Analysis methods for energy dispersive X-ray diffraction patterns
AssigneeRutgers, The State University
InventorsWilliam E. Mayo, Zwi Kalman, Mark C. Croft, Joseph Wilder, Richard Mammone, Adam B. Fineberg
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Abstract
Energy dispersive x-ray diffraction spectra are obtained from numerous volume elements within an object. A feature set such as a set of cepstrum coefficients is extracted from each spectrum and classified by a trained classifier such as a neural network to provide an indication of whether or not contraband such as explosives is present in the volume element. Indications for adjacent volume elements are evaluated in conjunction with one another, as by an erosion process, to suppress isolated indications and thereby suppress false alarms.
Claims51
A method of examining crystal structure of an object by energy dispersive x-ray diffraction comprising the steps of:
- (a) applying a beam of incident X-ray radiation, detecting diffracted X-ray radiation and deriving an energy spectrum of the diffracted X-rays from said object;
- (b) extracting a plurality of features from said spectrum constituting a feature set;
- and
- (c) classifying the structure of the object by a probabilistic technique wherein a plurality of said features in said feature set contribute to the probability that the structure of the object belongs to a particular one of a plurality of classes.
A method examining crystal structure of an object comprising the steps of:
- (a) obtaining structural information with respect to each of a plurality of volume elements in the object;
- (b) classifying the structural information so as to provide a separate indication with respect to each said volume element as to whether a substance of a preselected class is present in such volume element;
- and
- (c) evaluating the indications obtained with respect to adjacent volume elements in conjunction with one another so as to suppress indications that a substance of such class is present in isolated volume elements remote from other volume elements having indications that such substance is present.
A method as claimed in claim 30 wherein said plural erosion processes include a plurality of two-dimensional erosion processes using planar arrays of volume elements, the planar arrays of volume elements used in different ones of said plural erosion processes lying planes having different orientations.
A method of examining an object by energy dispersive x-ray diffraction comprising the steps of:
- (a) applying an incident beam of X-ray radiation to an object;
- (b) detecting diffracted X-rays from said incident beam diffracted by the object over a range of Bragg angles greater than zero, and obtaining an uncorrected spectrum of said diffracted X-rays, whereby said uncorrected spectrum will include the true diffraction spectrum of the object convolved with the spectrum of the incident beam, absorption by the object and a broadening effect caused by said non-zero range of Bragg angles;
- (c) deriving a raw transmission spectrum, including the spectrum of the incident beam with the effect of absorption by the object;
- (d) subjecting said raw transmission spectrum to an algorithm simulating convolution of said raw transmission beam spectrum with said broadening effect to obtain a modified transmission spectrum;
- and
- (e) obtaining a normalized spectrum by dividing said uncorrected spectrum by said modified transmission spectrum.
A method of examining an object by energy dispersive x-ray diffraction comprising the steps of:
- (a) applying an incident beam of X-ray radiation to an object;
- (b) detecting diffracted X-rays from said incident beam diffracted by the object over a range of Bragg angles greater than zero, and obtaining an uncorrected spectrum of said diffracted X-rays, whereby said uncorrected spectrum will include the true diffraction spectrum of the object convolved with the spectrum of the incident beam, absorption by the object and a broadening effect caused by said non-zero range of Bragg angles;
- (c) deriving a raw transmission spectrum including the spectrum of the incident beam with the effect of absorption by the object;
- (d) obtaining a modified diffraction spectrum by subjecting said uncorrected spectrum to a deconvolution algorithm effective to substantially reverse said broadening effect;
- and
- (e) obtaining a normalized spectrum by dividing said modified diffraction spectrum by said raw transmission spectrum.
A method of examining an object by energy dispersive x-ray diffraction comprising the steps of obtaining a spectrum of X-rays diffracted by said object and extracting a plurality of features from said spectrum constituting a feature set, said step of extracting said features from said spectrum including the step of applying a transform to said spectrum so as to provide a set of coefficients such that each said coefficient depends on the entirety of said spectrum, said set of features including at least some of said coefficients provided by said transform.
Dependencies are inferred from the claim text.