WO2006134362A2 - Dispositif de detection par rayons x - Google Patents

Dispositif de detection par rayons x Download PDF

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Publication number
WO2006134362A2
WO2006134362A2 PCT/GB2006/002186 GB2006002186W WO2006134362A2 WO 2006134362 A2 WO2006134362 A2 WO 2006134362A2 GB 2006002186 W GB2006002186 W GB 2006002186W WO 2006134362 A2 WO2006134362 A2 WO 2006134362A2
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WO
WIPO (PCT)
Prior art keywords
detector
source
ray
sampling volume
radiation
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PCT/GB2006/002186
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English (en)
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WO2006134362A3 (fr
Inventor
Simon Xerxes Godber
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STEREO SCAN SYSTEMS Ltd
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STEREO SCAN SYSTEMS Ltd
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Publication of WO2006134362A2 publication Critical patent/WO2006134362A2/fr
Publication of WO2006134362A3 publication Critical patent/WO2006134362A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V5/00—Prospecting or detecting by the use of ionising radiation, e.g. of natural or induced radioactivity
    • G01V5/20—Detecting prohibited goods, e.g. weapons, explosives, hazardous substances, contraband or smuggled objects
    • G01V5/22—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays
    • G01V5/228—Active interrogation, i.e. by irradiating objects or goods using external radiation sources, e.g. using gamma rays or cosmic rays using stereoscopic means

Definitions

  • the present invention relates to x-ray screening apparatus and x-ray imaging systems, and in particular relates to a portable x-ray apparatus for examining the contents of objects.
  • X-ray imaging techniques are widely used to examine the contents of objects and to inspect materials having layered structures, due to the penetrative energy of x- rays and the inherent transmissivity of most materials to x-rays.
  • FIG. 1 The basic principle of operation is illustrated in figure 1, where a static x-ray detector 1 and static x-ray source 2 are oppositely disposed on either side of a moving object 4, which is typically mechanically driven transversely across the axis separating the detector 1 and source 2 (shown by the arrow 5).
  • the interaction of the object 4 with the x-ray slit beam from source 2 attenuates the energy within the beam, such that the energy incident on the detector 1 forms a shadowgraph which is representative of each spatially resolvable volume element within the object through which the beam has passed.
  • the object 4 can remain at rest and the x-ray source 2 can be adapted to produce a cone of x-ray emission which is sufficiently wide so as to completely irradiate the object 4, as shown in figure 2.
  • the detector 1 may then be mechanically driven transversely across the cone of radiation (as shown by arrow 6) within the enclosure 7.
  • x-ray laminography and tomosynthesis are non-destructive radiographic techniques whereby individual layers of a 3 -dimensional object can be inspected one at a time.
  • the principle of x-ray laminography relies on the synchronised motion of any two of the x-ray source, detector and object, to form a geometric focus plane corresponding to a particular slice in the object.
  • the object remains at rest while the source and detector are moved in a synchronised manner around the object. Images are collected continuously throughout the synchronised motion and are then averaged together to form a final image.
  • Digital x-ray laminographic techniques allow all layers of an object to be imaged at the same time, as the projections can be reconstructed using computer processing techniques which can co-register particular features in multiple images so as to select the desired focal plane. In this way, each layer of the object can be inspected as desired, permitting a 3-dimensional model of the object to be constructed.
  • a technique of image co-registration in relation to x-ray laminography is discussed in US5583904.
  • a drawback of x-ray laminographic and tomosynthesis techniques is that they typically require complex and expensive drive mechanisms and control circuitry, so as to achieve the required synchronised motion of any two of the source, detector and object. Moreover, due to the synchronised motion, such techniques tend to be relatively slow, and therefore have only a limited speed of inspection.
  • the present invention is directed to an x-ray screening apparatus in which two or more of the source, detector and sampling volume, in which an object resides, are relatively displaceable, such that complex drive mechanisms and associated control circuitry are not required to invoke synchronised or coordinated motion.
  • the x-ray screening apparatus can be adapted to automatically determine the relative displacement and/or orientation of the source and detector with respect to each other, so that the particular configuration of the source and detector can be determined during image capture.
  • the x-ray screening apparatus of the present invention is able to provide depth information concerning items within an object under inspection by constructing stereoscopic images for viewing by an operator. Therefore, the present invention is particularly suited for airport environments, or other locations, where inspection of baggage, luggage or other personal items is required, e.g. at check-in points in government and military buildings etc.
