Method and apparatus for the detection and imaging of heavy metals

• US 5,060,249 A
• Filed: 08/15/1989
• Issued: 10/22/1991
• Est. Priority Date: 08/26/1988
• Status: Expired due to Fees

• Current Assignee: The State of Israel Atomic Energy Commission Soreq Nuclear Research/Center
• Original Assignee: The State of Israel Atomic Energy Commission Soreq Nuclear Research/Center
• Inventors: Eisen, Yosef, Kedem, Drora, Yellin, Emanuel
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): Porta, David P.
• Application Number:
  US07/394,016
• Time in Patent Office: 798 Days
• Field of Search: 378/53, 378/57, 378/56, 378/62, 378/157, 378/158, 378/159
• US Class Current: 378/57
• CPC Class Codes: G01V 5/22 Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays

Abstract

Method and apparatus for the fast inspection of objects for the detection of elementary or compounded metals of the kind that are capable of producing with impinging X-radiation within the range of 60-160 KeV a detectable photoelectric interaction. A 110-160 KeV X-ray source is used in association with collimating and filtering apparatus, capable of generating a collimated X-ray beam consisting of repeating cycles comprising each one energy bin having a flux centred around the K-edge energy of the target metal and, if desired, comprising additionl energy bins. There is also provided a linear array of solid state, spectroscopy grade detectors. Objects to be searched for these metals are scanned by moving them across the beam at a location intermediary between the X-ray source and the detector, at a speed so selected that during each of the predetermined pixels the full energy range of the said cycle impinges a full cross-section of an inspected object without any mutual dislocation between said X-ray source and linear array of solid state, spectroscopy grade detectors. For each pixel the intensity of transmitted radiation of selected bands is recorded and the ratios of the transmitted radiation in these bands is determined. The results are processed to an image of any detected article.

Claims

1. An automatic method of detaching in sequentially inspected objects a target article made of or containing an elemental or compounded target metal of the kind capable of producing with impinging X-ray radiation within the range of 60-160 KeV a detachable photoelectric interaction, said method comprising the steps of

providing a radiation generating assembly comprising a 110-160 KeV X-ray source in association with collimating and filtering means, which filtering means are designed to successively generate several energy bins during each one of repeating cycles;

generating with such assembly a collimated X-ray beam consisting of repeating cycles each comprising several energy bins centered around the K-energy of said target meal;

placing at a distance from said radiation generating assembly and in the region flushed by said collimated X-ray beam a linear array of slid state, spectroscopy grade detectors in association with signal counting, processing and imaging means;

providing object carrier means intermediary between said radiation generating assembly and linear array of solid state, spectroscopy grade detectors;

placing objects on said object carrier means;

arranging for said energy generating assembly on the one hand and said object carrier means on the other hand to be displaced relative to each other at a relative velocity so adjusted that during each one of predetermined pixels commensurate with the expected smallest size of said target article the full energy range of one of said repeating cycles impinges a full cross-section of an inspected object without any mutual dislocation of said radiation generating assembly and linear array of solid state detectors;

whereby successive electrical signals are produced in said linear array of spectroscopy grade detectors;

using said electrical signals for recording for each pixel the intensity of transmitted radiation of selected energy bands;

determining for each pixel the ratios between the transmitted radiation in said selected energy bands; and

processing the resulting data to produce an image of any detected target article.

2. The method of claim 1, wherein the relative displacement between the radiation generating assembly and the object carrier means is brought about by moving the object carrier means.

3. The method of claim 1, wherein the relative displacement between the radiation generating assembly and the object carrier means is brought about by moving synchronically the radiation generating assembly and linear array of solid stat detectors.

4. The method of claim 1, wherein the relative displacement between the object carrier means and the radiation generating assembly is continuous.

5. The method of claim 1, wherein the relative displacement between the object carrier means and the radiation generating assembly is intermittent.

