Importance

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Abstract

Method and apparatus are disclosed for providing Moire distance and displacement measurements of a diffusely reflective surface of an object or support. More particularly, a first grating is physically located, formed, or printed on the diffusely reflective surface. An image of the first grating is formed on a second grating by an imaging means for generating a Moire pattern behind the second grating. At an initial position of the diffusely reflective surface relative to the imaging means, the periods of the image of the first grating and the second grating match. Movement of the diffusely reflective surface in a direction normal thereto and away from the initial position produces a spatially varying intensity pattern caused by the Moire between a shifting and changing magnified pattern of the image of the first grating and a pattern of the second grating. The temporal intensity changs in the Moire pattern are detected and are used to produce information related to the instantaneous distance and displacement of the diffusely reflective surface from the initial position.

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First Claim