SYSTEM AND METHOD TO DETECT ANOMALIES

• US 20150060673A1
• Filed: 03/25/2013
• Published: 03/05/2015
• Est. Priority Date: 03/23/2012
• Status: Active Grant

• Current Assignee: Luna Innovations, Inc.
• Original Assignee: Picometrix LLC (Luna Innovations, Inc.)
• Inventors: Zimdars, David
• Granted Patent: US 10,024,963 B2
• Time in Patent Office: Days
• US Class Current: 250/341.2
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/10 using transmission of interrupted, pulse modulated waves determination of distance by phase measurement G01S13/32
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• CPC Class Codes: G01S 17/04 Systems determining the presence of a target
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/88 Lidar systems specially adapted for specific applications
• CPC Class Codes: G01S 7/412 based on a comparison between measured values and known or stored values
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays

Abstract

A system and method for detecting anomalies concealed upon a person may include a detection probe having an electromagnetic transmitter and an electromagnetic receiver. The electromagnetic transmitter is configured to emit electromagnetic pulses, while the electromagnetic receiver is configured to sample electromagnetic pulses from the electromagnetic receiver at specified times within a waveform window. The electromagnetic pulses may span the terahertz spectral region of 0.04 to 4 THz. The system may also have optical fibers connected to the electromagnetic transmitter and electromagnetic receiver, wherein femtosecond laser pulses are directed from a source to the electromagnetic transmitter and the electromagnetic receiver by the optical fibers.

Claims

1. A system for detecting anomalies concealed upon a person, the system comprising:

a detection probe having an electromagnetic transmitter and an electromagnetic receiver, the electromagnetic transmitter is configured to emit electromagnetic pulses, the electromagnetic receiver is configured to sample electromagnetic pulses from the electromagnetic receiver at specified times within a waveform window;

an objective optic incorporated in the detection probe for directing the pulsed electromagnetic radiation through a concealment stack and collecting reflections of the concealment stack at a defined distance, wherein the detection probe may be focused at the depth of concealed skin of the person without the exterior of the detection probe contacting a top of the concealment stack

the transmitter and receiver configured in a monostatic reflection geometry with respect to an objective optic; and

a time domain data acquisition system in communication with the receiver, the time domain data acquisition system configured to capture reflections from a range thickness of the concealment stack, the waveform window having the reflection time corresponding to the focus of the objective lens.

2. The system of claim 1, where the concealment stack over the skin of the person further comprises clothing or coverings sufficiently small thickness, density or mass, wherein time domain data acquisition system determines the concealment stack to not contain an anomaly or a shield.

3. The system of claim 2, wherein the clothing or coverings further comprise natural or synthetic cloth, leather, rubber, vinyl, paper, plastic and/or other thin fibers, sheets or weaves.

4. The system of claim 1, wherein the concealment stack further comprises one or more intereferent components located at any position within the concealment stack and composed of material of the same type as an anomaly or shield, wherein the time domain data acquisition system is configured to determine that the intereferent is smaller in either volume, density, or mass than a threshold value to be considered an anomaly.

5. The system of claim 4, wherein the concealment stack further comprises one or more anomaly placed at any level within the concealment stack, where the anomaly is an object of greater thickness, lateral extent, volume, density, or mass than a threshold value.

6. The system of claim 1, wherein the time domain data acquisition system is configured to choose a quantitative threshold for thickness, lateral extent;

volume, density, or mass to be considered an anomaly by scaling thresholds to electromagnetic properties of the anomaly material in comparison to a benign material in the concealment stack and evaluating the measurement from the system as an anomaly when the waveform contains one or more features indicating that an object within the concealment stack exceeds the scaled thresholds.

7. The system of claim 1, where the electromagnetic pulses span the terahertz spectral region of 0.04 to 4 THz.

8. The system of claim 1, further comprising a light source that projects an illuminated pattern onto the concealment stack on the person under test indicating a region of inspection.

9. The system of claim 1, further comprising optical fibers connected to the electromagnetic transmitter and electromagnetic receiver, wherein femtosecond laser pulses are directed from a source to the electromagnetic transmitter and the electromagnetic receiver by the optical fibers.

10. The system of claim 9, further comprising a compensator located between the source and the electromagnetic transmitter or electromagnetic receiver, wherein the compensator compensates the pulses so that the pulses are sufficiently short at the electromagnetic transmitter or electromagnetic receiver.

11. The system of claim 10, wherein the compensator is a grating sequence, a prism sequence, a grism sequence, a fiber bragg grating, or anomalous dispersion fiber.

12. The system of claim 1, further comprising a sensor connected to the detection probe, wherein the sensor is configured to provided coordinates of the detection probe'"'"'s position in one or more dimensions of space or angle.

13. The system of claim 1, further comprising a sensor connected to the detection probe, wherein the sensor is configured to detect in a different modality than the waveforms reflected from the concealment stack and interrogate a substantially same region of concealment stack on the person.

14. The system of claim 1, further comprising a secondary transmitter connected to the detection, wherein the secondary transmitter if configured to emit alpha, beta, x-ray, or gamma rays.

15. A method for evaluating a time domain reflected waveform for criteria corresponding to features which indicate an anomaly in a region of a concealment stack on a person, the method comprising the steps of:

illuminating a concealment stack with an electromagnetic pulse directed from a transmitter located in a dynamically positioned probe;

collecting the waveform by a receiver in the probe;

parsing the waveform into a candidate group of positive or negative going peaks corresponding to reflection interfaces within the concealment stack; and

determining if an anomaly is present if one or more peaks within the candidate group quantitatively correspond to one or more thresholds computed from the amplitudes and/or one or more differences in time between one or more peaks in the candidate group.

16. The method of claim 15, further comprising the step of deconvolving the waveform with a pre-recorded reference reflection waveform.

17. The method of claim 16, wherein the pre-recorded reference reflection waveform is a single reflection from an air-metal interface.

18. The method of claim 15, further comprising the step of scaling the amplitude of the peaks as a function of a relative increase of the peaks in time with respect to a first peak in the waveform for compensating for a loss from intervening concealment as the thickness of the concealment stack increases.

19. The method of claim 15, further comprising the step of scaling the amplitude of the peaks as a function of a relative number after a first peak in the waveform for compensating for a loss from intervening concealment as the thickness of the concealment stack increases.

20. The method of claim 15, further comprising the step of not evaluating a waveform if any peak in the waveform falls outside a window of minimum or maximum time for reducing a false alarm rate.

21. The method of claim 15, further comprising the steps of:

ordering the peaks in the candidate group from lesser to greater time; and

determining if a difference in time between a first and a second peak exceeds a minimum threshold.

22. The method of claim 15, further comprising the step of determining the presence of an anomaly if a positive going peak in the candidate group exceeds a threshold corresponding to a maximum expected reflection amplitude from a benign concealment, wherein additional peaks must be present after the positive going peak.