Method and device for use in detecting moving targets
First Claim
1. A method for use in detecting moving targets in a scene, the method comprising:
- receiving signals representing a sequence of mutually registered images R ( . . . , Rn-1, Rn, Rn+1, . . . ), the registered images R being representative of radiation exiting the scene;
deriving signals representing a sequence of differential images D ( . . . , Dn-1, Dn, Dn+1, . . . ) from the signals representing the registered images R;
filtering the signals representing the differential images D to obtain signals representing a sequence of spatially low pass filtered images F ( . . . , Fn-1, Fn, Fn+1. . . ), each of the filtered images F being made up of pixels which each have a position (i,j) in that filtered image and an intensity level; and
deriving a signal representing a motion filtered image Gn from the signals representing filtered images Fn-m, where m ranges from 0 to M, the motion filtered image Gn being made of up of pixels which each have a position (i,j) in the motion filtered image Gn which corresponds to the positions (i,j) in each of the filtered images F, and which each have an intensity level derived by;
(a) summing intensity levels of pixels at respective positions (i+m·
dx,j+m·
dy) in the filtered images Fn-m along a selected direction (dx,dy), the respective positions lying increasingly further from the position (i,j) in the filtered images Fn-m as the filtered images Fn-m precede a filtered image Fn in the sequence of filtered images F, to obtain a directional pixel sum, and repeating that process for different selected directions (dx,dy); and
(b) selecting the directional pixel sum which is largest, and choosing a value representative of that directional pixel sum to serve as the intensity level of the pixel which has a position (i,j) in the motion filtered image Gn.
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Abstract
A method and device for use in detecting moving targets in a scene represented by a sequence of mutually registered images R ( . . . , Rn-1, Rn, Rn+1, . . . ) over time wherein differential images D ( . . . , Dn-1, Dn, Dn+1, . . . ) are derived from succeeding images R, and spatially low pass filtered to obtain a sequence of filtered differential images F ( . . . , Fn-1, Fn, Dn+1, . . . ). For each pixel of a plurality of pixels (i,j) and for each of a plurality of directions (dx,dy), a sum of intensities is formed from a number of successive frames of the sequence of filtered differential images Fn-m (m=0,1 . . . M) at pixel locations (i+mdx,j+mdy) located, as the image is further back in time, along the direction progressively outwards from the pixel. For each pixel of the plurality of pixels, an intensities is determined which represents for the maximum size among the sums among the plurality of directions, the intensity for each pixel collectively forming an image Gn.
28 Citations
13 Claims
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1. A method for use in detecting moving targets in a scene, the method comprising:
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receiving signals representing a sequence of mutually registered images R ( . . . , Rn-1, Rn, Rn+1, . . . ), the registered images R being representative of radiation exiting the scene; deriving signals representing a sequence of differential images D ( . . . , Dn-1, Dn, Dn+1, . . . ) from the signals representing the registered images R; filtering the signals representing the differential images D to obtain signals representing a sequence of spatially low pass filtered images F ( . . . , Fn-1, Fn, Fn+1. . . ), each of the filtered images F being made up of pixels which each have a position (i,j) in that filtered image and an intensity level; and deriving a signal representing a motion filtered image Gn from the signals representing filtered images Fn-m, where m ranges from 0 to M, the motion filtered image Gn being made of up of pixels which each have a position (i,j) in the motion filtered image Gn which corresponds to the positions (i,j) in each of the filtered images F, and which each have an intensity level derived by; (a) summing intensity levels of pixels at respective positions (i+m·
dx,j+m·
dy) in the filtered images Fn-m along a selected direction (dx,dy), the respective positions lying increasingly further from the position (i,j) in the filtered images Fn-m as the filtered images Fn-m precede a filtered image Fn in the sequence of filtered images F, to obtain a directional pixel sum, and repeating that process for different selected directions (dx,dy); and(b) selecting the directional pixel sum which is largest, and choosing a value representative of that directional pixel sum to serve as the intensity level of the pixel which has a position (i,j) in the motion filtered image Gn. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A device for use in detecting moving targets in a scene, the device comprising:
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receiving means for receiving signals representing a sequence of mutually registered images R ( . . . , Rn-1, Rn, Rn+1, . . . ), the registered images R being representative of radiation exiting the scene; differential means for deriving signals representing a sequence of differential images D ( . . . , Dn-1, Dn, Dn+1, . . . ) from the signals representing the registered images R; first filter means for filtering the signals representing the differential images D to obtain signals representing a sequence of spatially low pass filtered images F ( . . . , Fn-1, Fn, Fn+1, . . . ), each of the filtered images F being made up of pixels which each have a position (i,j) in that filtered image and an intensity level; second filter means for deriving a signal representing a motion filtered image Gn from the signals representing filtered images Fn-m, where m ranges from 0 to M, the motion filtered image Gn being made of up of pixels which each have a position (i,j) in the motion filtered image Gn which corresponds to the positions (i,j) in each of the filtered images F, and which each have an intensity level, said motion filter means comprising; (a) summing means for summing intensity levels of pixels at respective positions (i+m·
dx,j+m·
dy) in the filtered images Fn-m along aselected direction (dx,dy), the respective positions lying increasingly further from the position (i,j) in the filtered images Fn-m as the filtered images Fn-m precede a filtered image Fn in the sequence of filtered images F, to obtain directional pixel sums; and (b) selection means for selecting that one of the directional pixel sums which is largest and choosing a value which is representative of that one of the directional pixel sums to serve as the intensity level of the pixel having the position (i,j) in the motion filtered image Gn. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification