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As part of a series of studies of the properties of human glioma cells that contribute to their ability to escape cell-mediated immune attack (Gately et al.,(1982)we have examined the ultrastructural features of a protective... more
As part of a series of studies of the properties of human glioma cells that contribute to their ability to escape cell-mediated immune attack (Gately et al.,(1982)we have examined the ultrastructural features of a protective mucopolysaccharide coat secreted by some of these brain tumor cell lines. This ruthenium red-positive coat or "halo" is formed or greatly increases in size in response to the presence of lymphocytes or a soluble factor released therefrom. It blocks the approach of cytotoxic lymphocytes to the tumor cells and hence tumor cell killing. Hyaluronidase appears to be a major structural component. The "halo" is destroyed by bovine testicular or streptomyces hyaluronidase, and chondritinase ABC.To determine the ultrastructural features of this halo we have examined 5 human glioma cell lines in vitro. These were derived from I Grade II and 4 Grade IV astrocytomas, specimens of which were removed at surgery. Glioma derived (1000 per Costar well) were p...
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Because the quadrate and the eardrum are connected, the hypothesis was tested that birds attenuate the transmission of sound through their ears by opening the bill, which potentially serves as an additional protective mechanism for... more
Because the quadrate and the eardrum are connected, the hypothesis was tested that birds attenuate the transmission of sound through their ears by opening the bill, which potentially serves as an additional protective mechanism for self-generated vocalizations. In domestic chickens, it was examined if a difference exists between hens and roosters, given the difference in vocalization capacity between the sexes. To test the hypothesis, vibrations of the columellar footplate were measuredex vivowith laser Doppler vibrometry (LDV) for closed and maximally opened beak conditions, with sounds introduced at the ear canal. The average attenuation was 3.5 dB in roosters and only 0.5 dB in hens. To demonstrate the importance of a putative protective mechanism, audio recordings were performed of a crowing rooster. Sound pressures levels of 133.5 dB were recorded near the ears. The frequency content of the vocalizations was in accordance with the range of highest hearing sensitivity in chicken...
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The thickness of the tympanic membrane has to be known for the formulation of mathematical ear models. Using a commercial confocal laser scanning microscope we have found that the tympanic membrane has parts thinner than 10 micron. In... more
The thickness of the tympanic membrane has to be known for the formulation of mathematical ear models. Using a commercial confocal laser scanning microscope we have found that the tympanic membrane has parts thinner than 10 micron. In this study we were forced to excise the tympanic membranes and due the restricted working distance of the microscope objective, we had to flatten the tympanic membrane onto a glass plate. Although we were able to measure thickness in fresh samples, thickness could still have been altered by the preparation procedure. S. Khanna developed over the years a powerful heterodyne interferometer with confocal pinholes in the illumination and observation arms. Thanks to its sectioning capabilities it can measure vibrations of structures embedded within other tissue without the need to expose the structure. While using this equipment in measuring vibrations in the middle ear, the idea grew that the interferometer could also be used to measure thickness, by tracking the carrier level of the interferometer while the laser focus is driven through the membrane. The method looks full of promises as measurements on animals with the tympanic membrane still in its original niche are possible without a prior preparation of the membrane.
