Double-exposure Holographic Interferometry Research Articles

Gas Dynamics Processes above the Polymers Surface under Irradiation with Broadband High-Brightness Radiation in the Vacuum Ultraviolet Spectrum Region.

Obtaining new data on the gas-dynamic responses from the polymer samples (polytetrafluoroethylene, PTFE) irradiated by powerful VUV radiation from compressed plasma flows is in the focus of the present study. An erosion type magnetoplasma compressor (MPC), a type of plasma focus discharge, was used as a radiation source. The operating voltages of the MPC were between 15 and 25 kV, the maximum measured discharge current was 200 kA, and the radiation energy in the VUV range was ≈1–2 kJ. The VUV fluxes on the sample surface were high and equal to ≈1022–1024 photons cm−2·s−1. Double-exposure laser holographic interferometry and schlieren photography were used to diagnose and visualize the gas-dynamic structures. The spatial distribution of the parameters (temperature, pressure and concentrations of electrons and ions) was defined based on the assumption of local thermodynamic equilibrium. It has been demonstrated that the maximum temperature ranged from ≈ 10 to 15 kK in the plasma layer. The electron concentration was ≈ (0.7–1.6) × 1018 cm−3 in this region. The used techniques of optical diagnostics and procedures of result processing make it possible to obtain data on the dynamics of polymer ablation, which occurs when their surface is exposed to powerful energy fluxes (thermal, shock-wave, radiation, and other extreme loads).

Noise free defect detection in ceramic tableware using a portable digital holographic camera.

This paper describes detection of cracks in ceramic tableware using a portable digital holographic camera working on the principle of double-exposure digital holographic interferometry. Digital image processing techniques are applied on amplitude and phase information obtained from the numerically reconstructed wavefronts of the test object to locate position of the defect. Speckles generated due to illumination of the rough surface of the ceramic cup with the coherent light source deteriorate quality of the interferometric phase. Several iterations of the averaging filter with optimized kernel size are applied on sine and cosine components of the interferometric phase to minimize the speckle noise. The effect of kernel size of the matrix used in the averaging filter on quality of the interferometric phase is analyzed by evaluating the signal-to-noise ratio. The experimentally obtained size of crack on a ceramic cup (0.08 mm) is validated by a mechanical profiler with an error of 6.6%. This study may help in improving the quality criteria of tableware items.

Surface Deformation of Cadmium Selenide Thin Films By DEHI Technique

Abstract Here, the Double Exposure Holographic Interferometry (DEHI) technique is used to study the surface deformation of CdSe films electrodeposited on stainless steel substrate. The electrodeposition of CdSe thin films is carried out by varying the time of deposition. The deposition potential of the compound was studied by cyclic voltammetry. The structural, surface morphological and optical properties of the deposited films have been studied by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical absorption technique respectively. Also the contact angle measurements are carried out. The DEHI technique is used to determine, thickness of thin films, mass deposited, fringe width and stress to substrate of electrodeposited CdSe thin films for various deposition time with different solution concentrations. With increasing deposition time fringe width was decreased due to the reduction in film stress

Regulation of the sensitivity of measurements in holographic interferometry of dynamic periodic structures

This paper discusses the features of the recording of a hologram of a periodic structure that make it possible when implementing a method of either real-time or double-exposure holographic interferometry to adjust the measurement sensitivity when investigating the temporal behavior of the periodic structure of an object. Experimental test results of the real-time holographic interferometry method, devised while studying the dynamics of two-dimensional periodic structures in time, are presented.

