U.S. patent application number 09/760418 was filed with the patent office on 2001-10-25 for method and apparatus for determining a material of a detected item.
Invention is credited to Cordes, Frank, Hartick, Martin.
Application Number | 20010033636 09/760418 |
Document ID | / |
Family ID | 7928938 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033636 |
Kind Code |
A1 |
Hartick, Martin ; et
al. |
October 25, 2001 |
Method and apparatus for determining a material of a detected
item
Abstract
A method for determining the material of a detected item in
objects, especially explosives in luggage, using X-ray diffraction.
In this method, wherein scatter radiation deflected at the crystal
source of the material is measured and compared to characteristic
energy spectra or diffraction spectra of the various explosives,
the absorption by the material influences the X-ray diffraction
spectrum, so that information is missing, and inaccurate
conclusions may be drawn regarding the material. To improve this
method, the primary beam of an X-ray source is used for measuring
the absorption. The beam passes through the material, and, from the
absorption, an average atomic number of the material is determined,
and this information additionally is used in the comparison to
known diffraction spectra. For this purpose, a collimation/detector
arrangement preferably has only one collimator (8) and one detector
(9), with the collimator (8) having a conically-expanding circular
slot (1), which simulates a predetermined angle of the beam path,
and a central blind bore (1) opening toward the X-ray source. First
and second detectors (13, 14) are disposed in the bore to detect
lower and higher X-ray energy, respectively.
Inventors: |
Hartick, Martin; (Bad
Nauheim, DE) ; Cordes, Frank; (Neustadt, DE) |
Correspondence
Address: |
VENABLE
P.O. Box 34385
Washington
DC
20043-9998
US
|
Family ID: |
7928938 |
Appl. No.: |
09/760418 |
Filed: |
January 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09760418 |
Jan 16, 2001 |
|
|
|
09645485 |
Aug 25, 2000 |
|
|
|
Current U.S.
Class: |
378/88 ; 378/57;
378/90 |
Current CPC
Class: |
G01N 23/20 20130101;
G21K 5/04 20130101; G01V 5/0041 20130101; G01V 5/0025 20130101;
G01V 5/0016 20130101 |
Class at
Publication: |
378/88 ; 378/90;
378/57 |
International
Class: |
G01N 023/201 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 13, 1999 |
DE |
199 54 663.0 |
Claims
What is claimed is:
1. A method for determining a material of a detected item in an
object comprising: irradiating the material with a primary X-ray
beam; measuring a diffraction spectrum of the material, with the
spectrum comprising X-rays of the primary beam diffracted from the
material; measuring an X-ray absorption of the material and an
average atomic number of the material by measuring X-rays of the
primary beam transmitted through the material; determining the
average atomic number of the material from the measured absorption;
comparing the measured diffraction spectrum and determined average
atomic number of the material to known diffraction spectra and
known average atomic numbers of known materials.
2. The method according to claim 1, wherein the average atomic
number is determined by a multi-energy method.
3. The method according to claim 1, wherein the comparing step
comprises comparing the measured diffraction spectrum only with the
known diffraction spectra of known materials having an average
atomic number approximately the same as the determined average
atomic number.
4. The method according to claim 1, wherein the comparing step
comprises comparing the measured diffraction spectrum with known
diffraction spectrum only within energy ranges not substantially
absorbed by the material.
5. The method according to claim 1, wherein the object is
luggage.
6. An apparatus for determining a material of a detected item in an
object comprising a diffraction apparatus and a computer connected
thereto, and wherein said diffraction apparatus comprises an X-ray
source for producing a primary X-ray beam and a collimator/detector
arrangement positioned to receive the primary X-ray beam after
passing through an object and including a detector a collimator;
said detector comprises an X-ray detector positioned downstream of
the collimator and having an X-ray sensitive surface oriented
toward the collimator; said collimator has a central, blind-bore
closed at the end facing the detector and at least one conically
expanding circular slot that simulates a predetermined angle and is
oriented toward said X-ray sensitive surface of the detector; and
first and second spaced detection devices mounted within the blind
bore and connected to the computer, with said first and second
detection devices detect relatively lower and relatively higher
energy X-rays, respectively, and being spaced in the central
opening such that the second detection device located behind the
first detection device.
7. The apparatus according to claim 6, wherein the
collimator/detector arrangement is oriented toward the primary beam
of the X-ray source, and is alignable such that the primary beam
passes into the central opening.
