Digital Holographic Interferometry Research Articles

The cuspal deflection caused by dental composite polymerization shrinkage analyzed by digital holography

Background/Aim. Polymerization shrinkage of filling materials is one of the main disadvantages of adhesive restorative dentistry. The objective of the study was to measure tooth cusps deflection caused by polymerization shrinkage of a resin-based dental material (RDM) in real-time using digital holographic interferometry (DHI) in two groups of cavities restored with and without an additional wall. Simultaneously, internal tooth mechanical behavior was monitored. Methods. Standardized three class I cavities were prepared on third molar teeth. The teeth were cut in two halves in the longitudinal plane, obtaining six samples for the study (now with class II cavities), divided into two groups (group G1 ? with the additional wall, group G2 ? without it), and mounted in aluminum blocks. The cavities were filled with the RDM, cured with a light emitting diode (LED) for 40 sec from the occlusal direction, and monitored during the curing and post-curing period using DHI. Data were analyzed using the Student's t-test for independent samples and the Anderson-Darling test, with an alpha level of 0.05. Results. At the end of the examined period, the samples from the group G1 showed significantly in-creased tooth cusps deflection [t (10) = 4.7; p = 0.001] compared to samples from the group G2. Conclusion. Within the limitations of this study, it was concluded that the presence of the additional wall simulating a dental matrix band had a significant influence on the increase and prolonged deflection of tooth cusps during the examined RDM polymerization shrinkage.

Two-wavelength digital holographic interferometry for unambiguous range extended measurements in fluid mechanics

Non-contact optical methods such as digital holographic interferometry are highly suitable in measurements where the phenomena is fast, performed in transparent or semi-transparent environment and mustn’t be obstructed as when applying local contact techniques. Such specific application can be studying dynamic events during transonic and supersonic blade flutter. Fast, sensitive and rather easy access to the phase information make these techniques very attractive in the study of phase objects/phenomena. However, since light’s phase is bounded to a repetitive cycle of 2π radians, the range of measurement is limited to one cycle of the phase, limiting applications to small gradient phenomena. This paper presents a new interesting way of by-passing this limitation, while still keeping noise values low, by introducing a second laser with a close value wavelength, giving rise to a new interferometric pattern with an extended unambiguous range of measurement. Image acquisition is done simultaneously for both wavelengths and all reconstructions are digitally performed. The principle and preliminary results are included in this paper.

Dispersion of Cloud Droplet Based on Pulsed Digital Holographic Interferometry

Dispersion of Cloud Droplet Based on Pulsed Digital Holographic Interferometry

Importance of the Higher Order Terms of the Williams series expansion: Experimental Aspects and Finite Element Simulations

The study is devoted to the multi-point Williams series expansion for the crack-tip fields in isotropic linear elastic materials and methods of estimating the coefficients of higher order terms in the power expansion. It is shown that higher order terms are very important in processing of the experimental data obtained from interference – optic methods. It is demonstrated that the accurate interpretation of the experimental data requires keeping, considering and evaluating the higher order terms of the Williams expansion. A large cohort of experiments on cracked specimens from optically sensitive materials using digital photoelasticity method was performed. The interference fringe patterns obtained show that the correct description of the stress fields in the vicinity can be given if we take into account higher order terms in the asymptotic presentation of the near crack tip fields. Two interference-optical methods were used. Digital photoelasticity method and digital holography interferometry technique are applied for determination of the coefficients of the Williams series expansion. It is shown that we can restore theoretically the stress field in the vicinity of the crack tip if at least fifteen terms in the power expansion are hold. The classical over-deterministic method is used for the evaluation of the coefficients.

