Holographic Interference Fringes Research Articles

Rapid flowing cells localization enabled by spatiotemporal manipulation of their holographic patterns.

Lab-on-a-Chip microfluidic devices present an innovative and cost-effective platform in the current trend of miniaturization and simplification of imaging flow cytometry; they are excellent candidates for high-throughput single-cell analysis. In such microfluidic platforms, cell tracking becomes a fundamental tool for investigating biophysical processes, from intracellular dynamics to the characterization of cell motility and migration. However, high-throughput and long-term cell tracking puts a high demand on the consumption of computing resources. Here, we propose a novel strategy to achieve rapid 3D cell localizations along the microfluidic channel. This method is based on the spatiotemporal manipulation of recorded holographic interference fringes, and it allows fast and precise localization of cells without performing complete holographic reconstruction. Conventional holographic tracking is typically based on the phase contrast obtained by decoupling the calculation of optical axial and transverse coordinates. Computing time and resource consumption may increase because all the frames need to be calculated in the Fourier domain. In our proposed method, the 2D transverse positions are directly located by morphological calculation based on the hologram. The complex-amplitude wavefronts are directly reconstructed by spatiotemporal phase shifting to calculate the axial position by the refocusing criterion. Only spatial calculation is considered in the proposed method. We demonstrate that the computational time of transverse tracking is only one-tenth of the conventional method, while the total computational time of the proposed method decreases up to 54% with respect to the conventional approach. The proposed approach can open the route for analyzing flow cytometry in quantitative phase microscopy assays.

Strong-field photoelectron holography beyond the electric dipole approximation: A semiclassical analysis

Strong-field photoelectron holography denotes the interference of various electron paths in laser-induced ionization of atoms, leading to interference patterns in the final momentum distribution. For a quantitative description of holography beyond the electric dipole approximation and in the presence of the Coulomb potential, we develop a semiclassical model in which the initial conditions of outgoing electrons are set according to the beyond-dipole strong-field approximation for the ionization step. The phases associated with trajectories are evaluated following the prescription for semiclassical propagators. The validity of the method is confirmed by comparison to the numerical solution of the time-dependent Schr\"odinger equation in two spatial dimensions. The semiclassical model reproduces correctly the backward and forward shifts of the photoelectron momenta along the laser propagation axis that arise from beyond-dipole dynamics. The position of the central holographic interference fringe can be estimated already from a simplified Coulomb-free interference model that provides closed-form expressions for the beyond-dipole shifts. In three dimensions, Coulomb focusing causes a breakdown of the semiclassical model for final momenta with directions close to the polarization axis. We implement a beyond-dipole regularization procedure based on the concept of glory scattering, which was recently used to describe Coulomb focusing in the dipole approximation. While the position of the central maximum and higher-order fringes can already be obtained approximately by simpler semiclassical modeling, this glory model is able to predict the shape of the distribution in the close vicinity of the central maximum. The violation of the dipole approximation in holography should be observable with mid-infrared fields, for which the forward/backward shifts can be comparable with the fringe spacing.

Semiclassical two-step model for ionization of the hydrogen molecule by a strong laser field

We extend the semiclassical two-step model for strong-field ionization that describes quantum interference and accounts for the Coulomb potential beyond the semiclassical perturbation theory to the hydrogen molecule. In the simplest case of the molecule oriented along the polarization direction of a linearly polarized laser field, we predict significant deviations of the two-dimensional photoelectron momentum distributions and the energy spectra from the case of atomic hydrogen. Specifically, for the hydrogen molecule the electron energy spectrum falls off slower with increasing energy, and the holographic interference fringes are more pronounced than for the hydrogen atom at the same parameters of the laser pulse.

Aberration Corrected Off-Axis Electron Holography of Layered Transition Metal Dichalcogenides

Figure 1 shows representative results acquired at 80 kV using off-axis electron holography from an MoS2 flake. The holographic interference fringe spacing was 30 pm and a mask corresponding to a spatial resolution of 90 pm was applied to the sideband (Fig. 1c) before reconstructing the phase image. Figure 1d shows part of a phase image reconstructed from the hologram, showing a two and three monolayer region of the flake and the presence of some contamination at the specimen edge.

Comparison of approaches and artefacts in the measurement of detector modulation transfer functions

In order to investigate the reproducibility of measurements of transmission electron microscope detector modulation transfer functions (MTFs) we measure the MTF of a charge-coupled device (CCD) camera using five different methods. MTFs derived from a sharp edge, a circular aperture and electron holographic interference fringes are found to agree closely with one other. The difficulty of obtaining accurate measurements of MTFs and the potential of using focused electron probes to make direct measurements of MTFs is discussed. We highlight the sensitivity of image contrast after deconvolution to small differences in the measured MTF.