8. The apparatus according to claim 6, wherein the X-ray source is
laterally adjustable, and the collimator/detector arrangement is
adjustable in height relative to the X-ray source and adjustable
laterally in synchronization with lateral adjustments of the X-ray
source.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of application Ser. No.
09/645,485 filed Aug. 25, 2000.
[0002] This application is related to concurrently filed U.S.
applications (Attorney Docket 31659-152913A, Attorney Docket,
Attorney Docket 315659-152916A and Attorney Docket 31659-152918A),
and which are continuations of respective U.S. application Ser.
Nos. 09/645,484, and 09/645,486 and 09/645,487), each filed Aug.
25, 2000, the subject matter of each such application being
incorporated herein by reference.
FIELD OF THE INVENTION
[0003] The invention relates to a method wherein the material is
X-rayed by a primary beam that is diffracted at the material and an
apparatus for determining the material of a detected item in an
object.
BACKGROUND OF THE INVENTION
[0004] To assure safety in situations such as air travel, it is
necessary to check luggage (object) with travel items (items),
particularly for explosive substances or agents, by employing the
most modern technical equipment.
[0005] A useful technique for checking for explosives is X-ray
diffraction, in which X-ray irradiation scattered at the crystal
structure of an item is measured and compared to the characteristic
energy spectra of different explosives, for example. The measured
energies can provide an indication of the presence of an explosive,
and can thereby provide information about the presence and nature
of an explosive material in the object.
[0006] Apparatuses and methods that operate according to this
principle are known from, for example, DE 195 10 168 A1, EP 0 354
045 A2 and U.S. Pat. No. 4,956,856. A drawback of these methods is
that absorption of the X-ray irradiation by, for example, the
object and item affects the X-ray diffraction spectrum.
Consequently, if spectral information is missing due to absorption,
inaccurate conclusions may be drawn regarding the type of material
and the identification of the substances examined.
BRIEF SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide a method and an
apparatus of the type originally mentioned above, with which
materials of an item can be identified unambiguously.
[0008] The above object generally is achieved according to the
first aspect of the invention by a method for determining the
material of a detected item in an object that comprises the steps
of irradiating the material with a primary X-ray beam; measuring a
diffraction spectrum of the material, with the spectrum comprising
X-rays of the primary beam diffracted from the material; measuring
the X-ray absorption of the material and an average atomic number
of the material by measuring X-rays of the primary beam transmitted
through the material; and comparing the measured diffraction
spectrum and measured average atomic number of the material to
known diffraction spectra and known average atomic numbers of known
materials to determine the material.
[0009] The apparatus for determining the material of a detected
item in an object comprises a diffraction apparatus and a computer
connected thereto, wherein the diffraction apparatus comprises an
X-ray source and a collimator/detector arrangement, including a
detector located behind a collimator, with the detector comprising
an X-ray sensitive surface oriented toward the collimator. The
collimator defines a central, blind-bore opening and at least one
conically expanding slot, with the at least one conically expanding
slot simulating a predetermined angle and being oriented toward the
X-ray sensitive surface of the detector. The central opening is
closed to the detector and has first and second detection devices
mounted therein, with the first and second detection devices being
connected to the computer detecting relatively lower and relatively
higher energy X-rays, respectively, and being spaced in the central
opening with the second detection device located behind the first
detection device.
[0010] The concept underlying the invention is to obtain additional
information about the absorption behavior of the materials from the
central X-ray beam during a diffraction measurement, and to make
this information available along with the diffraction spectrum for
evaluation and identification of the material.
[0011] The diffraction apparatus which as indicated above,
generally comprises a collimator/detector arrangement and an X-ray
source for generating a central beam or primary beam that is aimed
at the arrangement. According to the invention, collimator of the
collimator/detector arrangement has a central, blind-bore open to
and facing the X-ray source, in which first and second detector
devices are arranged, with the first and second detector devices
being spatially separate from each other and disposed one behind
the other. The detector device that is impacted first by the
primary beam is designed as a detector for relatively lower X-ray
energies, and the device impacted second is designed as a detector
for relatively higher X-ray energies. In a known manner, an average
atomic number (ordinal number) of the material of the item located
in the primary beam is additionally determined.
[0012] The diffraction apparatus is preferably adjustably mounted
in an X-ray testing machine, with the collimator/detector
arrangement being adjustable in height relative to the X-ray
source.
