A Technique for Rapidly Measuring Surface Roughness Using a Laser

Abstract

A noncontact optical technique for rapidly measuring surface roughness using a laser is proposed. The reflected light intensity distribution of a laser beam illuminated on the surface of a specimen will broaden as the surface roughness increases. The intensity distributions reflected on the surface of aluminum specimens were measured with a plasma-coupled device (PCD). The reflected intensity curve can be approximated by a Gaussian function. The broadness of the intensity distribution curve was evaluated with the standard deviation, called a Gaussian curve parameter (GCP), of a Gaussian function approximating the intensity curve. The center-line averaged roughness Ra increased with increasing GCP, which can be determined in two seconds. The roughness Ra within the range of 0.1 to 0.5 μm can be obtained from measured GCP by using the experimental equation given by Ra=0.088GCP+0.032.