Granted Patent B2

US 8,625,740 · App. 13/087,191 · Granted Jan 7, 2014

Abstract

Claims (58)

1. A method for correcting an X-ray diffraction (XRD) profile measured by an X-ray diffraction imaging (XDi) system that includes an anode, a detector, and a control system, said method comprising:

obtaining an emission spectrum of the anode using the control system, the emission spectrum including spectral structures including a Kα peak, a Kβ peak, and a K edge;

calculating a piecewise spectral-correction function using the spectral structures in the emission spectrum comprising defining a plurality of windows of the emission spectrum based on energies of the spectral structures at least partially as a function of the Kβ peak and the K edge;

obtaining a measured spectrum of an object; and

applying the spectral-correction function to the measured spectrum to generate a spectrally-corrected measured spectrum.

2. A method in accordance with claim 1 , wherein defining the plurality of windows of the emission spectrum at least partially as a function of the Kβ peak and the K edge comprises:

defining a first window from a beginning point of the emission spectrum to a center of the Kβ peak;

defining a second window from the center of the Kβ peak to an end of the K edge; and

defining a third window from the end of the K edge to an end point of the emission spectrum.

3. A method in accordance with claim 2 , wherein calculating a piecewise spectral-correction function further comprises:

defining a spectral band on each side of the Kα peak;

fitting a straight line to the spectral bands;

calculating a ratio of the emission spectrum to the straight line; and

defining a first window portion of the piecewise spectral-correction function using the ratio and unity.

4. A method in accordance with claim 3 , wherein calculating a piecewise spectral-correction function comprises defining a second window portion of the piecewise spectral-correction function as the ratio of the emission spectrum to the straight line.

5. A method in accordance with claim 3 , wherein calculating a piecewise spectral-correction function comprises:

calculating a K edge ratio of an average number of photon counts to a height of the straight line;

multiplying a numerical difference between unity and the K edge ratio by a function that is unity at an energy of the K edge and exponentially decreases with increasing photon energy; and

defining a third window portion of the piecewise spectral-correction function as the multiplication.

6. A method in accordance with claim 1 , wherein applying the spectral-correction function to the measured spectrum further comprises dividing the measured spectrum by the spectral-correction function to generate the spectrally-corrected measured spectrum.

7. A method in accordance with claim 1 further comprising correcting the spectrally-corrected measured spectrum for variation in scatter angle.

8. A method in accordance with claim 7 , wherein correcting the spectrally-corrected measured spectrum for variation in scatter angle comprises:

obtaining a first calibration spectrum that is generated by scanning a calibration substance and detecting scattered radiation at a first scatter angle;

obtaining a second calibration spectrum that is generated by scanning the calibration substance and detecting scattered radiation at a second scatter angle different than the first scatter angle; and

calculating an angular-correction function using the first calibration spectrum and the second calibration spectrum.

9. A method in accordance with claim 8 , wherein calculating an angular-correction function comprises dividing the first calibration spectrum by the second calibration spectrum.

10. A method in accordance with claim 8 , wherein the spectrally-corrected measured spectrum is detected at the second scatter angle, said method further comprising applying the angular-correction function to the spectrally-corrected measured spectrum to transform spectrally-corrected measured spectrum from the second scatter angle to the first scatter angle.

11. A control system for use with an X-ray diffraction imaging (XDi) system comprising a radiation source configured to generate a primary beam of radiation, the radiation source comprising an anode, and a detector configured to detect radiation scattered by an interaction of the primary beam with an object, said control system configured to:

obtain an emission spectrum of the anode, the emission spectrum including spectral structures including a Kα peak, a Kβ peak, and a K edge;

calculate a piecewise spectral-correction function using the spectral structures in the emission spectrum comprising defining a plurality of windows of the emission spectrum based on energies of the spectral structures at least partially as a function of the Kβ peak and the K edge;

obtain a measured spectrum of an object; and

apply the spectral-correction function to the measured spectrum to generate a spectrally-corrected measured spectrum.

12. A control system in accordance with claim 11 further configured to correcting the spectrally-corrected measured spectrum for variation in scatter angle.

13. A control system in accordance with claim 11 , wherein and a K edge, said control system configured to define a plurality of windows of the emission spectrum based on energies of the spectral structures at least partially as a function of the Kβ peak and the K edge further configured to define a first portion, a second portion, and a third portion of the piecewise spectral-correction function based on energies of the Kα peak, the Kβ peak, and the K edge.

14. A control system in accordance with claim 13 further configured to:

define a spectral band on each side of the Kα peak;

fit a straight line to the spectral bands;

calculate a ratio of the emission spectrum to the straight line; and

define the first portion of the piecewise spectral-correction function using the ratio and unity.

15. A control system in accordance with claim 13 further configured to define the second portion of the piecewise spectral-correction function as a ratio of the emission spectrum to a straight line, the straight line fit to spectral bands adjacent to the Kα peak.

16. A control system in accordance with claim 13 further configured to:

calculating a K edge ratio of an average number of photon counts to a height of a straight line that is fit to spectral bands adjacent to the Kα peak;

multiplying a numerical difference between unity and the K edge ratio by a function that is unity at an energy of the K edge and exponentially decreases with increasing photon energy; and

defining the third portion of the piecewise spectral-correction function as the multiplication.

17. An X-ray diffraction imaging (XDi) system comprising:

a radiation source configured to generate a primary beam of radiation, said radiation source comprising an anode;

a detector configured to detect radiation scattered by an interaction of the primary beam with an object; and

a control system coupled in communication with said detector, said control system configured to:

obtain a measured spectrum detected by said detector at a first scatter angle;

perform a spectral-correction procedure on the measured spectrum to remove spectral structures from an emission spectrum of said anode; and

perform an angular-correction procedure on the measured spectrum to transform the measured spectrum from the first scatter angle to a second scatter angle comprising:

obtaining a first calibration spectrum that is generated by scanning a calibration substance and detecting scattered radiation at a first scatter angle;

obtaining a second calibration spectrum that is generated by scanning the calibration substance and detecting scattered radiation at a second scatter angle different than the first scatter angle;

calculating an angular-correction function by dividing the first calibration spectrum by the second calibration spectrum; and

applying the angular-correction function to the measured spectrum.

18. An XDi system in accordance with claim 17 , wherein said control system is configured to perform the spectral-correction procedure by:

calculating a piecewise spectral-correction function using energies of the spectral structures in the emission spectrum; and

applying the spectral-correction function to the measured spectrum.

Assignments (6)