  • An object of the present invention is to provide a portable x-ray screening apparatus which can produce stereoscopic images of a sampling volume which is at rest during inspection.
  • Another object of the present invention is to provide an x-ray screening apparatus which can produce stereoscopic images of a sampling volume under inspection by enabling fully independent relative displacement of each of the x-ray source, x-ray detector and the sampling volume.
  • Another object of the present invention is to provide an x-ray screening apparatus which can produce stereoscopic images of a sampling volume under inspection by using at least two x-ray sources and a detector which are relatively displaceable along an axis that is transverse to the axis of separation of the sources and detector.
  • Another object of the present invention is to provide an x-ray screening apparatus which can provide depth information relating to items within the sampling volume under inspection.
  • Another object of the present invention is to provide an x-ray screening apparatus which can automatically determine the relative displacement and/or orientation of a source and a detector which are independently displaceable with respect to each other.
  • an x-ray screening apparatus comprising: at least one x-ray source; at least one x-ray detector; and a sampling volume disposed between the source and the detector; the apparatus being configured such that the at least one detector is able to receive radiation from the at least one source which radiation has passed through each spatially resolvable volume element within the sampling volume at at least two different angles of incidence, and in which at least two of the source, detector and sampling volume are relatively displaceable so as to enable fully independent relative displacement of each of the source, detector and sampling volume.
  • an x-ray screening apparatus comprising: at least two spatially separated x-ray sources; at least one x-ray detector; a sampling volume disposed between the sources and the detector; the apparatus being configured such that the at least one detector is able to receive radiation from the at least two sources which radiation has passed through each spatially resolvable volume element within the sampling volume at at least two different angles of incidence, and in which the sources and detector are relatively displaceable along an axis that is transverse to the axis of separation of the sources and detector.
  • an x-ray screening apparatus comprising: . . at least one x-ray source; at least one x-ray detector; and a sampling volume disposed between the source and the detector; the apparatus being configured such that the source and detector are able to move independently of each other, and further comprising means associated with at least one of the source and the detector adapted to automatically determine the relative displacement and/or orientation of the source and detector with respect to each other.
  • Figure 1 is a perspective view of a conventional x-ray screening apparatus in which an object is passed through an x-ray slit beam.
  • Figure 2 is a perspective view of another conventional x-ray screening apparatus in which a detector scans across a cone of x-ray radiation.
  • Figure 3 is a perspective view of a preferred arrangement of the x-ray screening apparatus of the present invention.
  • Figure 4 is a perspective view of another preferred arrangement of the present x-ray screening apparatus.
  • Figure 5 shows the x-ray screening apparatus of figure 3 with a detector arrangement for use with the present invention.
  • Figures 6 and 7 are perspective views of other detector arrangements for use with the present x-ray screening apparatus.
  • Figure 8 is a perspective view of preferred detector arrangement according to the present invention.
  • Figure 9 is a schematic perspective view of a preferred arrangement of the present x-ray screening apparatus.
  • the screening apparatus 20 comprises at least one x-ray source 2 0 and at least one x-ray detector 1 arranged on substantially opposing sides of a sampling volume 4, such that the sampling volume 4 is disposed between the source 2 0 and detector 1 so as to receive x-ray radiation from the source 2 0 .
  • the x-ray source and x-ray detector may be any suitable conventional devices, adapted for use with the present x-ray screening apparatus as prescribed in the following arrangements.
  • the sampling volume is a space suitable for receiving objects for inspection which have at least a partial inherent transmissivity to x-ray radiation.
  • the objects would typically be baggage and luggage or other personal belongings, which are associated with passengers and aircrew.
  • the objects could be any type of object in which the contents (herein referred to "items") need to be inspected and identified.
  • the sampling volume 4 (and therefore any objects therein) remains at rest during the screening process.
  • references to a "screening process" are to be taken as corresponding to a single or multiple imaging cycle of the sampling volume, in which two or more images of the sampling volume are obtained per imaging cycle by the detector 1.
  • the sampling volume may be 'moved', i.e. any objects therein are moved, by provision of a suitable conveyor or the like.