Double-exposure holographic interferometry for radiation dosimetry: A new developed model

The main drawback of the double exposure holographic interferometry (DEHI) systems is that their initial setting up is a difficult and time-consuming task. This hinders their use in radiation dosimetry that requires observing necessary precautions to protect the users from radiation. In this paper, a detailed theoretical model capable of predicting the DEHI system response before its use for radiation dosimetry is developed which can partly overcome this limitation. In this model, radiation dosimetry by the DEHI systems is described in steady-state and transient modes. Physical background of hologram recordation and heat transfer within the absorbing material are fully described and it is shown how the whole process can be numerically modelled. Specifically, radiation dosimetry with two different homogeneous and inhomogeneous geometries is modelled in this work. For 3 MeV electrons in an inhomogeneous geometry, it is shown that the model results are in good agreement with the previous experimental results. It is also described how the model can be used to calculate the heat transfer correction factors in dosimetry by the DEHI systems.

Study of Dimensional Stability of Metal-ceramic Prostheses By Holographic Interferometry

.

Measurement of the Diffusion Coefficient of Water in RP-3 and RP-5 Jet Fuels Using Digital Holography Interferometry

The diffusion coefficient of water in jet fuel was measured employing double-exposure digital holographic interferometry to clarify the diffusion process and make the aircraft fuel system safe. The experimental method and apparatus are introduced in detail, and the digital image processing program is coded in MATLAB according to the theory of the Fourier transform. At temperatures ranging from 278.15 K to 333.15 K in intervals of 5 K, the diffusion coefficient of water in RP-3 and RP-5 jet fuels ranges from 2.6967 × 10 −10 m2·s−1 to 8.7332 × 10 −10 m2·s−1 and from 2.3517 × 10 −10 m2·s−1 to 8.0099 × 10−10 m2·s−1, respectively. The relationship between the measured diffusion coefficient and temperature can be well fitted by the Arrhenius law. The diffusion coefficient of water in RP-3 jet fuel is higher than that of water in RP-5 jet fuel at the same temperature. Furthermore, the viscosities of the two jet fuels were measured and found to be expressible in the form of the Arrhenius equation. The relationship among the diffusion coefficient, viscosity and temperature is analyzed according to the classic prediction model, namely the Stokes–Einstein correlation, and this correlation is further revised via experimental data to obtain a more accurate predication result.

Determination of Young’s Modulus of Aluminium, Copper, Iron, Brass and Steel Alloys by Using Double Exposure Holographic Interferometry (DEHI) Technique

Double Exposure Holographic Interferometry (DEHI) technique has wide applications in the field of science and engineering. DEHI can be used to determine very small surface changes in an object at very small interval of time. In present case, DEHI technique is used to record the hologram of the same object at different times subjected to different loads. This method has been advantageously used to determine Young’s Modulus (Y) of Aluminium, Copper, iron, brass and some steel alloys. It is found that the values of Y obtained by using DEHI technique are in close agreement with standard values of Y available for respective metals and their alloys. The method is also used to make standard relation between effect of carbon composition and Y of steel alloys.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Digital off-axis holographic interferometry with simulated wavefront

The paper presents a novel algorithm based on digital holographic interferometry and being promising for evaluation of phase variations from highly noisy or modulated by speckle-structures digital holograms. The suggested algorithm simulates an interferogram in finite width fringes, by analogy with classical double exposure holographic interferometry. Thus obtained interferogram is then processed as a digital hologram. The advantages of the suggested approach are demonstrated in numerical experiments on calculations of differences in phase distributions of wave fronts modulated by speckle structure, as well as in a physical experiment on the analysis of laser-induced heating dynamics of an aqueous solution of a photosensitizer. It is shown that owing to the inherent capability of the approach to perform adjustable smoothing of compared wave fronts, the resulting difference undergoes noise filtering. This capability of adjustable smoothing may be used to minimize losses in spatial resolution. Since the method allows to vary an observation angle of compared wave fields, an opportunity to compensate misalignment of optical axes of these wave fronts arises. This feature can be required, for example, when using two different setups in comparative digital holography or for compensation of recording system displacements during a set of exposures in studies of dynamic processes.

Capture and display mismatch compensation for real-time digital holographic interferometry.