Recent advances in speckle decorrelation modeling and processing in digital holographic interferometry

Digital holography, and especially digital holographic interferometry, is a powerful approach for the characterization of modifications at the surface or in the volume of objects. Nevertheless, the reconstructed phase data from holographic interferometry is corrupted by the speckle noise. In this paper, we discuss on recent advances in speckle decorrelation noise removal. Two main topics are considered. The first one presents recent results in modelling the decorrelation noise in digital Fresnel holography. Especially the anisotropy of the decorrelation noise is established. The second topic presents a new approach for speckle de-noising using deep convolution neural networks. Full Text: PDF ReferencesP. Picart (ed.), New techniques in digital holography (John Wiley & Sons, 2015). CrossRef T.M. Biewer, J.C. Sawyer, C.D. Smith, C.E. Thomas, "Dual laser holography for in situ measurement of plasma facing component erosion (invited)", Rev. Sci. Instr. 89, 10J123 (2018). CrossRef M. Fratz, T. Beckmann, J. Anders, A. Bertz, M. Bayer, T. Gießler, C. Nemeth, D. Carl, "Inline application of digital holography [Invited]", Appl. Opt. 58(34), G120 (2019). CrossRef M.P. Georges, J.-F. Vandenrijt, C. Thizy, Y. Stockman, P. Queeckers, F. Dubois, D. Doyle, "Digital holographic interferometry with CO2 lasers and diffuse illumination applied to large space reflector metrology [Invited]", Appl. Opt. 52(1), A102 (2013). CrossRef E. Meteyer, F. Foucart, M. Secail-Geraud, P. Picart, C. Pezerat, "Full-field force identification with high-speed digital holography", Mech. Syst. Signal Process. 164 (2022). CrossRef L. Lagny, M. Secail-Geraud, J. Le Meur, S. Montresor, K. Heggarty, C. Pezerat, P. Picart, "Visualization of travelling waves propagating in a plate equipped with 2D ABH using wide-field holographic vibrometry", J. Sound Vib. 461 114925 (2019). CrossRef L. Valzania, Y. Zhao, L. Rong, D. Wang, M. Georges, E. Hack, P. Zolliker, "THz coherent lensless imaging", Appl. Opt. 58, G256 (2019). CrossRef V. Bianco, P. Memmolo, M. Leo, S. Montresor, C. Distante, M. Paturzo, P. Picart, B. Javidi, P. Ferraro, "Strategies for reducing speckle noise in digital holography", Light: Sci. Appl. 7(1), 1 (2018). CrossRef V. Bianco, P. Memmolo, M. Paturzo, A. Finizio, B. Javidi, P. Ferraro, "Quasi noise-free digital holography", Light. Sci. Appl. 5(9), e16142 (2016). CrossRef R. Horisaki, R. Takagi, J. Tanida, "Deep-learning-generated holography", Appl. Opt. 57(14), 3859 (2018). CrossRef E. Meteyer, F. Foucart, C. Pezerat, P. Picart, "Modeling of speckle decorrelation in digital Fresnel holographic interferometry", Opt. Expr. 29(22), 36180 (2021). CrossRef M. Piniard, B. Sorrente, G. Hug, P. Picart, "Theoretical analysis of surface-shape-induced decorrelation noise in multi-wavelength digital holography", Opt. Expr. 29(10), 14720 (2021). CrossRef P. Picart, S. Montresor, O. Sakharuk, L. Muravsky, "Refocus criterion based on maximization of the coherence factor in digital three-wavelength holographic interferometry", Opt. Lett. 42(2), 275 (2017). CrossRef P. Picart, J. Leval, "General theoretical formulation of image formation in digital Fresnel holography", J. Opt. Soc. Am. A 25, 1744 (2008). CrossRef S. Montresor, P. Picart, "Quantitative appraisal for noise reduction in digital holographic phase imaging", Opt. Expr. 24(13), 14322 (2016). CrossRef S. Montresor, M. Tahon, A. Laurent, P. Picart, "Computational de-noising based on deep learning for phase data in digital holographic interferometry", APL Photonics 5(3), 030802 (2020). CrossRef M. Tahon, S. Montresor, P. Picart, "Towards Reduced CNNs for De-Noising Phase Images Corrupted with Speckle Noise", Photonics 8(7), 255 (2021). CrossRef E. Meteyer, S. Montresor, F. Foucart, J. Le Meur, K. Heggarty, C. Pezerat, P. Picart, "Lock-in vibration retrieval based on high-speed full-field coherent imaging", Sci. Rep. 11(1), 1 (2021). CrossRef