[0013] The collimator/detector arrangement further comprises a
circular-slot collimator having an energy-sensitive detector behind
it.
[0014] The invention is described below in detail by way of an
embodiment illustrated in the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic representation of an embodiment of the
invention in an X-ray testing machine.
[0016] FIG. 2 further illustrates the apparatus of the invention of
FIG. 1 in more detail.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0017] As shown in FIG. 1, an object 1 to be X-rayed is located in
an X-ray tunnel 2 of an X-ray testing machine 3. Located inside the
X-ray tunnel 2 is a diffraction apparatus 4, comprising a
collimator/detector arrangement 5 and an X-ray source 6. The
collimator/detector arrangement is directed at a primary beam FX',
a "pencil beam," of an X-ray bundle of this X-ray source 6, which,
in this embodiment, is preferably disposed beneath a transport
device 7 for an object to be transported in the X-ray tunnel 2. The
collimator/detector arrangement 5 preferably can be adjusted in
height relative to the X-ray source 6.
[0018] FIG. 2 shows parts of the diffraction apparatus 4 in greater
detail.
[0019] The collimator 8 possesses a circular slot 10 in the form of
a conical jacket such that, of the scatter radiation emanating from
the tested point of the object, only the components that fall
within a specific angle .THETA..sub.M are allowed through. The
energy-sensitive surface 9.1 of a detector 9 located behind the
collimator 8 thus detects the scatter radiation FX" at the scatter
angle .THETA..sub.M. To attain a primary beam FX' for this testing
process a screen arrangement 11, for example an aperture-plate
arrangement, is mounted in front of the X-ray source 6.
[0020] If the primary beam FX' impacts a material, this primary
beam FX' is known to be partially deflected at the crystal-lattice
structure of the material (Bragg's Law) as scatter radiation FX".
Accordingly, the energy spectrum obtained with the energy-sensitive
detector 9 reveals the crystal structure of the material, and thus
the identity of the material. In particular, explosives can be
identified and distinguished in this manner.
[0021] According to the method, in a first step, the material is
X-rayed by the primary beam FX', and in a second step, the primary
beam FX' is diffracted at the material, thereby producing a
diffraction spectrum, which is measured with the detector 9 in a
third step. In a fourth step, this measured energy spectrum or
diffraction spectrum is compared to known diffraction spectra that
are stored in the computer 16 for determining the type of
material.
[0022] In practice, the measured diffraction spectrum is influenced
by the absorption behavior of the material located in the beam path
of the primary beam FX'. For assessing and considering this
influence, a central, bore-like opening 12 acting as a central,
collimator is cut into the collimator 8, the opening being closed
against the detector 9 disposed behind it, i.e., a blind bore.
Disposed in the opening 12 are a first detection device 13 and,
behind it at a defined distance, a second detection device 14. The
first detection device 13 is designed as a detector for relatively
lower X-ray energies, and the second detection device 14 is
designed as a detector for relatively higher X-ray energies.
[0023] These detection devices 13, 14 can be used in a conventional
manner to measure the absorption behavior of the material and, from
this, to determine in a computer 16 the average atomic number of
the material according to, for example, a multi-energy measurement
method. In the presence of a highly-absorbent material,
lower-energy diffraction lines disappear in the diffraction
spectrum of the material to be determined, so the corresponding
diffraction lines are missing in the measured energy spectrum or
diffraction spectrum. This information can be supplied to the
computer 16, which then classifies these as missing, for example,
and therefore as diffraction lines that are not to be tested in the
evaluation of the energy spectra. In this way, an improved
identification of the material is attained with the combination of
the average atomic number and the determined energy spectrum or
diffraction spectrum.
[0024] The collimator/detector arrangement 5 and the X-ray source 6
are mounted to be adjusted in the X-ray testing machine 3, and are
preferably guided synchronously for determining the material of an
item. This is effected, for example, by way of linear guides having
a spindle drive, not shown, which are actuated centrally by the
computer 16.
[0025] In principle, the detection devices can also be used in
other diffraction apparatuses whose primary beam is configured
differently, in which case the detectors 13 and 14 must accordingly
be directed at the primary beam.
[0026] The invention now being fully described, it will be apparent
to one of ordinary skill in the art that many changes and
modifications can be made thereto without departing from the spirit
or scope of the invention as set forth herein.
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