Device for material separation using nondestructive inspection imaging

• US 5,481,584 A
• Filed: 11/23/1994
• Issued: 01/02/1996
• Est. Priority Date: 11/23/1994
• Status: Expired due to Fees

• Current Assignee: Jihong Tang, Yao-Jin Qian
• Original Assignee: Jihong Tang, Yao-Jin Qian
• Inventors: Qian, Yao-Jin, Tang, Jihong
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): WONG, DON KITSUN
• Application Number:
  US08/344,171
• Time in Patent Office: 405 Days
• Field of Search: 378/98.8, 378/98, 378/98.2, 378/45, 378/46, 378/49, 378/53, 378/57, 378/83, 378/82, 378/88
• US Class Current: 378/98.9
• CPC Class Codes: G01N 23/083 the radiation being X-rays

Abstract

Device and method are provided for separating images according to material species in nondestructive x-ray or γ-ray imaging. Using the x-ray (or γ-ray) attenuation coefficient of materials as functions of x-ray energy, simultaneous linear equations are set up and solved for obtaining the image for a specific material when multiple x-ray (or γ-ray) energies are used. The device disclosed in this invention features real-time, material-specific image separation. Applications include x-ray security inspection and industrial x-ray or γ-ray noninvasive structural inspection.

Claims

1. An x-ray inspection system for separating material-specific images generated by transmitting x-rays through an ensemble of unknown materials, comprising:

generating means for generating and emitting N different x-ray energy distributions, each energy distribution being labelled by E_k and having an x-ray intensity I₀ (E_k), where k ranges from 1 to N, and where N is an integer greater than 1;

a device storing an N by N matrix μ

^-1, where μ

^-1 is an inversion of a matrix t*, and where each matrix element μ

_jk for the matrix μ

is defined as the linear attenuation coefficient of a certain material group j (of N material groups) at the x-ray energy E_k, the N material groups being generated from sorting the ensemble of unknown materials into N possible groups of materials according to the closeness of linear attenuation coefficients or equivalent characteristics of materials at different incident x-ray energy distributions prior to inspection, wherein at least two μ

^-1 matrices are stored in the device and each μ

^-1 matrix corresponds to a different set of N material groups;

reshaping means for reshaping the N different x-ray energy distributions emitted from the generating means;

first detecting means for detecting the x-ray intensities I₀ (E_k) at each of the reshaped N x-ray energy distributions labelled E_k, the detecting occurring before transmission of the reshaped N x-ray energy distributions through the ensemble of unknown materials, the first detecting means outputting a first signal corresponding to the detection by the first detecting means;

second detecting means for detecting a portion of the reshaped N x-ray energy distributions labelled E_k that have passed through the ensemble of unknown materials, the second detecting means outputting a second signal corresponding to the detection by the second detecting means;

first converting means for receiving the first signal from the first detecting means and for converting the first signal into first image information;

second converting means for receiving the second signal from the second detecting means and for converting the second signal into second image information;

logarithmic means for logarithmically processing the first and second image information;

switching means for dynamically switching from one μ

^-1 matrix for one set of N material groups to another μ

^-1 for another set of N material groups during the inspection, wherein the switching is for the purpose of finding an appropriate set of N material groups that best represents the actual material groups existing in the ensemble under inspection;

image-generating means for generating material-specific images for the N groups of materials, using the logarithmically processed first and second image information and the μ

^-1 matrix; and

processing means for processing and displaying the material-specific images.

2. The x-ray inspection system according to claim 1, wherein the detecting means comprises a semiconductor detector.

3. The x-ray inspection system according to claim 1, wherein luggage is carried past the inspection system on a conveyer belt.

4. The x-ray inspection system according to claim 1, further comprising N displays, each displaying one of the N material groups.

5. The x-ray inspection system according to claim 1, further comprising controlling means for controlling one or more of the following:

the operation and timing of the generating means, the reshaping means, the first and second detecting means, the first and second converting means, the logarithmic means, the switching means, image receivers, the image-generating means, the processing means, and a conveyer belt.

6. The x-ray inspection system according to claim 1, wherein the controlling means includes means for controlling saturation and underexposure.

