Showing papers on "Speckle imaging published in 2007"
Journal Article•
TL;DR: In this article, the authors reviewed the development of laser speckle imaging, starting with the connection established between speckles fluctuations and movement in the nineteen-seventies, and ten years later a digital version was used to monitor retinal blood flow.
Abstract: When a diffuse object is illuminated with laser light, a random interference effect known as a speckle pattern is produced. If there is movement in the object, the speckles fluctuate in intensity. These fluctuations can be used to provide information about the movement. A simple way of accessing this information is to image the speckle pattern the fluctuations cause a blurring of the speckle, leading to a reduction in the local speckle contrast. Thus velocity distributions are coded as speckle contrast variations. The same information can be obtained by using the Doppler effect, but producing a two -dimensional Doppler map requires scanning: speckle imaging provides the same information without the need to scan. This paper reviews the development of laser speckle imaging, starting with the connection established between speckle fluctuations and movement in the nineteen-seventies. In the eighties, a photographic technique for monitoring retinal blood flow was developed, and ten years later a digital version was used to monitor capillary blood flow in the skin. Today, many groups around the world are either using or researching the technique, and the paper will close by presenting some of their recent results.
167 citations
TL;DR: A number of whole-field blood velocity measurement techniques are concisely reviewed, focusing on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry, laser speckle contrast imaging and particle image velocIMetry (including particle tracking).
Abstract: In this article a number of whole-field blood velocity measurement techniques are concisely reviewed. We primarily focus on optical measurement techniques for in vivo applications, such as laser Doppler velocimetry (including time varying speckle), laser speckle contrast imaging and particle image velocimetry (including particle tracking). We also briefly describe nuclear magnetic resonance and ultrasound particle image velocimetry, two techniques that do not rely on optical access, but that are of importance to in vivo whole-field blood velocity measurement. Typical applications for whole-field methods are perfusion monitoring, the investigation of instantaneous blood flow patterns, the derivation of endothelial shear stress distributions from velocity fields, and the measurement of blood volume flow rates. These applications require individual treatment in terms of spatial and temporal resolution and number of measured velocity components. The requirements further differ for the investigation of macro-, meso-, and microscale blood flows. In this review we describe and classify those requirements and present techniques that satisfy them.
154 citations
TL;DR: The digital image correlation method is extended to the study of transient deformations such as the one associated with a rapid growth of cracks in materials, and the entire crack tip deformation history, from the time of impact to complete fracture is mapped.
Abstract: The digital image correlation method is extended to the study of transient deformations such as the one associated with a rapid growth of cracks in materials. A newly introduced rotating mirror type, multichannel digital high-speed camera is used in the investigation. Details of calibrating the imaging system are first described, and the methodology to estimate and correct inherent misalignments in the optical channels are outlined. A series of benchmark experiments are used to determined the accuracy of the measured displacements. A 2%-6% pixel accuracy in displacement measurements is achieved. Subsequently, the method is used to study crack growth in edge cracked beams subjected to impact loading. Decorated speckle patterns in the crack tip vicinity at rates of 225,000 frames per second are registered. Two sets of images are recorded, one before the impact and another after the impact. Using the image correlation algorithms developed for this work, the entire crack tip deformation history, from the time of impact to complete fracture, is mapped. The crack opening displacements are then analyzed to obtain the history of failure characterization parameter, namely, the dynamic stress intensity factor. The measurements are independently verified successfully by a complementary numerical analysis of the problem.
134 citations
01 Jan 2007
TL;DR: Holographic and laser speckle interferometry as discussed by the authors can be used to make interferometric measurements on objects with rough surfaces, which is a very powerful method for mapping changes in the shape of three-dimensional objects with very high accuracy.
Abstract: This chapter explores the techniques based on holography and laser speckle. These techniques can be used to make interferometric measurements on objects with rough surfaces. The chapter describes holographic interferometry, which is a very powerful method for mapping changes in the shape of three-dimensional objects with very high accuracy. It is used widely for nondestructive testing and strain analysis. It is also very useful for the analysis of vibrations. Holographic and speckle interferometry permit measurements on objects with rough surfaces. The chapter also presents a brief introduction to holographic strain analysis and holographic vibration analysis. The simplest and most commonly used method for studying vibrating objects is time-average holographic interferometry. Speckle interferometry is explained in detail, in which the speckled image of an object is made to interfere with a reference field. The chapter also presents studies of vibrating objects. If the object vibrates, the speckle in the vibrating areas is averaged while the nodes stand out as regions of high-contrast speckle.