  • spatially resolvable volume element we mean the smallest physical volume discernable within the sampling volume 4. It is to be appreciated that this quantity is dependent on the resolution of the screening apparatus, which in turn is governed by the resolution of the x-ray detector 1.
  • the technique of imaging the sampling volume 4 at at least two different angles is achieved by having the source 2 0 and detector 1 mounted in such a way, that each is relatively displaceable with respect to the other.
  • the sampling volume 4 i.e. any objects within it
  • the source 2 0 and detector 1 are then moved relative to the sampling volume 4 and each other.
  • the source 2o and detector 1 are displaced relative to the sampling volume, such that the radiation is made to pass through each spatially resolvable element within the sampling volume at at least two different angles of incidence.
  • the source 2o may be moved along an axis that is substantially transverse to the axis of separation of the source 2 0 and detector 1.
  • This feature is represented in figure 3 by sources 2 0 to 2 n , in which each labelled source indicates a position that may be assumed during the screening process relative to the sampling volume 4. It is to be appreciated that the positions shown are illustrative only and are not intended to be limiting, and consequently any suitable position may be adopted by the source 2 0 during the screening process.
  • the source is adapted to preferably emit a cone of x-ray radiation 3, as shown in figure 3, which preferably has an angular extent (i.e. width and height) at the position of the sampling volume 4 that is sufficient to completely irradiate the sampling volume 4.
  • cone we mean a geometric volume that is substantially conical, pyramidal or tetrahedral in form, whether symmetrical or not. However, it is to be appreciated that any suitable emission volume may be used.
  • the detector 1 is mounted so as to be able to move along an axis that is transverse to the axis of separation of the source 2o and detector 1. However, so as to avoid the need for complex mechanical drive mechanisms, this motion need not be synchronised with motion of the source 2 0 .
  • the detector 1 sweeps across the radiation cone 3 of the source (indicated by arrow 6 in figure 3), moving relatively to the sampling volume 4 and source 2 0 , and detects the radiation that has passed through each spatially resolvable volume element within the sampling volume 4. On each sweep, the detector 1 captures a shadowgraph image of the sampling volume 4, as determined by the particular relative configuration of source 2 0 , sampling volume 4 and detector 1 at the time of the sweep.
  • the detector 1 need only obtain one image for each particular configuration, or alternatively multiple images can be obtained depending on the application.
  • a “detector sweep” corresponds to a physical pass of the detector 1 through the radiation cone 3 of the source 2 0 in either azimuthal direction, and therefore “detector sweeps” are to be construed accordingly.
  • the detector 1 is a 1 -dimensional array of x-ray sensitive elements arranged so that the vertical axis of the array is substantially orthogonal to the direction of motion of the array, as shown in figure 3. It is to be appreciated therefore, that the detector only receives radiation from a source along a plane aligned with the vertical axis of the array. Hence, from the detector's point of view, the source effectively corresponds to a slit beam source, as typically used in conventional x-ray screening apparatus, as shown in figure 1.
  • the source 2 0 may remain at rest and the sampling volume 4 and detector 1 may be displaced relative to each other and the source 2 0 .
  • the detector 1 may remain at rest and the source 2o and sampling volume 4 may be displaced relative to the detector 1.
  • displacement of the sampling volume we mean displacement of any objects therein.
  • any of at least two of the source 2 0 , detector 1 and sampling volume 4 are relatively displaceable, such that the screening apparatus 20 enables fully independent relative displacement of each of the source 2o, detector 1 and sampling volume 4, i.e. without requiring corresponding synchronised motion of the others.
  • the source 2o, detector 1 and sampling volume 4 can be moved in any desired pattern of coordinated motion, but the individual motions of the components do not need to be synchronised.
  • at least one of the source 2o, detector 1 and sampling volume 4 are adapted to move in a linear or arcuate motion.
  • the sampling volume remains at rest, however each one of the source 2 0 and the detector 1 has an associated drive mechanism, which is operable to displace the source 2 0 and detector 1 relative to each other and to the sampling volume 4.
  • this too has an associated drive mechanism.
  • the drive mechanisms are preferably configured so as to permit independent movement of any of the source 2o, detector 1 and sampling volume 4.
  • the source 2 0 is adapted to operate over a variable range of x-ray energies or at a plurality of discrete x-ray energies.
