Abstract: For the grinding surface with weak texture and low roughness, the traditional machine vision roughness measurement method was difficult to extract surface texture features, and the measurement accuracy was affected by the direction of surface texture,thus a color light measurement method insensitive to the texture direction was proposed. Firstly, based on the Beckmann-Spizzichino light reflection model, the light reflection mechanism of rough surface was analyzed. Then the grinding surface was used as the reflective surface, a plan of color light reflection image-based grinding surface roughness measurement was proposed, and the measurement platform was built. Finally, in combination with the texture direction characteristics of the grinding surface, a color uniformity sensitivity measurement index Cusd was designed, which established a strong correlation with the grinding surface roughness and realized the measurement of the grinding surface roughness. The experimental results show that the performance of the measurement index Cusd is better than other gray-scale indexes; the correlation with the roughness is 0.978, which has a strong positive correlation, and the index is not sensitive to the direction of texture; for the grinding surface with the roughness range of 0.017~0.646 μm, the mean square error of prediction was 0.000 84 and the average measurement error was 0.02 μm, which meets the requirements of grinding surface measurement.

Key words:  grinding surface roughness; color uniformity sensitivity; roughness measurement; light reflection model; texture direction