Optically induced light diffraction in photopolymer of fuchsin basic

In the paper, a holographic storage experiment on laser optically induced light diffraction in acrylamide photopolymer thin film is reported, in which the semiconductor laser of 532nm is used as writing and reading light source, and fuchsin basic is used as sensibilizer. The appearance of diffraction rings can readily be explained as being holographic interference fringes formed by the original laser beam and light scattered from internal or surface inhomogeneities in the unexposed photopolymer. According to phase match condition of degenerate four-wave mixing theory, the diffraction cones of double laser beam holographic writing and single laser beam radiative reading are explained separately. The relationship between angle of incidence and diffraction cone angle is deeply studied by using holographic scattering theory with the help of trigonometric functions.

Studies on the Diffusion Coefficients of Amino Acids in Aqueous Solutions

The diffusion of amino acids in aqueous solution was investigated experimentally by a holographic interferometric technique where the real-time holographic interference fringes indicating the concentration profiles of the liquid were obtained by an automatic photographing and memorizing program. The reliability of the instrument was verified by the measurement of the diffusion coefficient of KCl and sucrose in aqueous solution at 298.15 K. Furthermore, the diffusion coefficients of glycine, l-alanine, l-valine, l-isoleucine, l-serine, l-threonine, and l-arginine in aqueous solution at 298.15 K were measured, and the affecting factors of molecular structure and polarity were analyzed and discussed. In addition, on the basis of the Gordon model of the diffusion coefficient in the literature, a new semiempirical model was proposed to predict the liquid diffusion coefficients of amino acids in aqueous solutions. The equation parameters were fitted by the experimental data of seven amino acids in this work and...

Holographic interferometry for measuring residual stresses by using probing holes

An original method of determining residual stresses by using probing holes and measuring the difference in the holographic interference fringe orders for two sets of pairs of points taken on the principal strain axes is suggested. The optical scheme of the interferometer is based on the use of reflection holograms. The principal residual strains are found by solving an overdetermined set of linear equations. The effect of rigid displacement on the fringe pattern is taken into account. The method is experimentally verified by measuring elastic stresses in uniaxially and biaxially strained specimens.

Application of correlation speckle photography for measuring contact pressures

A method for measuring contact pressures based on the measurement of irreversible changes in a surface microrelief by the speckle photography technique is presented. The analytic dependence between the change in the contrast of the carrying Young’s fringes and the relative area of change in the microrelief is considered. An example of a contact interaction between a cylinder end and a flat slab, the latter with a specially produced regular roughness on its contact surface, is used to experimentally verify the relation between the irreversible change in the roughness, the change in the contrast of the holographic interference fringes, and the change in the contrast of the carrying Young’s fringes. It is shown that the sensitivity of correlation speckle photography is higher than the sensitivity of the correlation holographic interferometry technique.

Computer generated optical holographic fringe patterns for the analysis of vibrating structures

Optical holographic interference fringe patterns on rods and bars vibrating in ultrasonic resonance (standing waves) are predicted by computer simulations. The simulations are based on a combination of finite element calculations with calculations based on the theory of holographic interference fringe generation. The hypothetical fringe patterns are then compared to holographic fringe images obtained by the experiment (time average holograms). The holographic arrangement and the mechanical part of the ultrasonic system (transducer, horn and specimen) were fixed on a commercial rigid optical table supported on air bags to isolate it from ground vibrations. Thus it is shown that the scope of the study can be reached with a minimum of experimental effort, i.e., with basic laser optical equipment. It is shown that provided the system operates in the desired mode, good agreement between the theoretical and the real image is given. Finally examples of the possible influence of defects or of parasitic modes of vibration on the appearance of the fringe patterns are given.

Characterization of JEOL 3000f TEM Equipped for Electron Holography

Abstract Quantitative off-axis electron holography in a transmission electron microscope (TEM) requires careful design of experiment specific to instrumental characteristics. For example, the spatial resolution desired for a particular holography experiment imposes requirements on the spacing of the interference fringes to be recorded. This fringe spacing depends upon the geometric configuration of the TEM/electron biprism system, which is experimentally fixed, but also upon the voltage applied to the biprism wire of the holography unit, which is experimentally adjustable. Hence, knowledge of the holographic interference fringe spacing as a function of applied voltage to the electron biprism is essential to the design of a specific holography experiment. Furthermore, additional instrumental parameters, such as the coherence and virtual size of the electron source, for example, affect the quality of recorded holograms through their effect on the contrast of the holographic fringes.

EPITAXIAL GROWTH OF SrF2 ON Ge(111)-c(2×8) AS STUDIED BY PHOTOELECTRON DIFFRACTION AND HOLOGRAPHY

We have investigated the photoelectron diffraction (PED) from a SrF 2 epitaxial thin film on Ge(111) from the viewpoint of holographic inversion for imaging the atomic structure. The holographic interference fringes were retrieved from the PED pattern including a wide variety of diffraction features via averaging the pattern around each forward-scattering peak. Furthermore, another method for enhancing holographic fringes by subtracting one photoelectron hologram from another at slightly different kinetic energies was theoretically investigated.

