Dynamic Speckle Analysis Research Articles

Following the drying process of Fevicol (adhesive) by dynamic speckle measurement

This work presents the study of drying of Fevicol (adhesive) using dynamic laser speckle technique. Dynamic laser speckle analysis is a non-invasive method that does not disturb the drying process. A low power laser light illuminates the sample and corresponding speckle images of the sample resulting from the phenomenon of interference are registered. If the sample shows activity, the speckle pattern changes in time. Following this evolution, we can analyze the drying process by means of image processing algorithms. In this work, the application of dynamic speckle technique to follow the drying process of Fevicol with different drying times is presented. Results obtained using numerical methods of Inertia Moment and cross-correlation show that quantitative evaluation of spatial temporal speckle activities can be used to monitor Fevicol drying process. The approaches such as auto-correlation and speckle contrast using temporal correlation allowed differentiating different stages of drying. In addition, the techniques allowed their applicability to follow the slow streaming of Fevicol from the coin surface.

Performance of intensity-based non-normalized pointwise algorithms in dynamic speckle analysis

Intensity-based pointwise non-normalized algorithms for 2D evaluation of activity in optical metrology with dynamic speckle analysis are studied and compared. They are applied to a temporal sequence of correlated speckle patterns formed at laser illumination of the object surface. Performance of each algorithm is assessed through the histogram of estimates it produces. A new algorithm is proposed that provides the same quality of the 2D activity map for less computational effort. The algorithms are applied both to synthetic and experimental data.

System of acquisition and processing of images of dynamic speckle

In this paper we show the design and implementation of a system to capture and analysis of dynamic speckle. The device consists of a USB camera, an isolated system lights for imaging, a laser pointer 633 nm 10 mw as coherent light source, a diffuser and a laptop for processing video. The equipment enables the acquisition and storage of video, also calculated of different descriptors of statistical analysis (vector global accumulation of activity, activity matrix accumulation, cross-correlation vector, autocorrelation coefficient, matrix Fujji etc.). The equipment is designed so that it can be taken directly to the site where the sample for biological study and is currently being used in research projects within the group.

Assessment of Fevicol (adhesive) Drying Process through Dynamic Speckle Techniques

Dynamic laser speckle (or biospeckle) analysis is a useful measurement tool to analyze micro-motion on a sample surface via temporal statistics based on a sequence of speckle images. The aim of this work was to evaluate the use of dynamic speckles as an alternative tool to monitoring Fevicol drying process. Experimental demonstration of intensity-based algorithm to monitor Fevicol drying process is reported. The experiment was explored with the technique called Inertia Moment of co-occurrence matrix. The results allowed verifying the drying process and it was possible to observe different activity stages during the drying process. Statistical Tukey test at 5% significance level allowed differentiating different stages of drying. In conclusion, speckle activity, measured by the Inertia Moment, can be used to monitor drying processes of the Fevicol.

Quality test protocol to dynamic laser speckle analysis

Biospeckle (BSL) is a phenomenon that develops when a dynamic process occurs under laser illumination in a material containing considerable information on biological and non-biological activity. Analysis of such data has been a challenge because of complex interaction between light and material, and therefore, of high sensitivity of the BSL and variability of biological material. This study was aimed at improving the robustness of BSL techniques and thus reducing its subjectivity and dependence on human expertise. The work presents a protocol that aids in a quality test of three key features of the speckle patterns, particularly those related to saturation, under-exposure, homogeneity and contrast of the grains. The quality test was carried out with data from a maize seed and a paint drying under biospeckle laser monitoring, where it was possible to identify some problems in the images related to the tested features. The results establish the feasibility of the quality test control, which form the early steps of the biospeckle laser analysis, and serves in helping the judgment of the setup.

Normal vector based dynamic laser speckle analysis for plant water status monitoring

The analysis of dynamic laser speckle is widely known as an effective non-contact technique for detecting micro-activity on a sample surface. However, the analysis obtained using conventional statistical methods is heavily influenced by the properties of the sample, laser beam and ambient lighting. Recently, we proposed a new normal vector based dynamic speckle analysis method and demonstrated its ability to remove interference due to non-uniform reflectivity, illumination, and time-varying ambient lighting. In this paper, the normal vector based statistical technique for dynamic speckle analysis is further justified by the application to leaf surface micro-motion detection for monitoring plant water status. We carried out experiments for surface activity detection of attached leaves to monitor variation of leaf water status. The presented results highlight the advantage of the normal vector based analysis over image intensity based methods and demonstrate the potential of measuring plant water status via dynamic laser speckle analysis.

