Square anti-symmetric uniformly redundant array coded aperture imaging system
First Claim
1. A square anti-symmetric uniformly redundant array coded aperture for imaging a source of non-focusable radiation, the coded aperture comprising transparent cells and opaque cells and exhibiting a full mask pattern, the full mask pattern having elements, the elements having values including a first value and a second value, the transparent cells and the opaque cells being respectively assigned locations corresponding to the elements having the first value and the second value, the full mask pattern being generated from a primitive mask pattern of order ν
- , having a center, the primitive mask pattern being defined by a relationship;
space="preserve" listing-type="equation">A.sub.ij =0 if i=0
space="preserve" listing-type="equation">A.sub.ij =1 if j=0 and i˜
0
space="preserve" listing-type="equation">A.sub.ij =1 if B.sub.i =B.sub.j
space="preserve" listing-type="equation">A.sub.ij =0 otherwisewhere A is a uniformly redundant array coding function and B is a skew-Hadamard quadratic residue sequence, the full mask pattern being constructed by repeating the primitive mask pattern diagonally outward from the center of the primitive mask pattern whereby the full mask pattern includes a total of (2 ν
-1)×
(2 ν
-1) elements.
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Abstract
A square anti-symmetric uniformly redundant array coded aperture includes transparent and opaque cells and exhibits a normal mask pattern at a first position and a complementary mask pattern when rotated to a second position rotationally offset by 90° from the first position. The coded aperture is utilized in a coded aperture imaging system for imaging a source of non-focusable radiation such as a gamma ray or x-ray emitting source. Such a coded aperture imaging system basically includes a square anti-symmetric uniformly redundant array coded aperture for receiving radiation emitted by a source and generating a first coded shadow therefrom at the first position, and a second coded shadow therefrom at the second position, a rotating platform and motor for rotating the coded aperture between the first and second position, a position sensitive detector situated with respect to the coded aperture to allow the first and second coded shadows to sequentially impinge on the detector, the detector respectively generating a first coded optical signal and a second coded optical signal in response thereto, an optical signal convertor responsive to the first and second coded optical signals and respectively generating a first coded electrical signal and a second coded electrical signal in response thereto and a signal processor responsive to the first and second coded electrical signals and decoding the coded electrical signals to generate an image signal which is representative of an image of the source of non-focusable radiation.
80 Citations
9 Claims
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1. A square anti-symmetric uniformly redundant array coded aperture for imaging a source of non-focusable radiation, the coded aperture comprising transparent cells and opaque cells and exhibiting a full mask pattern, the full mask pattern having elements, the elements having values including a first value and a second value, the transparent cells and the opaque cells being respectively assigned locations corresponding to the elements having the first value and the second value, the full mask pattern being generated from a primitive mask pattern of order ν
- , having a center, the primitive mask pattern being defined by a relationship;
space="preserve" listing-type="equation">A.sub.ij =0 if i=0
space="preserve" listing-type="equation">A.sub.ij =1 if j=0 and i˜
0
space="preserve" listing-type="equation">A.sub.ij =1 if B.sub.i =B.sub.j
space="preserve" listing-type="equation">A.sub.ij =0 otherwisewhere A is a uniformly redundant array coding function and B is a skew-Hadamard quadratic residue sequence, the full mask pattern being constructed by repeating the primitive mask pattern diagonally outward from the center of the primitive mask pattern whereby the full mask pattern includes a total of (2 ν
-1)×
(2 ν
-1) elements.
- , having a center, the primitive mask pattern being defined by a relationship;
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2. A square anti-symmetric uniformly redundant array coded aperture for imaging a source of non-focusable radiation, the coded aperture comprising transparent and opaque cells, the coded aperture being positionable in a first position and a second position rotatably offset from the first position by 90°
- , the coded aperture exhibiting a square normal mask pattern at the first position, the coded aperture exhibiting a square complementary mask pattern at the second position whereby substantially all of the opaque cells exchange locations with substantially all of the transparent cells.
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3. A method of constructing a square anti-symmetric uniformly redundant array coded aperture for imaging a source of non-focusable radiation, the coded aperture having transparent cells and opaque cells, the method comprising the steps of:
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generating a primitive mask pattern of order ν
, having a center, the primitive mask pattern being defined by a relationship;
space="preserve" listing-type="equation">A.sub.ij =0 if i=0
space="preserve" listing-type="equation">A.sub.ij =1 if j=0 and i˜
0
space="preserve" listing-type="equation">A.sub.ij =1 if B.sub.i =B.sub.j
space="preserve" listing-type="equation">A.sub.ij =0 otherwisewhere A is a uniformly redundant array coding function and B is a skew-Hadamard quadratic residue sequence; generating a full mask pattern having elements, the elements having values including a first value and a second value, the full mask pattern being generated by repeating the primitive mask pattern diagonally outward from the center of the primitive mask pattern whereby the full mask pattern includes a total of (2 ν
-1)×
(2 ν
-1) elements; andassigning the transparent cells and the opaque cells, respectively, to the elements of the full mask pattern having the first value and the second value.
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4. A coded aperture imaging system for imaging a source of non-focusable radiation, the system comprising:
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a coded aperture, the coded aperture including transparent cells and opaque cells, the coded aperture being positionable in a first position and a second position rotationally offset from the first position by 90°
, the coded aperture exhibiting a square normal mask pattern at the first position, the coded aperture exhibiting a square complementary mask pattern at the second position whereby substantially all of the opaque cells exchange locations with substantially all of the transparent cells;means for rotating the coded aperture between the first position and the second position, the coded aperture receiving non-focusable radiation emitted by the source at both the first position and the second position, the coded aperture generating a first coded shadow in response to the radiation received when the coded aperture is at the first position, the coded aperture generating a second coded shadow in response to the radiation received when the coded aperture is at the second position; a position sensitive detector situated with respect to the coded aperture to allow the first coded shadow and the second coded shadow to sequentially impinge thereon, the position sensitive detector respectively generating a first coded optical signal and a second coded optical signal in response to the first coded shadow and the second coded shadow sequentially impinging thereon; means for converting an optical signal to an electrical signal, the converting means being responsive to the first coded optical signal and the second coded optical signal and respectively generating a first coded electrical signal and a second coded electrical signal in response thereto; and a signal processor, the signal processor being responsive to the first coded electrical signal and the second coded electrical signal and decoding the first coded electrical signal and the second coded electrical signal, the signal processor generating an image signal therefrom, the image signal being representative of an image of the source of non-focusable radiation. - View Dependent Claims (5, 6, 7, 8, 9)
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Specification