X-ray imaging particularly adapted for low Z materials

• US 5,313,511 A
• Filed: 12/18/1991
• Issued: 05/17/1994
• Est. Priority Date: 06/20/1986
• Status: Expired due to Term

• Current Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Original Assignee: American Science and Engineering Incorporated (OSI Systems Incorporated)
• Inventors: Bjorkholm, Paul J., Annis, Martin
• Primary Examiner(s): Porta, David P.
• Application Number:
  US07/809,246
• Time in Patent Office: 881 Days
• Field of Search: 378/86-90, 378/99.62, 378/57
• US Class Current: 378/87
• 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
• CPC Class Codes: G01V 5/222 measuring scattered radiation
• CPC Class Codes: G21K 5/10 with provision for relative movement of beam source and object to be irradiated

Abstract

An imaging device for increasing the ability to recognize, in x-ray produced images, materials of low atomic number. A flying spot scanner illuminates an object to be imaged in a raster pattern; the flying spot repeatedly sweeps a line in space, and the object to be imaged is moved so that the illuminating beam intersects the object. At least a pair of x-ray detectors are employed, each pair associated with signal processing apparatus and a display. The two detectors employed (and the associated electrons and display) are selected from a set of three which includes a transmitted detector located at the line in space which is repeatedly traversed by the pencil beam, a forward scatter detector which is located further from the x-ray beam than the object to respond to photons scattered by the object being illuminated out of the path of the beam, and a back scatter detector which is located closer to the x-ray source than the object being imaged and also arranged to detect photons scattered out of the beam path by the object. In another embodiment of the invention all three detectors and their associated electronics/displays are employed.

Claims

1. An imaging system for inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said system comprising:

a) a source of penetrating radiation,

b) means for forming radiation emitted by said source into a beam of predetermined cross-section,

c) means for scanning said beam across said object to be inspected,

d) means for moving said object relative to said source of radiation,

e) first radiant energy detector means located to be responsive to radiant energy penetrating said object and emerging from said object, substantially unchanged in direction, for producing first electrical signals primarily representative of high Z material components of said object,

f) second radiant energy detector means responsive to radiant energy scattered by said object for producing second electrical signals primarily representative of low Z material components of said object, and

g) display means responsive to said first and second electrical signals for separately, independently and simultaneously producing first and second separate visual displays, said display means including a first display means responsive only to said first electrical signals to produce said first visual display representative of the high z material components of the object, a second display means responsive only to said second electrical signals to produce said second visual display representative of the low z material components of the object, said first and second display means located closely adjacent to one another to facilitate comparison of said first and second visual displays with one another,

wherein said first radiant energy detector means includes a radiant energy detector with the dimension of an effective active region substantially identical to one dimension of said beam cross-section and in which said second radiant energy detector means includes a radiant energy detector with all dimensions of an effective active region substantially larger than any dimension of said beam cross-section.

2. An imaging system for inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said system comprising:

a) a source of penetrating radiation,

b) means for forming radiation emitted by said source into a beam of predetermined cross-section and for repeatedly sweeping said beam across a line in space,

c) means for moving an object to be imaged relative to said source in a direction perpendicular to said line in space,

d) first radiant energy detector means located to be responsive to radiant energy penetrating said object and emerging from said object, substantially unchanged in direction, for producing first electrical signals primarily representative of high Z material components of said object,

e) second radiant energy detector means located nearer to said source than said object and responsive to radiant energy scattered by said object for producing second electrical signals primarily representative of low Z material components of said object, and

f) first and second display means responsive respectively to said first and second electrical signals for separately, independently and simultaneously producing first and second separate visual displays that are representative respectively of the high Z and low Z material components of said object, said first and second display means located closely adjacent to one another to facilitate comparison of said first and second visual displays with one another,

wherein said first radiant energy detector means includes a radiant energy detector with the dimension of an effective active region substantially identical to one dimension of said beam cross-section, and in which said second radiant energy detector means includes a radiant energy detector with all dimensions of an effective active region substantially larger than any dimension of said beam cross-section.

3. A method of inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said method comprising:

a) scanning a beam of penetrating radiation across an object being inspected,

b) moving said object relative to said scanning beam,

c) during the scanning of said beam, detecting first radiant energy that penetrates and emerges from said object substantially unchanged in direction,

d) in response to said first radiant energy, generating first electrical signals that are primarily representative of high Z material components of said object,

e) during the scanning of said beam, detecting radiant energy that is scattered by said object,

f) in response to said scattered radiant energy, generating second electrical signals that are primarily representative of low Z material components of said object,

g) using said first electrical signals to generate a first visual display that is primarily representative of the high Z material components of said object, and

h) simultaneous with the generation of said first visual display, using said second electrical signals to generate a second visual display that is primarily representative of low Z material components of said object, said second visual display being separate from but adjacent to said first visual display,

wherein said step (e) comprises detecting said scattered radiant energy in a detector with an effective detecting region substantially greater in dimension than a detection region of a detector detecting said first radiant energy.

