Dynamic Speckle Patterns Research Articles

Remote sensing of human skin temperature by AI speckle pattern analysis

Analysis of dynamic differential speckle patterns, scattered from human tissues illuminated by a laser beam, has been found by many researchers to be applicable for noncontact sensing of various biomedical parameters. The COVID-19 global pandemic brought the need for massive rapid-remote detection of a fever in closed public spaces. The existing non-contact temperature measurement methods have a significant tradeoff between the measurement distance and accuracy. This paper aims to prove the feasibility of an accurate temperature measurement system based on speckle patterns analysis, enabling the sensing of human temperature from an extended distance greater than allowed by the existing methods. In this study, we used speckle patterns analysis combined with artificial intelligence (AI) methods for human temperature extraction, starting with fever/no fever binary classification and continuing with temperature measurement at higher resolution.

Evaluation of pitting corrosion by dynamic speckle pattern analysis

There is an increasing interest in non-destructive and real-time high-resolution approaches for corrosion studies in metals. In this paper, we propose the dynamic speckle pattern method as a low-cost, easy-to-implement, and quasi in-situ optical technique for the quantitative evaluation of pitting corrosion. This type of corrosion occurs in a specific area of a metallic structure and causes holes formation leading to structural failure. A Custom 450 stainless steel sample, placed in 3.5 wt% NaCl solution and applied to a 350 ,hbox {mV}_{SCE} potential to initiate the corrosion, is used as the sample. The speckle patterns formed by the scattering of a He-Ne laser light is changed over time due to any corrosion in the sample. The analysis of the time-integrate speckle pattern suggests that the growth rate of pitting decreases with time.

Consideration of Laser Speckle Contrast Analysis for Shunt Management

In hemodialysis, normal venipuncture cannot deliver large amounts of blood, so about 90% of patients make an arteriovenous anastomosis called an internal shunt. In addition, since dialysis is performed multiple times a week, frequent puncture and pressure hemostasis are required. As a result, blood vessels are stressed, resulting in stenosis and occlusion. In order to detect and treat such shunt troubles at an early stage, daily shunt management is important. Laser speckle contrast analysis is of interest in the field of visualization of the hemodynamics of living tissues. In this study, the relationship between the flow rate and the contrast value was investigated by a technique for quantifying the amount of change in the dynamic speckle pattern.

Improvement of activity level detection in dynamic speckle patterns with fuzzy logic operators

In this work, the design of a multi-descriptor model is proposed to improve the identification of activity levels in dynamic laser speckle (DLS) image sequences. Fuzzy predicates evaluated with operators of different logic systems were used. The model considers both temporal and spatial effects of the DLS phenomenon. Experiments were carried out to characterize the drying times of a sample painted with water-based paint, illuminated with a coherent light, whose image sequences were captured with a CCD camera. To assess the improvement of the proposed model with respect to single descriptors, the Kruskal–Wallis test and the silhouette index were used. The compensatory logic operators achieved the best results to improve the discrimination of the activity levels, according to the different drying times in the dynamic laser speckle sequences.

Detection of intralayer alignment in multicomponent lipids by dynamic speckle pattern analysis.

Multicomponent mixtures of bilayer lipids, thanks to the coexistence of liquid-crystalline phases in their structures, may be used in the development of functional membranes. In such membranes interlayer ordering distributes across membrane lamellae, resulting in long-range alignment of phase-separated domains. In this paper, we explore the dynamics of this phenomenon by laser speckle pattern analysis. We show that cholesterol content decreases the activity, and the rate of the domains size development is related to the change of physical roughness of the multicomponent lipid mixture. Our results are in agreement with the previous experimental reports. However, our experimental procedure is an easy-to-implement and effective methodology.

Nondestructive Testing of Thin Composite Structures for Subsurface Defects Detection Using Dynamic Laser Speckles

ABSTRACT A novel nondestructive testing method for subsurface defects detection in thin composite structures using dynamic laser speckles is proposed. In this method, a laminated composite panel containing a subsurface defect is excited by a frequency scanned ultrasonic (US) wave and is illuminated by an expanded laser beam. If one of resonant frequencies of the defect coincides with the US frequency, a local area (a region of interest or ROI) of the panel optically rough surface, placed directly above the defect, begins to vibrate, and the sequences of difference speckle patterns containing the spatial response from the defect are recorded. The formation of this response is caused by both decorrelation and speckle blurring within the local speckle pattern generated by the vibrating ROI at its opposite tilts. The accumulation of difference speckle patterns increases the intensity of the spatial response. This method differs from similar ones in that defects are detected using dynamic speckle patterns of a composite rough surface, illuminated by a single expanded laser beam. The verification of the proposed method was performed using a hybrid optical-digital experimental breadboard to test composite panels containing artificial subsurface defects, as well as a real defect.

