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Research on the magnetorheological finishing of large aperture off-axis aspheric optical surfaces for zinc sulfide

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2017-03-08
JournalProceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE
AuthorsYunfei Zhang, Wen Huang, Yongcheng Zheng, Fang Ji, Min Xu
InstitutionsFudan University, China Academy of Engineering Physics
Citations2

Abstract

Section titled ā€œAbstractā€

Zinc sulfide is a kind of typical infrared optical material, commonly produced using single point diamond turning (SPDT). SPDT can efficiently produce zinc sulfide aspheric surfaces with micro-roughness and acceptable figure error. However the tool marks left by the diamond turning process cause high micro-roughness that degrades the optical performance when used in the visible region of the spectrum. Magnetorheological finishing (MRF) is a deterministic, sub-aperture polishing technology that is very helpful in improving both surface micro-roughness and surface figure.This paper mainly investigates the MRF technology of large aperture off-axis aspheric optical surfaces for zinc sulfide. The topological structure and coordinate transformation of a MRF machine tool PKC1200Q2 are analyzed and its kinematics is calculated, then the post-processing algorithm model of MRF for an optical lens is established. By taking the post-processing of off-axis aspheric surfacefor example, a post-processing algorithm that can be used for a raster tool path is deduced and the errors produced by the approximate treatment are analyzed. A polishing algorithm of trajectory planning and dwell time based on matrix equation and optimization theory is presented in this paper. Adopting this algorithm an experiment is performed to machining a large-aperture off-axis aspheric surface on the MRF machine developed by ourselves. After several timesā€™ polishing, the figure accuracy PV is proved from 3.3Ī» to 2.0Ī» and RMS from 0.451Ī» to 0.327Ī». This algorithm is used to polish the other shapes including spheres, aspheres and prisms.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
  1. 2012 - The Development and Application of the Materials for Infrared Windows and Domes
  2. 2013 - Research on Processing Technology of ZnS Crystal
  3. 2013 - Magnetorheological finishing with chemically modified fluids for studying material removal of single-crystal ZnS
  4. 2007 - Improving surface figure and microroughness of IR materials and diamond turned surfaces with Magnetorheological Finishing (MRF)
  5. 2006 - Research on Key CNC Technique of the Magnetorheological Finishing Machine Tool
  6. 2004 - Dwell time algorithm for MRF of axis-sysmmetrical aspherical parts
  7. 2010 - Post processing for magnetorheological finishing of optical mirrors
  8. 2010 - Dwell time algorithm based on optimization theory for magnetorheological finishing

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