Correlated ghost imager
A method and system for detecting concealed weapons and explosives by imaging THz scenes using conventional optics and detectors is provided. Photon fields with two different wavelengths can be sent through a chopper and towards a wavelength-selective mirror. A light beam with a wavelength in the visible or IR range is sent toward a visible photon array detector. Similarly, light beams with wavelengths in the THz range can be sent towards a target, which are reflected and/or absorbed by objects in the target. The reflected or transmitted light continues on through an optional filter to remove background light, then into a non-imaging detector. The visible photon array detector can be coupled with the non-imaging detector, which will register an image of the scene that is illuminated by the THz photons.
1. A method for imaging THz (terahertz) scenes of potentially concealed weapon carriers, comprising:
directing a sequence of photon fields having a visible light beam and a terahertz beam through a chopper and towards a wavelength selective mirror for alternately transmitting and reflecting said plurality of photon fields;
transmitting said visible light beam towards an imaging array through a refractive element and transmitting said terahertz beam towards a target, which gets absorbed and/or reflected by a plurality of objects in said target, which is then sent to a non-imaging detector; and
coupling said non-imaging detector with said imaging array in order to capture an image of said target on said imaging array.
2. The method of claim 1 wherein said imaging array comprises a CCD (charged coupled device) array.
3. The method of claim 1 wherein said non-imaging detector comprises a bucket detector.
4. The method of claim 1 wherein said visible light beam leaves said chopper and heads toward a single pixel in said CCD array.
5. The method of claim 1 wherein said CCD array comprises a plurality of pixels that are smaller than the wavelength of said THz beam in order to enable said images of said target to be orders of sharper magnitude.
6. The method of claim 1 further comprising;
placing an up-conversion crystal in a detector path for detecting said THz beam of said images with said imaging array.
7. The method of claim 1 further comprising;
generating said sequence of photon fields having said visible light beam and said terahertz beam utilizing a down-conversion crystal; and
placing said down-conversion crystal and a pump-laser on a gimbaled platform in order to enable a raster scanning of said THz beam at said target.
8. The method of claim 1 wherein said sequence of photon fields comprises an IR (infrared) beam and a terahertz beam.
9. The method of claim 1 wherein said plurality of objects in said target comprises at least one concealed weapons and a plurality of imaging chemicals that have a unique spectral fingerprints in said THz beam.
10. A system for imaging THz (terahertz) scenes of potentially concealed weapon carriers, comprising:
a chopper adapted to receive a plurality of photon fields having a visible light beam and a terahertz beam and direct the plurality of photon fields towards a wavelength selective mirror;
a wavelength selective mirror adapted to alternately transmit and reflect the plurality of photon fields by further transmitting said visible light beam towards an imaging array through a refractive element and transmitting said terahertz beam towards a target, which gets absorbed and/or reflected by a plurality of objects associated with the target, wherein reflected portions of the terahertz beam are received by a non-imaging detector;
a non-imaging detector adapted to receive terahertz beams; and
a imaging array coupled to said non-imaging detector, said imaging array adapted to capture an image of said target.
11. The method of claim 10 wherein said imaging array comprises a CCD (charged coupled device) array.
12. The method of claim 10 wherein said non-imaging detector comprises a bucket detector.
13. The method of claim 10 wherein said visible light beam leaves said chopper and heads toward a single pixel in said CCD array.
14. The method of claim 10 wherein said CCD array comprises a plurality of pixels that are smaller than the wavelength of said THz beam in order to enable said images of said target to be orders of sharper magnitude.
15. The system of claim 10 further comprising;
an up-conversion crystal placed between the detector and the wavelength selective mirror for facilitating the detection of said THz beam images by said imaging array.
16. The system of claim 10 further comprising;
a down-conversion crystal adapted to generate said plurality of photon fields having a visible light beam and a terahertz beam.
17. The system of claim 16 wherein said down-conversion crystal is placed together with a pump-laser on a gimbaled platform, wherein said placement facilitates raster scanning of said THz beam at said target.
18. A system for imaging THz (terahertz) scenes of potentially concealed weapon carriers, comprising:
a down-conversion crystal adapted to generate a plurality of photon fields having a visible light beam and a terahertz beam;
a chopper adapted to receive said plurality of photon fields having a visible light beam and a terahertz beam and direct the plurality of photon fields towards a wavelength selective mirror;
a wavelength selective mirror adapted to alternately transmit and reflect the plurality of photon fields by further transmitting said visible light beam towards an imaging array through a refractive element and transmitting said terahertz beam towards a target, which gets absorbed and/or reflected by a plurality of objects associated with the target, wherein reflected portions of the terahertz beam are received by a non-imaging detector;
a non-imaging detector adapted to receive terahertz beams;
an up-conversion crystal placed between the detector and the wavelength selective mirror for facilitating the detection of said THz beam images by said imaging array; and
a imaging array coupled to said non-imaging detector, said imaging array adapted to capture an image of said target.
19. The system of claim 18 wherein said imaging array comprises a CCD (charged coupled device) array.
20. The system of claim 18 wherein said down-conversion crystal is placed together with a pump-laser on a gimbaled platform, wherein said placement facilitates raster scanning of said THz beam at said target.