Surface Roughness Measurement from Shape-from-focus

To measure the surface roughness of objects, a non-contact measurement method based on shape from focus was proposed. This method uses sequences of captured two-dimensional images to reconstruct the three-dimensional surface shape, and calculates surface roughness parameters based on the reconstructed height data. The accuracy of three-dimensional reconstruction depends on the accuracy of the initial focus volume of the image and the optimization of the initial depth map. To solve this problem, it is proposed to use the curvature-based focus measurement method to calculate the focus value at each position, and classify and remove the noise of the initial depth map to obtain a high-precision reconstructed depth map, thereby ensuring accurate measurement of surface roughness. The experimental results show that the relative errors of roughness measurement are all within 6%, which not only enables evaluation in the line direction, but also enables comprehensive evaluation on the surface. This method can meet the requirements of measurement accuracy and has very good flexibility, which has obvious advantages for surface shape measurement of small-sized targets.