Backscattering peak of hexagonal ice columns and plates.

The backward cross section of hexagonal ice crystals of arbitrary orientation is calculated for visible light by means of a ray-tracing code. It is shown that backscattering of the tilted crystals is caused by a corner-reflector-like effect. A very large peak of backscattering is found for a tilt of 32.5 degrees between the principal particle axis and the incidence direction. This peak is caused by multiple total internal reflections for part of the rays that are incident upon the skewed rectangular faces. Slant lidar measurements for remote sensing of cirrus clouds are proposed.

Shape characterization of a large nonspherical particle by use of its Fraunhofer diffraction pattern.

We characterize the shape of a large nonspherical particle by means of the two-dimensional Fourier transformation of its diffraction pattern, called the S function. The main properties of S functions are considered. Some ways in which to retrieve the geometric parameters of a particle by use of its S function are discussed. In particular, the parameter of nonsphericity of a particle is defined by means of the S function.

Scattering of light by a red blood cell.

The optical parameters of a red blood cell suspended in the blood plasma and, namely, the scattering and absorption cross sections and the scattering phase function describing the small-angle distribution of the scattered light are calculated. Dependence of the optical parameters on all possible values of size, shapes, orientations, hemoglobin concentration, and oxygenation degree is considered. The data are calculated with the so-called straight-ray approximation. The accuracy of the approximation is estimated by comparison with the Mie theory. © 1998 Society of Photo-Optical Instrumentation Engineers.

Fresnel's rings in reconstruction of scattering media holograms.

The theoretical description of the field reconstructed from an in-line hologram of dispersed media is presented. The intensity distribution in the focal plane of a lens placed behind a hologram is analyzed. It is shown that two overlapped patterns are observing in this plane. The first pattern is entirely in accordance with the small-angle spectrum of radiation scattered by the ensemble of particles, and its view does not depend on the distances between the particles, the hologram, and the lens. The second pattern is made of Fresnel's rings and depends on the distance between the particles and the hologram. A statistical interpretation of the distribution of intensity in the focal plane of a lens is proposed. Experimental results and discussion are presented.