Method for Enhancing a Three Dimensional Image from a Plurality of Frames of Flash Lidar Data
First Claim
1. A method for enhancing a three dimensional image from a plurality of frames of flash LIDAR data, comprising:
- (1) emitting laser light from an emitter of a flash LIDAR apparatus to a surface;
(2) capturing light reflected from the surface by a first detector i of the flash LIDAR apparatus;
(3) generating a frame of flash LIDAR data from the captured light, the frame comprising a first distance Ri measured from the first detector i to a first point on the surface Si;
(4) selecting an elevation map with a mesh Θ
defining a plurality of cells k;
(5) initializing a first array S(k), a second array M(k), and a third array D(k), wherein the first array is associated with the surface, the second array is associated with the elevation map, and the third array D(k) receives an output comprising an output elevation map for the mesh Θ
;
(6) projecting the surface onto a reference surface Ω
to create a projection, wherein the projection comprises a zero elevation level;
(7) selecting a set of cells from the mesh Θ
that overlaps with the projection;
(8) calculating a second distance Rk from a second point on the mesh Θ
to the detector, wherein a location of the second point corresponds with a location of the first point;
(9) calculating a height hki, between the first point and the second point according to the equation
hki=(RkRi)×
sin θ
i,wherein θ
i is an angle between the surface and the reference surface Ω
;
(10) updating the first and second arrays according to the equations
S(k1)=S(k1)+hk1
M(k1)+M(k1)+1;
(11) after completing the updating for all detectors i in the frame of flash LIDAR data, normalizing according to the equation
D(k)=S(k)/M(k) for all k thereby calculating the third array D(k);
(12) repeating steps (6) through (11) for each subsequent frame of LDAR data.
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Abstract
A method for enhancing a three dimensional image from frames of flash LIDAR data includes generating a first distance Ri from a first detector i to a first point on a surface Si. After defining a map with a mesh Θ having cells k, a first array S(k), a second array M(k), and a third array D(k) are initialized. The first array corresponds to the surface, the second array corresponds to the elevation map, and the third array D(k) receives an output for the DEM. The surface is projected onto the mesh Θ, so that a second distance Rk from a second point on the mesh Θ to the detector can be found. From this, a height may be calculated, which permits the generation of a digital elevation map. Also, using sequential frames of flash LIDAR data, vehicle control is possible using an offset between successive frames.
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Citations
20 Claims
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1. A method for enhancing a three dimensional image from a plurality of frames of flash LIDAR data, comprising:
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(1) emitting laser light from an emitter of a flash LIDAR apparatus to a surface; (2) capturing light reflected from the surface by a first detector i of the flash LIDAR apparatus; (3) generating a frame of flash LIDAR data from the captured light, the frame comprising a first distance Ri measured from the first detector i to a first point on the surface Si; (4) selecting an elevation map with a mesh Θ
defining a plurality of cells k;(5) initializing a first array S(k), a second array M(k), and a third array D(k), wherein the first array is associated with the surface, the second array is associated with the elevation map, and the third array D(k) receives an output comprising an output elevation map for the mesh Θ
;(6) projecting the surface onto a reference surface Ω
to create a projection, wherein the projection comprises a zero elevation level;(7) selecting a set of cells from the mesh Θ
that overlaps with the projection;(8) calculating a second distance Rk from a second point on the mesh Θ
to the detector, wherein a location of the second point corresponds with a location of the first point;(9) calculating a height hki, between the first point and the second point according to the equation
hki=(RkRi)×
sin θ
i,wherein θ
i is an angle between the surface and the reference surface Ω
;(10) updating the first and second arrays according to the equations
S(k1)=S(k1)+hk1
M(k1)+M(k1)+1;(11) after completing the updating for all detectors i in the frame of flash LIDAR data, normalizing according to the equation
D(k)=S(k)/M(k) for all kthereby calculating the third array D(k); (12) repeating steps (6) through (11) for each subsequent frame of LDAR data. - View Dependent Claims (2, 3, 4, 5, 8, 9, 10, 11, 12, 13)
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9. The method of claim 2, further comprising the step of:
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(14) determining a vector of state for the flash LIDAR apparatus according to the following equation
T(Vn+1)−
T(Vn)=Rn+1−
Rnwherein T(V) is a function of the vector of state, wherein the first detector comprises a first plurality of pixels having a plurality of first distances measured from the first plurality of pixels to a plurality of first points on the surface Si, wherein Rn is a matrix comprising the plurality of first distances, wherein the second detector comprises a second plurality of pixels having a plurality of second distances measured from the second plurality of pixels to a plurality of second points on the surface Si, wherein Rn+1 is a matrix comprising the plurality of second distances.