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Tony Abi-Salloum Bernhard Adams Mehdi Alavinejad Victor V. Apollonov Mete Atature Bradley Atcheson David Atchison Nicolas Avdelidis Sergey Babin Hans Bachor Burm Baek Daniel Balageas* Salvador Bará Marco Barbieri Cesare Barbieri Yury... more
Tony Abi-Salloum Bernhard Adams Mehdi Alavinejad Victor V. Apollonov Mete Atature Bradley Atcheson David Atchison Nicolas Avdelidis Sergey Babin Hans Bachor Burm Baek Daniel Balageas* Salvador Bará Marco Barbieri Cesare Barbieri Yury Barmenkov Liam Barry Michael Bass Yahya Baykal* Wilhelm Becker Gregorius C.G. Berkhout Shrikant Bharadwaj Raymond Bishop Paolo Bison Allan Boardman Maria Bondani John Botsis Lindsay Botten Alex Bowers Christian Brackmann Arthur Bradley Howard Brandt J. Bravo-Abad P. Brevet Giorgio Brida Neil Broderick Gerald Buller* John Bullough Stephen Burns Yangjian Cai* Qing Yu Cai Juan Campos Stefan Carp* Stefania Castelletto Andrey Chabanov Prem Chahal Uday Chakraborty Benoit Champagne Neil Charman Y.F. Chauvet Pierre Chavel Sabino Chavez Cerda Nanguang Chen Zhigang Chen Yihang Chen C. Chen K. Chen Weibin Chen Xi Chen Vladimir Chernyak Jessica Cheung Frederic Chevy Demetrios Christodoulides Christopher Chunnilall* Bernard Claudet C. Clavero Leon Cohen Dan Cojoc Roger Colbeck Hendrik Coldenstrodt-Ronge Carlo Corsi Stelios Couris Lorenzo Crocco Jiri Ctyroky Salvador Cuevas M. da Luz Jerry Dadap Jean Daillant Iyad Dajani G. Dattoli Eric Dauler Jon Davis* F. De Leornadis Gilbert De Mey Diego de Ortueta Ivo Degiovanni Fu-Guo Deng Mark Dennis* Yujie Ding José Dintinger Joris Dirckx C.R. Doerr Adrian Doicu John Donohue S. Dubey John Dudley Christopher Dunsby Jan Dutkiewicz Geoffrey Duxbury Chris Edwards H.J. Eichler F. Eilenberger* Jens Eisert Hichem Eleuch Andrew Ellis R. Eplee Daniel Erni Harmut Erzgraber Joerg Evers* Halil Eyyuboglu Claude Fabre Yi-Chin Fang Zoltán Fazekas A. Felipe
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Ossicular fixation through otosclerosis, chronic otitis media and other pathologies, especially tympanosclerosis, are treated by surgery if hearing aids fail as an alternative. However, the best hearing outcome is often based on knowledge... more
Ossicular fixation through otosclerosis, chronic otitis media and other pathologies, especially tympanosclerosis, are treated by surgery if hearing aids fail as an alternative. However, the best hearing outcome is often based on knowledge of the degree and location of the fixation. Objective methods to quantify the degree and position of the fixation are largely lacking. Laser vibrometry is a known method to detect ossicular fixation but clinical applicability remains limited. A new method, minimally invasive laser vibrometry (MIVIB), is presented to quantify ossicle mobility using laser vibrometry measurement through the ear canal after elevating the tympanic membrane, thus making the method feasible in minimally invasive explorative surgery. A floating mass transducer provides a clinically relevant transducer to drive ossicular vibration. This device was attached to the manubrium and drove vibrations at the same angle as the longitudinal axis of the stapes and was therefore used t...
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Recently, synchrotron radiation computed microtomography (SRµCT) has emerged as a promising tool for non-destructive, in situ visualization of cochlear implant electrode arrays inserted into a human cochlea. Histological techniques have... more
Recently, synchrotron radiation computed microtomography (SRµCT) has emerged as a promising tool for non-destructive, in situ visualization of cochlear implant electrode arrays inserted into a human cochlea. Histological techniques have been the `gold standard' technique for accurate localization of cochlear implant electrodes but are suboptimal for precise three-dimensional measurements. Here, an SRµCT experimental setup is proposed that offers the benefit of a high spatial and contrast resolution (isotropic voxel size = 4.95 µm and propagation-based phase-contrast imaging), while visualizing the soft-tissue structures and electrode array of the cochlear implant simultaneously. In this work, perimodiolar electrode arrays have been tested, which incorporate thick and closely spaced platinum–iridium contacts and wiring. These data can assist cochlear implant and hearing research, can be used to verify electrode segmentation techniques for clinical computed tomography or could be ...
