 12 to output a binary-coded signal S2 of ''1'' when it is larger and ''0'' when it is smaller. A hologram image signal S1 picked up by the first television camera 8 through the window of an electron microscope body 1 and the signal S2 picked up by the television camera 9 and binary-coded enter a switching circuit 13 in synchronism. A synchronizing signal generator 14 feeds a synchronizing signal S0 to the television cameras 8, 9, threshold value discriminator 12 and switching circuit 13 for synchronization. The switching circuit 13 passes the hologram image signal S1 as it is to a monitor 15 when S0=1, and modulates the corresponding hologram image signal S1 to zero and sends it to the monitor 15 when S0=0 and the dark portion of the basic stripe becomes smaller than the threshold value.

Investigation of synthesis peculiarities inherent to computer-generated rainbow holograms of 3D images

Investigation of synthesis peculiarities inherent to computer-generated rainbow holograms of 3D images

Multidimensional Holography by Persistent Spectral Hole Burning

Persistent spectral hole burning (PSHB) in organic molecules doped in a polymer matrix at low temperatures allows optical recording of information in the dimensions of frequency and time, as well as in space and externally applied electric field. We use this special property to demonstrate new types of holograms, which extend conventional spatial-domain optical data storage into the new dimensions. Basic aspects of recording and playback of holograms by persistent spectral hole burning, including relation between frequency- and time-domain response function, is discussed. This paper is elucidating inherent relations between the time- and frequency-domain versions of PSHB holography. We show that by multiplexing holograms in the frequency dimension, we can store a large number (up to 12 000) of image holograms using a single spectral hole burning sample. In the time domain, we show storage and reproduction of ultrashort time-space images on the scale of 10-12−10-13 s. Experiments demonstrating unusual hologram properties, such as causality-related asymmetry of diffraction, inversion of time coordinate, and ultrafast processing, are presented.

陰影付けした表面モデル３次元物体の全方向視差計算機合成ホログラム

A method has been developed for synthesizing full-parallax binary-amplitude holograms that can shade three-dimensional objects expressed in a surface model. The brightness of plane surfaces formed with point sources of light is modeled based on radiometry. A procedure is used to compensate for the change in brightness as the direction of observation changes. A masking technique is used to modify the brightness of the plane surfaces and to shade reconstructed images of binary holograms. Optically reconstructed three-dimensional images of objects with shading were demonstrated using this method.

計算機合成ディスプレイホログラム用高解像度プリンタ

A special-purpose high-resolution printer has been constructed for fabricating computer-generated holograms. This printer is capable of drawing fringe patterns exceeding 104 dpi in resolution. The patterns are numerically synthesized and have a continuous gray level. The print time is less than an hour for holograms measuring 1 cm2. The mechanism and structure of the constructed printer and optically reconstructed images of holograms fabricated by using the printer are described.

Single femtosecond exposure recording of an image hologram by spectral hole burning in an unstable tautomer of a phthalocyanine derivative

We demonstrate, for what we believe is the first time, recording of a femtosecond image hologram by illumination with a single pair of high-intensity femtosecond pulses in a broad inhomogeneous bandwidth spectral hole-burning material consisting of a polymer film doped with anthraceno-phthalocyanine dye molecules. High efficiency of spectral hole burning is achieved by preillumination of the sample at a low temperature to convert the dye molecules into an unstable tautomer form.

Computer-generated holograms of images reconstructed on curved surfaces

When one illuminates a computer-generated hologram by a plane wave, the obtained two-dimensional image is usually displayed on a planar plane. Other possibilities for reconstructing images on arbitrary curved surfaces are discussed herein. As an example, the reconstruction of an image on a virtual spherical surface is demonstrated.

Diffraction efficiency and signal-to-noise ratio of diffuse-object holograms in real time in polyvinyl alcohol photopolymers

We studied the influence of the beam ratio and intensity on the optical quality of the transmission hologram images of diffuse objects stored in a photopolymer and reconstructed in real time. The signal-to-noise ratio and the diffraction efficiency were used as measures of the optical quality. We obtained a signal-to-noise ratio of 0.94 with a diffraction efficiency of 13% for a beam ratio of 20 and an intensity of 1.2 mW/cm2.

