In a study published in Results in Physics, a research group led by Prof. ZHANG Xuejun from the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Academy of Sciences (CAS) proposed an optimized strategy ensuring relatively complete convolution of the dwell-time algorithm to control the mid-spatial-frequency surface error and simultaneously ensure high optical manufacturing efficiency.

In computer-controlled optical surfacing (CCOS), the paths of the lap tools were limited inside the optical surface; this restricted convolution in the dwell-time algorithm and causes mid-spatial-frequency surface errors. The mid-spatial-frequency residual surface error was a significant obstacle to opticians involved in further improving the precision of optics.

In CCOS, the use of different-sized grinding or polishing laps in manufacturing optics is a routine practice. Increased time consumption when using small laps to correct surface errors. When using large laps, the resulting mid-spatial-frequency errors become one of the main reasons for limiting the optical accuracy. Therefore, in order to suppress mid-spatial-frequency surface error and ensure a high manufacturing efficiency, how to use large and small laps is an urgent problem to be solved.

The research team analyzed the phenomenon and influence of the incomplete convolution in the dwell-time algorithm because a lap tool path is limited inside the optical surface. The complete convolution in the dwell-time algorithm was built to restrain mid-spatial-frequency surface error and an optimized strategy of using different-sized laps was proposed to realize higher manufacturing efficiency for optics.

Simulations and experiments for a large off-axis SiC aspherical mirror indicate that the manufacturing accuracy of the aspherical mirror was greatly improved, and the mid-spatial frequency was controlled effectively, which was favorable for the post-manufacturing process. This demonstrated the validity of the optimized combination strategy, which ensures high manufacturing efficiency while simultaneously improving surface accuracy.

The strategy developed could be widely applied to CCOS in both grinding and polishing processes.