A Portable Surface Roughness Measurement System Using Laser Speckle Imaging Based on GLCM

Laser is a light that has a coherent and high intensity compared to other light sources. If the rough surface is illuminated by a laser beam, speckle patterns will be formed, this occurs because of the laser light scattering. The speckle laser pattern holds a lot of information, one of which is the level of roughness of a surface. This research study aims to measure the level of surface roughness in a metal plate. For that purpose, a simple system has been developed to acquire laser speckle images generated from a metal surface that is illuminated by laser. This system consists of a laser source, beam expander and a CMOS camera. In order to process the speckle patterns, a digital image processing algorithm is used based on Gray Level Co-occurrence Matrix (GLCM) analysis. The sample used in this study is nickel metal, which is processed by flat grinding. To calibrate the measurement system used 6 standard specimens from Surface Roughness Comparator with different surface roughness levels. The results obtained show a good correlation between the level of roughness and Contrast features generated by the GLCM analysis. The testing for the accuracy and precision of this measurement system has also been carried out in this study, with accuracy of 96% and 97% precision. Apart from having relatively good precision and accuracy, this measurement system has several other advantages, which are non-contact and easy to use for in- process measurements.