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Digital holography is applied to make microdisplacement determination of a steel bar and an aluminum sheet. The displacement of aluminum sheet is made under immersion conditions in water and air. An experimental installation is presented for digital hologram registration with plane reference beam, using a CCD camera as detector. The “HOLODIG” compu...
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... user interface is compounded by the main menu formed by five items: File, Data, Options, Analysis and Tools, all accessible through the main window of application, Fig. 2. Many results are shown by means of child dialog, promoting a comparison between results of multiple ...
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... ð x ; y Þ takes values between À p and p as a result of arctan function. This phase field is said to be modulated or wrapped in the interval [ À p ; p ]. Our investigation group has begun to work in the field of digital holography and developed the computing system ‘‘HOLODIG’’ capable of solving the fundamental digital holographic problems. This system is supported by MatLab version 6.0. The process of digital reconstruction of the holographic image is programmed, and includes in general the following possibilities: reconstruction of intensity and phase image; reconstruction of intensity and phase interferograms corresponding to the displacement of object; procedures of 3D contouring starting from data obtained from two wavelengths or two source configurations; unwrapping algorithm and integration of phase. Including a novel adaptive filter to improve performance and speed; 3D representation of the displacement, considering the pixel camera dimensions (CCD) and the pixel dimension into the image plane; several procedures of miscellaneous image processing and filtering. The user interface is compounded by the main menu formed by five items: File , Data , Options , Analysis and Tools , all accessible through the main window of application, Fig. 2. Many results are shown by means of child dialog, promoting a comparison between results of multiple windows. During program execution, in the central part of main window it shows partial and final results which can be image or graphics. Each result has associated a title and in the status bar the calculation performed by the software at each moment is visualized. To show all calculations realized by the software, we present block diagrams of the five main menu items with general information about its function: FILE : Through this item, Fig. 3, it is possible to work all data input/output and some general task of image processing. DATA : This menu item, Fig. 4, permits handling of the real value of data that forms the partial or final result without conversion to values of level intensity; additionally, it is possible to dissolve any operation realized on the image carried out previously. OPTIONS : With the options menu, Fig. 5, users can modify the manner of the reconstructing process calculation. The activation of some items, i.e. phase correction (ON) and reference wave fronts (plane) imply input of additional parameters of experimental setup. That is accomplished through dialog windows with the name of corresponding parameters. The item unwrapping direction is referred at the required initial direction of the unwrapping, because it goes on as in Huntley’s algorithm. ANALYSIS : With this menu item, Fig. 6, users can perform the three main calculations carried out with digital holographic data: deformation, contouring and interferometric analysis. The data and parameters in calculations of each item are supplied through the dialog window according to the characteristics of experimental setup. TOOLS : Additional data manipulations of active image can be performed by means of this menu item, Fig. 7. In this software we introduce a novel algorithm of filter phase fringe pattern ‘‘Adaptive by residues’’ to avoid the image corruption effect during the application of unwrapping process. The algorithm is developed using a combination ...
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Citations
... The method allows for the successful assessment of mechanical distortions and structural inhomogeneities related to the condition of complex constructions. DHSPI and the combined postprocessing with the one-dimensional exponential analysis applied to the obtained experimental results operate as a compact, integrated optical detection and evaluation platform, which to the best of our knowledge has not been applied in this form for the characterization of solid samples [24,27,33]. Other monitoring studies have been accompanied by additional detection schemes, primarily holographic techniques coupled with infrared thermography arrangements [10,34,35]. ...
The mechanical response of an inhomogeneous sample, simulating wooden marquetry, is studied after the application of thermal load and increased initial temperature of the object. The presence of defects in the inner parts of the sample creates areas of diverse material properties, which respond in a different manner and rate during relaxation towards equilibrium. Energy is locally transferred, resulting in a spatially non-uniform deactivation process and deformations among the different parts of the object. With the performed experiments monitoring of the real-time mechanical response of the full surface of the target after thermal excitation towards equilibrium is achieved, within a completely non-destructive optical scheme. The experimental set-up used is a Digital Holographic Speckle Pattern Interferometry optical scheme. The set-up provides high-resolution, full-field dynamic information on the differential mechanical displacements, through the wrapped sequentially recorded interferometry fringes. Through a one-dimensional investigation and analysis of the temporal evolution of the displacement, the evaluation of the relaxation process of complex targets becomes feasible. The results are discussed in the context of the structural condition of the targets, of certain thermal material properties. After thermal loading, an initial fast energy redistribution dominates. On longer time intervals, long after the equilibrium temperature is reached, a slower mechanical relaxation takes place. The local rise in the number of interference fringes brings to light an ongoing transfer of kinetic energy values between areas in the interior of the object. This observation indicates a mechanical effect lasting long after the total volume of the sample reaches initial mean temperature values.