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The file contains the Matlab data and code belonging to the manuscript entitled "Sound attenuation in the ear of domestic chickens (Gallus gallus domesticus) as a result of beak opening" by Muyshondt et al
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The study of energy transmission on plate-like structures is widely documented in literature. Its analysis requires the computation of the spatial derivatives of the out-of-plane displacement field of the studied sample and a priori... more
The study of energy transmission on plate-like structures is widely documented in literature. Its analysis requires the computation of the spatial derivatives of the out-of-plane displacement field of the studied sample and a priori knowledge of its material properties. However, if the structural intensity is to be assessed on irregular shells, such a study requires a more elaborate data processing. In addition to in-plane displacements, also the spatial derivatives along the sample’s local coordinates are needed. For this purpose, a method was developed to approximate both the experimental displacement data and the spatial coordinates of a given arbitrary shell using a Finite-Element-Method model. After measuring the global displacement fields and their corresponding spatial coordinates for a given sample, the data was transferred to a shell model whose basis functions were properly defined in accordance to the application’s demands and whose individual elements were assumed to beh...
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9 Deformation of the ferromagnetic material, known as magnetostriction, causes 10 vibrations and noise of electrical machines and transformer cores. A setup by using 11 heterodyne laser interferometers has been built to measure the... more
9 Deformation of the ferromagnetic material, known as magnetostriction, causes 10 vibrations and noise of electrical machines and transformer cores. A setup by using 11 heterodyne laser interferometers has been built to measure the magnetostriction strains 12 as a function of the applied magnetic field. The measurement results on a sample of 13 nonoriented electrical steel are presented in this work. These results are compared with 14 those obtained by using a strain gauge setup. The laser measurements are less disturbed 15 by noise, especially for measurements under low amplitude magnetisation. In addition, 16 contrary to the strain gauge samples, the sample preparation for the laser setup does 17 not require removal of the protective coating. Measurement results on the coated 18 samples are highly helpful for the calculation of the magnetostriction noise of the 19 device. The coated samples show smaller deformation, since the coating applies tensile 20 stress to the material. For ...
Characterization of material parameters from experimental data remains challenging, especially on biological structures. One of such techniques allowing for the inverse determination of material parameters from measurement data is the... more
Characterization of material parameters from experimental data remains challenging, especially on biological structures. One of such techniques allowing for the inverse determination of material parameters from measurement data is the virtual fields method (VFM). However, application of the VFM on general structures of complicated shape has not yet been extensively investigated. In this paper, we extend the framework of the VFM method to thin curved solids in three-dimensional, commonly denoted shells. Our method is then used to estimate the Young's modulus and hysteretic damping of the human eardrum. By utilizing Kirchhoff plate theory, we assume that the behavior of the shell varies linearly through the thickness. The total strain of the shell can then be separated in a bending and membrane strain. This in turn allowed for an application of the VFM based only on data of the outer surface of the shell. We validated our method on simulated and experimental data of a human eardru...
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Compared to single source systems, stereo X-ray CT systems allow acquiring projection data within a reduced amount of time, for an extended field-of-view, or for dual X-ray energies. To exploit the benefit of a dual X-ray system, its... more
Compared to single source systems, stereo X-ray CT systems allow acquiring projection data within a reduced amount of time, for an extended field-of-view, or for dual X-ray energies. To exploit the benefit of a dual X-ray system, its acquisition geometry needs to be calibrated. Unfortunately, in modular stereo X-ray CT setups, geometry misalignment occurs each time the setup is changed, which calls for an efficient calibration procedure. Although many studies have been dealing with geometry calibration of an X-ray CT system, little research targets the calibration of a dual cone-beam X-ray CT system. In this work, we present a phantom-based calibration procedure to accurately estimate the geometry of a stereo cone-beam X-ray CT system. With simulated as well as real experiments, it is shown that the calibration procedure can be used to accurately estimate the geometry of a modular stereo X-ray CT system thereby reducing the misalignment artifacts in the reconstruction volumes.
