Real-time holographic surveillance system

• US 5,455,590 A
• Filed: 03/14/1994
• Issued: 10/03/1995
• Est. Priority Date: 08/30/1991
• Status: Expired due to Term

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Collins, H. Dale, Gribble, R. Parks, McMakin, Douglas L., Hall, Thomas E.
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US08/212,432
• Time in Patent Office: 568 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: A61B 5/745 using a holographic display
• 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 holographic surveillance system including means for generating electromagnetic waves; means for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; means for receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; means for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and means for displaying the processed information to determine nature of the target.

The means for processing the electrical signals includes means for converting analog signals to digital signals followed by a computer means to apply a backward wave algorithm.

Claims

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

(a) a holographic array having a plurality of low-gain, end-fire antenna units spaced apart from about 0.25 to about 1.5 wavelength, wherein each unit both sends and receives millimeter wave radiation, said units connected by a plurality of electronic millimeter wave switches permitting sequential operation of said units, said array spaced apart from said target with a low f-number;

(b) a holographic transceiver system means for operating said 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 analog oscillated reference signal, together with an analog reflected target signal;

(c) a real-to-imaginary converter for converting the analog oscillated reference signal and the analog reflected target signal to an analog real part of a hologram and an analog imaginary part of the hologram;

(d) an analog to digital converter for converting said analog real part and said analog imaginary part to corresponding digital parts; and

(e) a computer for applying a backward wave propagation algorithm that preserves the low f-number to the digital real and digital imaginary parts of the hologram to reconstruct a holographic image.

2. The apparatus as recited in claim 1, wherein said antenna elements have a beam width from about 10 degrees to about 50 degrees.

3. The apparatus as recited in claim 1, wherein said low-gain, end-fire antenna units are monostatic.

4. The apparatus as recited in claim 1, wherein said low-gain, end-fire antenna units are bistatic.

5. The apparatus as recited in claim 2, wherein the low-gain, end-fire antenna units are polyrod antennas.

6. The apparatus as recited in claim 2, wherein the low-gain, end-fire antenna units are printed circuit antennas.

7. The apparatus as recited in claim 1, wherein the electronic millimeter wave switch is a first set of pin diode switches in a first and second binary switch array, and a second set of ferrite switches that directs outgoing millimeter wave signals to the successive antenna unit.

8. The apparatus as recited in claim 1, wherein the low f-number is from about 1 to about 3.

9. The holographic apparatus as recited in claim 1, wherein the computer for applying the backward wave propagation algorithm comprises:

(a) a digital computer having,

(i) a first set of instructions for computing a two-dimensional Fourier transform of a given field f(x,y,z) from phase and amplitude information obtained from the oscillated reference digital signal and from the reflected target digital signal,

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

(iii) a third set of instructions for computing an inverse transform of a plane wave angular spectrum at the target plane yielding a target image, and

(iv) a fourth set of instructions for computing a target intensity image from the target image.

10. The holographic 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.

11. The holographic apparatus as recited in claim 10, 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 vertical resolution as the upper and lower horizontal rows are moved vertically.

12. The holographic apparatus as recited in claim 10, wherein the two arrays are moved across an aperture in less than two seconds.

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

14. The apparatus as recited in claim 13, wherein a multi-dimensional array is a planar two-dimensional array that is electronically scanned in less than 0.5 seconds.

15. A method of holographic surveillance, comprising the steps of:

(a) scanning an aperture with a holographic array having a plurality of low-gain, end-fire antenna units spaced apart from about 0.25 to about 1.5 wavelength, wherein each unit both sends and receives millimeter wave radiation, said units connected by a plurality of electronic millimeter wave switch means permitting sequential operation of said units, said array spaced apart from said target with a low f-number;

(b) operating individual antenna elements with a holographic transceiver system means for operating said 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 analog oscillated reference signal together with an analog reflected target signal;

(c) converting the analog oscillated reference signal and the analog reflected target signal to an analog real part of a hologram and an analog imaginary part of the hologram;

(d) converting said analog real part and said analog imaginary part to corresponding digital parts; and

(e) applying a backward wave propagation algorithm that preserves the low f-number to the digital real and digital imaginary parts of the hologram to reconstruct a holographic image.

16. The method of holographic surveillance as recited in claim 15, wherein applying the backward wave propagation algorithm comprises:

(a) computing a two-dimensional Fourier transform of a given field f(x,y,z) from phase and amplitude information obtained from the oscillated reference digital signal and from the reflected target digital signal;

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

(c) computing an inverse transform of the backward wave product yielding target image; and

(d) computing a target intensity image from the target image.

17. The method of holographic surveillance as recited in claim 15, wherein the low f-number is from about 1 to about 3.

18. An apparatus for near real-time holographic imaging of a target, comprising:

(a) a holographic array having a plurality of low-gain, end-fire antenna units spaced apart from about 0.25 to about 1.5 wavelength, wherein each unit both sends and receives millimeter wave radiation having a frequency from about 26.5 to about 110 GHz, said units connected by a plurality of electronic millimeter wave switches permitting sequential operation of said units, said holographic array spaced apart from said target with a low f-number of from about 0.1 to about 10;

(b) a holographic transceiver that provides millimeter wave energy to the units, then receives millimeter wave reflection from said target and collected by the units, and converts the reflected millimeter wave energy together with an oscillator to an analog real part of a hologram and an analog imaginary part of a hologram;

(c) an analog to digital converter that converts the analog real part and the analog imaginary parts of the hologram to corresponding digital parts; and

(d) a backward wave propagator that reconstructs a holographic image from the real and imaginary digital parts and preserves the low f-number.