Random matrix description of dynamically backscattered coherent waves propagating in a wide-field-illuminated random medium

The wave propagation in a random medium plays a critical role in optics and quantum physics. Multiple scattering of a coherent wave in a random medium determines the transport procedure. Brownian motions of scatterers perturb each propagation trajectory and form dynamic speckle patterns in the backscattered direction. In this study, we applied the random matrix theory to investigate the eigenvalue density of the backscattered intensity matrix. We find that the dynamic speckle patterns can be utilized to decouple the single and multiple backscattered components. The Wishart random matrix of the multiple scattering component is well described by the Marčenko–Pastur law, while the single scattering part has a low-rank characteristic. We, therefore, propose a strategy for estimating the first and second order moments of single and multiple scattering components, respectively, based on the Marčenko–Pastur law and trace analysis. Electric field Monte Carlo simulation and in vivo experiments demonstrate its potential applications in hidden absorbing object detection and blood flow imaging. Our method can be applied to other coherent domain elastic scattering phenomena for wide-field propagation of microwave, ultrasound, etc.

Simulation of statistically accurate time-integrated dynamic speckle patterns in biomedical optics.

The simulation of statistically accurate time-integrated dynamic speckle patterns using a physics-based model that accounts for spatially varying sample properties is yet to be presented in biomedical optics. In this Letter, we propose a solution to this important problem based on the Karhunen-Loève expansion of the electric field and apply our method to the formalisms of both laser speckle contrast imaging and diffuse correlation spectroscopy. We validate our technique against solutions for speckle contrast for different forms of homogeneous field and also show that our method can readily be extended to cases with spatially varying sample properties.

Экспериментальное определение вибрационных характеристик рабочих лопаток турбин помехоустойчивым цифровым спекл-интерферометром

The paper notes the wide possibilities and high efficiency of vibration diagnostics of parts and assemblies of power units by the method of electronic speckle interferometry (ESI), shows the feasibility of developing and improving methods for obtaining speckle interferograms of vibrating objects. A patented by the authors' scheme of a digital speckle interferometer (DSI) for determining the dynamic parameters of products is presented. The diffuse reference wave greatly simplifies its alignment, mainly the aligned channels of propagation of interfering beams determine the resistance to mechanical and thermal disturbances, and the separate beam splitter and diffuser make it easy to optimize the optical scheme for the object under study. Speckle interferograms are obtained by speckle correlation methods and a developed method for determining the contrast of the dynamic speckle pattern. It does not impose special requirements on the parameters of the video system, does not require the use of a specialized video camera, and allows, by using a rotary platform, to organize a panoramic view of the oscillatory forms of asymmetric structures. The use of this method in combination with the proposed optical scheme provides an express analysis of products in off-bench conditions. The increased noise immunity of the installation allows the determination of the spectrum of frequencies and vibration modes (SFVM) of samples under free boundary conditions, which is rarely realized in interferometry. The paper presents examples of such speckle interferograms, the expediency of obtaining which is important in the resonance study of the elastic properties of the material and vibration resonance flaw detection. The implemented software and hardware solutions increase the resolution and visibility of the band patterns; facilitate their quantitative interpretation and the extraction of numerical information on the distribution of vibration amplitudes. The area of scientific interests and the specificity of the author's developments have determined the preferential adaptation of the proposed device with a complex of software and methodological developments for vibration testing of gas turbine engine (GTE) blades.

Spatio-temporal analysis of dynamic speckle patterns using singular value decomposition

The ability to non-destructively visualize transient phenomenon via spatial and temporal statistics of fluctuating speckle patterns is determined primarily by the contrast between regions of differing activity levels. We demonstrate a singular value decomposition-based method for extracting spatio-temporal correlation parameters from temporal sequences of dynamic speckle patterns. Each pattern in the temporal sequence is reduced to a representation using column vectors which are subsequently grouped to form a matrix encoded with localized spatio-temporal speckle intensity data. A correlation metric is defined using the singular values of this matrix and is subsequently utilized for generating a correlation map by interpolating the correlation computed at each individual patch. Via a comparison with synthetic data that we generate using known decorrelation parameters, we are able to show that our algorithm produces activity maps with enhanced contrast that are closest to the ground truth.

Remote photonic sensing of blood oxygen saturation via tracking of anomalies in micro-saccades patterns.

Speckle pattern analysis has been found by many researchers to be applicable to remote sensing of various biomedical parameters. This paper shows how analysis of dynamic differential speckle patterns scattered from subjects' sclera illuminated by a laser beam allows extraction of micro-saccades movement in the human eye. Analysis of micro-saccades movement using advanced machine learning techniques based on convolutional neural networks offers a novel approach for non-contact assessment of human blood oxygen saturation level (SpO2). Early stages of hypoxia can rapidly progress into pneumonia and death, and lives can be saved by advance remote detection of reduced blood oxygen saturation.