7. The x-ray inspection system according to claim 1, wherein the controling means includes means for controlling an amount of light entering the first and second detecting means by controlling x-ray intensity.

8. The x-ray inspection system according to claim 1, wherein the inspection operates to display the material-specific images in real-time.

9. An x-ray inspection system for separating material-specific images generated by transmitting x-rays through an ensemble of unknown materials, comprising:

generating means for generating and emitting N different x-ray energy distributions, each energy distribution being labelled by E_k and having an x-ray intensity I₀ (E_k), where k ranges from 1 to N, and where N is an integer greater than 1;

a device storing an N by N matrix μ

^-1, where μ

^-1 is the inversion of a matrix μ

, and where each matrix element μ

_jk for

the matrix μ

is defined as the linear attenuation coefficient of a certain material group j (of N material groups) at the x-ray energy E_k, the N material groups being generated from sorting the ensemble of unknown materials into N possible groups of materials according to closeness of linear attenuation coefficients or equivalent characteristics of materials at different incident x-ray energy distributions prior to inspection;

reshaping means for reshaping the N different x-ray energy distributions emitted from the generating means;

first detecting means for detecting the x-ray intensities I₀ (E_k) at each of the reshaped N x-ray energy distributions labelled E_k, the detecting occurring before transmission of the reshaped N x-ray energy distributions through the ensemble of unknown materials, the first detecting means outputting a first signal corresponding to the detection by the first detecting means;

second detecting means for detecting a portion of the reshaped N x-ray energy distributions labelled E_k that have passed through the ensemble of unknown materials, the second detecting means outputting a second signal corresponding to the detection by the second detecting means;

first converting means for receiving the first signal from the first detecting means and for converting the first signal into first image information;

second converting means for receiving the second signal from the second detecting means and for convening the second signal into second image information;

logarithmic means for logarithmically processing the first and second image information;

means for generating material-specific images for the N groups of materials, using the logarithmically processed first and second image information and the matrix μ

^-1 ; and

means for processing and displaying the material-specific images.

10. The x-ray inspection system according to claim 9, wherein luggage is carried past the inspection system on a conveyer belt.

11. The x-ray inspection system according to claim 9, further comprising N displays, each displaying one of the N material groups.

12. The x-ray inspection system according to claim 9, wherein the means for generating material-specific images incorporates a matrix operation using N independent arithmetic channels where each independent channel corresponds to one independent vector component of the vector, and where N is a dimension of the vectors.

13. The x-ray inspection system according to claim 9, wherein the inspection operates to display the material-specific images in real-time.

14. The x-ray inspection system according to claim 9, further comprising controlling means for controlling one or more of the following:

the operation and timing of the generating means, the reshaping means, the first and second detecting means, the first and second converting means, the logarithmic means, a switching means, image receivers, the image-generating means, the processing means, and a conveyer belt.

15. The x-ray inspection system according to claim 9, further including controlling means for controlling saturation and underexposure.

16. The x-ray inspection system according to claim 9, further including controling means for controlling an amount of light entering the first and second detecting means by controlling x-ray intensity.

17. An x-ray inspection system for separating material-specific images generated by transmitting x-rays through an ensemble of unknown materials, comprising:

generating means for generating and emitting N different x-ray energy distributions, each energy distribution being labelled by E_k and having an x-ray intensity I₀ (E_k), where k ranges from 1 to N, and where N is an integer greater than 1, the generation means comprising at least two different x-ray sources simultaneously emitting two different x-ray energies;

a device storing an N by N matrix μ

^-1, where μ

^-1 is the inversion of a matrix μ

, and where each matrix element μ

_jk for the matrixμ

is defined as the linear attenuation coefficient of a certain material group j (of N material groups) at the x-ray energy E_k, the N material groups being generated from sorting the ensemble of unknown materials into N possible groups of materials according to closeness of linear attenuation coefficients or equivalent characteristics of materials at different incident x-ray energy distributions prior to inspection;

reshaping means for reshaping the N different x-ray energy distributions emitted from the generating means;

