Evaluation of surface roughness of a machined metal surface based on laser speckle pattern

摘要

The surface roughness of a machined metal surface is crucial to its appearance and performance. There are hardly any in-situ methods for surface roughness measurement of moving surfaces. A study of the digital speckle patterns generated by rough surfaces illuminated by a laser is performed experimentally. Laser speckle phenomenon can be used to monitor the surface roughness in a non-contact way. By investigating the effect of the surface roughness on the statistical and fractal parameters of the laser speckle pattern, an assessment method for evaluating surface roughness is discussed. The results show that some of the proposed statistical parameters have definite relationships with the surface roughness and can be explored to evaluate the surface roughness. Furthermore, the fractal parameters of the speckle pattern are sensitive to the type of machining process and therefore they can be used to classify the machined surface. The method can be a practical tool to achieve in-situ surface roughness measurement of moving surfaces.