Target detection utilizing image array comparison

• US 9,250,323 B2
• Filed: 05/24/2012
• Issued: 02/02/2016
• Est. Priority Date: 12/10/2008
• Status: Active Grant

• Current Assignee: United States Department Of Health And Human Services
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Ranney, Kenneth I., Martone, Anthony F., Innocenti, Roberto, Nguyen, Lam H.
• Primary Examiner(s): Brainard, Timothy A
• Application Number:
  US13/480,420
• Publication Number:
  US 20150061926A1
• Time in Patent Office: 1,349 Days
• Field of Search: 342/25.B
• US Class Current: 1/1
• CPC Class Codes: G01S 13/888 through wall detection
• CPC Class Codes: G01S 13/9017 with time domain processing of the SAR signals in azimuth G01S13/9005 takes precedence
• CPC Class Codes: G01S 13/9029 specially adapted for moving target detection within a single SAR image or within multiple SAR images taken at the same time
• CPC Class Codes: G01S 13/9089 SAR having an irregular aperture
• CPC Class Codes: G01S 7/414 Discriminating targets with respect to background clutter

Abstract

A method and system for forming an image comprising at least one processor for performing the following: initializing an N by P image array I_O by setting all values to a large number; inputting at least one image frame; randomly selecting and removing a subset of pixel locations from the total number of available pixel locations to form a preliminary image array I_C; for each pixel location comparing the complex magnitude of each pixel in the image array I_O with the magnitude of the corresponding pixel in image array I_C, and if the pixel value in the image array I_C is smaller than the corresponding pixel in the image array I_O or if the I_C value equals 0, then the current pixel value in image array I_O is replaced by the pixel value in the image array I_C; and repeating for a number of iterations to form an image.

Claims

1. A method for generating images comprising:

receiving, via a radar, radar return signals from an area of interest at a number of radar positions;

acquiring radar return data and positional data from the radar;

each of the positional data forming a positional record in an array of positional records;

each of the radar data comprising a first number of radar data points in the frequency domain;

forming an image comprising an array of pixel values comprising;

a) randomly setting a percentage of the first number of radar data points to zero;

thereby selecting subsets of receive channels for removal from the complete first number of radar data points;

b) transforming the first number of radar data points into time domain signature data;

c) differentiating the signature data in the time domain to create a new set of signature data indicating the location of moving targets;

d) forming an image by processing the signature data utilizing an imaging subsystem that combines the positional and signature data to form the moving target indication image utilizing one of a back-projection algorithm or range migration algorithm;

e) saving the pixel values for each of the image pixels into a composite image;

f) repeating the step of randomly setting a percentage of the radar data points to zero;

g) transforming the first number of radar data points into time domain signature data;

h) differentiating the signature data in the time domain to create a new set of signature data indicating the location of moving targets;

i) forming a second image by processing the signature data utilizing an imaging subsystem that combines the positional and signature data to form SAR imagery utilizing one of a back-projection algorithm or range migration algorithm;

j) comparing the pixel values at each of the pixel locations in the second image to the corresponding pixel values of the composite image;

k) replacing the pixel values in the composite image if the pixel value is less in the second image than it is in the composite image;

l) repeating steps i) through k) for a pre-determined number of iterations;

whereby the composite image is outputted with reduced sidelobes and noise.

2. The method of claim 1 wherein the percentage of the first number of radar data points set to zero is in the range of approximately twenty to fifty percent.

3. The method of claim 1, further comprising the step of processing return radar signals using a signal processing subsystem, the signal processing subsystem comprising at least one signal processing algorithm performed to suppress unwanted noise from the returned radar data.

4. The method of claim 1 wherein data is collected at later points in time so that the target may be observed in different locations.

5. The method of claim 1 wherein the number of iterations is within the range of 10 to 1000 and preferably within the range of 20 to 150.

6. The method of claim 1 wherein the radar signature data comprises synchronous impulse reconstruction radar data.

7. The method of claim 1 wherein prior to inputting from at least one receive channel data collected at first and second predetermined times, the pixel locations in the array are initialized by setting all values to a number in the range of approximately 10¹⁰ to 10³¹, and wherein the image is formed using one of time-differencing or Doppler processing.

