A registration-based stitching method for obtaining high-accuracy material removal distribution in the sub-aperture polishing process

Abstract

In the research of rapidly developed deterministic sub-aperture polishing technologies, the analysis of material removal distribution is vital for promoting the precision, efficiency, and stability of the polishing process. To obtain a high-accuracy material removal distribution over a large-scale freeform surface with a high lateral resolution, sub-aperture stitching measurements are indispensable. Due to the limitation of traditional stitching methods, it remains a great challenge to obtain precise freeform surface topographies. This paper proposes a registration-based stitching method, which minimizes the negative impact of stitching error, to yield a material removal distribution with both high accuracy and fine lateral resolution. Firstly, to obtain an initial estimate of the rigid transformation for each sub-aperture, conventional stitching and registration based on the least-square stitching method and the robust iterative closest point algorithm are implemented. Secondly, a registration-based stitching model considering the invariance characteristic of the unpolished region is developed to cancel out the inconsistent stitching errors for obtaining a more precise material removal distribution. Finally, a polishing experiment has been conducted to validate the effectiveness of the proposed method. The registration-based stitching method and a commercial stitching program are utilized individually to obtain the material removal distribution. Comparison results show that the proposed method can largely improve the measuring accuracy of material removal distribution, which promotes the further study of the deterministic sub-aperture polishing process.