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The reed is the primary component in single-reed woodwind instruments to generate the sound. The airflow of the player’s mouth is the energy source and the airflow is modulated by the reed. The oscillations of the reed control the... more
The reed is the primary component in single-reed woodwind instruments to generate the sound. The airflow of the player’s mouth is the energy source and the airflow is modulated by the reed. The oscillations of the reed control the airflow. Traditionally, instrument reeds are made out of natural cane (Arundo Donax), but in efforts to overcome variability problems, synthetic reeds have been introduced. Previous investigations mainly focused on natural cane reeds and direct elasticity measurements did not discriminate between elasticity moduli along different directions. In order to obtain the mechanical properties along the direction of the reed fibres and in the orthogonal direction separately, a three-point bending testing setup was developed, which accommodates the small samples that can be cut from an instrument reed. Static moduli of elasticity were acquired in both directions. Much higher ratios between longitudinal and transversal moduli were seen in the natural cane reed as co...
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Malleus handle fractures are rare but can cause tremendous hearing loss. Due to the small number of known clinical malleus fracture cases, little is known about the mechanics of middle ears with a malleus fracture. Laser Doppler... more
Malleus handle fractures are rare but can cause tremendous hearing loss. Due to the small number of known clinical malleus fracture cases, little is known about the mechanics of middle ears with a malleus fracture. Laser Doppler vibrometry and finite element simulations are used to gain more knowledge about malleus fractures. The experimental measurements show remarkably that at low frequencies an increase in sound transmission can occur and minimal hearing loss occurs below the intact middle ear resonance frequency due to a resonance shift. The simulations do not show these observations when only a fracture is introduced. The addition of other features possibly related to malleus fractures to the models such as the post-fracture eardrum prestress release improve the simulation results. However, features such as post-fracture eardrum deformation could play an important role too.
Research Interests: Physics and Proceedings
Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the... more
Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko’s beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and ...
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The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack... more
The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack formation and propagation in asphalt pavements and healing of these cracks during the rest periods. The healing effect in asphalt mixtures has been observed and verified by many researchers and different methods exist to evaluate this phenomenon. However, current methods are still inadequate to fully observe and quantify the healing phenomenon in asphalt mixtures. In this study, a digital image correlation (DIC) method is used to calculate the strain map on the surface of cylindrical asphalt specimens during the indirect tensile fatigue test. This strain map is used to detect the location of crack initiations and development of the microcracks during the experiments. Next, the specimens are unloaded and the temperature of the climate chamber is increase...
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Structural intensity on plates or shells can provide insights on how the vibrational energy is transmitted throughout a sample. Its assessment via experimental deflections are widely documented in the case of plates, which just requires... more
Structural intensity on plates or shells can provide insights on how the vibrational energy is transmitted throughout a sample. Its assessment via experimental deflections are widely documented in the case of plates, which just requires the computation of spatial derivatives of out-of-plane displacements or velocities and a knowledge of the sample's material properties. However, if the structural intensity is to be assessed on arbitrary shells, a more elaborate data processing is required. The in-plane displacements become relevant terms and the spatial derivatives along a predefined local coordinate system need to be computed. Here, a method from which experimental data is interpolated on a finite element mesh is proposed. First, the global displacements and shape of a sample's outer-surface are measured. These data are then projected on a quadratic mesh, where the Kirchhoff plate theory is invoked for the individual elements. The data differentiation is computed via quadratic shape functions, from which the strains and structural intensity are estimated. Through the obtained vibrational energy results on the basis of measured displacement and shape data and by validating the method via a numerical simulation, the proposed work has shown to be a reliable tool to assess energy transmission on irregular shells.
