TY - GEN
T1 - Dwell time calculation and curvature effect compensation method of magnetorheological finishing for large-aperture aspheric optics
AU - Gao, Qing
AU - Wang, Shanshan
AU - Shi, Feng
AU - Zhang, Nansheng
AU - Hao, Qun
N1 - Publisher Copyright:
© 2026 SPIE.
PY - 2026/1/9
Y1 - 2026/1/9
N2 - Aspheric optics are widely utilized in high-performance optical systems due to superior properties. The fabrication of projection objectives for extreme ultraviolet lithography (EUVL) imposes extremely stringent requirements on surface accuracy, yet the ultraprecision machining of aspheric optics remains a fundamental challenge in optical manufacturing. Magnetorheological finishing (MRF), characterized by high material removal efficiency, minimal subsurface damage, and excellent surface error convergence ability, has become a key technology of optical manufacturing. However, large-aperture aspheric optics significantly increase the number of trajectory points, and the polishing paradigm based on a constant tool influence function (TIF) fails to accommodate the complex curvature distribution of aspheric optics. This instability in the TIF leads to large-scale and ill-conditioned dwell time computation, which severely constrain manufacturing accuracy and consistency. Based on the characteristics of MRF process and the principles of fluid mechanics, this paper analyzes the TIF model for aspheric surfaces in MRF, and compensates the curvature effect of aspheric surface based on point-by-point adaptive compensation method. Through the theoretical model, the curvature of the dwell point is solved point by point and the global spherical mapping is realized, which avoids the local fitting error and significantly improves the compensation efficiency and accuracy. Based on the solution method of linear equations of dwell time, a splicing removal efficiency matrix construction model is established and converted into a C language package, which significantly expands the computational scale and improves solution efficiency. Finally, the simulation experiment is conducted on an aspheric mirror with an aperture of 300mm×300mm and a conic constant of -15.6. The results demonstrate that the root mean square (RMS) of the surface error is reduced from 98.53nm to 0.96nm, thereby verifying the applicability of the proposed method in high-precision aspheric polishing, and provides an effective technical path for the ultra-precision manufacturing of aspheric lenses in the EUVL system.
AB - Aspheric optics are widely utilized in high-performance optical systems due to superior properties. The fabrication of projection objectives for extreme ultraviolet lithography (EUVL) imposes extremely stringent requirements on surface accuracy, yet the ultraprecision machining of aspheric optics remains a fundamental challenge in optical manufacturing. Magnetorheological finishing (MRF), characterized by high material removal efficiency, minimal subsurface damage, and excellent surface error convergence ability, has become a key technology of optical manufacturing. However, large-aperture aspheric optics significantly increase the number of trajectory points, and the polishing paradigm based on a constant tool influence function (TIF) fails to accommodate the complex curvature distribution of aspheric optics. This instability in the TIF leads to large-scale and ill-conditioned dwell time computation, which severely constrain manufacturing accuracy and consistency. Based on the characteristics of MRF process and the principles of fluid mechanics, this paper analyzes the TIF model for aspheric surfaces in MRF, and compensates the curvature effect of aspheric surface based on point-by-point adaptive compensation method. Through the theoretical model, the curvature of the dwell point is solved point by point and the global spherical mapping is realized, which avoids the local fitting error and significantly improves the compensation efficiency and accuracy. Based on the solution method of linear equations of dwell time, a splicing removal efficiency matrix construction model is established and converted into a C language package, which significantly expands the computational scale and improves solution efficiency. Finally, the simulation experiment is conducted on an aspheric mirror with an aperture of 300mm×300mm and a conic constant of -15.6. The results demonstrate that the root mean square (RMS) of the surface error is reduced from 98.53nm to 0.96nm, thereby verifying the applicability of the proposed method in high-precision aspheric polishing, and provides an effective technical path for the ultra-precision manufacturing of aspheric lenses in the EUVL system.
KW - Adaptive compensation of aspheric curvature effects
KW - Large-scale dwell time solution
KW - MRF tool influence function modeling
KW - Removal efficiency matrix construction based on coordinate transformation
UR - https://www.scopus.com/pages/publications/105027940851
U2 - 10.1117/12.3093841
DO - 10.1117/12.3093841
M3 - Conference contribution
AN - SCOPUS:105027940851
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Fifth International Computational Imaging Conference, CITA 2025
A2 - Su, Ping
A2 - Liu, Fei
PB - SPIE
T2 - 5th International Computational Imaging Conference, CITA 2025
Y2 - 19 September 2025 through 21 September 2025
ER -