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Position measuring apparatus utilizing two-beam interferences to create phase displaced signals

  • US 5,120,132 A
  • Filed: 11/01/1990
  • Issued: 06/09/1992
  • Est. Priority Date: 11/02/1989
  • Status: Expired due to Term
First Claim
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1. An apparatus for measuring the relative position of two objects comprising:

  • an illumination source;

    a detector attached to one of the two objects;

    a measuring graduation in the form of a diffraction grating attached to the other object wherein a light beam emitted from said source is diffracted into partial beam clusters;

    deflection means for deflecting said partial beam clusters onto said measuring graduation wherein said partial beam clusters are diffracted once again so that a two-beam interference is created; and

    at least one detector for detecting and converting the modulation in the intensity of said two-beam interference into an electrical signal,said diffraction grating being configured such that at least one partial beam cluster of the zero order of diffraction is involved at least in the formation of one of the two-beam interferences, and that the modulations that occur in the two-beam interference upon a motion of the measuring graduation in the measuring direction are phase-displaced relative to one another.

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