first detecting means for detecting the x-ray intensities I₀ (E_k) at each of the reshaped N x-ray energy distributions labelled E_k, the detecting occurring before transmission of the reshaped N x-ray energy distributions through the ensemble of unknown materials, the first detecting means outputting a first signal corresponding to the detection by the first detecting means;

second detecting means comprising at least two detectors functioning simultaneously, for detecting a portion of the reshaped N x-ray energy distributions labelled E_k that have passed through the ensemble of unknown materials, the second detecting means outputting a second signal corresponding to the detection by the second detecting means;

scanning means for performing simultaneous scanning of x-ray energies by moving either the x-ray sources or the ensemble of unknown materials;

correcting means for correcting an image time lag which originates from spatial arrangements of the x-ray sources and detectors, by considering the speed of the ensemble of unknown material or the x-ray sources in motion;

first converting means for receiving the first signal from the first detecting means and for convening the first signal into first image information;

second converting means for receiving the second signal from the second detecting means and for converting the second signal into second image information;

logarithmic means for logarithmically processing the first and second image information;

image-generating means for generating material-specific images for the N groups of materials, using the logarithmically processed first and second image information and the matrix μ

^-1 ; and

means for processing and displaying the material-specific images.

18. The x-ray inspection system according to claim 17, further comprising controlling means for controlling one or more of the following:

the scanning means, the operation and timing of the generating means, the reshaping means, the first and second detecting means, the first and second converting means, the logarithmic means, a switching means, image receivers, the image-generating means, the processing means, and a conveyer belt.

19. The x-ray inspection system according to claim 17, wherein the detecting means comprises a semiconductor detector.

20. The x-ray inspection system according to claim 17, further comprising controlling means for controlling image saturation and underexposure.

21. The x-ray inspection system according to claim 17, wherein the scanning means comprises a conveyer belt.

22. The x-ray inspection system according to claim 17, wherein the scanning means comprises means for moving the generating means past an object containing the ensemble of unknown materials.

23. The x-ray inspection system according to claim 17, further comprising N displays, each displaying one of the N material groups.

24. The x-ray inspection system according to claim 17, wherein the inspection operates to display the material-specific images in real-time.

25. The x-ray inspection system according to claim 17, wherein the controlling means includes means for controlling saturation and underexposure.

26. The x-ray inspection system according to claim 17, wherein the controling means includes means for controlling an amount of light entering the first and second detecting means by controlling x-ray intensity.

27. An x-ray inspection system for separating material-specific images generated by transmitting x-rays through an ensemble of unknown materials, comprising:

generating means for generating and emitting N different x-ray energy distributions, each energy distribution being labelled by E_k and having an x-ray intensity I₀ (E_k), where k ranges from 1 to N, and where N is an integer greater than 1;

a device storing an N by N matrix μ

^-1, where μ

^-1 is the inversion of a matrix μ

, and where each matrix element μ

_jk for the matrix μ

is defined as the linear attenuation coefficient of a certain material group j (of N material groups) at the x-ray energy E_k, the N material groups being generated from sorting the ensemble of unknown materials into N possible groups of materials according to the closeness of linear attenuation coefficients or equivalent characteristics of materials at different incident x-ray energy distributions prior to inspection;

reshaping means for reshaping the N different x-ray energy distributions emitted from the generating means;

first detecting means for detecting the x-ray intensities I₀ (E_k) at each of the reshaped N x-ray energy distributions labelled E_k, the detecting occurring before transmission of the reshaped N x-ray energy distributions through the ensemble of unknown materials, the first detecting means outputting a first signal corresponding to the detection by the first detecting means;

second detecting means for detecting a portion of the reshaped N x-ray energy distributions labelled E_k that have passed through the ensemble of unknown materials, the second detecting means outputting a second signal corresponding to the detection by the second detecting means;

first converting means for receiving the first signal from the first detecting means and for converting the first signal into first image information;

second converting means for receiving the second signal from the second detecting means and for converting the second signal into second image information;

splitting means for splitting or transporting the second image information at different x-ray energies among at least two image receivers;

controlling means for controlling the timing of the generating means, the reshaping means, second detecting means, image receivers, and for controlling the timing of acquisition and processing of the second image information at each image receiver;

logarithmic means for logarithmically processing the first and second image information;

means for generating material-specific images for the N groups of materials, using the logarithmically processed first and second image information and the matrix μ

^-1 ; and

means for processing and displaying the material-specific images.