Dynamic laser speckle analysis via normal vector space statistics

Dynamic laser speckle analysis is a useful measurement technique which can be used to analyze micro-motion on a sample surface via temporal statistics based on a sequence of speckle images. The existing analysis methods in the literature are based on intensity variation of the speckle images over time. It is observed that the robustness of these methods can be significantly influenced by the presence of non-uniform incidence and reflectivity, and unrelated image intensity variations. Hence, their applicable circumstances are limited. In this paper, a novel method for dynamic speckle analysis is proposed to address the interference of non-uniform incidence and reflectivity, and unrelated intensity variations. The dynamics of the speckle pattern at a pixel is measured by the temporal statistics for the directions of local normal vectors (rather the intensities) on every speckle image over time. The proposed method can effectively eliminate the aforementioned impacts in a dynamic speckle analysis process. Moreover, the local normal vector at a particular pixel in a speckle image also carries local geometry information regarding to its neighboring pixels. Three algorithms for computing the statistics of the directions of local normal vectors over time are subsequently presented. The effectiveness of the proposed method is demonstrated via the analysis of dynamic speckle patterns measured from a paint drying experiment. The robustness of the proposed method is compared with that of the typical existing methods through processing the dynamic speckle of simulation experiments under non-uniform and varying lighting conditions.

Modeling Dynamic Laser Speckle Patterns of Plant Leaves

t is known that dynamic speckle patterns can be used to identify the temporal evolution of an active sample and some desired properties of the sample may therefore be detected via the dynamic laser speckle analysis. Mathematically understand the structure of sample surface which gives arise to the dynamic speckle patterns is crucial to the analysis. In this paper, a simulation model of the dynamic speckle patterns for plant leaves is proposed. The developed model is derived from the principle of coherent electromagnetic wave scattering off a randomly textured and time varying surface and is demonstrated via the simulation of dynamic speckle patterns of a fresh unattached leaf surface along the true laser speckle measurements. Both simulated and true measurements of the dynamic speckle patterns of the leaf are analyzed via several statistical techniques and a consistent agreement between the results of the two is observed. The proposed statistical model is helpful to gain the insight of the relationship between speckle dynamics and the activity of the leaf surface which is supposed to be an measurement of plant water stress and water status.

Time history speckle pattern under statistical view

The dynamic speckle analysis has been done because speckle interference began to be evaluated as an important source of information, especially those related to biological samples under laser beam. The time history speckle pattern, a THSP image, is an approach to analyze, which allows a summary to represent the activity monitored. THSP adoption has compelled the research to evaluate the information and the reliability of its inner pattern. This study presents a statistical approach to analyze the data using white noise tests and cross-spectrum analysis. The data analyzed was a set of THSP from animal sperm samples. The evaluation of white noise among lines was conducted using the Fischer test over eight THSP and the cross-spectral approach has been conducted by comparing the information in each THSP. The results presented that the THSP of the sperm did not behave as a white noise in a global evaluation, and specifically in the Gaussian white noise test over 4096 lines; only six lines presented the behavior of a white noise pattern. The strong rejection of white noise test confirms that the THSP pattern allows reliable information. The results obtained with the cross-spectral analysis presented differences between lines within the same THSP, showing that the information of an inner pattern varies in relation to space, which is against the findings in literature.

Coherence experiments at the white-beam beamline of BESSYII

The third-generation X-ray source BESSYII (Berlin, Germany) provides coherent X-ray radiation which can be used for static and dynamic speckle analysis. Recently we have demonstrated that one can perform experiments with coherent white radiation provided by a bending magnet (5 < E < 20 keV). In this paper we show that the diffraction figure of the initial pinhole must be considered for the interpretation of coherent experiments. The reflectivity spectrum of a sample results from the Fresnel diffraction of the incident pinhole deformed by the static speckle features of the sample surface. For dynamical experiments all speckle like features alter with time whereas the pure Fresnel fringes remain constant.