Multi-dimensional Assessment of Precision Machined Surface Texture Based on Laser Speckle Pattern Analysis

Surface texture of precision machined surfaces plays an important role in providing various functions to product surfaces. This paper presents a surface texture assessment method based on a laser speckle pattern analysis. Considered as simple light scattering phenomenon, laser speckle intensity can represent surface roughness. On the other hand, considered as diffraction phenomenon, the period of anisotropic pattern on a laser speckle is estimated to be inversely proportional to the period of micro structure. The proposed method evaluates multiple properties of surface texture from a laser speckle pattern, such as roughness, period, and degree of similarity in periodic micro surface structures. By investigating experimentally the relation between surface texture and laser speckle pattern of machined surfaces, several characteristic parameters of laser speckle, such as the mean intensity, the autocorrelation length of intensity distribution, and the degree of similarity between adjacent speckle patterns are proposed for evaluating surface texture properties. In addition, the anisotropy of micro surface structure is assessed by using the proposed parameters of laser speckle pattern.