90 citations
TL;DR: This work presents an application of the technique using temporal contrast processing to image cerebral vascular structures with a field of view a few millimeters across and approximately 20 microm resolution through a thinned skull to enable the perception of approximately 10%-30% more vascular structures without the introduction of any contrast agent.
Abstract: High-resolution cerebral vasculature imaging has applications ranging from intraoperative procedures to basic neuroscience research. Laser speckle, with spatial contrast processing, has recently been used to map cerebral blood flow. We present an application of the technique using temporal contrast processing to image cerebral vascular structures with a field of view a few millimeters across and approximately
20 μm resolution through a thinned skull. We validate the images using fluorescent imaging and demonstrate a factor of 2-4 enhancement in contrast-to-noise ratios over reflectance imaging using white or spectrally filtered green light. The contrast enhancement enables the perception of approximately 10%-30% more vascular structures without the introduction of any contrast agent.
76 citations
TL;DR: This work has applied the digital holographic optical coherence imaging technique for the depth-resolved imaging of rat osteogenic tumor multicellular spheroids and acquired cross-section images of the anterior segment and the retinal region of a mouse eye.
Abstract: Digital holographic optical coherence imaging is a full-frame coherence-gated imaging approach that uses a CCD camera to record and reconstruct digital holograms from living tissue. Recording digital holograms at the optical Fourier plane has advantages for diffuse targets compared with Fresnel off-axis digital holography. A digital hologram captured at the Fourier plane requires only a 2D fast Fourier transform for numerical reconstruction. We have applied this technique for the depth-resolved imaging of rat osteogenic tumor multicellular spheroids and acquired cross-section images of the anterior segment and the retinal region of a mouse eye. A penetration depth of 1.4 mm for the tumor spheroids was achieved.
68 citations
TL;DR: Analytical models for the relevant transfer functions of an adaptive optics systems including the effect of an arbitrary correction as well as anisoplanatism are presented.
Abstract: Adaptive optics supported solar speckle imaging requires the calibration of the
source's Fourier amplitudes with the transfer function of atmosphere and optics. We
present analytical models for the relevant transfer functions of an adaptive optics
systems. The models include the effect of an arbitrary correction as well as
anisoplanatism. The proposed models have been compared with observational data using
measurements of α-Orionis and of the solar surface delivering both a direct and
indirect method (using the spectral ratio technique) for validation. We find that
measurements and model agree to a satisfactory degree.
60 citations
TL;DR: Experimental results show that the proposed method does not require classical filtering technique and is simple and effective in reducing speckle noise in digital holography.
Abstract: An effective method for reducing speckle noise in digital holography is proposed in this paper. The proposed method does not require classical filtering technique; instead it utilizes multiple holograms of an object generated by rotating an illuminating light continuously. The reconstructed hologram intensity fields possess different speckle patterns, and by properly averaging the intensity fields, speckle noise in the reconstructed images is reduced significantly. A merlion sculpture is evaluated and experimental results show that the proposed method is simple and effective in reducing speckle noise in digital holography.
59 citations
TL;DR: The results of speckle interferometric observations of 104 binary and 6 triple stars performed at the BTA 6 m telescope in 2004 October are presented in this article, among which 59 there are new binaries recently discovered by the Hipparcos astrometric satellite.
Abstract: The results of speckle interferometric observations of 104 binary and 6 triple stars performed at the BTA 6 m telescope in 2004 October are presented. Nearby low-mass stars are mostly observed for the program, among which 59 there are new binaries recently discovered by the Hipparcos astrometric satellite. Concurrently with the diffraction-limited position measurements we obtained 154 brightness ratio measurements of binary and multiple star components in different bands of the visible spectrum. New, first-resolved binaries are the symbiotic star CH Cyg with a weak companion at 0.043″ separation and the pair of red dwarfs, GJ 913 = HIP 118212. In addition, we derived the orbital parameters for two interferometric systems: the CN-giant pair HD 210211 = HIP 109281 (P = 10.7 yr) and the G2V-K2V G2V-K2V binary GJ 9830 = HIP 116259 (P = 15.7 yr).
