For large-scale high-power laser devices, the transmitted wavefront gradient root mean square (GRMS) is one of themost important indexes for evaluating the low-frequency distortion of spherical lenses. In this paper, for the low-frequencyerror index requirement of large-diameter spatial filter lens, a conformed polishing method based on composite tool isproposed in the spherical CCOS polishing stage. Based on the detection results of the optical components, the GRMSdistribution is separated by low-pass filtering, and the high value of GRMS is partitioned by K-means algorithm todetermine the polishing path and dwelling time. A composite conformed polishing tool is designed and the simulationanalysis of the polishing tool structure and polishing stress distribution are carried out to optimize the parameters, inorder to obtain an ideal GRMS convergence removal function. After experiments and production verifications ofseveral 440×440 sized spatial filter lenses, the results show that the GRMS can be quickly converged below 7nm/cm,and the convergence rate is improved by about 50% compared with the traditional CNC polishing.
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