Optical holographic interferometry (HI) is realized by two well-known techniques: double exposure holographic interferometry (DEHI) and real-time holographic interferometry (RTHI). However, the digital version of HI is typically realized numerically by DEHI. The main problem in digital implementation of RTHI is the lack of commercially available cameras and spatial light modulators with the same pixel size. This mismatch results in lateral and transversal magnifications of an object wavefront reconstruction. In real-time digital HI the reconstruction of an object in an initial state has to be superimposed on top of the loaded object. In this work, we present and analyze five approaches to overcome the mismatch problem, and the performance of these procedures is numerically quantified and compared. The experimental suitability of these approaches is investigated.

Method for calculating the dynamic phase delay in holographic interferometry without phase unwrapping

A method for calculating the difference between two arbitrary spatial phase distributions reconstructed from digital holograms is presented. The method is promising for application in double-exposure digital holographic interferometry, especially for the evaluation of phase variations in heavily noised or speckle-structure-modulated digital holograms, because it does not use the phase unwrapping procedure for each reconstructed spatial phase distribution. Instead, by analogy with classical double-exposure holographic interferometry, an interference pattern formed by two reconstructed object waves is calculated first. The interferogram thus obtained is then processed as a digital hologram by the same method that was used for reconstruction of physically recorded holograms. The advantages of the proposed method are demonstrated by both by the numerical computation of the difference of the phase distributions of speckle-structure-modulated wavefronts and the experimental observation of the laser-induced temperature gradients in an aqueous solution of a photosensitizer.

Effect of Heat Transfer on Natural Convection in a Square Cavity With Two Source Pairs

In this paper, the influence of a small heating source, positioned in the lateral walls of a square cavity, is investigated. Numerical and experimental analyses are performed to investigate natural convection heat transfer in a square cavity heated by hot strips in the side walls. The H side square cavity is filled with air and heated by two hot strips with heights of H/4. The effect of placing the hot strips at two different positions is evaluated. The temperature distribution and the Nusselt numbers at different Rayleigh numbers are experimentally measured using both real-time and double-exposure holographic interferometry. The isothermal patterns obtained through the holographic interferometry are compared with the temperature and velocity fields from a numerical study performed using the finite-volume code Fluent.

Visual investigation on the heat dissipation process of a heat sink by using digital holographic interferometry

We present a method for visually and quantitatively investigating the heat dissipation process of plate-fin heat sinks by using digital holographic interferometry. A series of phase change maps reflecting the temperature distribution and variation trend of the air field surrounding heat sink during the heat dissipation process are numerically reconstructed based on double-exposure holographic interferometry. According to the phase unwrapping algorithm and the derived relationship between temperature and phase change of the detection beam, the full-field temperature distributions are quantitatively obtained with a reasonably high measurement accuracy. And then the impact of heat sink's channel width on the heat dissipation performance in the case of natural convection is analyzed. In addition, a comparison between simulation and experiment results is given to verify the reliability of this method. The experiment results certify the feasibility and validity of the presented method in full-field, dynamical, and quantitative measurement of the air field temperature distribution, which provides a basis for analyzing the heat dissipation performance of plate-fin heat sinks.

Underwater Shock Wave Research Applied to Therapeutic Device Developments

The chronological development of underwater shock wave research performed at the Shock Wave Research Center of the Institute of Fluid Science at the Tohoku University is presented. Firstly, the generation of planar underwater shock waves in shock tubes and their visualization by using the conventional shadowgraph and schlieren methods are described. Secondly, the generation of spherical underwater shock waves by exploding lead azide pellets weighing from several tens of micrograms to 100 mg, that were ignited by irradiating with a Q-switched laser beam, and their visualization by using double exposure holographic interferometry are presented. The initiation, propagation, refl ection, focusing of underwater shock waves, and their interaction with various interfaces, in particular, with air bubbles, are visualized quantitatively. Based on such a fundamental underwater shock wave research, collaboration with the School of Medicine at the Tohoku University was started for developing a shock wave assisted therapeutic device, which was named an extracorporeal shock wave lithotripter (ESWL). Miniature shock waves created by irradiation with Q-switched HO:YAG laser beams are studied, as applied to damaged dysfunctional nerve cells in the myocardium in a precisely controlled manner, and are effectively used to design a catheter for treating arrhythmia.

