Héctor Rabal

Dynamic laser speckle and applications

Preface The Author Contributors List The Speckle Phenomenon N. G. Gaggioli and J. A. Pomarico Dynamic Speckle Origin and Features M. Trivi Speckle and Dynamic Speckle phenomena Theoretical and Numerical Models M. F. Ruiz Gale, E. N. Hogert, N. G. Gaggioli, H. J. Rabal, Dr., and A. T. da Costa Junior Methods of Dynamic Speckle Analysis-Statistical Analysis R. Arizaga, Lic. Activity Images Generalized Differences, Fujiis, Lasca, and Related Methods H. J. Rabal, Ph.D. Frequency Analysis L. I. Passoni, G. H. Sendra, and C. M. Arizmendi Granular Computing in THSP Fuzzy Granular Analysis A. L. Dai Pra and L. I. Passoni Applications in Biological Samples R. A Braga Jr, Ph.D., G. F Rabelo, Ph.D., J. B. Barreto Fo.,Ph.D., F. M Borem, Ph.D., J. Pereira, Ph.D., M. Muramatsu, Ph.D.,and I. M. Dal Fabbro, Ph.D. Applications in Nonbiological Materials H. Jorge Rabal and R. A. Braga Jr. Didactic Dynamic Speckle Software M. Marcon and R.A. Braga Jr. Perspectives H. Jorge Rabal, Ph.D., and R. A. Braga Jr., Ph.D.

Speckle time evolution characterization by the co-occurrence matrix analysis

Abstract We describe some aspects of the measurement of dynamic speckle activity. We propose the use of the co-occurrence matrix of the time history of the intensity of a speckle pattern. Then we suggest a measure of the activity based on the use of one of its second order moments. Some numerical simulations were performed for testing purposes. The method was applied to the study of the drying of paint and was compared with gravimetric measurements. Experimental results obtained are shown and a good correlation is obtained.

Display of local activity using dynamical speckle patterns

We present a display to distinguish loci of equal activity in samples showing dynamic speckle patterns. Regions differing in their activity are shown as different gray levels. We define the generalized differences and the weighted generalized difference operations and we compare the results with previously reported methods. Results obtained with seeds are shown.

Bio-speckle assessment of bruising in fruits

The dynamic speckle patterns or bio-speckle is a phenomenon produced by laser illumination of active materials, such as a biological tissue. Fruits, even hard peel ones, show a speckle activity that can be related to maturity, turgor, damage, aging, and mechanical properties. In this case, we suggest a bio-speckle technique as a potential methodology for the study of impact on apples and the analysis of bruises produced by them. The aim is to correlate physical properties of apples with quality factors using a non-contact and non-invasive technique.

Application of dynamic speckle interferometry to the drying of coatings

In this work a new tool to study the drying of paints, based on an optical technique known as dynamic speckle interferometry is presented. The basic concepts of the technique are described and applied to the drying process of white solvent-borne and white water-borne paints (latex paint) following the time evolution of the activity of dynamic speckle patterns. For processing the data an alternative method based on the use of the second-order moment of the modified co-occurrence matrix of the time history of its intensity was used. The experimental results obtained were compared with the gravimetric technique and the resulting curves from the speckle-time evolution compared favorably with gravimetric drying curves. The results were also discussed on the basis of the knowledge of the coating drying process and factors related with the surface properties. Dynamic speckle interferometry seems to be a useful technique for assessing the time evolution of surfaces and, its sensitivity to refractive index changes helps to determine the start of different stages during the drying of latex paints. The dynamic speckle method tests mainly the activity on the surface and the measurements seem to confirm that the initial stage of drying is like a pure solvent. Finally, the study of different aspects of the drying process using this technique is proposed.

Decomposition of biospeckle images in temporary spectral bands

We present a method of analysis of images of dynamic speckle based on the filtering in frequency bands of the temporary history of each pixel. Butterworth filters are applied to the temporary evolution, and different images are constructed showing the energy in each frequency band. Different degrees of activity of the sample in study, presumably attributed to different origins, are found. The method is exemplified with images of bruising damage in fruits and of biological activity in germinating corn seeds. It is found that the activity in the bruised region of an apple differs from the activity of healthy regions in a certain characteristic frequency range. The activity of the embryo can also be distinguished from that of the endosperm in corn seeds during germination.

Transient phenomena analysis using dynamic speckle patterns

The full width at half maximum (FWHM) is sometimes used to characterize the autocorrelation function of the time history of a speckle pattern. We propose to include more autocorrelation points to diminish the variability of the measurement. The width of the equivalent rectangle (WER) and the X*LOG X measurements are defined and some simulations and experimental results obtained are shown.

Analysis of bacterial chemotactic response using dynamic laser speckle

Chemotaxis has a meaningful role in several fields, such as microbial physiology, medicine and biotechnology. We present a new application of dynamic laser speckle (or biospeckle) to detect different degrees of bacterial motility during chemotactic response experiments. Encouraging results showed different bacterial dynamic responses due to differences in the hardness of the support in the swarming plates. We compare this method to a conventional technique that uses white light. Both methods showed to be analogous and, in some cases, complementary. The results suggest that biospeckle processed images can be used as an alternative method to evaluate bacterial chemotactic response and can supply additional information about the bacterial motility in different areas of the swarm plate assay that might be useful for biological analysis.

Wavelet transform analysis of dynamic speckle patterns texture.

We propose the use of the wavelet transform to characterize the time evolution of dynamic speckle patterns. We describe it by using as an example a method used for the assessment of the drying of paint. Optimal texture features are determined and the time evolution is described in terms of the Mahalanobis distance to the final (dry) state. From the behavior of this distance function, two parameters are defined that characterize the evolution. Because detailed knowledge of the involved dynamics is not required, the methodology could be implemented for other complex or poorly understood dynamic phenomena.

Digital speckle pattern shearing interferometry using diffraction gratings

A digital speckle pattern shearing interferometer with the aid of a diffraction grating as shearing element, is presented. A brief theoretical approach for qualitative purposes is outlined. A comparison with Michelson shearing and phase stepping measurements are presented to show the validity of the proposal. Real time visualization, compactness of the setup and good quality fringes are main advantages.