| US 7,550,969 B2 | ||
| Security screening and inspection based on broadband electromagnetic holographic imaging | ||
| Michael S. Zhdanov, Salt Lake City, Utah (US) | ||
| Assigned to University of Utah Research Foundation, Salt Lake City, Utah (US) | ||
| Filed on Apr. 30, 2002, as Appl. No. 10/135,926. | ||
| Application 10/135926 is a continuation in part of application No. 09/876262, filed on Jun. 06, 2001, granted, now 6,876,878. | ||
| Application 09/876262 is a continuation in part of application No. 09/214217, filed on Dec. 23, 1998, granted, now 6,253,100. | ||
| Prior Publication US 2009/0119040 A1, May 07, 2009 | ||
| Int. Cl. G01R 33/12 (2006.01); G01N 27/72 (2006.01) | ||
| U.S. Cl. 324—243 [324/232] | 44 Claims |
| 12. A system of security screening a body and attached object, comprising:
a portal including at least one transmitter coil and at least one receiver coil, wherein said portal is configured to accommodate
said body and attached object passing therethrough; wherein said transmitter coil is configured to generate a broadband electromagnetic
field comprising a frequency domain electromagnetic field and/or time domain electromagnetic field that propagates through
said body and attached object and interacts with said body and attached object to result in a scattered electromagnetic field;
and wherein said receiver coil is configured to record said scattered electromagnetic field;
a computer configured to simulate a first background electromagnetic field existing within said portal when there is no body
and attached object within said portal, to compute a first backscattering electromagnetic field obtainable by transmitting
said scattered electromagnetic field from said receiver coil, to produce an image of electric conductivity and/or dielectric
permittivity of said body and attached object, and to determine at least one characteristic of the attached object;
wherein said computer is configured to produce said image iteratively by:
calculating a second background electromagnetic field in response to said first background electromagnetic field with a previously
obtained complex conductivity;
calculating a residual electromagnetic field between the second background electromagnetic field and the first backscattering
electromagnetic field;
calculating a second backscattering field for the residual electromagnetic field by simulating illumination of the updated
background medium with electric and magnetic currents equivalent to those of the updated residual electromagnetic field recorded
at the location of the receivers; and
constructing updated volume images of anomalous conductivity σa(n)(r) and of anomalous permittivity ∈a(n)(r) on the basis of updated cross power spectrum or cross correlation functions between said first background field and said
second backscattering field, using regularization procedures.
|