Interpolation Method for Computer-Generated Holograms Using Random Phase Technique

An interpolation method for reconstructed images of computer-generated holograms (CGHs) enables one to synthesize CGHs with a large space bandwidth product (SBWP) from CGHs with a small SBWP. The phase information of objects is regarded as constant because the method is based on digital image processing techniques. Therefore, diffraction efficiency is low due to the saturation effect in the recording process. To improve the diffraction efficiency, a random phase technique is employed for the interpolation method to the CGH. Effects of the random phase in the reconstructed image are discussed in several interpolation types. The interpolation method is also applied to a kinoform. Some computer simulations and optical experiments are presented.

Effect of the sensitizer on the properties of fully functionalized photorefractive epoxy polymers and their performance in the hologram image storage

The 3-amino-9-ethyl carbazole (AEC)/Dispersed Orange 3 (DO3)/diglycidyl 1,2 cyclohexanedicarboxylate (DCD) main chain copolymers are synthesized and studied on their photorefractive (PR), photoconductive, and holographic characteristics. They are good hologram recording media because not only the stored hologram exhibits excellent fringe contrast with the resolution at about 20 μm, but also the image can be stored, erased, and overwritten. The UV/Vis spectra shows that AEC segments may form charge transfer complexes with either DO3 segments or TNF sensitizers. By incorporating the sensitizer or increasing the charge transfer component concentration, the grating growth rate can be speeded up. Applying an electric field on the polymer film containing no sensitizer helps to elevate the grating growth speed, but it shows little influence on the grating growth speed of the films with sensitizers. More nonlinear optical (NLO) segments in the copolymer result in higher diffraction efficiency. The dark decay of the film depends on the dark conductivity. Incorporating sensitizers or more charge transport segments leads to more dark decay because of increasing dark conductivity. The dark decay of the PR properties at elevated temperature can also be evaluated by the thermal stimulated discharge current (TSDC) spectroscopy technique. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1057–1068, 1999

Effect of the sensitizer on the properties of fully functionalized photorefractive epoxy polymers and their performance in the hologram image storage

The 3-amino-9-ethyl carbazole (AEC)/Dispersed Orange 3 (DO3)/diglycidyl 1,2 cyclohexanedicarboxylate (DCD) main chain copolymers are synthesized and studied on their photorefractive (PR), photoconductive, and holographic characteristics. They are good hologram recording media because not only the stored hologram exhibits excellent fringe contrast with the resolution at about 20 μm, but also the image can be stored, erased, and overwritten. The UV/Vis spectra shows that AEC segments may form charge transfer complexes with either DO3 segments or TNF sensitizers. By incorporating the sensitizer or increasing the charge transfer component concentration, the grating growth rate can be speeded up. Applying an electric field on the polymer film containing no sensitizer helps to elevate the grating growth speed, but it shows little influence on the grating growth speed of the films with sensitizers. More nonlinear optical (NLO) segments in the copolymer result in higher diffraction efficiency. The dark decay of the film depends on the dark conductivity. Incorporating sensitizers or more charge transport segments leads to more dark decay because of increasing dark conductivity. The dark decay of the PR properties at elevated temperature can also be evaluated by the thermal stimulated discharge current (TSDC) spectroscopy technique. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1057–1068, 1999

Obstruction effect in reconstruction of synthetic near field holograms

An important cue for the depth perception is the hidden surface effect (obstruction). We discuss two methods which allow the hidden surface effect to be implemented in synthetic image holograms. Both methods make it possible to produce image holograms which provide simultaneously the most important depth cues: binocular vision, parallax effect, accommodation and hidden surface effect. Optical reconstructions obtained with each one of the methods are shown.

Holographic Grating Formed by Photochemical Phase Transition of Polymer Azobenzene Liquid Crystal

ABSTRACTWe explored the formation of holographic gratings by means of a polymer azobenzene liquid crystal (PALC). When two writing beams (argon-ion laser, 488 nm, unpolarized) were interfered on the surface of the PALC film (thickness, 500 ∼ 600 nm), multiple diffraction beams were observed immediately, resulting from grating formation. Such generation of the diffraction beams was assumed to be due to a periodic induction of photochemical phase transition in the bright fringes of the interference pattern. The grating is namely made up of a periodic arrangement of nematic (N, dark fringes) and isotropic (I, bright fringes) phases. Observation of recorded interference patterns under a cross-polarized optical microscope supported our speculation for the structure of the grating. On the basis of these results, we succeeded in recording an image hologram of a photomask as an object.

