An overview of optical methods for in-process and on-line measurement of surface roughness

Surface roughness is one of the important technical requirements of machine parts. There are some difficulties to measure surface roughness on-line specially in-process. At present optical methods are often used to measure surface roughness. These methods mainly contain: using fibre optics as a sensor to measure; using light scattering technique to measure; using the speckle contrast to measure; using the dark ratio and bright ratio to measure; using the machine vision-based data method to measure. All these methods need to measure in a clean environment, so such taking some measure can be used in in-process and online measurement.