Security portal with THz trans-receiver

• US 20070114418A1
• Filed: 08/30/2006
• Published: 05/24/2007
• Est. Priority Date: 09/20/2005
• Status: Active Grant

• Current Assignee: Coherent Inc (Coherent Corp.)
• Original Assignee: Coherent Inc (Coherent Corp.)
• Inventors: Mueller, Eric, Michaud, Raymond
• Granted Patent: US 7,378,658 B2
• Time in Patent Office: Days
• US Class Current: 250/341.100
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/3581 using far infrared light; using Terahertz radiation
• CPC Class Codes: G01N 2201/10 Scanning
• CPC Class Codes: G01S 13/887 for detection of concealed objects, e.g. contraband or weapons

Abstract

A portal for security screening of transport passengers includes a THz trans-receiver. In one example of the portal, the trans-receiver includes a small-spot, reflective scanning arrangement including a single detector in a heterodyne receiver configuration. In another example, the trans-receiver includes a large-beam reflective scanning arrangement with the trans-receiver in a synthetic aperture radar (SAR) configuration.

Claims

1. Apparatus for examining a clothed person for detecting an object or substance concealed by the person'"'"'s clothing, the apparatus comprising:

a portal defining a position in the apparatus in which the person is positioned for examination;

a terahertz (THz) trans-receiver arranged to provide a beam of THz radiation having a frequency such that the THz radiation is transmitted by the positioned person'"'"'s clothing;

an optical system for directing a beam of THz radiation from the THz trans-receiver to the positioned person and directing radiation reflected from the positioned person back to the THz trans-receiver, the optical system including a vertically movable mirror for directing the beam to a plurality of different heights on the positioned person and an angular scanning device for moving the beam to a plurality of different horizontal locations on the positioned person along each of the plurality of different heights; and

signal processing electronics for recording data including at least one parameter of radiation reflected from the positioned person at the different heights and locations therealong and for processing the recorded data to provide an image of at least some portion of the positioned person.

2. The apparatus of claim 1, wherein the movable mirror and the scanning device of the optical system are incorporated in a scanner head vertically movable in vertically oriented guides attached to the portal.

3. The apparatus of claim 1, wherein the vertically movable mirror is a ring mirror vertically movable in vertically oriented guides attached to the portal and having a diameter sufficient to encircle the person, wherein there optical system further includes a ring mirror fixedly attached to the portal at a height thereon above the positioned person and the scanning device is a periscope head including a rotatable mirror;

and wherein the rotatable mirror directs the THz-radiation beam horizontally to the fixed ring mirror, the fixed ring mirror, directs the THz-radiation beam vertically to the movable ring mirror, and the movable ring mirror directs the THz-radiation beam laterally to the person.

4. The apparatus of claim 1, wherein the apparatus has a predetermined target resolution dimension and the optical system is arranged to focus the THz-radiation beam on the person with the a maximum dimension of the focused THz-radiation beam being about equal to the target resolution dimension.

5. The apparatus of claim 4, wherein the maximum beam dimension on the person is about one millimeter or less.

6. The apparatus of claim 4, wherein the optical system includes a rangefinder arranged to measure an instant distance of the person from the THz trans-receiver, and wherein the optical system is an active variable-focus system arranged to focus the beam on the person in response to the rangefinder measurement.

7. The apparatus of claim 1, wherein the apparatus has a predetermined target resolution dimension defining a target resolution element, wherein the optical system is arranged to deliver the THz-radiation beam on the person with a maximum dimension of the THz-radiation beam being sufficient that the beam illuminates a plurality of target resolution elements, and wherein the recorded parameters are processed using synthetic aperture radar algorithms to provide the image of at least some portion of the positioned person.

8. The apparatus of claim 7, wherein the target resolution dimension is about 1.0 millimeter or less and the THz-radiation beam on the person has a maximum dimension of about 35 millimeters.