Mutual diffusion coefficients of dimethyl carbonate + n-heptane and dimethyl carbonate + isooctane from 288.15 K to 318.15 K

The mutual diffusion coefficients of dimethyl carbonate + n-heptane and dimethyl carbonate + isooctane binary systems were measured at temperatures from 288.15 K to 318.15 K with the mass fraction of dimethyl carbonate from 0.05 to 0.95 under atmospheric pressure. All the mutual diffusion coefficients we reported are Fick diffusion coefficients, which were measured by the digital holographic interferometry. The expanded relative uncertainty for the measured mutual diffusion coefficients is estimated to 2.4% with the level of confidence of 0.95 (coverage factor k = 2). Moreover, a theoretical model (UNIDIF) of mutual diffusion coefficients for dimethyl carbonate + n-heptane and dimethyl carbonate + isooctane binary mixtures was given by fitting the experimental results, and the adjustable parameters and infinite dilution diffusion coefficients of these two solutions were given. The influences of temperature and composition on the mutual diffusion coefficients were discussed.

3D deformation measurement in digital holographic interferometry using a multitask deep learning architecture.

The extraction of absolute phase from an interference pattern is a key step for 3D deformation measurement in digital holographic interferometry (DHI) and is an ill-posed problem. Estimating the absolute unwrapped phase becomes even more challenging when the obtained wrapped phase from the interference pattern is noisy. In this paper, we propose a novel multitask deep learning approach for phase reconstruction and 3D deformation measurement in DHI, referred to as TriNet, that has the capability to learn and perform two parallel tasks from the input image. The proposed TriNet has a pyramidal encoder-two-decoder framework for multi-scale information fusion. To our knowledge, TriNet is the first multitask approach to accomplish simultaneous denoising and phase unwrapping of the wrapped phase from the interference fringes in a single step for absolute phase reconstruction. The proposed architecture is more elegant than recent multitask learning methods such as Y-Net and state-of-the-art segmentation approaches such as UNet++. Further, performing denoising and phase unwrapping simultaneously enables deformation measurement from the highly noisy wrapped phase of DHI data. The simulations and experimental comparisons demonstrate the efficacy of the proposed approach in absolute phase reconstruction and 3D deformation measurement with respect to the existing conventional methods and state-of-the-art deep learning methods.

0.1-5 MHz ultrahigh-speed gas density distributions using digital holographic interferometry.

Gas density distributions for an underexpanded jet at several different pressure ratios were measured at ultrahigh speeds in this work using digital holographic interferometry (DHI). DHI measurements have generally been performed on the order of several Hz in the literature, although some recent groups report measurements at 10 and 100 kHz. We demonstrate 2D imaging of gas density distributions at imaging rates up to 5 MHz, which is an increase by a factor of 50 compared to the previous DHI literature. A narrow-linewidth, continuous-wave laser was used in a Mach-Zehnder configuration, and the holograms were recorded using one of two different CMOS cameras. The interferograms were analyzed using the Fourier method, and a phase unwrapping was performed. Axisymmetric flow was assumed for the region near the nozzle exit, and an Abel inversion was performed to generate a planar-slice gas density distribution from the line-of-sight unwrapped phase. The challenges and opportunities associated with performing DHI measurements at ultrahigh speeds are discussed.

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.

Digital holographic interferometry for the measurement of temperature distribution around textile conductive yarn embedded in heating garments

Due to the development of wearable smart/electronic integrated textiles, the heating compression bandages, conductive fabrics, and electrically heated garments have been extensively used in many fields. Heating garments could be widely applied in the field of body warming and physical therapy. To impart heating therapy through garments, we need to select conductive yarn to be incorporated into the fabric. In addition to this, voltage supply, resistance, temperature distribution, temperature gradient, heating area, and spacing between the two consecutive conductive yarns are some major factors that have to be optimized for heating garments. Therefore, identifying the proper conductive yarn and approximate spacing between them is important in the electrically heated garments. The measurement of temperature and temperature profile around heated textile conductive yarn is demonstrated using digital holographic interferometry (DHI). DHI has been widely used to measure temperature and temperature profile of gaseous flames and heat conduction studies, etc., as it is more accurate, precise, and provides better spatial resolution. DHI is chosen to measure temperature distribution around copper and stainless-steel yarns used in textiles. DHI is a noncontact, noninvasive, full-field, and almost real-time interferometric technique. We have chosen copper and stainless-steel yarn to study the temperature profile and uniform heating to approximate spacing between two yarns.