58 citations
TL;DR: This work will compare algorithms using the example of a 1D temporal evaluation of interferogram sequences and extend these algorithms to 2D and 3D processing, so that accurate kinematic and deformation parameters of moving objects can be evaluated with different types of optical interferometry.
Abstract: In recent years, optical interferometry has been applied to the whole-field, noncontact measurement of vibrating or continuously deforming objects. In many cases, a high resolution measurement of kinematic (displacement, velocity, and acceleration, etc.) and deformation parameters (strain, curvature, and twist, etc.) can give useful information on the dynamic response of the objects concerned. Different signal processing algorithms are applied to two types of interferogram sequences, which were captured by a high-speed camera using different interferometric setups: (1) a speckle or fringe pattern sequence with a temporal carrier and (2) a wrapped phase map sequence. These algorithms include Fourier transform, windowed Fourier transform, wavelet transform, and even a combination of two of these techniques. We will compare these algorithms using the example of a 1D temporal evaluation of interferogram sequences and extend these algorithms to 2D and 3D processing, so that accurate kinematic and deformation parameters of moving objects can be evaluated with different types of optical interferometry.
55 citations
TL;DR: This study shows the feasibility of imaging objects having different optical scattering coefficients relative to the surrounding scattering medium using ultrasound-modulated optical tomography (UOT), and complements previous UOT experiments that demonstrated optical absorption contrast.
Abstract: We show the feasibility of imaging objects having different optical scattering coefficients relative to the surrounding scattering medium using ultrasound-modulated optical tomography (UOT). While the spatial resolution depends on ultrasound parameters, the image contrast depends on the difference in scattering coefficient between the object and the surrounding medium. Experimental measurements obtained with a CCD-based speckle contrast detection scheme are in agreement with Monte Carlo simulations and analytical calculations. This study complements previous UOT experiments that demonstrated optical absorption contrast.
TL;DR: The results of speckle interferometric observations of 104 binary and 6 triple stars performed at the BTA 6 m telescope in 2004 October are presented in this article, among which 59 there are new binaries recently discovered by the Hipparcos astrometric satellite.
Abstract: The results of speckle interferometric observations of 104 binary and 6 triple stars performed at the BTA 6 m telescope in 2004 October are presented. Nearby low-mass stars are mostly observed for the program, among which 59 there are new binaries recently discovered by the Hipparcos astrometric satellite. Concurrently with the diffraction-limited position measurements we obtained 154 brightness ratio measurements of binary and multiple star components in different bands of the visible spectrum. New, first-resolved binaries are the symbiotic star CH Cyg with a weak companion at 0.043'' separation and the pair of red dwarfs, GJ 913 = HIP 118212. In addition, we derived the orbital parameters for two interferometric systems: the CN-giant pair HD 210211 = HIP 109281 (P=10.7 yr) and the G2V-K2V binary GJ 9830 = HIP 116259 (P=15.7 yr).
TL;DR: The simultaneous quantitative measurement of out-of-plane displacement and slope using the fast Fourier transform method with a single three-aperture digital speckle pattern interferometry (DSPI) arrangement is demonstrated.
Abstract: The simultaneous quantitative measurement of out-of-plane displacement and slope using the fast Fourier transform method with a single three-aperture digital speckle pattern interferometry (DSPI) arrangement is demonstrated. The method coherently combines two sheared object waves with a smooth reference wave at the CCD placed at the image plane of an imaging lens with a three-aperture mask placed in front of it. The apertures also introduce multiple spatial carrier fringes within the speckle. A fast Fourier transform of the image generates seven distinct diffraction halos in the spectrum. By selecting the appropriate halos, one can directly obtain two independent out-of-plane displacement phase maps and a slope phase map from the two speckle images, one before and the second after loading the object. It is also demonstrated that by subtracting the out-of-plane displacement phase maps one can generate the same slope phase map. Experimental results are presented for a circular diaphragm clamped along the edges and loaded at the center.
Book•
01 Oct 2007
TL;DR: In this paper, the authors introduce Electromagnetic Theory Wave Optics and Polarization Interference and Diffraction Image Formation Theory of Atmospheric Turbulence Speckle Imaging Adaptive Optics High Resolution Detectors Image Processing Astronomy Fundamentals Astronomical Applications
Abstract: Introduction to Electromagnetic Theory Wave Optics and Polarization Interference and Diffraction Image Formation Theory of Atmospheric Turbulence Speckle Imaging Adaptive Optics High Resolution Detectors Image Processing Astronomy Fundamentals Astronomical Applications.