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Cardiovascular diseases (CVD) are the most prevalent cause of death in the Western World, and their prevalence is only expected to rise. Several screening modalities aim at detecting CVD at the early stages. A common target for early... more
Cardiovascular diseases (CVD) are the most prevalent cause of death in the Western World, and their prevalence is only expected to rise. Several screening modalities aim at detecting CVD at the early stages. A common target for early screening is common carotid artery (CCA) stiffness, as reflected in the pulse wave velocity (PWV). For assessing the CCA stiffness using ultrasound (US), one-dimensional (1D) measurements along the CCA axis are typically used, ignoring possible boundary conditions of neck anatomy and the US probe itself. In this study, the effect of stresses and deformations induced by the US probe, and the effect of anatomy surrounding CCA on a simulated 1D stiffness measurement (PWVus) is compared with the ground truth stiffness (PWVgt) in 60 finite-element models (FEM) derived from anatomical computed tomography (CT) scans of ten healthy male volunteers. Based on prior knowledge from the literature, and from results in this study, we conclude that it is safe to appro...
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A method is presented to assess the transmission path of vibration energy and to localize sources or sinks on shells with arbitrary shape, constant thickness, and isotropic material properties. The derived equations of the structural... more
A method is presented to assess the transmission path of vibration energy and to localize sources or sinks on shells with arbitrary shape, constant thickness, and isotropic material properties. The derived equations of the structural intensity (SI) are based on the Kirchhoff–Love postulates and are formulated in terms of displacements, Lamé parameters, principal curvatures, and their partial derivatives with respect to the principal curvilinear coordinates (PCC). To test the accuracy of the method, two numerical models of thin shells with nonuniform curvatures were developed. The coordinates, displacements, and principal curvature directions (PCDs) at the shell's outer surface were used to estimate the SI vector fields and the energy density at the shell's middle surface. The power estimated from the surface integral of the divergence of the SI over the source was compared to the actual power injected in the shell. The absolute error in both models did not exceed 1%, showing...
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A laser Doppler vibrometer (LDV) is a noncontact optical measurement device to measure the vibration velocities of particular points on the surface of an object. Even though LDV has become more popular in road engineering in recent years,... more
A laser Doppler vibrometer (LDV) is a noncontact optical measurement device to measure the vibration velocities of particular points on the surface of an object. Even though LDV has become more popular in road engineering in recent years, their signal-to-noise ratio (SNR) is strongly dependent on light scattering properties of the surface which, in some cases, needs to be properly conditioned. SNR is the main limitation in LDV instrumentation when measuring on low diffusive surfaces like pavements; therefore, an investigation on the SNR of different LDV devices on different surface conditions is of great importance. The objective of this research is to investigate the quality of two types of commercially available LDV systems—helium–neon (He–Ne)-based vibrometers and recently developed infrared vibrometers—on different surface conditions, i.e., retroreflective tape, white tape, black tape, and asphalt concrete. Both noise floor and modal analysis experiments are carried out on these...
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To compare stapes vibrations in different partial ossicular replacement prosthesis (PORP) applications. Stapedial vibrations were measured on fresh frozen human temporal bones with laser Doppler vibrometry. Eight different types of common... more
To compare stapes vibrations in different partial ossicular replacement prosthesis (PORP) applications. Stapedial vibrations were measured on fresh frozen human temporal bones with laser Doppler vibrometry. Eight different types of common ossiculoplasty methods were compared regarding recovery of stapes vibrations in relation with the normal ossicular chain. The PORPs were divided into three groups: 1) PORPs with the lateral contact only with the tympanic membrane, 2) PORPs with lateral contact only to the malleus handle, and 3) PORPs with lateral contact with both the malleus handle and the tympanic membrane. The PORPs with lateral contact only to the malleus handle performed better than the PORPs with lateral contact to the tympanic membrane only at 2 kHZ, but the best recovery was found in the group with contact both to the malleus handle and the tympanic membrane. The best sound transmission might be achieved by placing a PORP in contact with both the tympanic membrane and the h...
