Method and apparatus for absolute Moire distance measurements using a grating printed on or attached to a surface
First Claim
1. A method of providing absolute Moire distance measurements comprising the steps of:
- (a) locating, forming, or printing a first grating on a diffusely reflective surface;
(b) forming an image of the first grating on a second grating with an imaging means for generating a Moire pattern formed by the product of a pattern of the image of the first grating and a pattern of the second grating; and
(c) detecting a difference in magnification between the pattern of the image of the first grating and the pattern of the second grating as the diffusely reflective surface moves normal to a plane thereof for generating information related to the absolute distance of the diffusely reflective surface from a reference position.
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Abstract
Method and apparatus are disclosed for providing absolute Moire distance measurements of a diffusely reflective surface from a reference position. More particularly, a first grating is located, formed, or printed on the diffusely reflective surface. An image of the first grating is formed on a second grating or detector array by imaging means for generating a Moire pattern that is detected by a detector means. At the reference 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 from the reference position in a direction normal thereto, produces a spatially varying intensity pattern at the detector means which results from the shifting and magnification mismatch between the pattern of the image of the first grating and the pattern of the second grating. Measuring the amount of magnification differences between the two patterns provides information related to the instantaneous absolute distance of the diffusely reflective surface from the reference position. Various methods are disclosed for using the information from the detector means for determining the absolute distance measurements.
139 Citations
30 Claims
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1. A method of providing absolute Moire distance measurements comprising the steps of:
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(a) locating, forming, or printing a first grating on a diffusely reflective surface; (b) forming an image of the first grating on a second grating with an imaging means for generating a Moire pattern formed by the product of a pattern of the image of the first grating and a pattern of the second grating; and (c) detecting a difference in magnification between the pattern of the image of the first grating and the pattern of the second grating as the diffusely reflective surface moves normal to a plane thereof for generating information related to the absolute distance of the diffusely reflective surface from a reference position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. Absolute Moire distance measurement apparatus comprising:
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a first grating which is located, formed, or printed on a diffusely reflective surface to be measured; a second grating; imaging means for forming an image of the first grating on the second grating to generate a Moire pattern formed by the product of a first pattern of the image of the first grating and a second pattern of the second grating; optical detecting means for detecting a difference in magnification between the first pattern of the image of the first grating and the second pattern of the second grating of the Moire pattern as the diffusely reflective surface moves normal to the plane thereof and generating an output signal representative of such difference in magnification; and information generating means, responsive to the output signal from the optical detecting means, for generating information related to the absolute distance of the diffusely reflective surface from a reference position. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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Specification