Electron Holographic Imaging of Magnetic Materials at Nanometer Scale Resolution

Abstract Traditional electron microscopy techniques for imaging magnetic microstructure include out-of-focus Fresnel or Lorentz imaging, Foucault imaging and differential phase contrast (DPC). Off-axis electron holography provides access to both the amplitude and phase of the electron wave which has passed through the sample and therefore can provide direct, quantitative information about the in-plane component of the magnetic induction. The Philips CM200-FEG microscope which was used for the holography described here is equipped with a powerful mini-lens below the specimen enabling 2nm spatial resolution and only a small residual field at the sample. The combination of high coherence and increased magnification enable quantitative mapping of magnetic induction at the nanometer scale. Electrostatic or magnetic potentials give rise to phase shifts in the holographic interference fringes which can be quantified following reconstruction. In the presence of a magnetic field, the phase equation (for constant composition and neglecting diffraction effects) becomes:

３次元画像情報技術 複素振幅パターンマッチングを用いたホログラフィック３次元情報検出

We worked on a method for extracting three-dimensional information from holographic interference fringe patterns by using an interferometer. So far, we identified the matching method by using the sum of products and the method that used an optical correlation system. In the handling that used the optical correlation system, we made a lot of masks for the depth direction and had to exchage them. In the work described in this paper, we used only one mask as complex amplitude distribution instead of the amplitude distribution, Here we present the method that extracts three-dimensional information by sifting the plane of observation phase information data with the improved optical correlation system.

Holographic Interferometry Principles and Methods

This study provides an up-to-date source of information on a rapidly expanding field. The contributions cover the principles and methods currently in use. The scope of the book has been limited to the study of opaque objects and ample space has been devoted to a comprehensive treatment of the phenomena of fringe formation and a quantitative evaluation of the holographic interference fringe patterns. The emergence of computer-aided fringe analysis and phase-shifting techniques have considerably simplified the quantative real-time measurements of object shapes and deformations. This volume also includes an overview of full-field holographic methods for the measurement of shapes, displacements, derivatives, difference displacements and vibrations.

Automating the analysis of results of a holographic experiment

This article examines an algorithm for the computer analysis of holographic interference fringes of cylindrical shells in a three-hologram, double-exposure experiment conducted to study displacements. The method, based on graphical input of the coordinates of reference points on lines of equal order and approximation of order surfaces on the basis of regression analysis, makes it possible to formalize selection of the type of nonlinear mathematical model and speed up subsequent calculations. The statistical characteristics of the model and the regression process improve with an increase in the number of points. An analysis is made of the accuracy of the analysis of holographic interference fringes by the proposed method using the example of results of tests of a cylindrical shell with a nonplanar end in uniaxial compression. Satisfactory agreement is seen between data obtained by the proposed method and the traditional method.

Residual-stress determination by single-axis holographic interferometry and hole drilling—Part I: Theory

A method is described for the rapid, accurate determination of residual stresses from a holographic interference fringe pattern. The pattern is generated by the displacement field caused by localized relief of residual stresses via the introduction of a small, shallow hole into the surface of a component or test specimen. The theoretical development of the holographic method is summarized. An example is given showing how the method can be applied to a typical experimentally observed fringe pattern to determine principal residual stresses and directions.

特集 次世代画像技術 ２次元受光素子列を用いたホログラフィック３次元情報検出

A method for extracting three-dimensional information from holographic interference fringe patterns by using an interferometer is studied and its effectiveness is confirmed experimentally. The holographic fringe patterns of the object surface, which is assumed to be a set of point sources, are compared with standard patterns calculated assuming that a corresponding point object exists in the measured space. We show theoretically that three-dimensional information can be extracted by three methods : for the sum of products of each pixel, computational correlation using Fourier transformation, and optical correlation. We also simulate extractions of a set of point sources by correlation and optical correlation, and we experimentally confirm the effectiveness of this method applying to actual point-source object and line objects and using interference fringe pattern captured by a CCD camera.

Real-time electroholographic system using liquid crystal television spatial light modulators

Matrix-addressed liquid crystal devices, such as liquid crystal television spatial light modulators (LCTV-SLM5) have a suitability for displaying holograms electrically in real time because of their ability to easily display image patterns by electric signals. In our electroholographic system, a CCD camera reads a holographic interference fringe pattern, i.e., a hologram, which is then transmitted to and subsequently displayed on an LCTV-SLM by video signals. The LCTV-SLM is illuminated with collimated laser light and the image of the electrohologram is reconstructed in real time. Because the carrier frequency of the hologram is very low, a limitation imposed by the relatively low resolution of the CCD camera and the LCTV-SLM, a spatial-filtering technique is applied to remove the zeroth-order diffracted light from the reconstructed image.

B203 見えないサブミクロン粒子の可視化

A new laser holographic technique has been developed to visualize sub-micron particles. If the size of the particle is comparable with or less than wavelength, it is very difficult to obtain the image of small particles by the conventional optical method.We have obtained the holographic interference fringes by means of superposition of the reference light and the scattered light of comparable intensity by a particle irradiated at the beam waist of focused coherent light. The two-dimensional particle location is measured in terms of the center of holographic fringes, and the three dimensional depth of particle position from the recording plane is obtained by the reconstruction of the hologram.