Quantization of dynamic speckle patterns with spatially varying statistics.

Raw data compression is mandatory for monitoring of processes by dynamic speckle analysis when two-dimensional activity maps are built by pointwise statistical processing of correlated speckle patterns formed on the surface of diffusely reflecting objects under laser illumination. Coarse quantization of speckle patterns enables storage and transfer of a huge amount of images, but it may be inefficient at spatially varying speckle statistics, such as for patterns recorded at non-uniform illumination or reflectivity. We prove efficacy of coarse quantization of the raw speckle data with varying statistics for a normalized algorithm by simulation and a polymer drop drying experiment. Both uniform and non-uniform quantization are proposed for treating such data. Decreasing the bit depth from 8 to 3 is possible without worsening the quality of the activity map.

Application of laser biospeckle analysis for assessment of seed priming treatments

‘Priming’ is one of the well-established and low-cost pre-sowing treatments for improving seed germination properties and productivity. Priming treatments are based on controlled imbibition, allowing seeds to attain first reversible phase of germination prior to radical protrusion from the seed coat. Existing techniques for evaluating the effectiveness of priming require bulky experimental arrangements, long operating times, indirect and destructive analyses, and high costs. In this work, we demonstrate the use of a laser biospeckle technique for the characterization of priming treatments. The study employed two priming methods namely; hydropriming and chemical priming. To characterize the effect of priming, the treated seeds were illuminated by a spatially filtered laser beam. The resultant successive dynamic speckle patterns were captured using a CCD camera and analysed. Both, non-normalized histograms and a Gaussian fitting based robust indexing method were used to assess the qualitative and quantitative mapping of dynamicity. The effect of different priming treatments on seed imbibition behavior was evaluated and the results were benchmarked with the standard germination test. Biospeckle activity was found to be strongly correlated with the germination percentage (R = 0.88, p < 0.01) and negatively correlated with the mean germination time (R = −0.92, p < 0.01). The obtained results demonstrate that laser biospeckle can be advantageously used as an efficient, automated, fast, and non-destructive tool to evaluate seed priming treatments.

Ultrasound simulation with deformable and patient-specific scatterer maps.

Ray-tracing-based simulations model ultrasound (US) interactions with a custom geometric anatomical model, where US texture can be emulated via real-time point-spread function convolutions of a tissue scatterer representation. Such scatterer representations for realistic appearance are difficult to parameterize or model manually and do not respond to volumetric deformations such as those caused with tissue compression by the probe. Herein we utilize brightness mode (B-mode) estimated scatterer maps for ray tracing and propose to enhance the realism of ray-tracing-based simulations by incorporating dynamic speckle patterns that change compliant with tissue deformation. In this work, we realistically simulate US texture deformations in the scatterer domain via back-projection of ray segments into a nominal state before sampling during simulation runtime. We estimate scatterer maps from background in vivo images using a pretrained generative adversarial network. We demonstrated our proposed scatterer estimation and runtime background fusion method on simulated transvaginal US scans of detailed surface-based foetal models. We show the viability of modelling deformations in the scatterer domain at interactive frame rates of 28 frames per second. A quantitative and a qualitative evaluations indicated improved realism in comparison to the state of the art. Transferring a background image in a scatterer representation enables us to capture anatomical content in a physical space, in which deformations can be incorporated physically consistently before convolving with a US point-spread function during simulation runtime. This then uses the same imaging model on both the background and the hand-crafted models leading to a consistent and seamless compounding of contents in the scatterer space.

Assessment of the functional state of skin microhemodynamics by the methods of Doppler fluumetry and speckle-metry

The characteristics of blood microcirculation in human tissues have been investigated by recording and analyzing a dynamic speckle pattern. Methodical approaches have been proposed for evaluating the obtained data in order to verify speckle measurements using the widely used Doppler flowmetry technique.

Fully automated extraction of the fringe skeletons in dynamic electronic speckle pattern interferometry using a U-Net convolutional neural network

With the development of artificial intelligence technology, intelligent fringe processing is a goal of relevant researchers in optical interferometry. We propose an intelligent method to achieve fully automated extraction of the fringe skeletons in electronic speckle pattern interferometry (ESPI) based on U-Net convolutional neural network. In the proposed method, the network is first trained by the samples that consist of the noisy ESPI fringe patterns and the corresponding skeleton images. After training, the other multiframe ESPI fringe patterns are fed to the trained network simultaneously; the corresponding skeleton images can be obtained in batches. Using our method, it is not necessary to process fringe patterns frame by frame. Our method is especially suitable for multiframe fringe patterns processing. We apply the intelligent method to one computer-simulated and one real-dynamic ESPI measurement, respectively. For the simulated measurement, it takes just 40 s to obtain the skeleton images of 20 noisy ESPI fringe patterns using our method. Even for low-quality experimental obtained ESPI fringe patterns, our method can also give desired results.