8. A method for generating images comprising:

receiving, via a radar, radar return signals from an area of interest at a number of radar positions;

acquiring radar return data and positional data from the radar;

each of the positional data forming a positional record in an array of positional records;

each of the radar data comprising a first number of radar data points in the frequency domain,

forming an image comprising an array of pixel values comprising;

a) randomly setting a percentage of the first number of radar data points to zero;

b) transforming the first number of radar data points into time domain projection data;

c) differentiating the projection data in the time domain to create a new set of projection data indicating the location of moving targets;

d) forming an image by processing the projection data utilizing an imaging subsystem that combines the positional and projection data to form the moving target indication (MTI) imagery utilizing one of a back-projection algorithm or range migration algorithm;

e) forming the complete aperture A₀ for MTI image formation comprising combining the projection data, the coordinates of the receiver, and the coordinates of the transmitter for each positional record;

f) forming an imaging grid comprising M image pixels wherein each pixel in the imaging grid is located at coordinate (x_P(i),y_P(i), z_P(i));

g) saving the pixel values for each of the M image pixels into a composite image grid;

h) randomly setting a percentage of the first number of radar data points to zero;

i) transforming the first number of radar data points into time domain projection data;

j) differentiating the projection data in the time domain to create a new set of projection data indicating the location of moving targets;

k) forming an image by processing the projection data utilizing an imaging subsystem that combines the positional and projection data to form the SAR imagery utilizing one of a back-projection algorithm or range migration algorithm;

l) forming the complete aperture A₀ for MTI image formation comprising combining the projection data, the coordinates of the receiver, and the coordinates of the transmitter for each positional record;

m) forming an imaging grid comprising M image pixels wherein each pixel in the imaging grid is located at coordinate (x_P(i),y_P(i), z_P(i));

n) comparing the pixel values of the imaging grid to the corresponding pixel values of the composite image;

o) replacing the pixel values in the composite image grid if the pixel value is less in the imaging grid than the corresponding pixel value of the composite image grid to form a new composite image grid;

p) repeating the steps h) through o) for a predetermined number of iterations;

whereby the composite image grid is outputted with reduced sidelobes and noise.

9. The method of claim 8 wherein the percentage of the first number of radar data points set to zero is in the range of approximately twenty to fifty percent.

10. The method of claim 8 wherein the radar projection data comprises synchronous impulse reconstruction radar data.

11. A method for generating images comprising:

receiving, via a radar, radar return signals from an area of interest at a number of radar positions;

acquiring positional data and radar return data at different frequencies from the radar;

each of the positional data forming a positional record in an array of positional records;

each of the radar data comprising a first number of radar data points in the frequency domain;

forming an image comprising an array of pixel values comprising the steps of;

a) randomly setting a percentage of the first number of radar data points to zero;

thereby selecting subsets of receive channels for removal from the complete first number of radar data points;

b) transforming the first number of radar data points into time domain signature data;

c) differentiating the signature data in the time domain to create a new set of signature data indicating the location of moving targets;

d) forming an image by processing the signature data utilizing an imaging subsystem that combines the positional and signature data to form the moving target indication image utilizing one of a back-projection algorithm or range migration algorithm;

e) saving the pixel values for each of the image pixels into a composite image;

f) repeating the step of randomly setting a percentage of the radar data points to zero;

g) transforming the first number of radar data into time domain signature data;

h) differentiating the signature data in the time to create a new set of signature data indicating the location of moving targets;

i) forming a second moving target indication image by processing signature data utilizing an imaging subsystem that combines the positional and signature data to form SAR imagery utilizing one of a back-projection algorithm or range migration algorithm;

j) comparing the pixel values at each of the pixel locations in the second image to the corresponding pixel values at each of the pixel locations in the composite image;

k) replacing the pixel values in the composite image if the pixel value in the second moving target indication image is less than the corresponding pixel value of the composite image; and

l) repeating steps f) through k) for a pre-determined number of iterations;

whereby the composite image is outputted with reduced sidelobes and noise.