Position encoding optical device and method
First Claim
1. An optical device for encoding the position of a light spot image formed at an input image plane, said device comprising:
- a diffractive optical element disposed within said input image plane and including an array of diffractive cells each being disposed at a predetermined position with respect to a predetermined reference point on said diffractive optical element, each said cells being capable of generating a unique optical diffraction pattern when illuminated, at least one of said cells being positioned to receive said light spot input image generating its unique optical diffraction pattern accordingly at an output image plane; and
one or more optical detectors disposed at said output image plane and responsive to said unique optical diffraction pattern to generate one or more encoded signals indicative of the position of said light spot image with respect to said reference point.
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Abstract
A simple optical position encoder of detecting the position of a light spot generated by any light source of either light generating or light reflecting type, directly in a binary or other encoded format at very high speed, comprises a diffractive optical element including an array of diffractive cells each being formed by a unique arrangement of diffractive sub-cells and being disposed at a predetermined position with respect to a predetermined reference point on the diffractive optical element. Each cell is capable of generating a unique optical diffraction pattern when illuminated. When an image of the light spot is formed on the diffractive element, at least one cell is positioned to receive the light spot input image, generating its unique optical diffraction pattern accordingly at an output image plane, where one or more optical detectors are disposed. The detectors are responsive to the unique optical diffraction pattern to generate one or more encoded signals indicative of the position of the light spot image with respect to said reference point. Described applications of the basic embodiment of the position encoder includes absolute three-dimensional position measurement of a light spot formed on a object, position encoding of a light peak generated by an optical processor or correlator and absolute/relative position detection of a light spot generated by or reflected onto an object in a two-dimensional coordinates system.
55 Citations
40 Claims
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1. An optical device for encoding the position of a light spot image formed at an input image plane, said device comprising:
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a diffractive optical element disposed within said input image plane and including an array of diffractive cells each being disposed at a predetermined position with respect to a predetermined reference point on said diffractive optical element, each said cells being capable of generating a unique optical diffraction pattern when illuminated, at least one of said cells being positioned to receive said light spot input image generating its unique optical diffraction pattern accordingly at an output image plane; and
one or more optical detectors disposed at said output image plane and responsive to said unique optical diffraction pattern to generate one or more encoded signals indicative of the position of said light spot image with respect to said reference point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. An optical device for encoding the position of a light peak generated by an optical processor receiving an image to be processed as generated by an imaging device illuminated by a laser source, said processor comprising first Fourier transform means for performing the Fourier transform of said input image to generate a corresponding transformed input image in the spatial frequency domain within an area defined by a Fourier transform filter plane, optical mask means disposed within said area, said second optical mask means implementing a filter mask function to generate a combined image in the spatial domain, and second Fourier transform means for performing the inverse Fourier transform of said combined image to generate said light peak at a peak image plane, said optical device comprising:
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a diffractive optical element disposed within said peak image plane and including an array of diffractive cells each being disposed at a predetermined position with respect to a predetermined reference point on said diffractive optical element, each said cells being capable of generating a unique optical diffraction pattern when illuminated, at least one of said cells being positioned to receive said light peak and generating its unique optical diffraction pattern accordingly at an output image plane; and
one or more optical detectors disposed at said output image plane and responsive to said optical diffraction pattern to generate one or more encoded signals indicative of the position of said light peak with respect to said reference point. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of encoding the position of a light spot, said method comprising the steps of:
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a) forming an image of said light spot at a corresponding position within an input image plane and with respect to a predetermined reference point of said plane;
b) generating a unique optical diffraction pattern associated with said corresponding position at an output image plane; and
c) detecting said unique optical diffraction pattern to generate one or more encoded signals indicative of the position of said light spot image with respect to said reference point. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
d) deriving from said encoded signals a further signal indicative of an absolute position of said light spot in a reference system.
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36. The method of claim 35, wherein said reference system is a two-dimensional coordinates system extending within a reference plane substantially normal to an input optical axis extending through said input image plane.
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37. The method of claim 35, wherein said light spot is produced by a laser projecting a laser beam toward a reflecting surface of an object and along a direction of incidence forming a predetermined angle with respect to a reference direction, said reference system being a three-dimensional coordinates system, said deriving step d) being performed using triangulation calculation.
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38. The method of claim 37, wherein said light spot is produced while varying the direction of incidence of said laser beam to scan the surface of said object reflecting said light spot accordingly, said deriving step d) being repeatedly performed as said surface is scanned to measure the profile thereof.
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39. The method of claim 37, wherein said light spot is produced while imparting a relative movement between said laser and the object to scan the surface thereof forming said light spot, said deriving step d) being repeatedly performed as said surface is scanned to measure the profile thereof.
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40. The method of claim 29, further comprising the step of:
d) deriving from said encoded signals a further signal indicative of a relative position of said light spot in a two-dimensional coordinates system extending within a reference plane substantially normal to an input optical axis extending through said input image plane, said reference plane having its origin at an intersection of said optical axis with said reference plane.
Specification