Noncontact measurements of sanding and raising effects

The method presented in this paper pertains to an optical roughness meter t hat considers a fabric in all surface directions. A previous paper presente d a tribological method for investigating textile fabrics, which used a rou ghness meter with a contact between the probe and the surface. However, a c ontact is not always acceptable, and sometimes a noncontact method is bette r. Thus, an optical multidirectional roughness meter with the same signal p rocessing and sample movement of the earlier apparatus has been developed. The principle is to consider the reflection of a laser beam by a fabric. Th e reflected ray is converted into an electrical signal with a photomultipli er, and this signal is subjected to Fourier analysis. The power spectral de nsity versus frequency presents some peaks that reveal the basic directions of the fabric structure, the function of the weave or knit, and the fabric density. The height of these frequency peaks decreases after sanding or ra ising, thus characterizing the state of the fabric surface.