X-ray or gamma ray systems or devices – Specific application – Absorption
Reexamination Certificate
1999-05-05
2001-06-26
Church, Craig E. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Absorption
C378S086000
Reexamination Certificate
active
06252929
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the inspection of large containers by means of x-ray radiation, and more particularly to the x-ray inspection of cargo containers by means of transmitted and back scattered radiation.
BACKGROUND ART
The interdiction of illicit drugs, explosives, and other contraband is an important goal of law enforcement. To that end, a variety of technologies have been developed and deployed for the non-intrusive inspection of containers not readily susceptible to visual scrutiny from the outside. The non-intrusive aspect of these inspection techniques is important; the great majority of containers do not carry contraband, and the public would not long tolerate the delays, disruption (and in some cases damage) of property, and invasions of privacy that would occur if invasive inspection means were commonly used. Non-intrusive inspection is typically non-destructive and can usually be accomplished faster than intrusive inspection, hereby increasing productivity of inspectors. Increased productivity means more containers inspected and more contraband interdicted.
Among non-intrusive inspection methods, x-ray imaging in its many forms has been a proven technology capable of detecting a variety of contraband. X-ray systems have been based on transmission imaging in any of a variety of implementations: cone-beam (fluoroscopes), fanbeam, flying-spot, multi-projection configurations; dual-energy imaging; computed tomography; as well as on imaging incorporating the detection of x-ray radiation scattered in various directions.
With only a few exceptions, x-ray imaging systems for contraband detection have operated within the source-energy range of 70 keV to 160 keV. Since the penetrating power of these sources is limited, inspection is limited to relatively small parcels and containers. A few large, expensive, high-energy transmission imaging systems have also been built for the inspection of large containers or vehicles. These systems typically operate within the range of 6 MeV to 12 MeV, require heavily-shielded, fixed installations, and provide no means to distinguish organic materials.
Radiant energy imaging with a scanning pencil beam is the subject of U.S. Pat. No. 3,780,291. The creation and use of images from scattered x-radiation in conjunction with direct transmission images is the subject of U.S. Pat. No. 5,313,511. These patents are hereby incorporated herein by reference. Neither of the foregoing references, nor any prior art known to the inventors herein, discloses or suggests how x-ray images, in a sense defined below, may be formed of cargo containers on the scale of motor vehicles or railroad cars using a source of penetrating radiation and detectors mounted on a mobile platform.
SUMMARY OF THE INVENTION
The current invention extends the role of inspection by penetrating radiation to encompass large containers and over-the-road vehicles, and at the same time retains the advantages of discriminating among materials as provided by backward, forward, or sideward scatter imaging.
In a preferred embodiment, the invention provides a device for inspecting a cargo container with penetrating radiation. The device of this embodiment has a bed moveable along a first direction having a horizontal component, a source of penetrating radiation, mounted on the bed, for providing a beam, a motorized drive for moving the bed in the first direction, and at least one detector mounted on the bed and having a signal output so that the beam is caused to traverse the cargo container as the bed is moved and each detector provides a signal for characterizing the cargo container and any contents of the cargo container. In further embodiments of the invention, the source of penetrating radiation may be an x-ray source, and the at least one detector may be a backscatter detector, a transmission detector, a sidescatter detector, or a forward scatter detector. The beam may be a pencil beam scanned repeatedly along a second direction having a vertical component.
In a further embodiment, the device also has a boom, movably linked to the bed. The boom has a storage position, substantially fixed with respect to the bed, and an operation position that is transverse to the first direction, as well as an end region. A beam catcher is attached to the end region of the boom for impeding the further passage of penetrating radiation in the second direction when the boom is in the operation position. The back scatter detector has upper and lower elements, the upper element being movably mounted with respect to the lower element, so that in a first position the upper element is transversely disposed with respect to the lower element and in a second position the upper element is substantially collinear with respect to the lower element. The source of penetrating radiation may provide a pencil beam that is scanned repeatedly over an angle of regard, the angle having an orientation with respect to the horizontal, and the device also includes a steering arrangement for steering the orientation of the angle of regard with respect to the horizontal.
Instead of fitting the boom with a beam catcher, the boom may be alternatively provided, at its end region, with a transmission detector attached to respond to penetrating radiation transmitted through the container, so as to provide a signal for forming a transmission image of the container. In further embodiments, the source of penetrating radiation includes an x-ray tube operating at a voltage in substantial excess of 200 kV, and may operate in a region of approximately 450 kV.
In a further embodiment, the invention provides a method, for producing an x-ray image of a large object, utilizing a device such as described above, along with an arrangement for processing the signal from the signal output of the detector to form an image of the object.
In a further embodiment, the invention is a scatter image of an object. The image is formed by (a) providing a device such as described above, then (b) using the motorized drive to move the device past an object so as to cause the object to be scanned along two dimensions; and (c) processing the signal from the signal output of the detector to form an image of the object. The object may, for example, be a motor vehicle having at least two pairs of wheels. The object may also, for example, be a trailer, a railroad car, a sea cargo container, an air cargo container, or a freight pallet.
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Swift Roderick
Tybinkowski Andrew
American Science & Engineering, Inc.
Bromberg & Sunstein LLP
Church Craig E.
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