  • the use of variable or discrete x-ray energies provides a useful diagnostic tool in discriminating between materials of items within the sampling volume 4, as, for example, the x-ray transmissivity of organic materials is inherently different to that of metallic and other materials.
  • the x-ray screening apparatus 20 of the present invention can not only provide depth information in respect of items within the sampling volume 4, but also additionally discriminate between different materials.
  • the source x-ray energies can be varied during a particular imaging cycle, or else can be varied after each imaging cycle, depending on the desired application and nature of the sampling volume 4 under inspection.
  • the x-ray source corresponds to a source assembly 2, which is a mounting or housing that remains physically at rest during the screening process.
  • the source assembly 2 comprises a plurality of spatially separated emission sites
  • each site effectively corresponding to an individual x-ray source and operable to emit radiation independently of the other sites.
  • Each emission site H 0 ... H n on the source assembly 2 may be formed by a respective collimation device, or alternatively by some other suitable mechanical slit and shielding arrangement etc.
  • each emission site H 0 ... H n are disposed along an axis that is substantially transverse to the axis of separation of the source and detector, as shown in figure 4.
  • each emission site H 0 ... H n can be configured to emit radiation as part of an ordered sequence of emission, e.g. one-after-another along the axis, which is preferably coordinated with sweeps of the detector 1 during the screening process.
  • the order in which the emission sites H 0 ... H n are switched to emit radiation is to some degree dependent on the position of the detector 1 relative to the source and sampling volume 4, as the detector 1 must be able to sweep across the radiation cone of the switched emission site so as to detect the radiation.
  • the ordered sequence of emission is preferably cyclic, with images of the sampling volume 4 being obtained by virtue of radiation emitted by whichever emission site is active at the time of the particular detector sweep.
  • the emission sites H 0 ... H n are preferably adapted to emit a cone of x-ray radiation 3, in the manner of the other preferred arrangements.
  • the radiation cone 3 of emission site H 0 is preferably of a sufficient angular extent at the position of the sampling volume, so as to completely irradiate the sampling volume 4,
  • the radiation cones of emission sites H 1 to H n have not been shown, but it is to be appreciated that the cones would be displaced as the emission sites 11 0 ...1 I n are sequentially switched on and off.
  • the detector 1 may then sweep across the respective radiation cones 3, so as to obtained images of the sampling volume 4 at different angles.
  • the emission sites 11 0 ...1 I n may be adapted to emit a variable range of x-ray energies or else emit discrete x-ray energies, so as to derive material/compositional data concerning the contents of the sampling volume 4.
  • the emission sites Ho... H n (recalling that these act as individual sources) and detector 1 are relatively displaceable along an axis that is transverse to the axis of separation of the sources and detector. Therefore, no complex mechanical drive mechanisms are required to achieve synchronised motion of the emission sites and detector.
  • the detector for use with the present x-ray screening apparatus 20.
  • the detector includes a plurality of 1 -dimensional arrays I 0 ... I n of x-ray sensitive elements, arranged one-in-front-of-the-other, along a line of sight between the source 2 0 and detector.
  • the source 2 0 is shown as being displaceable at positions represented by sources 2o to 2 n , it is to be appreciated that this detector arrangement can be used with the source assembly of the other preferred arrangements.
  • x-ray sensitive element we mean a detector element that is capable of detecting x-ray radiation, so as to produce a corresponding discernable signal or other indicator in response to the x-ray radiation.
  • Any suitable x-ray detector element may be used with the x-ray screening apparatus of the present invention, including, but not limited to, semiconductors, high-energy counters and phosphor/scintillation-based devices.
  • additional x-ray energy information can be derived, as depending of the number n of arrays used, particular energy bands can be selected for imaging purposes, which again can be useful in assessing which materials, or types of material, are present in the sampling volume 4 under inspection.
  • optimisation of the x-ray energy band can be a useful technique in tailoring the present screening apparatus 20 to identify specific materials or types of material. This feature could be particularly important in airport environments and security check-in points, where typically the identification of metallic objects (e.g. weaponry) is a primary concern.
  • FIG. 6 the x-ray sensitive elements of the array 1 are arranged in an alternating pattern of varying thickness (see inset 8), while instead, or in addition, a conventional x-ray absorbent layer (e.g. copper) may be associated with the array, as shown in figure
  • any suitable technique of optimising the x-ray energy band information may be used with the x-ray screening apparatus 20 of the present invention.
