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Optical system for surface topography measurement

  • US 4,340,306 A
  • Filed: 02/04/1980
  • Issued: 07/20/1982
  • Est. Priority Date: 02/04/1980
  • Status: Expired due to Term
First Claim
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1. A non-contacting method for measuring deviations between a reference wavefront representing a reference surface and a test wavefront representing a test surface comprising,establishing a white light interference pattern on a detector between two wavefronts, one wavefront from at least one point on a reference surface of known topography and another wavefront from a corresponding point on a test surface of unknown topography,determining positions of maximum fringe contrast of the white light interference pattern thereby establishing zero optical path differences between said wavefronts,repeatedly translating one of the wavefronts from said surfaces by known incremental distances relative to the detector and establishing other white light interference patterns while establishing zero optical path differences between wavefronts from points on the reference surface and corresponding points on the test surface of unknown topography,recording the positions in each interference pattern of maximum fringe contrast and the corresponding step of incremental distance of surface translation relative to the starting point for each interference pattern, whereby the points of maximum fringe contrast at a given step represent points, the locus of which defines contours for which there is zero optical path difference between the test surface and the reference surface.

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