Dynamic displacement measurement in digital holographic interferometry using eigenspace analysis.

Non-contact measurement of displacement undergone by a deformed object is an important application problem in digital holographic interferometry. Such measurements usually demand reliable estimation of interference phase even in the presence of severe noise. This article describes a method for non-contact displacement testing by investigating a robust phase retrieval approach in digital holographic interferometry. The approach is based on eigenspace processing of the complex interference field signal in digital holographic interferometry. The performance of the proposed method for phase retrieval under severe noise conditions is illustrated using simulation results. The practical utility of the proposed method is demonstrated for dynamic deformation analysis using experimental data from digital holographic interferometry.

Interaction of vapor cloud and its effect on evaporation from microliter coaxial well

The evaporation of volatile heavy hydrocarbon liquid from coaxial well configuration is studied to understand the vapor phase transport, vapor cloud interaction and its effect on the local evaporation rate of two evaporating coaxial cavities of microliter volume. The gap between the two coaxial cavities is varied without varying the dimensions (width and depth) of the coaxial cavities for studying the vapor cloud interaction. Digital holographic Interferometry (DHI) is used to decipher the vapor mole fraction field above the coaxial well. Gravimetric measurement has been carried out for measuring the evaporation rate. Diffusion-limited simulation of evaporation process has been carried out using COMSOL Multiphysics software to understand the role of convective motion. IR thermography measurement of liquid interface temperature has been carried out to correlate the vapor cloud interaction with local evaporation rate and evaporation induced cooling. A flat-disk shaped vapor cloud surrounds the coaxial cavities. Total evaporation rate measured from DHI shows good agreement with the gravimetric measurement having maximum deviation of 3%. Good match between the evaporation rate measured from gravimetry and holography with diffusion limited model is observed at low Grashof number. The mismatch in evaporation rate with the diffusion limited model is observed at high Grashof number due to higher radius of the coaxial cavity indicating the dominance of convective motion. The evaporation rate from individual well decreases when liquid simultaneously evaporates from the inner and outer coaxial cavities. This reduction in evaporation rate increases with decrease in gap between the two coaxial cavities due to increase in interaction between the vapor cloud. The decrease in local evaporation rate from individual cavity due to presence of a neighboring evaporating cavity correlates with the evaporative cooling effect using temperature measurement of the interface from IR thermography. Vapor cloud interactions of microliter volume coaxial cavities can influence the evaporation rate of individual coaxial cavity and the convection inside the liquid phase. The present study demonstrates the capability to precisely control the evaporation process by appropriate design of coaxial well configuration. The results from the present study can be useful for controlling the evaporation rate in several applications i.e. protein crystal growth, DNA/RNA sequencing and microfabrication etc. by suitable design of coaxial well.

Digital holographic study of vapor transport of heavy hydrocarbon from heated well cavity

Thin film evaporative cooling is one of the liquid cooling technologies, capable of removing high heat flux with lower junction temperature due to the utilization of latent heat of vaporization. To understand the various transport processes involved in vapour phase during thin film evaporation, evaporation from a heated well cavity of diameter 3 mm and height 2 mm is studied using Digital holographic interferometry technique. A flat disk-shaped vapour cloud is appeared for heated as well as not- heated well surface case. This signifies radial outward natural convection instead of pure diffusion. A higher vapour concentration is obtained at each time instants for heated surface case due to the higher evaporation rate as compared to non-heated, ambient case.

Fast measurement of phase and its derivatives in digital holographic interferometry using graphics processing unit assisted state space method

We propose a method for rapid and simultaneous estimation of interference phase and its derivatives in digital holographic interferometry. The method is based on graphics processing unit (GPU) assisted implementation of state space approach for interferogram processing and provides a massive improvement in computational efficiency over the conventional sequential approach. As a result, the proposed method offers feasibility for dynamic non-contact deformation metrology. We validate the method’s application potential in digital holographic interferometry for analyzing dynamic deformation of a test object.

