Anisotropic speckle patterns in the light scattered by rough cylindrical surfaces

Profiling Suspensions in Natural Water by a Simplified Dynamic Light Scattering Procedure and Sedimentation

A coherent light scattering experiment was carried out. The samples were aqueous natural water suspensions picked from the same river. While sedimentation occurred in the samples, they were subjected to a dynamic light scattering (DLS) experiment and the time series was recorded at certain time intervals. For each recording, a program written for this purpose, performing at least square minimisation, computed the average diameter of the particles in suspension. The variation of the average diameter in time indicates the dominant type of suspensions in water.

Estimating Particle Concentration in Natural Water by Speckle Contrast

A coherent light scattering experiment was carried out on an aqueous clay suspension with an extended range of concentrations. The far field speckle was recorded as a video recording in an unconventional manner using a charged coupled device. A computer code for image processing, written for this purpose, was used to compute the average far field contrast. The variation of average contrast with particle concentration was analysed, and a possible fast procedure for assessing the particle concentration over an extended concentration range was suggested.

Measurement of red blood cell aggregation using X-ray phase contrast imaging

When a coherent beam illuminates spatially disordered particles, speckle patterns are formed due to interference of the scattered light waves. Speckle patterns from biological tissues using synchrotron phase contrast X-ray imaging can provide functional information about micro-scale morphological structures of the tissues. In this study, we investigated the size and contrast variations of the speckles of aggregated red blood cells (RBCs) suspensions with varying the degree of RBC aggregation. Results show that the degree of RBC aggregation is a governing parameter on the change of speckle characteristics. This blood speckle analysis method can be used as a novel modality for monitoring RBC aggregation.

Laser-based displays: a review

After the invention of lasers, in the past 50 years progress made in laser-based display technology has been very promising, with commercial products awaiting release to the mass market. Compact laser systems, such as edge-emitting diodes, vertical-cavity surface-emitting lasers, and optically pumped semiconductor lasers, are suitable candidates for laser-based displays. Laser speckle is an important concern, as it degrades image quality. Typically, one or multiple speckle reduction techniques are employed in laser displays to reduce speckle contrast. Likewise, laser safety issues need to be carefully evaluated in designing laser displays under different usage scenarios. Laser beam shaping using refractive and diffractive components is an integral part of laser displays, and the requirements depend on the source specifications, modulation technique, and the scanning method being employed in the display. A variety of laser-based displays have been reported, and many products such as pico projectors and laser televisions are commercially available already.

Speckle size of light scattered from slightly rough cylindrical surfaces

This research is an extension of the optical method of quality control presented in a previous paper [Appl. Opt. 39, 5811 (2000)] to the case of slightly rough cylindrical surfaces. Applying the Kirchhoff scalar diffraction theory yields an analytical expression of the autocorrelation function of the intensity scattered from slightly rough cylindrical surfaces. This function, which is related to speckle size and shape, is shown to depend on the surface correlation length, unlike for plane surfaces for which the speckle depends on the illuminated area only. The theoretical expression is compared with that for the speckle produced by the light scattered from a cylindrical bearing and from various high-quality wires, showing that the method allows the correlation lengths of high-quality cylindrical surfaces to be determined.

Study of speckle size of light scattered from cylindrical rough surfaces

The autocorrelation function of the intensity scattered from cylindrical rough surfaces is analytically obtained with the Kirchhoff scalar diffraction theory. It is shown that, in contrast to the case in which planar rough surfaces scatter radiation, this function, related to the speckle size, depends on the statistical parameters that characterize the surface and on the scattering direction. This result suggests a new, to our knowledge, optical method that can be applied to the characterization of cylindrical rough surfaces, such as in on-line quality assessment, in manufacturing processes. The calculated theoretical expression was tested, showing good agreement with experiments.