Method for measuring position-dependent volume reflection.

The position dependence of volume reflection caused by the illumination of a turbid material by a pencil beam of light yields information about the optical parameters of that material. Existing methods to measure the position dependence of the volume-reflection profile usually require scanning the sample surface and are hardly applicable to the area near the illuminating pencil beam. This paper describes an experimental set up based on a two-dimensional CCD camera with 14-bit dynamic range and a spatial resolution down to 20 µm. As a demonstration of its use, measurements are compared with theoretical results from the random-walk and diffusion theories. The conclusions are made that the equipment is suitable for measuring close to the illuminating beam without the need for scanning and that it gives an indication in terms of the product of radial distance toward the center of the beam and reduced scattering coefficient (rµ(s)') for the area where the theoretical results presented are valid.