TL;DR: An efficient tool is introduced, the inter-image distance, to evaluate the speckle dynamics, and the concept of "speckle rate" (SR, in Hz) is introduced to quantify this dynamics.
Abstract: We describe an extension of multi-speckle diffusing wave spectroscopy adapted to follow the non-stationary microscopic dynamics in drying films and coatings in a very reactive way and with a high dynamic range. We call this technique “Adaptive Speckle Imaging Interferometry”. We introduce an efficient tool, the inter-image distance, to evaluate the speckle dynamics, and the concept of “speckle rate” (SR, in Hz) to quantify this dynamics. The adaptive algorithm plots a simple kinetics, the time evolution of the SR, providing a non-invasive characterization of drying phenomena. A new commercial instrument, called HORUS®, based on ASII and specialized in the analysis of film formation and drying processes is presented.
TL;DR: In this paper, a simple exponential model for quantifying speckle motion was proposed to quantify local motion in optical coherence tomography image sequences of an engineered tissue construct undergoing dynamic compression.
Abstract: We demonstrate through a series of simulations that by parameterizing the temporal speckle contrast statistic from a sequence of translating speckle images on a number of experimental constants, the local temporal contrast can be used to quantitatively assess local motion, provided that the spatial and temporal Nyquist sampling criteria are both met. We develop a simple exponential model for quantifying speckle motion for speckle patterns that display arbitrary intensity statistics and provide suggestions for optimizing both the experimental acquisition of speckle data and the temporal contrast analysis of the data. The confounding effects of uncorrelated noise are also discussed. The model is demonstrated by applying it to an optical coherence tomography image sequence of an engineered tissue construct undergoing dynamic compression. Applications to tissue mechanics are shown, although the discussion is equally relevant for fluid motion studies.
TL;DR: An effective method for speckle noise removal in digital Speckle pattern interferometry is presented, which is based on a wave-atom thresholding technique that improves the sparse representation of fringe patterns when compared with traditional expansions.
Abstract: We present an effective method for speckle noise removal in digital speckle pattern interferometry, which is based on a wave-atom thresholding technique. Wave atoms are a variant of 2D wavelet packets with a parabolic scaling relation and improve the sparse representation of fringe patterns when compared with traditional expansions. The performance of the denoising method is analyzed by using computer-simulated fringes, and the results are compared with those produced by wavelet and curvelet thresholding techniques. An application of the proposed method to reduce speckle noise in experimental data is also presented.
TL;DR: The Cramer-Rao bound of the degree of polarization estimation is determined and it is proposed to illustrate this result by analyzing the variance of different simple estimators.
Abstract: We address the problem of the estimation of the degree of polarization from a single intensity image. For that purpose, one considers the case of coherent active imagery that leads to speckle fluctuations and assumes that the measured intensity image corresponds to a fully developed speckle for each polarized component of the electric field. In particular, we determine the Cramer-Rao bound of the degree of polarization estimation and propose to illustrate this result by analyzing the variance of different simple estimators.
TL;DR: In this paper, a laser shearography instrument that utilizes coherent imaging fiber bundles to port four spatially multiplexed speckle images to a single CCD camera via a shearing Michelson interferometer is presented.
Abstract: Shearography is a full-field interferometric speckle technique used to determine displacement derivatives. Measurement of surface strain is possible using shearography if six components of displacement gradient are calculated. This can be achieved using shearography instrumentation that incorporates at least three measurement channels combined with two orthogonal shear directions. This paper presents a laser shearography instrument that utilizes coherent imaging fibre bundles to port four spatially multiplexed speckle images to a single CCD camera via a shearing Michelson interferometer. The four images are spatially multiplexed onto the sensor of a CCD camera. Wrapped phase maps are derived from the recorded speckle interferograms using temporal phase stepping. The unwrapped phase maps are combined with the measurement channel sensitivity vectors using a matrix operation to determine the required displacement derivatives. Results from an out-of-plane displacement of a flat aluminium plate are presented and compared with a computational model. Results from a second test object that show in-plane and out-of-plane strain components are also shown.
