Method and device for use in detecting moving targets

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 ( . . . , R n-1 , R n , R n+1 , . . . ), the registered images R being representative of radiation exiting the scene; deriving signals representing a sequence of differential images D ( . . . , D n-1 , D n , D n+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 ( . . . , F n-1 , F n , F n+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 G n from the signals representing filtered images F n-m , where m ranges from 0 to M, the motion filtered image G n being made of up of pixels which each have a position (i,j) in the motion filtered image G n 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·d x ,j+m·d y ) in the filtered images F n-m along a selected direction (d x ,d y ), the respective positions lying increasingly further from the position (i,j) in the filtered images F n-m as the filtered images F n-m precede a filtered image F n in the sequence of filtered images F, to obtain a directional pixel sum, and repeating that process for different selected directions (d x ,d y ); 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 G n .

Claim 2

A method for use in detecting moving targets in a scene, the method comprising: receiving signals representing a sequence of mutually registered images R ( . . . , R n-1 , R n , R n+1 , . . . ), the registered images R being representative of radiation exiting the scene; deriving signals representing a sequence of differential images D ( . . . , D n-1 , D n , D n+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 ( . . . , F n-1 , F n , F n+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 G n from the signals representing filtered images F n-m , where m ranges from 0 to M, the motion filtered image G n being made of up of pixels which each have a position (i,j) in the motion filtered image G n 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·d x ,j+m·d y ) in the filtered images F n-m along a selected direction (d x ,d y ), the respective positions lying increasingly further from the position (i,j) in the filtered images F n-m as the filtered images F n-m precede a filtered image F n in the sequence of filtered images F, to obtain a directional pixel sum, and repeating that process for different selected directions (d x ,d y ); 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 G n .

Claim 9

A device for use in detecting moving targets in a scene, the device comprising: receiving means for receiving signals representing a sequence of mutually registered images R ( . . . , R n-1 , R n , R n+1 , . . . ), the registered images R being representative of radiation exiting the scene; differential means for deriving signals representing a sequence of differential images D ( . . . , D n-1 , D n , D n+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 ( . . . , F n-1 , F n , F n+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 G n from the signals representing filtered images F n-m , where m ranges from 0 to M, the motion filtered image G n being made of up of pixels which each have a position (i,j) in the motion filtered image G n 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·d x ,j+m·d y ) in the filtered images F n-m along a selected direction (d x ,d y ), the respective positions lying increasingly further from the position (i,j) in the filtered images F n-m as the filtered images F n-m precede a filtered image F n 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 G n .

Claim 10

A device for use in detecting moving targets in a scene, the device comprising: receiving means for receiving signals representing a sequence of mutually registered images R ( . . . , R n-1 , R n , R n+1 , . . . ), the registered images R being representative of radiation exiting the scene; differential means for deriving signals representing a sequence of differential images D ( . . . , D n-1 , D n , D n+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 ( . . . , F n-1 , F n , F n+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 G n from the signals representing filtered images F n-m , where m ranges from 0 to M, the motion filtered image G n being made of up of pixels which each have a position (i,j) in the motion filtered image G n 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·d x ,j+m·d y ) in the filtered images F n-m along a selected direction (d x ,d y ), the respective positions lying increasingly further from the position (i,j) in the filtered images F n-m as the filtered images F n-m precede a filtered image F n 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 G n .