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.