In: Physical Review A, 2007, vol. 75, no. 5, p. 053815
We derive an extension of the Van Cittert and Zernike theorem (VCZT), which holds very near to planar quasihomogeneous radiation sources. This derivation is based on paraxial propagation of the Wigner distribution function of the scalar field. We identify a critical distance from the source. Below this distance (deep Fresnel region) the field autocorrelation function is invariant upon propagation...
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In: Physical Review Letters, 2008, vol. 100, no. 18, p. 188102
We demonstrate the use of an ordinary white-light microscope for the study of the q-dependent dynamics of colloidal dispersions. Time series of digital video images are acquired in bright field with a fast camera, and image differences are Fourier analyzed as a function of the time delay between them. This allows for the characterization of the particle dynamics independent of whether or not they...
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In: Physical Review Materials, 2017, vol. 1, no. 7, p. 073804
Particle-tracking microrheology (PT-μr) exploits the thermal motion of embedded particles to probe the local mechanical properties of soft materials. Despite its appealing conceptual simplicity, PT-μr requires calibration procedures and operating assumptions that constitute a practical barrier to its wider application. Here we demonstrate differential dynamic microscopy microrheology...
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In: Optics Express, 2008, vol. 16, no. 7, p. 4819-4823
We present results of experiments of diffraction by an amplitude screen, made of randomly distributed circular holes. By careful selection of the experimental parameters we obtain an intensity pattern strongly connected to the Voronoi diagram (VD) generated by the centers of the apertures. With the help of simulations we give a description of the observed phenomenon and elucidate the optimal...
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In: Soft Matter, 2014, vol. 10, no. 22, p. 3938–3949
Polarised microscopy is shown to be a powerful alternative to light scattering for the determination of the viscoelasticity of aligned nematic liquid crystals. We perform experiments in a wide range of temperatures by using an adapted version of the recently introduced differential dynamic microscopy technique, which enables us to extract scattering information directly from the microscope...
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In: Physical Review E, 2009, vol. 80, no. 3, p. 031403
We describe the use of a bright-field microscope for dynamic light scattering experiments on weakly scattering samples. The method is based on collecting a time sequence of microscope images and analyzing them in the Fourier space to extract the characteristic time constants as a function of the scattering wave vector. We derive a theoretical model for microscope imaging that accounts for (a) the...
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In: Current Opinion in Colloid & Interface Science, 2007, vol. 12, no. 1, p. 50-57
In this article we review some of the most important new developments in light scattering that have emerged over the past 10 years. Some of the new methods substantially extend the range of accessible time and length scales. Different cross-correlation methods are now available to suppress multiple scattering over a large concentration range. Novel low coherent light sources on the other hand...
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In: Optics Express, 2010, vol. 18, no. 14, p. 14519-14534
We study the noise of the intensity variance and of the intensity correlation and structure functions measured in light scattering from a random medium in the case when these quantities are obtained by averaging over a finite number N of pixels of a digital camera. We show that the noise scales as 1/N in all cases and that it is sensitive to correlations of signals corresponding to adjacent...
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