Surface texture assessment of ultra-precision machined parts based on laser speckle pattern analysis

• A novel surface texture assessment method using several laser speckle characteristic parameters was proposed.
• Laser speckle patterns were classified with surface texture characteristics.
• Laser speckle characteristic parameters were proposed, and the surface texture parameters Ra, Rc, and RSm could be evaluated with them.
• The surface texture was described qualitatively with radar charts of the proposed laser speckle characteristic parameters.
• The proposed surface texture assessment method could describe the surface texture of ultra-precision machined parts quantitatively and qualitatively in a wide range.

Surface texture plays an important role in overall product specification, because the surface quality of the product is dominated by the nano-scale surface texture. This paper presents a surface texture assessment method for evaluating roughness and periodicity of surface structure with a laser speckle pattern analysis. By investigating the relation between surface texture and laser speckle pattern, characteristic parameters for describing a laser speckle pattern are proposed. The proposed characteristic parameters can evaluate the surface texture in entire observed area and in limited area in any given direction. Furthermore, the surface texture can be qualitatively assessed with a radar chart of the proposed laser speckle characteristic parameters.