6. An automatic method of detecting in sequentially inspected objects a target article made of or containing an elemental or compounded target metal of the kind capable of producing with impinging X-radiation within the range of 60-160 KeV a detectable photoelectric interaction, said method comprising the steps of

providing a radiation generating assembly comprising a 110-160 KeV X-ray source in association with collimating and filtering means, which filtering means are designed to generate during each of said cycles one single, energy bin;

generating with such assembly a collimated X-ray beam consisting of repeating cycles each comprising one single energy bin having a flux centered around the K-edge energy of said target metal;

placing at a distance from the radiation generating assembly and in a region flushed by said collimated X-ray beam a linear array of solid state, spectroscopy grade detector in association with signal counting, processing and imaging means, which detectors are arranged in such a way as to differentiate between simultaneous different radiation flux attenuations within predetermined energy ranges of said single energy bin;

providing object carrier means intermediary between said radiation generating assembly and linear array of solid state, spectroscopy grade detectors;

placing objects on said object carrier means;

arranging for said radiation generating assembly on the one hand and said object carrier means on the other hand to be displaced relative to each other at a relative velocity so adjusted that during each one of predetermined pixels commensurate with the expected smallest size of said target article, the full energy range of one of said repeating cycles impinges a full cross-section of an inspected object without any mutual dislocation between said radiation generating assembly and linear array of solid state detectors, whereby successive electrical signals are produced in said linear array of spectroscopy grade detectors;

using said electrical signals for recording for each pixel the intensity of transmitted radiation of selected energy bands;

determining for each pixel the ratios between the transmitted radiation in said selected energy bands; and

processing the resulting data to produce an image of any detected target article.

7. The method of claim 6, wherein the relative displacement between the radiation generating assembly and the object carrier means is brought about by moving the object carrier means.

8. The method of claim 6, wherein the relative displacement between the radiation generating assembly and the object carrier means is brought about by moving synchronically and radiation generating assembly and linear array of solid state detectors.

9. The method of claim 6, wherein the relative displacement between the object carrier means and the radiation generating assembly is continuous.

10. The method of claim 6, wherein the relative displacement between the object carrier means and the radiation generating assembly is intermittent.

11. An apparatus for automatically detecting in sequentially inspected objects a target article made of or containing an elemental or compounded target metal of the kind capable of producing with impinging X-radiation within the range of 60-160 KeV a detectable photoelectric interaction, said apparatus comprising

a radiation generating assembly comprising a 60-160 KeV X-ray source in association with collimating and filtering means capable of generating a collimated X-ray beam consisting of repeating cycles each holding several energy bins centered around the K-edge energy of said target metal;

a linear array of solid state spectroscopy grade detectors and signal counting, processing and imaging means connected therewith, which detectors are spaced from said radiation generating assembly;

object carrier means intermediary between said radiation generating means and said linear array of solid state, spectroscopy grade detectors; and

means for causing the radiation generating assembly and linear array of solid state detectors on the one hand, and said object carrier means on the other hand to be displaced relative to each other at a relative velocity so adjusted that during each of a predetermined pixels commensurate with the expected smallest size of said target article, the full energy band of one of said repeating cycles impinges a full cross-section of said object carrier means without any mutual dislocation between said radiation generating means and solid state detector array.

12. The apparatus of claim 11, wherein said object carrier means is a conveyor belt.

13. The apparatus of claim 11, comprising means for synchronically, continuously or intermittently moving the radiation generating means and linear array of solid state, spectroscopy grade detectors.

14. An apparatus for automatically detecting in sequentially inspected objects a target article made of or containing an elemental or compounded target metal of the kind capable of producing with impinging X-radiation within the range of 60-160 KeV a detectable photoelectric interaction, said apparatus comprising

a radiation generating assembly comprising a 60-160 KeV X-ray source in association with collimating and filtering means capable of generating a collimated X-ray beam consisting of repeating cycles each comprising one single energy bin having a flux centered around the K-edge energy of said target metal;

a linear array of solid state spectroscopy grade detectors and signal counting, processing and imaging means connected therewith, which detectors are spaced from said radiation generating assembly and are arranged in such a way that in association with said signal counting means they are capable of differentiating between simultaneous different radiation flux attenuations within predetermined energy ranges of said single energy bin;

object carrier means intermediary between said radiation generating means and said linear array of solid state, spectoscopy grade detectors; and

means for causing the radiation generating assembly and linear array of solid state detectors on the one hand, and said object carrier means on the other hand, to be displaced relative to each other at a relative velocity so adjusted that during each of predetermined pixels commensurate with the expected smallest size of said target article the full energy range of one of said repeating cycles impinges a full cross-section of an inspected object without any mutual dislocation between said radiation generating means and slid stage detector array.

15. The apparatus of claim 14, wherein said object carrier means is a conveyor belt.

16. The apparatus of claim 14, comprising means for synchronically, continuously or intermittently moving the radiation generating means and linear array of solid state, spectroscopy grade detectors.