Spectral analysis of surface roughness and form profile of a machined surface after low pressure lapping

Zhuolin Li, C. Y. Chan, Wing Bun Lee, Yuegang Fu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

1 Citation (Scopus)


The optical performance of lens machined by single-point diamond ultra-precision turning can be affected by both form errors and surface roughness. The former can be characterized by the spectra of lower spatial frequencies of surface variations while the latter by much higher spatial frequencies. Fast Fourier transform method is used to analyze the surface profile and to decompose the surface features in terms of relative spatial frequencies (or periods). Most of the conventional post-machining lapping processes are aimed at improving the surface finish mainly, and the form accuracy would very likely be tempered. A lapping process with very low lapping pressure is used to study the relationship between the various spatial frequency groups with various lapping process parameters. The preferred spectral group is found to change with lapping time. As the lapping time is increased beyond a certain point, the spatial period of the preferred spectral group shifts to a lower spatial frequency region. Thus, it is possible to improve the surface finish while maintaining the form accuracy. The study would have important implications in the lapping of aspheric or freeform surfaces.
Original languageEnglish
Pages (from-to)1399-1405
Number of pages7
JournalProceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
Issue number8
Publication statusPublished - 1 Aug 2016


  • fast Fourier transform
  • Lapping process
  • optical performance
  • spatial frequency
  • surface finish

ASJC Scopus subject areas

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering


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