9. The apparatus of claim 1, wherein the parameters of radiation reflected from the positioned person is the phase of the radiation and the image provided is a phase-contrast image.

10. The apparatus of claim 1, wherein the THz radiation has a frequency of about 1.56 THz.

11. Apparatus for examining a clothed person for detecting an object or substance concealed by the person'"'"'s clothing, the apparatus comprising:

a portal defining a position in the apparatus in which the person is positioned for examination;

first and second terahertz (THz) trans-receivers for delivering first and second beams of terahertz radiation having respectively first and second wavelengths at which the positioned person'"'"'s clothing is at least partially transparent;

an optical system arranged to direct the beams of THz radiation from the THz trans-receivers to a plurality of areas on the positioned person at different heights on the positioned person and at a plurality of different horizontal locations on the positioned person along each of the plurality of different heights, the optical system being further arranged to direct THz radiation reflected from the positioned person back to the THz trans-receivers; and

signal processing electronics for recording data including at least one parameter of radiation reflected from the positioned person at the different heights and locations therealong at each of the different wavelengths and for processing the recorded data to provide an image of at least some portion of the positioned person.

12. The apparatus of claim 11, wherein the optical system includes first and second vertically movable mirrors for directing respectively the first and second beams of terahertz radiation to the plurality of different heights on the positioned person and first and second angular scanning devices for moving the beams to the plurality of different horizontal locations on the person along each of the plurality of different heights.

13. Apparatus for examining a clothed person for detecting an object or substance concealed by the person'"'"'s clothing, the apparatus comprising:

a portal defining a position in the apparatus in which the person is positioned for examination;

a terahertz (THz) trans-receiver arranged to provide a beam of THz radiation having a frequency such that the THz radiation is at least partially transmitted by the person'"'"'s clothing;

an optical system for directing a beam of THz radiation from the THz trans-receiver to the positioned person and directing radiation reflected from the position person back to the THz trans-receiver, the optical system including a rotatable mirror encircled by a fixed ring mirror located at a height above the person and a vertically movable ring mirror located below the fixed ring mirror and having a diameter sufficient that the mirror can encircle the positioned person, the beam being directed from the rotatable mirror to the fixed ring mirror from the fixed ring mirror to the movable ring mirror and from the movable ring mirror to the positioned person and wherein vertically moving the movable ring mirror directs the beam to a plurality of different heights on the positioned person and rotating the rotatable mirror moves the beam to a plurality of different horizontal locations on the person along each of the plurality of different heights; and

signal processing electronics for recording data including at least one parameter of radiation reflected from the positioned person at the different heights and locations therealong and for processing the recorded data to provide an image of at least some portion of the positioned person.

14. The apparatus of claim 13, wherein the apparatus has a predetermined target resolution dimension and the optical system is arranged to focus the THz-radiation beam on the person with the a maximum dimension of the focused THz-radiation beam being about equal to the target resolution dimension.

15. The apparatus of claim 14, wherein the maximum beam dimension on the person is about one millimeter or less.

16. The apparatus of claim 14, wherein the optical system includes a rangefinder arranged to measure an instant distance of the person from the THz trans-receiver, and wherein the optical system is an active variable-focus system arranged to focus the beam on the person in response to the rangefinder measurement.

17. The apparatus of claim 13, wherein the apparatus has a predetermined target resolution dimension defining a target resolution element, wherein the optical system is arranged to deliver the THz-radiation beam on the person with a maximum dimension of the THz-radiation beam being sufficient that the beam illuminates a plurality of target resolution elements, and wherein the recorded parameters are processed using synthetic aperture radar algorithms to provide the image of at least some portion of the positioned person.

18. The apparatus of claim 17, wherein the target resolution dimension is about 1.0 millimeter or less and the THz-radiation beam on the person has a maximum dimension of about 35 millimeters.

19. The apparatus of claim 13, wherein the parameters of radiation reflected from the positioned person is the phase of the radiation and the image provided is a phase-contrast image.