4. A method of inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said method comprising:

a) scanning a beam of penetrating radiation across an object being inspected,

b) moving said object relative to said scanning beam,

c) during the scanning of said beam, detecting first radiant energy that penetrates and emerges from said object substantially unchanged in direction,

d) in response to said first radiant energy, generating first electrical signals that are primarily representative of high Z material components of said object,

e) during the scanning of said beam, detecting radiant energy that is scattered by said object,

f) in response to said scattered radiant energy, generating second electrical signals that are primarily representative of low Z material components of said object,

g) using said first electrical signals to generate a first visual display that is primarily representative of the high Z material components of said object, and

h) simultaneous with the generation of said first visual display, using said second electrical signals to generate a second visual display that is primarily representative of low Z material components of said object, said second visual display being separate from but adjacent to said first visual display,

wherein said step (e) comprises detecting said scattered radiant energy in a detector with an effective detecting region substantially greater in dimension than any cross sectional dimension of said beam of penetrating radiation.

5. An imaging system for inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said system comprising:

a) a source of penetrating radiation of energy level selected to generate Compton scatter,

b) means for forming radiation emitted by said source into a beam of predetermined cross-section,

c) means for scanning said beam across said object to be inspected,

d) means for moving said object relative to said source of radiation,

e) first radiant energy detector means located to be responsive to radiant energy penetrating said object and emerging from said object, substantially unchanged in direction, for producing first electrical signals primarily representative of high Z material components of said object,

f) second radiant energy detector means responsive to Compton scatter generated by said object for producing second electrical signals primarily representative of low material components of said object, and

g) display means responsive to said first and second electrical signals for separately, independently and simultaneously producing first and second separate visual displays, said display means including a first display means responsive only to said first electrical signals to produce said first visual display representative of the high z material components of the object, a second display means responsive only to said second electrical signals to produce said second visual display representative of the low z material components of the object, said first and second display means located closely adjacent to one another to facilitate comparison of said first and second visual displays with one another,

wherein said first radiant energy detector means includes a radiant energy detector with the dimension of an effective active region substantially identical to one dimension of said beam cross-section and in which said second radiant energy detector means includes a radiant energy detector with all dimension of an effective active region substantially larger than any dimension of said beam cross-section.

6. An imaging system for inspecting an object to detect the presence and shape of high Z an low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said system comprising:

a) a source of penetrating radiation of energy level selected to generate Compton scattered energy,

b) means for forming radiation emitted by said source into a beam of predetermined cross-section and for repeatedly sweeping said beam across a line in space,

c) means for moving an object to be imaged relative to said source in a direction perpendicular to said line in space,

d) first radiant energy detector means located to be responsive to radiant energy penetrating said object and emerging from said object, substantially unchanged in direction, for producing first electrical signals primarily representative of high Z material components of said object,

e) second radiant energy detector means located nearer to said source than said object and responsive to Compton scattered energy scattered by said object for producing second electrical signals primarily representative of low Z material components of said object, and

f) first and second display means responsive respectively to said first and second electrical signals for separately, independently and simultaneously producing separate first and second visual displays that are representative respectively of the high Z and low Z material components of said object, said first and second display means being located closely adjacent to one another to facilitate comparison of said first and second visual displays with one another,

wherein said first radiant energy detector means includes a radiant energy detector with the dimension of an effective active region substantially identical to one dimension of said beam cross-section, and in which said second radiant energy detector means includes a radiant energy detector with all dimension of an effective active region substantially larger than any dimension of said beam cross-section.

7. A method of inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said method comprising:

a) scanning a beam of penetrating radiation across an object being inspected,

b) moving said object relative to said scanning beam,

c) during the scanning of said beam, detecting first radiant energy that penetrates and emerges from said object substantially unchanged in direction,

d) in response to said first radiant energy, generating first electrical signals that are primarily representative of high Z material components of said object,

e) during the scanning of said beam, detecting Compton scattered radiant energy that is scattered by said object,

f) in response to said scattered radiant energy, generating second electrical signals that are primarily representative of low Z material components of said object,

g) using said first electrical signals to generate a first visual display that is primarily representative of the high Z material components of said object, and

h) simultaneous with the generation of said first visual display, using said second electrical signals to generate a second visual display that is primarily representative of low Z material components of said object, said second visual display being separate from but adjacent to said first visual display,

wherein said step (e) comprises detecting said scattered radiant energy in a detector with an effective detecting region substantially greater in dimension than a detecting region of a detector detecting said first radiant energy.

8. A method of inspecting an object to detect the presence and shape of high Z and low Z material components of said object to facilitate simultaneous detection of high z components such as metal weapons and low z components such as narcotics, explosives and plastic weapons, said method comprising:

a) scanning a beam of penetrating radiation across an object being inspected,

b) moving said object relative to said scanning beam,

c) during the scanning of said beam, detecting first radiant energy that penetrates and emerges from said object substantially unchanged in direction,

d) in response to said first radiant energy, generating first electrical signals that are primarily representative of high Z material components of said object,

e) during the scanning of said beam, detecting Compton scattered radiant energy that is scattered by said object,

f) in response to said scattered radiant energy, generating second electrical signals that are primarily representative of low Z material components of said object,

g) using said first electrical signals to generate a first visual display that is primarily representative of the high Z material components of said object, and

h) simultaneous with the generation of said first visual display, using said second electrical signals to generate a second visual display that is primarily representative of low Z material components of said object, said second visual display being separate from but adjacent to said first visual display,

wherein said step (e) comprises detecting said scattered radiant energy in a detector with an effective detecting region substantially greater in dimension than any cross sectional dimension of said beam of penetrating radiation.