High-resolution white light scanning stitching measurement of full-surface microstructure

Abstract

With the development of ultra-precision machining technology, parts with microstructures on the surface are playing an increasingly important role in engineering practice. The scanning interference microscope measurement method is widely used in the measurement of microscopic surface topography. This paper proposes a method of interference microscopy combined with subaperture stitching. The first step is to divide and measure the sub-aperture. There is a partial overlap area between the divided adjacent subapertures. The white light interferometer measures each sub-aperture in turn. The second step is edge feature detection. There are highly steep edge features between the bottom of the groove and the surface of the surface microgroove. The stitching algorithm detects edge features by detecting the slope threshold of the sub-aperture. The third step is to correct the abscissa. Project the detected edge feature data onto the OXY plane to generate a 2D data set. The multi-dimensional motion scanning platform inevitably has motion errors in the measurement process, so the edge characteristic curves of adjacent sub-apertures have obvious lateral displacement in the overlapping area. The lateral displacement and angle of the lateral coordinate of each sub-aperture are corrected by the least square method. The fourth step is the height coordinate correction. The stitching algorithm minimizes the height difference between the corresponding points in the overlapping area, and solves it with a linear least squares problem model. We have completed the measurement of the fringe pattern on the computer-generated hologram (CGH) substrate and the complete topography of the long groove on the 10mm hemisphere. After the sub-aperture global iterative stitching algorithm, there is no stitching trace in the simulation result. For the long groove on the hemisphere, we designed a four-dimensional scanning motion platform and a special fixture to ensure that the long groove on the hemisphere rotates around an axis perpendicular to the geodesic line. The center of the white light interference fringe is always at the center of the long slot aperture.