Fractal box-counting technique for shelf life study of grapes by laser speckle image processing

Background: In agriculture, it is essential to follow the ripening of fruits and vegetables which is a subject of interest economically. The use of optical non-destructive method is the most suitable technique for evaluating the ripening stage of fruits when they ripen off-tree and eventually to predict the optimum storage life. Many methods are recently developed in optical image processing. The texture correlation function and the fractal box counting (FBC) of biospeckle pattern have been described. Materials and Methods: The dynamic speckle patterns known as boiling speckle are produced by a coherent light illumination incident on the active material of biological tissue. A high coherent laser source He-Ne with 632 nm with neutral density filter and charge-coupled device camera are the major components of the experimental setup. The same experiment may be done by a green laser of wavelength 541 nm (green color). The same procedure continues to take the speckle images in periodically. Results and Discussion: With the help of FBC method in image processing technique, we can assess optically rough surface fruits such as grapes in this work. According to the FBC theory, the speckle images (R1) give a binary counting value D = 1.7640 at the initial stage. Gray image converted into binary image which gives the fractal counting value D = 1.7554 at later on phase. It means that the specimen (grapes) becomes dry periodically and its value is affected by the surrounding environmental condition. Conclusion: Using the dynamic speckle phenomenon or biospeckle method, we demonstrated the assessment of shelf life activity of grapes. The visual phase of the autocorrelation function gives reliable results showing the variation in activity because of the internal changes caused by decreasing water content and then becomes dry grape stage. The correlation function of speckle patternand the Fractal Box Counting (FBC) technique has been proposed as a tool to estimate the postharvest stage of grapes. The bioactivities of fruits and vegetable materials are based on Brownian motion, due to subcellular organs. This indicates the senescence or biological aging characteristics. The quantification of the biospeckle phenomena is associated with the moment of inertia, time history of speckle pattern and grey level co-occurrence matrix. We proposed a new FBC technique to assess the shelf life of grapes.

Strong cytoskeleton activity on millisecond timescales upon particle binding revealed by ROCS microscopy.

Cells change their shape within seconds, cellular protrusions even on subsecond timescales enabling various responses to stimuli of approaching bacteria, viruses or pharmaceutical drugs. Typical response patterns are governed by a complex reorganization of the actin cortex, where single filaments and molecules act on even faster timescales. These dynamics have remained mostly invisible due to a superposition of slow and fast motions, but also due to a lack of adequate imaging technology. Whereas fluorescence techniques require too long integration times, novel coherent techniques such as ROCS microscopy can achieve sufficiently high spatiotemporal resolution. ROCS uses rotating back-scattered laser light from cellular structures and generates a consistently high image contrast at 150 nm resolution and frame rates of 100 Hz-without fluorescence or bleaching. Here, we present an extension of ROCS microscopy that exploits the principles of dynamic light scattering for precise localization, visualization and quantification of the cytoskeleton activity of mouse macrophages. The locally observed structural reorganization processes, encoded by dynamic speckle patterns, occur upon distinct mechanical stimuli, such as soft contacts with optically trapped beads. We find that a substantial amount of the near-membrane cytoskeleton activity takes place on millisecond timescales, which is much faster than reported ever before.

Evaluation of activity from binary patterns in dynamic speckle analysis

Pointwise intensity-based statistical processing of dynamic laser speckle patterns formed on the surface of a diffusely reflecting object is perspective for monitoring of ingoing processes of physical or biological activity within the object. The output of the measurement is a two-dimensional map, which shows qualitatively regions of higher or lower activity on the object surface. In the paper, we have proposed transforming the captured 8-bit encoded speckle patterns into binary patterns by applying a pointwise threshold. Motivation behind this study is the need for an algorithm, which is robust to non-uniform illumination and offers lowered computational complexity as time and memory consumption. We showed by simulation and experiment that quality of the map obtained by processing of correlated binary patterns approached that achieved with 8-bit encoded patterns. We analyzed statistical behavior of the estimates built from binary patterns and proved applicability of a non-stochastic threshold as e.g. a constant intensity level at uniform illumination. The proposed algorithm was applied for processing polymer drop drying experimental data.

A multi-camera speckle interferometer for dynamic full-field 3D displacement measurement: Validation and inflation testing of a human eye sclera

We developed and optimized a custom dynamic Electronic Speckle Pattern Interferometer (d-ESPI) for measuring time-dependent three-dimensional (3D) surface displacements during inflation testing of ocular tissues. The 3D displacement field was resolved under dynamic loading conditions for a simplified test case of a rubber phantom and a real-world test case of the posterior sclera of a human eye. We present the optical layout and calibration procedure of the d-ESPI, and demonstrate how the displacement field can be accurately resolved for specimen deformation rates up to 6 μm/s.