Surface roughness measurement

The paper deals with noncontacting nondestructive method of measuring surface roughness properties using speckle patterns. Compared to a stylus-type mechanical profilometer, the speckle pattern method is relatively easy to handle. The coherent light speckle contrast method is shown to be useful for measuring fine-scale surface roughness, less than 0.25 micron, while polychromatic speckle pattern methods are better suited for moderate surface roughnesses, 0.2 to 5 microns. Speckle pattern correlation is applicable for comparatively rough surfaces, 1 to 30 microns.