TL;DR: In this article, relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate, were presented.
Abstract: We present relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. We performed 214 new observations of 192 objects, with angular separations in the range 0.2-4.3arcsec, and with an average accuracy of 0.01arcsec. Most of the position angles could be determined without the usual 180° ambiguity, and their mean error is . Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long-term programme is to improve the accuracy of the orbits and constrain the masses of the components. For the first time with PISCO, the astrometric calibration was made with a grating mask mounted at the entrance of the telescope. The advantage of this procedure is to provide a reliable and fully independent scale determination. We have found two possible new triple systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS 4208.
TL;DR: The Fresnel approach of diffraction theory for the free-space geometry is applied and a simple analytical relationship between contrast, coherence length, size of illuminated spot, and distances between source, object, and observation plane is derived.
Abstract: Understanding speckle behavior is very important in speckle metrology application. The contrast of a polychromatic speckle depends not only on surface roughness and the coherence length of a light source, as shown in previous works, but also on optical geometry. We applied the Fresnel approach of diffraction theory for the free-space geometry and derived a simple analytical relationship between contrast, coherence length, size of illuminated spot, and distances between source, object, and observation plane. The effect of contrast reduction is found to be significant for low-coherence light sources.
TL;DR: In this paper, an extension of multi-speckle diffusing wave spectroscopy adapted to follow the nonstationary microscopic dynamics in drying films and coatings in a very reactive way and with a high dynamic range is presented.
Abstract: We describe an extension of multi-speckle diffusing wave spectroscopy adapted to follow the non-stationary microscopic dynamics in drying films and coatings in a very reactive way and with a high dynamic range. We call this technique "Adaptive Speckle Imaging Interferometry". We introduce an efficient tool, the inter-image distance, to evaluate the speckle dynamics, and the concept of "speckle rate" (SR, in Hz) to quantify this dynamics. The adaptive algorithm plots a simple kinetics, the time evolution of the SR, providing a non-invasive characterization of drying phenomena. A new commercial instrument, called HORUS(R), based on ASII and specialized in the analysis of film formation and drying processes is presented.
TL;DR: The experimental results show that the coupled nonlinear PDEs denoising model is capable of effectively removing noise, and the unwrapped phase values obtained by the BPNN method are much more accurate than those obtaining by the well-known traditional interpolation.
Abstract: We extend and refine previous work [Appl. Opt. 46, 2907 (2007)]. Combining the coupled nonlinear partial differential equations (PDEs) denoising model with the ordinary differential equations enhancement method, we propose the new denoising and enhancing model for electronic speckle pattern interferometry (ESPI) fringe patterns. Meanwhile, we propose the backpropagation neural networks (BPNN) method to obtain unwrapped phase values based on a skeleton map instead of traditional interpolations. We test the introduced methods on the computer-simulated speckle ESPI fringe patterns and experimentally obtained fringe pattern, respectively. The experimental results show that the coupled nonlinear PDEs denoising model is capable of effectively removing noise, and the unwrapped phase values obtained by the BPNN method are much more accurate than those obtained by the well-known traditional interpolation. In addition, the accuracy of the BPNN method is adjustable by changing the parameters of networks such as the number of neurons.
TL;DR: The results of 1424 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented in this paper.
Abstract: The results of 1424 speckle interferometric observations of double stars, made with the 26 inch (66 cm) refractor of the US Naval Observatory, are presented. Each speckle interferometric observation of a system represents a combination of over 2000 short-exposure images. These observations are averaged into 1053 mean relative positions and range in separation from 0.36'' to 61.92'', with a median separation of 10.31''. This is the 13th in a series of papers presenting measurements obtained with this system and covers the period 2006 January 12-December 29. Included in these data are nine older measurements whose positions were previously deemed possibly aberrant but are no longer classified this way following a confirming observation. This paper also includes the first data obtained using a new secondary camera, designed and built at USNO.
TL;DR: A phase-dislocation masking method is presented that can be used to detect and clean inconsistent data and improve the rms values of signal-to-noise ratio in unwrapped phase maps.
