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Two-wavelength confocal interferometer for measuring multiple surfaces

  • US 20040075842A1
  • Filed: 10/22/2002
  • Published: 04/22/2004
  • Est. Priority Date: 10/22/2002
  • Status: Active Grant
First Claim
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1. A scanning interferometer for measuring first and second surfaces of a test piece in sequence comprising:

  • a test arm and a reference arm that convey test and reference beams of light;

    a beamsplitter within the test arm that separates the test beam into first and second sub-test beams;

    a focusing optic within the test arm that focuses the first and second sub-test beams to different points of focus;

    a compound probe within the test arm that conveys the first and second sub-test beams to the different points of focus;

    an actuator that relatively moves the probe with respect to the test piece between a first position at which;

    (a) the point of focus of the first sub-test beam is positioned on the first surface of the test piece and (b) the point of focus of the second sub-test beam is positioned off both the first and second surfaces of the test piece, and a second position at which;

    (a) the point of focus of the second sub-test beam is positioned on the second surface of the test piece and (b) the point of focus of the first sub-test beam is positioned off both the first and second surfaces of the test piece; and

    a detection system that detects interference signals between the reference beam and the first sub-test beam when the probe is located at the first position and detects interference signals between the reference beam and the second sub-test beam when the probe is located at the second position.

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