28. The x-ray inspection system according to claim 27, wherein the detecting means comprises a semiconductor detector.

29. The x-ray inspection system according to claim 27, wherein the splitting means comprises fiber optics.

30. The x-ray inspection system according to claim 27, wherein luggage is carried past the inspection system on a conveyer belt.

31. The x-ray inspection system according to claim 27, wherein the controlling means includes means for controlling saturation and underexposure.

32. The x-ray inspection system according to claim 27, wherein the controling means includes means for controlling an amount of light entering the first and second detecting means by controlling x-ray intensity.

33. The x-ray inspection system according to claim 27, further comprising at least one image processor in addition to the controlling device as set forth in claim 5 where the purpose of the image processors is to improve the display of processed images from previous steps.

34. The x-ray inspection system according to claim 27, further comprising controlling means for controlling one or more of the following:

the operation and timing of the generating means, the reshaping means, the first and second detecting means, the first and second converting means, the splitting means, image receivers, the image receivers, the logarithmic means, a switching means, the image-generating means, the processing means, and a conveyer belt.

35. The x-ray inspection system according to claim 27, wherein the inspection operates to display the material-specific images in real-time.

36. An x-ray inspection system for separating material-specific images generated by transmitting x-rays through an ensemble of unknown materials, comprising:

generating means for generating and emitting N different x-ray energy distributions, each energy distribution being labelled by E_k and having an x-ray intensity I₀ (E_k), where k ranges from 1 to N, and where N is an integer equal to two;

a device storing an N by N matrix μ

, where μ

^-1 is an inversion of a matrix μ

, and where each matrix element μ

_jk for the matrix μ

is defined as the linear attenuation coefficient of a certain material group j (of N material groups) at the x-ray energy E_k, the N material groups being generated from sorting the ensemble of unknown materials into N possible groups of materials according to the closeness of linear attenuation coefficients or equivalent characteristics of materials at different incident x-ray energy distributions prior to inspection, wherein at least one μ

^-1 matrice are stored in the device and each μ

^-1 matrix corresponds to a different set of N material groups;

reshaping means for reshaping the N different x-ray energy distributions emitted from the generating means;

detecting means for detecting a portion of the reshaped N x-ray energy distributions labelled E_k that have passed through the ensemble of unknown materials, the detecting means outputting a signal corresponding to the detection by the detecting means;

converting means for receiving the signal from the detecting means and for converting the signal into image information;

logarithmic means for logarithmically processing the image information;

switching means for dynamically switching from one μ

^-1 matrix for one set of N material groups to another μ

^-1 for another set of N material groups during the inspection when more than one μ

^-1 matrices have been stored, wherein the switching is for the purpose of finding an appropriate set of N material groups that best represents the actual material groups existing in the ensemble under inspection;

image-generating means for generating material-specific images for the N groups of materials, using the logarithmically processed image information and the μ

^-1 matrix; and

processing means for processing and displaying the material-specific images.

37. The x-ray inspection system according to claim 36, wherein luggage is carried past the inspection system on a conveyer belt.

38. The x-ray inspection system according to claim 36, further comprising N displays, each displaying one of the N material groups.

39. The x-ray inspection system according to claim 36, wherein the means for generating material-specific images incorporates a matrix operation using N independent arithmetic channels where each independent channel corresponds to one independent vector component of the vector, and where N is a dimension of the vectors.

40. The x-ray inspection system according to claim 36, wherein the inspection operates to display the material-specific images in real-time.

41. The x-ray inspection system according to claim 36, further comprising controlling means for controlling one or more of the following:

the operation and timing of the generating means, the reshaping means, the detecting means, the converting means, the logarithmic means, a switching means, image receivers, the image-generating means, the processing means, and a conveyer belt.

42. The x-ray inspection system according to claim 36, further including controlling means for controlling saturation and underexposure.

43. The x-ray inspection system according to claim 36, further including controling means for controlling an amount of light entering the detecting means by controlling x-ray intensity.