Comparison between 3D Digital and Optical Microscopes for the Surface Measurement using Image Processing Techniques

摘要

Surface Engineering has been a scientific discipline studying various procedures for the improvement of surface properties since 1980. The surface roughness of manufactured parts is commonly measured by the tactile methods. The stylus profilometer is one of the standard techniques assessing surfaces. This is a worthy method for looking at small areas but the major disadvantage of using a stylus profilometer is that it requires direct physical contact limiting the measuring speed. In contrast to contact measurement systems, optical technique, which is a non-destructive and non-contact method, appears to be a proper alternative for performing measurement of surface quality including surface roughness. The optical measurement instruments were used for the experiments. One of them was based on the "Focus Variation" technology and the other one was the confocal laser scanning microscope. In this study, 3D digital microscope in addition to the optical microscopes was used. The aim of this study is to compare each technique with others. In this study, the surface roughness were evaluated by employing the image processing methods such as line scanning, speckle and fast fourier transform (FFT) with three different samples machined via different manufacturing processes. The surface roughness results from processed images were obtained using flexible image analysis techniques such as Dark-light technique developed by the authors. The values calculated with the proposed method were compared with the roughness values obtained from 3D digital and optical microscopes.