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10. The method of claim 9, further comprising the step of:
(15) solving a linear approximation equation as follows;
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11. The method of claim 10, further comprising the steps of:
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(17) applying 2-D discrete Fourier transform to the elevation map; (18) applying regularized inverse filter to the elevation map; (19) applying inverse 2-D discrete Fourier transform to the elevation map; (20) improving the spatial resolution of the elevation map.
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12. The method of claim 9, further comprising the step of (15) solving an internal inerative equation as follows:
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V2k=V1+(B+B)−
1×
(R(V2k−
1,h)−
T2), k=1, . . . , N
V20=V1(16) updating the elevation map.
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13. The method of claim 12, further comprising the steps of:
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(17) applying 2-D discrete Fourier transform to the elevation map; (18) applying regularized inverse filter to the elevation map; (19) applying inverse 2-D discrete Fourier transform to the elevation map; (20) improving the spatial resolution of the elevation map.
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- 7. The method of claim 7, wherein the array is a rectangular array, with A>
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14. A method for enhancing a three dimensional image from a plurality of frames of flash LIDAR data in real time, comprising:
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(1) emitting laser light from an emitter of a flash LIDAR apparatus to a surface; (2) capturing light reflected from the surface by a first detector i of the flash LIDAR apparatus; (3) generating a frame of flash LIDAR data from the captured light, the frame comprising a first distance Ri measured from the first detector i to a first point on the surface Si; (4) selecting an elevation map with a mesh Θ
defining a plurality of cells k;(5) initializing a first array S(k), a second array M(k), and a third array D(k), wherein the first array is associated with the surface, the second array is associated with the elevation map, and the third array D(k) receives an output comprising an output elevation map for the mesh Θ
;(6) projecting the surface onto a reference surface Ω
to create a projection;(7) selecting a set of cells from the mesh Θ
that overlaps with the projection;(8) calculating a second distance Rk from a second point on the mesh Θ
to the detector, wherein a location of the second point corresponds with a location of the first point;(9) calculating a height hki between the first point and the second point according to the equation
hki=(Rk−
Ri)×
sin θ
i,wherein θ
i is an angle between the surface and the reference surface Ω
;(10) updating the first and second arrays according to the equations
S(k1)=S(k1)+hk1
M(k1)=M(k1)+1;(11) after completing the updating for all detectors i in the frame of flash LIDAR data, normalizing according to the equation
D(k)=S(k)/M(k) for all kthereby calculating the third array D(k); and (12) repeating steps (6) through (11) for a frame of LIDAR data. - View Dependent Claims (15, 16, 17, 18)
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19. A method for enhancing a three dimensional image from a plurality of frames of flash LIDAR data, comprising:
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(1) emitting laser light from an emitter of a flash LIDAR apparatus to a surface; (2) capturing light reflected from the surface by a first detector i of the flash LIDAR apparatus; (3) generating a frame of flash LIDAR data from the captured light, the frame comprising a first distance R1 measured from the first detector i to a first point on the surface Si; (4) selecting an elevation map with a mesh Θ
defining a plurality of cells k;(5) initializing a first array S(k), a second array M(k), and a third array D(k), wherein the first array is associated with the surface, the second array is associated with the elevation map, and the third array D(k) receives an output comprising an output elevation map for the mesh Θ
;(6) projecting the surface onto a reference surface Ω
to create a projection;(7) selecting a set of cells from the mesh Θ
that overlaps with the projection;(8) calculating a second distance Rk from a second point on the mesh Θ
to the detector, wherein a location of the second point corresponds with a location of the first point;(9) calculating a height kki between the first point and the second point according to the equation
hki=(Rk−
Ri)×
sin θ
i,wherein θ
i is an angle between the surface and the reference surface Ω
, wherein the range Ri is calculated according the equation - View Dependent Claims (20)
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Specification