Real-time monitoring of the solution concentration variation during the crystallization process of protein-lysozyme by using digital holographic interferometry

We report a real-time measurement method of the solution concentration variation during the growth of protein-lysozyme crystals based on digital holographic interferometry. A series of holograms containing the information of the solution concentration variation in the whole crystallization process is recorded by CCD. Based on the principle of double-exposure holographic interferometry and the relationship between the phase difference of the reconstructed object wave and the solution concentration, the solution concentration variation with time for arbitrary point in the solution can be obtained, and then the two-dimensional concentration distribution of the solution during crystallization process can also be figured out under the precondition which the refractive index is constant through the light propagation direction. The experimental results turns out that it is feasible to in situ, full-field and real-time monitor the crystal growth process by using this method.

Magnetostriction measured by holographic interferometry with the simple and inexpensive arrowhead setup

Double-exposure holographic interferometry is applied to measure the linear or longitudinal magnetostriction constant of a soft-ferrite rod. This high-accuracy measurement is done indirectly, by measuring the small rotations of a lever in contact with the rod using double-exposure holographic interferometry implemented with a robust arrowhead-shaped holographic setup. Ferrite devices are used in a large number of well-known technologies and hold a promise for more advanced applications, so the study of ferrites properties is therefore very important. The experiments and methods described here and the magnetic phenomena studied are suitable for an undergraduate project or an open-ended experiment.

Studies on surface deformation of copper sulphide thin films by holographic interferometry technique

Holographic interferometry technique used to study the surface deformation of electrodeposited copper sulphide thin films on stainless steel substrate is here presented. It is concerned with the formation and interpretation of fringe patterns, which appears when a wave generated at some earlier time and stored in a hologram is later reconstructed by interfering with comparison wave. The proposed technique uses double exposure holographic interferometry (DEHI) together with simple mathematical relation, which allows immediate finding of stress, mass deposited and thickness of thin film. It must be further noted that, fringe spacing changes with time of deposition as well as solution concentration. The structural study (XRD) is carried out for the confirmation.

Single step electrochemical synthesis of Sb2Se3 thin films: effect of molarities of precursor solution

In the present investigation, we have successfully synthesized polycrystalline Sb2Se3 thin films by single-step electrochemical method. Effect of concentration of precursor solution on structural, morphological, optical, and wettability properties by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical absorption, and contact angle measurement have been investigated. It is evident from XRD pattern that Sb2Se3 thin films are polycrystalline having orthorhombic crystal structure. Also, as precursor concentration increases the diffraction peak intensity also increases. Scanning electron micrographs reveal that the increase in precursor concentration causes the formation of soap foam like microstructure which is spread in the form of ellipsoids over whole substrate surface. The optical band gap decreases from 1.49 to 1.35 eV and contact angle decreases from 40° to 13°, i.e., the surface of Sb 2Se3 thin films converts from hydrophilic to superhydrophilic nature due to increase in precursor concentration. In addition, the holographic interferometric properties have been studied. The thickness, stress to substrate and deposited mass of the thin films is determined using double exposure holographic interferometry (DEHI) technique.

Mastication effort study using photorefractive holographic interferometry technique

The purpose of this work was the force–displacement response analysis of the masticatory process in a dried human skull by Double-Exposure Photorefractive Holographic Interferometry Technique (2E-PRHI). The load concentration and dissipation of the forces from dried human skull were analysed at applied loading stands as a Simulation of Isolated Contraction (SIC) of some mastication muscles. The 2EHI and Fringe Analysis Method were used to obtain the quantitative results of this force–displacement response. These results document quantitatively the real biomechanical response from dried human skull under applied loading and it can be used for complementary study by finite element model and others analysis type.