Multi-modal detection of explosives, narcotics, and other chemical substances

• US 6,946,300 B2
• Filed: 06/11/2003
• Issued: 09/20/2005
• Est. Priority Date: 02/01/2002
• Status: Expired due to Fees

• Current Assignee: Control Screening LLC
• Original Assignee: Control Screening LLC
• Inventors: Klymowsky, Chris, Christensen, David L., Berry, Stewart, Nguyen, Dao Hinh
• Primary Examiner(s): Toatley, Jr., Gregory J.
• Assistant Examiner(s): VALENTIN, JUAN D
• Application Number:
  US10/459,889
• Publication Number:
  US 20040114130A1
• Time in Patent Office: 832 Days
• Field of Search: 356/36, 250/281, 250/287, 250/288, 250/286, 436/110, 436/156, 436/172, 422/52, 422/78, 422/82.08
• US Class Current: 436/110
• CPC Class Codes: G01N 1/24 Suction devices G01N1/22 - G01N1/2294 take precedence
• CPC Class Codes: G01N 2001/024 passengers or luggage
• CPC Class Codes: G01N 21/766 of gases
• CPC Class Codes: G01V 8/00 Prospecting or detecting by optical means
• CPC Class Codes: Y10T 436/173076 Nitrite or nitrate

Abstract

A compact scanning apparatus has an infrared laser adapted to emit light. The light is delivered as a beam by an optical system to illuminate an interrogation area on the surface of an object being scanned to cause selective desorption of molecules of the contraband substance, which are present on the surface, without substantially damaging the surface. A collection system collects at least a portion of the desorbed molecules. At least a portion of the collected molecules is thermally decomposed to form NO₂ and transferred to a reaction cell containing an aqueous, alkaline, luminol-containing solution. The NO₂ reacts with the luminol to produce light by chemiluminescence. A light detector registers the presence of this light to carry out a rapid screening of the object for the possible presence of the contraband substance. The apparatus further includes a supplemental detector such as a GC/IMS detector that is activated in response to the detection of the chemiluminescent light. The supplemental detector provides confirmation of the detection of contraband substance and activates a signaling device to provide an audible or visible alarm. The rapid pre-screening permits the apparatus to identify suspicious items, while the supplemental detection system can be optimized for more intense, but time-consuming scrutiny of just the suspicious items. Both effective detection and high throughput are thereby achieved in an accurate, reliable manner.

Claims

1. A system for screening at least a portion of the surface of a baggage item for the presence thereon of a contraband substance, the system comprising:

a) an infrared laser adapted to emit light;

b) an optical system adapted to deliver a beam of said light emitted from said infrared laser to illuminate an interrogation area of said surface, said illumination having sufficient intensity and duration to cause selective desorption of molecules of said contraband substance present within said interrogation area without substantially damaging said surface, and at least a portion of said desorbed molecules being thermally decomposed to produce NO₂ molecules;

c) a collection system having at least one aperture and being adapted to collect at least a portion of said desorbed molecules through said aperture;

d) a reaction cell in communication with said collection system, said reaction cell having a reaction zone, an inlet for receiving in said reaction zone said desorbed molecules collected by said collection system; and

an outlet for release of said desorbed molecules, and said reaction cell containing an alkaline, aqueous luminol-containing solution;

e) a light detector for detecting light produced chemiluminescently by a chemical reaction between said luminol and said NO₂ within said reaction cell, and for outputting a first electrical signal indicative of the detection of said light;

f) a supplemental detector in communication with said collection system for detecting said contraband substance and for outputting a second electrical signal indicative of the detection of said contraband substance;

g) signal means for indicating the presence of said NO₂ produced by the decomposition of said contraband substance, said signal means being operably connected to said light detector and said supplemental detector and responsive to the receipt of said first or second electrical signals.

2. A system as recited by claim 1, wherein said supplemental detector is at least one detector selected from the group consisting of gas chromatograph/ion mobility spectrometry, gas chromatograph/surface surface ionization, gas chromatography/mass spectrometry, field ion spectrometry, photoacoustic spectrometry, and gas-phase infrared spectrometry detectors.

3. A system as recited by claim 1, wherein said supplemental detector is a gas chromatograph/ion mobility spectrometry detector.

4. A system as recited by claim 1, wherein said supplemental detector is activated in response to the presence of said first electrical signal.

5. A system as recited by claim 4, further comprising a valve operable to open and close the communication between said collection system and said supplemental detector.

6. A system as recited by claim 5, wherein said valve is opened in response to the presence of said first electrical signal.

7. A system as recited by claim 1, wherein said contraband substance comprises an organo-nitro explosive.

8. A system as recited by claim 1, wherein said intensity and duration of said illumination is such that at least a portion of said contraband substance is thermally decomposed to produce molecules of NO₂.

9. A system as recited by claim 1, wherein said intensity and duration of said illumination is such that at least a portion of said desorbed molecules is comprised in particles of said contraband substance ablated from said surface by said illumination.

10. A system as recited by claim 1, said collection system comprising an air pump for urging said desorbed molecules through said collection system and into said reaction cell.

11. A system as recited by claim 1, further comprising:

h. a digital computer for controlling said apparatus and analyzing the output of said light detector and said supplemental detector.

12. A system as recited by claim 1, further comprising:

i. motion means for relatively moving said baggage item and said beam of light to illuminate an extended interrogation zone.

13. A system as recited by claim 1, further comprising a document sampling station.

14. A system as recited by claim 1, wherein said signal means comprises a computer display terminal adapted to display a mapping indicative of the locations on said baggage item at which a contraband substance has been detected.

15. A method of scanning at least a portion of the surface of a baggage item for the presence thereon of at least one contraband substance, the method comprising the steps of:

a) illuminating an interrogation area of said surface with infrared laser light to selectively desorb molecules of said contraband substance;

b) thermally decomposing at least a portion of said desorbed molecules to form NO₂;

c) passing said NO₂ into a reaction cell, said reaction cell having a reaction zone and comprising an aqueous, alkaline, luminol-containing solution;

d) reacting said NO₂ in said reaction cell with said luminol to produce light;

e) detecting said light;

f) activating a supplemental detector in response to the detection of said light; and

g) signaling the detection of said contraband substance by said supplemental detector to indicate the presence of said contraband substance on the surface of said baggage item.

16. A method as recited by claim 15, wherein said supplemental detector is activated solely in response to the detection of said light.