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One of the conditions for a laser scanning microscope to reach its optimal performance is for it to operate at its full numerical aperture (NA). In most commonly used systems, the illumination intensity at the back focal plane of the... more
One of the conditions for a laser scanning microscope to reach its optimal performance is for it to operate at its full numerical aperture (NA). In most commonly used systems, the illumination intensity at the back focal plane of the objective lens is apodized. This paper presents a simple method using a photodiode for checking the actual illumination intensity profile. We show as an example the measured profiles of a laser beam when working with two high-NA immersion objectives in two different confocal systems, and also show that in theoretical studies of the point-spread function, the assumption of a flat compared with a truncated Gaussian beam profile gives rise to severe discrepancies. The measured profiles also serve as an indication of the necessity of a realignment of the optical system.
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Recently, a measurement set-up was presented to detect small nonlinear distortions in the vibration of acoustically driven mechanical systems. A speaker generates a specially designed multisine excitation signal that drives the vibration... more
Recently, a measurement set-up was presented to detect small nonlinear distortions in the vibration of acoustically driven mechanical systems. A speaker generates a specially designed multisine excitation signal that drives the vibration of a test object. The generated sound pressure is measured with a probe microphone in front of the test object, and an heterodyne vibrometer measures the corresponding vibration. Due to the high degree of linearity of the heterodyne technique, very small nonlinear distortions can be detected. In this paper the set-up is used to verify whether small nonlinear distortions are present in the vibration of the middle ear system, which is classically considered to be a completely linear system. In vitro measurements on the right ear of an adult male gerbil proved that nonlinear distortions are present in the vibration of the tympanic membrane. Similar results were seen in measurements on the left ear. The influence of post-mortem changes on the nonlinear behaviour of the middle ear was verified in a number of successive measurements. These indicated that the nonlinear behaviour of the middle ear decreases in time.
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The jaws of different species of stag beetles show a large variety of shapes and sizes. The male jaws are used as weapons in fights, and they may exert a very forceful bite in some species. We investigated in 16 species whether and how... more
The jaws of different species of stag beetles show a large variety of shapes and sizes. The male jaws are used as weapons in fights, and they may exert a very forceful bite in some species. We investigated in 16 species whether and how their forcefulness is reflected in their jaw morphology. We found a large range of maximal muscle forces (1.8N-33N; factor 18). Species investing in large bite muscles, also have disproportionately large jaw volumes. They use this additional jaw volume to elongate their jaws, increasing their winning chances in battles. The fact that this also decreases the mechanical advantage, is largely compensated by elongated in-levers. As a result, high muscle forces are correlated with elevated bite forces (0.27N-7.6N; factor 28). Despite the large difference in forcefulness, all investigated species experience similar Von Mises stresses in their jaws while biting (29MPa–114MPa; factor 4.0; calculated with Finite Element simulations). Hence, stag beetles have s...
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It is well known that one of the features of a laser diode is its wavelength tunability which can be modulated with a variable injection current and/or temperature of its active region. For many industrial and scientific applications it... more
It is well known that one of the features of a laser diode is its wavelength tunability which can be modulated with a variable injection current and/or temperature of its active region. For many industrial and scientific applications it is desirable that the laser gets stabilized. In this paper, on the contrary, the laser diode is turned on-off for a short period of time. The generated peak variations of voltage and temperature will cause a modulation of its wavelength. This modulation is used to add phase-shifts in an unbalanced Twyman-Green interferometer and by using Carre algorithm the phase of the resulting interference wave will be retrieved.
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A low-cost and fully automated process for phase-shifting interferometry by continuously changing and turning on-off the input voltage of a laser diode under the scheme of an unbalanced Twyman-Green interferometer setup is presented. The... more
A low-cost and fully automated process for phase-shifting interferometry by continuously changing and turning on-off the input voltage of a laser diode under the scheme of an unbalanced Twyman-Green interferometer setup is presented. The input signal of a laser diode is controlled by a Data Acquisition (NI-DAQ) device which permits to change its wavelength according to its tunability features. The automation and data analysis will be done using LabVIEW in combination with MATLAB. By using Carré algorithm the phase map is obtained. Measurements of visibility and phase-shift to verify the PSI requirements are also shown.