... Problems like the suffered by the A.F.I.P. building in Paraná are quite common in historical concrete, which highlights the need to implement in situ non-destructive techniques to detect cracks prematurely. In this sense, digital holographic interferometry (DHI) has been used in different fields for the detection of compressive and tensile stresses, detachment, cracks, flaws, failure of paint/coating, etc. [2][3][4][5][6][7][8][9][10][11] In digital holographic interferometry (DHI) two holograms are captured in different states of the object and the fringe pattern is reconstructed by the digital combination of the individual phase holograms. Any localised defect in the surface of the object can provoke discontinuities in the interference fringe pattern and, from the shifts in the phase map, these defects or flaws can be detected and characterised. ...
... However, these devices are not effective for small structures due to their masses. Other devices are also being used as a substitute device for movement measurements (GPS, hologram interferometry, speckle photography, laser Doppler vibrometer) [27][28][29][30]. Thanks to the advanced technology in the image sensors and high-performance optical lenses, the vision-based measurement technique is also used for displacement measurement of different engineering structures [31,32]. ...
Vibration can be introduced in all mechanical fields in our life. Engineers try to avoid its negative effect leading in some cases to deformation in the machines. Many researches are dedicated to study the identification of damping especially in multi degree of freedom systems with particular attention to the source of energy dissipation. They focus on developing new tools or methods which may be used in real problems to obtain accurate results about the amount (or value) and the location of energy dissipation in the structure. The aim of this paper is to present an original procedure aims to experimentally determine the modal damping ratio of a mechanical structure. The proposed procedure consists of extracting the Frequency Response Function of the vibrating system using the video magnification method and then calculate the modal damping ratio using the 3-dB method. These experimental measurements are carried out by giving an external force on a cantilever beam, then the modal damping ratios are extracted using motion magnification. The obtained results show a relative error less than 4.2% between the experimental measurements and the analytical calculation for the Frequency Response Function (FRF) curves. The novelty of the paper is to combine the video magnification technique and the 3 dB method in a procedure that aims to experimentally measure the modal damping of a mechanical structure. The proposed procedure in this paper represents the damping identification as a simple and easy engineering application.
... However, contact sensor can affect the obtained results due to its mass, especially when it comes to small structures. Several non-contact sensors have been developed as a substitute of the contact measurement devices, such as GPS monitoring [6], hologram interferometry [7], speckle photography [8] and laser Doppler vibrometer [9][10][11]. These devices are well known for their high cost and design complexity. ...
The vibrations behavior analysis is an essential step in the mechanical design process. Several methods such as analytical modelling, numerical analysis and experimental measurements can be used for this purpose. However, the numerical or analytical models should be validated through experimental measurements , usually expensive. This paper introduces an inexpensive smartphone as an accurate, non-intrusive vibrations' behavior measurement device. An experimental measurement procedure based on the video processing method is presented. This procedure allows the measurement of the natural frequencies and the mode shapes of a vibrating structure, simply by using a smartphone built-in camera. The experimental results are compared to those obtained using an accurate analytical model, where the natural frequencies error is less than 2.7% and the modal assurance criterion is higher than 0.89. In order to highlight the obtained results, a comparison has been done using a high quality and high frame per second (fps) camera-based measurement of material properties. Since the highest recovered natural frequency and its associated mode shape depend on the frame per second rate of the recorded video, this procedure has great potential in low frequencies problems such as for big structures like buildings and bridges. This validated technique reintroduces the personal smartphone as an accurate inexpensive non-contacting vibration measurement tool.
... Current research shows that digital holography is not only a powerful tool for metrology [1][2][3][4][5][6][7][8][9][10][11][12] but also in the field of biomedical imaging [12][13][14][15][16][17][18][19][20][21][22][23][24]. In the recent past, many scientists and researchers have succeeded in imaging of biological samples through various optical methods [25][26][27] including digital holography. ...
In this paper, a volume phase holographic optical element based digital holographic interferometer is designed and used for quantitative phase imaging of biological cells [white blood cells, red blood cells, platelets, and Staphylococcus aureus (S. aureus) bacteria cells]. The experimental results reveal that sharp images of the S. aureus bacteria cells of the order of ${\sim}{1}\;{\unicode{x00B5}{\rm m}}$ ∼ 1 µ m can be clearly seen. The volume phase holographic grating will remove the stray light from the system reaching toward the grating and will minimize the coherent noise (speckle noise). This will improve the sharpness in the image reconstructed from the recorded digital hologram.
... The Fourier transform is applied in electronic speckle photography. The digital holography interferometry was applied by Valin et al., to determine the micro-displacement of a square section steel bar [15]. The displacement of the specimen is conducted in air and submerged in water. ...
Vibration measurement is a common method used to assess a structure’s condition. The basic premise for the detection of damage in a structure is based on vibration measurement, whereby changes of stiffness, vibration mode, and energy dissipation in the system can cause changes in the dynamic response. The vibration measurement is conducted by obtaining the fundamental period to judge the health condition of the monitored structure. This research used the high-speed camera (HSC) to capture the structure motion during the vibration of steel-plated structure. Laboratory experiments were performed on a thin steel plate (600 × 600 × 2.3 mm) and orthotropic steel deck. The HSC was used to measure the resonance frequency of the structure monitored.
