Real-time wideband holographic surveillance system

• US 5,557,283 A
• Filed: 05/12/1995
• Issued: 09/17/1996
• Est. Priority Date: 08/30/1991
• Status: Expired due to Term

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: McMakin, Douglas L., Sheen, David M., Severtsen, Ronald H., Hall, Thomas E., Prince, James M., Reid, Larry D., Collins, H. Dale, Gribble, R. Parks
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/440,279
• Time in Patent Office: 494 Days
• Field of Search: 342/179, 367/8
• US Class Current: 342/179
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01V 8/005 operating with millimetre waves, e.g. measuring the black losey radiation

Abstract

A wideband holographic surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply a three dimensional backward wave algorithm.

Claims

1. A holographic apparatus for near real-time imaging of a target, said apparatus utilizing millimeter wave radiation having a plurality of frequencies from about 1 to about 110 GHz, comprising:

(a) a holographic array having a plurality of antenna units spaced apart from about 0.25 to about 3 wavelength, wherein each unit sends and/or receives millimeter wave radiation, said array spaced apart from said target;

(b) a holographic wideband transceiver for operating said antenna units and providing each unit with millimeter wave radiation source, then receiving high frequency millimeter wave radiation reflection from said target and collected by the unit, then making an output;

(c) an analog to digital converter for converting said output to a corresponding digital signal; and

(d) a computer for applying a three-dimensional reconstruction algorithm to the corresponding digital signal that preserves an unlimited depth of field.

2. The apparatus as recited in claim 1, wherein said antenna elements have a beam width from about 10 degrees to about 180 degrees.

3. The apparatus as recited in claim 1, wherein said antenna units are monostatic.

4. The apparatus as recited in claim 1, wherein said antenna units are bistatic.

5. The apparatus as recited in claim 2, wherein the antenna units are polyrod antennas.

6. The apparatus as recited in claim 2, wherein the antenna units are printed circuit antennas.

7. The apparatus as recited in claim 1, wherein the holographic array is interconnected to an electronic millimeter wave switch having a first set of pin diode switches in a first and second binary switch array.

8. The apparatus as recited in claim 1, wherein a beam width of the antenna element in combination with a distance from the transceiver to the target provides a low f-number.

9. The apparatus as recited in claim 1, wherein said output is an in-phase output.

10. The apparatus as recited in claim 1, wherein the computer for applying the image reconstruction algorithm comprises:

(a) a digital computer having,

(i) a first set of instructions for receiving data from the A/D converter,

(ii) a second set of instructions for computing a two-dimensional Fourier transform of the received data for each frequency,

(iii) a third set of instructions for multiplying the two-dimensional Fourier transform by a complex backward wave propagator and forming a backward wave product,

(iv) a fourth set of instructions for interpolating the backward wave product onto a uniformly sampled grid and forming an interpolated product,

(v) a fifth set of instructions for computing a three-dimensional inverse transform of the interpolated product and obtaining a complex three-dimensional image,

(vi) a sixth set of instructions for computing a magnitude of the complex three-dimensional image and obtaining a three-dimensional image, and

(vii) a seventh set of instructions for displaying the three-dimensional image.

11. The apparatus as recited in claim 10, wherein the first set of instructions further comprises:

a subset of instructions for deriving complex data (Q) from in-phase data (I).

12. The apparatus as recited in claim 1, said array comprises:

a linear array, moved by a mechanical means during transmission and receipt of said high frequency millimeter wave radiation, thereby providing a simultaneous scan of source and reflection millimeter wave radiation.

13. The apparatus as recited in claim 12, wherein the linear array comprises:

(a) an upper horizontal row, and

(b) a lower horizontal row wherein the two rows are offset by half the spacing between antenna elements, thereby enhancing horizontal resolution as the upper and lower horizontal rows are moved vertically.

14. The apparatus as recited in claim 12, wherein the two arrays are moved across an aperture in less than two seconds.

15. The apparatus as recited in claim 1, wherein a plurality of antenna elements are spaced in a stationary, multi-dimensional array.

16. The apparatus as recited in claim 15, wherein a multi-dimensional array is a planar two-dimensional array that is electronically scanned in less than 0.5 seconds.

17. The apparatus as recited in claim 1, wherein said antenna units are connected by a plurality of electronic millimeter wave switches permitting sequential operation of said antenna units.

18. The apparatus as recited in claim 1, wherein said transceiver is a bistatic, heterodyne, in-phase output transceiver.

19. The apparatus as recited in claim 18, wherein said bistatic, heterodyne, in-phase output transceiver is also non-tracking.

20. A method of holographic surveillance of a target, comprising the steps of:

(a) scanning a two-dimensional aperture with a holographic array having a plurality of antenna units spaced apart from about 0.25 to about 3 wavelength, wherein each unit sends and/or receives millimeter wave radiation, said array spaced apart from said target;

(b) operating individual antenna elements with a wideband holographic transceiver system and providing each unit with a wideband millimeter wave radiation source, then receiving wideband millimeter wave radiation reflection from said target and collected by the unit(s), then making an output;

(c) converting said output in an A/D converter to a corresponding digital signal; and

(d) applying a three dimensional reconstruction algorithm to the digital signal that preserves a low f-number.

21. The method as recited in claim 20, wherein applying the three dimensional reconstruction algorithm includes applying a transform to derive an imaginary digital signal to reconstruct a holographic image.

22. The method as recited in claim 20, wherein said scanning is by sequential operating of said antenna units.

23. The method as recited in claim 20, wherein the applying the image reconstruction algorithm comprises the steps of:

(i) receiving data from the A/D converter,

(ii) computing a two-dimensional Fourier transform of the received data for each frequency,

(iii) multiplying the two-dimensional Fourier transform by a complex backward wave propagator and forming a backward wave product,

(iv) interpolating the backward wave product onto a uniformly sampled grid and forming an interpolated product,

(v) computing a three-dimensional inverse transform of the interpolated product and obtaining a complex three-dimensional image,

(vi) computing a magnitude of the complex three-dimensional image and obtaining a three-dimensional image, and

(vii) displaying the three-dimensional image.

24. The method as recited in claim 23, wherein receiving the data further comprises:

deriving complex data (Q) from in-phase data (I).