Comparing 2-D screen projections to 1-D goniometric measurements in scattering studies of surface roughness

Video goniometry was used to study the angular dependence of scattering from tissues and test materials. Tissues and standard roughness samples (sandpaper) were placed vertically in front of a 543 nm He-Ne laser with the tissue surface normal at 45 degrees from the incident beam. The scattered light patterns projected onto a screen that was photographed by a digital camera. The scatter pattern showed a specular peak centered at -45 degrees which was described by a Henyey-Greenstein function. The pattern also presented a diffuse Lambertian pattern at 0 degrees (normal to the tissue). The line between the peak specular and the peak Lambertian identified the scattering plane, despite any slight misalignment of the tissue. The analysis utilized a coordinate transform based on mathematics for mapping between a flat Mercator map and a spherical planetary surface. The system was used to study the surface roughness of muscle tissue samples (bovine striated muscle and chicken cardiac muscle).