... Different methods for crack detection have been reported (see e.g., Yao et al. [2]); however, optical methods have gained more and more attention, mainly because of their non-destructive character, high precision and sensitivity [5,6]. In this sense, digital holographic interferometry (DHI) has been used in different fields for the detection of cracks, flaws, failure of paint/coating, etc. [8][9][10][11][12][13]. ...
The aim of this work is to present an experimental procedure to improve crack detection in rough surfaces by means of lensless Fourier digital holographic interferometry (DHI). To overcome the problem of analyzing high speckle interferograms that blurs phase maps and hinders, or even prevents, crack detection, it is proposed the application of a non-uniform thermal load to the object under study, as excitation source, instead of the most common uniform heating. Different tests with mock ups of cracks of controlled width allowed us to demonstrate the effect of a non-uniform thermal load, and confirmed the enhancement in DHI information, especially in unwrapping phase maps. Finally, DHI was applied to the detection of a crack in a cast iron sample and the results obtained with both uniform and non-uniform heating procedures were compared and the improvement attained by means of non-uniform heating was confirmed.
... , se genera un mapa de fase del campo objeto como el mostrado en la figura 4. Para eliminar las ambigüedades o saltos de fase, es aplicado un algoritmo conocido como Phase Unwrapping [10,11], en este caso, el método aplicado está basado en el algoritmo de Volkov. ...
We present an experimental installation for the measurement of deformations of healthy superior premolar teeth implementing the method of projection of fringes. The samples were inserted in polyethylene resin and fixed in support, which has a stem that is responsible for the application of the load, the loads used being of the order of 25 N, 50 N, 75 N and 100 N. Each load was applied along the axis of the tooth by touching its two cusps and then again with the load touching only a cusp. Was developed a computer program supported in MATLAB for the reconstruction of images. The process of digital image reconstruction using the stripe projection method includes: Intensity and phase contrast images and deformation caused by the application of a force on the teeth. For the linearization of the phase was applied the algorithm of Volkov.
... La holografía digital puede ser utilizada para substituir la forma clásica de registro [1]. A través de la utilización de una matriz CCD (Dispositivo de Carga Acoplada), la holografía digital puede ser considerada una herramienta más simple, rápida y eficiente [2]. ...
The objective of this work is the application of an interferometric method for validating the result of wear in a cutting tool insert of hard metal. We describe in this paper the experimental setup for the application of Digital Holography technique, used with digital recording of holograms on a CCD camera. The cutting insert inspected with the optical technique was previously mounted on a support structure and slightly heated with a halogen lamp for evidence of defective regions. For image processing, the software used, ProITec. It was possible to detect, with high resolution and contactless defects that could compromise the structural integrity of the insert analyzed, no defect was found. Analysis of the images obtained, it is verified that the object is deformed as a whole, not to present any visible alteration in their pattern of fringes.
... , se genera un mapa de fase del campo objeto como el mostrado en la figura 4. Para eliminar las ambigüedades o saltos de fase, es aplicado un algoritmo conocido como Phase Unwrapping [10,11], en este caso, el método aplicado está basado en el algoritmo de Volkov. ...
Fue implementada la técnica de Moiré de proyección de franjas en la evaluación de deformaciones en dientes pre molares saludables, para esto fue diseñada una instalación experimental. Las muestras, fueron embutidas en resina de polietileno y fijadas en soporte, el cual, tiene un vástago que es responsable por la aplicación de la carga, siendo las cargas utilizadas de 25 N, 50 N, 75 N y 100 N. Cada carga fue aplicada a lo largo del eje del diente tocando sus dos cúspides y después nuevamente con la carga tocando solamente una cúspide. Fue desarrollado un programa soportado en MATLAB, para la reconstrucción de las imágenes. El proceso de reconstrucción digital de la imagen aplicando el método de proyección de franjas incluye: las imágenes de contraste de intensidad y de fase y la deformación causada por la aplicación de una fuerza sobre los dientes. Para la linealización de la fase fue aplicado el algoritmo de Volkov. Palabras claves: proyección de franjas, deformación, interferometría, phase unwrapping. Abstract We present an experimental installation for the measurement of deformations of healthy superior premolar teeth implementing the method of projection of fringes. The samples were inserted in polyethylene resin and fixed in support, which has a stem that is responsible for the application of the load, the loads used being of the order of 25 N, 50 N, 75 N and 100 N. Each load was applied along the axis of the tooth by touching its two cusps and then again with the load touching only a cusp. Was developed a computer program supported in MATLAB for the reconstruction of images. The process of digital image reconstruction using the stripe projection method includes: Intensity and phase contrast images and deformation caused by the application of a force on the teeth. For the linearization of the phase was applied the algorithm of Volkov.