Abstract: This work describes a rapid-phase unwrapping algorithm that combines the rapidity and simplicity of a path-dependent algorithm and the robustness of a path-independent algorithm by rotating the phase map or the unwrapping direction 90° after a scan in one direction. It offers a solution for noise-contaminated phase data, which includes artifacts, complex-shaped borders, or regions of holes. The algorithm can be used in real-time processing. In addition, a phase-dislocation masking method is presented that can be used to detect and clean inconsistent data and improve the rms values of signal-to-noise ratio in unwrapped phase maps.
TL;DR: It is shown that the speckle contrast depends on holographic fringes and the photorefractive effect, and it is demonstrated that a moving grating technique can be used to suppress the random Speckle.
Abstract: Speckle imaging was investigated by using dynamic holography and photorefractive AlGaAs/GaAs multiple quantum wells in a holographic optical imaging system. We showed that the speckle contrast depends on holographic fringes and the photorefractive effect. We further demonstrated that a moving grating technique can be used to suppress the random speckle.
TL;DR: An efficient method to reduce the noise from electrical speckle pattern interferometry (ESPI) phase fringe patterns obtained by any technique and can overcome the main disadvantages encountered by the two methods.
Abstract: An efficient method is proposed to reduce the noise from electrical speckle pattern interferometry (ESPI) phase fringe patterns obtained by any technique. We establish the filtering windows along the tangent direction of phase fringe patterns. The x and y coordinates of each point in the established filtering windows are defined as the sine and cosine of the half-wrapped phase multiplied by a random quantity, then phase value is calculated using these points' coordinates based on a least-squares fitting algorithm. We tested the proposed methods on the computer-simulated speckle phase fringe patterns and the experimentally obtained phase fringe pattern, respectively, and compared them with the improved sine/cosine average filtering method [Opt. Commun. 162, 205 (1999)] and the least-squares phase-fitting method [Opt. Lett. 20, 931 (1995)], which may be the most efficient methods. In all cases, our results are even better than the ones obtained with the two methods. Our method can overcome the main disadvantages encountered by the two methods.
TL;DR: The results suggest that UOT can potentially provide noninvasive functional imaging of the total concentration and oxygen saturation of hemoglobin in biological tissue.
Abstract: We used multiple optical wavelengths to study ultrasound-modulated optical tomography (UOT) in tissue phantoms. By using intense acoustic bursts and a CCD camera-based speckle contrast detection technique, we observed variations of the ultrasound-modulated signal at various optical absorptions. The experimental variations were found to be highly correlated with predictions from Monte Carlo simulations. By irradiating the sample at two optical wavelengths, we quantitatively estimated the total concentration and the concentration ratio of double dyes in objects embedded in tissue phantoms. The results suggest that UOT can potentially provide noninvasive functional imaging of the total concentration and oxygen saturation of hemoglobin in biological tissue.
TL;DR: In this article, the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler-Bernoulli equation is evaluated.
Abstract: The paper proposes an evaluation technique for the elastic modulus of a cantilever beam by vibration analysis based on time average electronic speckle pattern interferometry (TA-ESPI) and Euler–Bernoulli equation. General approaches for the measurement of elastic modulus of a thin film are the Nano indentation test, Buldge test, Micro-tensile test, and so on. They each have strength and weakness in the preparation of the test specimen and the analysis of experimental results. ESPI is a type of laser speckle interferometry technique offering non-contact, high-resolution and whole-field measurement. The technique is a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI can be used to find the resonance frequency for each vibration mode shape. And the elastic modules of a test material can be easily estimated from the measured resonance frequency and Euler–Bernoulli equation. The TA-ESPI vibration analysis technique can be used to find the elastic modulus of a material requiring simple preparation process and analysis.
TL;DR: The surface analysis of a peach points out the possibility of applying the technique in the quality control of food production and agricultural research and variations of the phase-stepping technique are investigated for fringe pattern evaluation.
Abstract: Profilometry by electronic speckle pattern interferometry with multimode diode lasers is both theoretically and experimentally studied. The multiwavelength character of the laser emission provides speckled images covered with interference fringes corresponding to the surface relief in single-exposure processes. For fringe pattern evaluation, variations of the phase-stepping technique are investigated for phase mapping as a function of the number of laser modes. Expressions for two, three, and four modes in four and eight stepping are presented, and the performances of those techniques are compared in the experiments through the surface shaping of a flat bar. The surface analysis of a peach points out the possibility of applying the technique in the quality control of food production and agricultural research.