Binary computer-generated holograms for security applications from a synthetic double-exposure method by electron-beam lithography

We have developed a new multiplexing method for producing binary computer-generated holograms (CGH's) for security applications. This method is based on double recording of two types of coding method upon binary CGH's. The CGH synthesized by the proposed method can have multiple image planes from the region close to the hologram (image region) to infinity (Fraunhofer region) without severe degradation of reconstructed images in the image region. A CGH containing simultaneous image- and Fourier-type holograms is fabricated by electron-beam lithography. Some experimental results are presented.

Image Processing Technique for the Reproduction of Deep 3-D Images By Holoprinter

A holographic 3-D printer (holoprinter) is being developed for the hardcopy output of 3-D image processing systems. In this paper, an image processing technique is proposed for the reproduction of deep 3-D images by the holoprinter. The sampling scheme of parallax information in the one-step and two-step holographic stereograms are compared, and it is shown that the image near the hologram plane has good parallax information in the one-step holographic stereogram, but the image far from the hologram plane is blurred. To suppress the image blur in the far image, a method to produce the image equivalent to two-step recording is developed. By this method, the image far from the hologram plane is displayed as a stereoscopic image hologram, resulting in the suppression of blur. But the image near the hologram plane is reproduced with fine sampling, and natural 3-D image can be displayed. Experimental results show the effectiveness of the proposed method.

Image holography in CdF 2:Ga crystals

The recording of an image hologram in CdF 2:Ga crystals at room temperature is reported. Writing the phase holographic pattern utilizes a unique property of Ga and In doped CdF 2 crystals, namely, the bistability of these dopants. In contrast to CdF 2:In crystals, in which there is only one bistable center, the holographic experiment reveals two different bistable centers in CdF 2:Ga. Room temperature bistability is related to Ga, while the low temperature center resembles very much the properties of In, likely a non-intentional In dopant of the CdF 2:Ga crystals. The holographic sensitivity of doped CdF 2 crystals compares favorably with sensitivity of standard photorefractive materials. The main advantage for some applications of using the novel mechanism is the inherently local nature of the light-induced refractive index changes.

Holographically corrected microscope with a large working distance: errata

We present a design for a microscope with a simple objective lens with a high numerical aperture. The large amounts of aberrations present in the system are removed when a point-source image hologram is recorded. The resultant instrument has a large working distance (>0.17 m) and a moderate field of view over a limited bandwidth. We demonstrate the application of this device to imaging submicrometer details inside a vacuum.

A high resolution, holographically corrected microscope with a Fresnel lens objective at large working distances

We present details of a microscope which incorporates an inexpensive, high numerical aperture Fresnel lens objective. The system aberrations are corrected by the use of an image hologram of the lens recorded using a point source of coherent illumination. This device gives high resolution, real time imaging while maintaining a large working distance. The same microscope can be used for micromachining and photolithography in situations where close proximity to the sample is impossible or undesirable.

Nondestructive Read-out of Two-color Photon-gated Spectral Holeburning Holograms

We recorded picosecond photochemically accumulated stimulated photon echo (PASPE) holograms by using two-color photon-gated persistent spectral hole- burning at liquid-helium temperature. Images stored using this technique have more than three orders of magnitude higher read-out stability compared with the one-color process. We used Zn-tetra-phenyl-tetrabenzoporphyrin in a polystyrene film with 20% hexachloroethan (C2Cl6) as recording material. The long lifetime of the triplet state allows the observation of a transient image prior to the fixation of the image. By restricting the green gating beam to a part of the transient hologram image on the polymer film, the photoreaction takes place only in the area illuminated with both colors, and this part of the image is stored permanently.

Holographically corrected microscope with a large working distance

We present a design for a microscope with a simple objective lens with a high numerical aperture. The large amounts of aberrations present in the system are removed when a point-source image hologram isrecorded. The resultant instrument has a large working distance(>0.17 m) and a moderate field of view over a limited bandwidth. We demonstrate the application of this device to imaging submicrometer details inside a vacuum.