Measurements of hair volume by laser stereometry

A three-dimensional laser stereometer was constructed utilizing an x-y two-dimensional translational stage and a laser device, which provides distance information in the z-direction. The distance data is obtained by triangulation of the reflecting red laser beam from the surface of the measured object, in this case hair. Since hair fiber assemblies do not have a continuous solid surface, each z-dimension reading is obtained as an average of measurements obtained from multiple reflections corresponding to fibers at various depths below the outermost hair surface. We demonstrate the utility of this technique to perform the analysis of either an entire hair tress or relatively short sections of tresses prepared from straight, curly, and frizzy hair and subjected to cosmetic treatments such as washing, conditioning, dyeing, etc. An interpretation is provided for the three-dimensional images of hair assemblies as well as for the calculated volume of space occupied by a hair tress. In addition, we investigated various strategies for testing the volume retention of styling polymers.