Modeling of speckle decorrelation in digital Fresnel holographic interferometry.

This paper presents analytical modeling of the speckle decorrelation noise in digital Fresnel holographic interferometry. The theoretical analysis is carried out by considering the complex coherence factor between two speckled images from two digitally reconstructed holograms at two different instants. The expression giving the modulus of the coherence factor is established and depends on the local surface deformation and parameters from the holographic setup. The analysis is supported by realistic simulations and experiments. Both simulations and experimental results exhibit a very good agreement with the theoretical prediction.

Investigation of Nonthermal Plasma Jet Excitation Mode and Optical Assessment of Its Electron Concentration

The results of a study of a plasma jet of atmospheric-pressure helium driven by a capacitive discharge using sine and pulsed modes of excitation are presented. The homogeneous discharge of a multi-channel plasma jet at gas temperature of 34 °C and helium flow rate of 0.5 L/min was achieved with short pulse excitation. A digital holography method is proposed to estimate a basic plasma parameter, i.e., its electron concentration. An automated digital holographic interferometry set-up for the observation and study of a nonthermal plasma jet in a pulse mode is developed and described. The synchronization features of recording devices with the generation of plasma pulses are considered. The electron concentration of the plasma jet is also estimated. The disadvantages of the proposed technique and its further application are discussed.

Non-invasive deformation metrology using subspace analysis in digital holographic interferometry

For non-invasive precision measurement of deformation using digital holographic interferometry (DHI), reliable estimation of interference phase from complex fringe signal is required. This article introduces a method for estimation of interference phase in DHI. The proposed method is based on computing roots of a frequency estimation function obtained from noise subspace of the fringe signal. The main advantage of the proposed method is robustness against severe noise. In addition, the method also offers the capability of direct phase derivative estimation. The performance of the proposed method is validated using numerical simulations. Our simulation results show that even for signal to noise ratio as low as −5 dB, the proposed method offers root mean square errors of less than 1 radian for phase retrieval. The practical utility of the method for non-invasive deformation analysis is demonstrated using experimental results in DHI.

A new calorimetric method for measuring the absolute dose of high-energy electron beams by digital holographic interferometry

A new calorimetric method for measuring the absolute dose of high-energy electron beams by digital holographic interferometry

Fish swim water bulk displacement visualization with digital holographic interferometry.

A collimated transmission beam interferometer is used to measure the water motion provoked by the fish swimming through it. An indirect measurement of the fish motion impact in the water contained in a home-type aquarium is detected. Measurements of the whole aquarium are possible due to a large diameter collimated laser beam in the interferometer's object arm. This beam goes through the aquarium, and any perturbation inside it deflects the collimated beam. The interferometer detects a phase difference, i.e., the beam through the disturbed water undergoes different optical paths. This optical phase change was first demonstrated by means of a simple test using spherical steel marbles placed in a cuvette. For this, the small water movements for a single steel marble are detected with the acquired optical phase. Next, the aquarium optical phase results show water movements according to the fishes' size and swimming speed. It is worth mentioning that no additives were added to the aquarium's fresh water during the tests, so the water was crystal clear.

Digital Holographic Interferometry for Temperature Measurement of Flame without Phase Unwrapping

Fast and precise measuring technique is required for vigilant monitoring of risk assessment of fire. In the present work, digital holographic interferometry has been applied for temperature profile measurement of single and coalesced candle flames without undergoing the tedious phase unwrapping procedure. Hence, it has also reduced time and effort. The impact of wick thickness on the temperature profile of single and coalesced candle flames has also been investigated. It is inferred that the peak temperature of the single and coalesced candle flame diminishes with an increase in the wick thickness of the candle. It has also been deduced that the coalescence of flame enhances the peak temperature of the flame. Maximum enhancement of peak temperature (103 K) on the coalescence of flame has been observed in the merged flames of the thinnest wick. The experimentally calculated value of temperature is in proximity to the temperature measured through the thermocouple.