  • the detector is preferably a single x- ray sensitive element 10, which is mounted to a drive mechanism that permits the element 10 to be moved in at least two degrees of freedom, such that motion is possible along at least two mutually orthogonal axes.
  • the detector may then perform a sweep of the radiation cone 3 (not shown), by being mechanically driven in azimuth (shown by arrow 6L) and altitude (shown by arrow 6V), thereby effectively performing the same detector sweep as a 1- dimensional array.
  • this technique need not be limited to only a single element 10, and that more than one element may be driven in this manner, in accordance with the present invention.
  • the present invention is intended to resolve the problems of the art, in that complex mechanical drive mechanisms are not required, since synchronised motion of the source 2o and detector 1, or detector 1 and object 4, as mandated by laminographic and tomosynthesis techniques is not required. Instead, the motion of the source 2 0 and detector 1 is greatly simplified, since although a degree of coordinated positioning of the source 20, detector 1 and sampling volume 4 is required, each of these components can be moved independently of the others, so that all of the components are relatively displaceable.
  • the present apparatus can be fabricated as a portable unit, such that the detector 1 and source 2o preferably are in the form of two separately deployable components. This is particularly advantageous for screening suspicious packages or objects in situ where the object should not be moved.
  • the detector 1 is integral with, or contained within, a detection head assembly 30 (also schematically represented as 7 in figures 3 to 5 and 8).
  • the head assembly 30 may be mounted on an adjustable stand 31 or support structure, which permits the height of the head assembly to be adjusted relative to a floor level 50.
  • the head assembly 30 preferably includes a mechanical drive mechanism 32 which is operable to impart motion of the detector 1, as described in relation to the foregoing arrangements.
  • the drive mechanism 32 may be any suitable drive device or motorised bearing etc., which is capable of moving the detector relative to the sampling volume 4 and the source
  • the source 2 0 is preferably mounted within a source assembly 2, which has a corresponding adjustable stand 33 or support structure, which permits the height of the source assembly to be adjusted relative to the floor level 50.
  • the source assembly 2 preferably includes a mechanical drive mechanism 34 which is operable to impart motion of the source 2 0 .
  • the drive mechanism 34 may be any suitable drive device or motorised bearing etc., which is capable of moving the source 2 0 relative to the sampling volume 4 and the detector 1.
  • the source assembly 2 need not be driven, therefore the drive mechanism 34 is either removed or deactivated.
  • the x-ray screening apparatus 20 of the present invention can be readily positioned with respect to a sampling volume 4 and objects therein, which may be at rest on a floor surface 50, or else residing on an intermediary platform (not shown), such as a table etc.
  • the head assembly 30 may be positioned on one side of the sampling volume, while the source assembly 2 is positioned substantially on the other side.
  • the x-ray screening apparatus 20 further comprises a control unit 40, which is preferably remotely located from the detection head and source assemblies 30, 2.
  • the control unit 40 is coupled to the detector 1 in the detection head assembly 30, to receive data from the detector 1 corresponding to the detected radiation.
  • the control unit 40 is preferably further coupled to the source assembly 2 so as to control the emission of the radiation.
  • the control unit 40 is a computing device, such as a desktop computer, laptop computer or even a hand-held portable device.
  • the control unit can be a purpose built station, preferably remote from the detection head and source assemblies 30, 2.
  • control unit is also preferably coupled to each of the drive mechanisms 32, 34 in the apparatus, such that the detector 1 and/or source 2o positions can be independently controlled via the control unit 40.
  • control unit 40 is coupled to at least one of the detection head assembly 30, source assembly 2 and drive mechanisms 32, 34 by wireless communications, such as, but not limited to, WiFi and Bluetooth, hi preferred arrangements, the entire operation, including data retrieval and imaging, are all performed via wireless protocols.
  • wireless communications such as, but not limited to, WiFi and Bluetooth, hi preferred arrangements, the entire operation, including data retrieval and imaging, are all performed via wireless protocols.
  • the operator may then examine and inspect the contents of a plurality of objects without needing to be in the physical vicinity of the objects at the time of the screening process. Should any suspect items be identified within a particular object, appropriate personnel can be notified and the immediate vicinity of the object can be evacuated, should this be deemed necessary.
  • the detection head and source assemblies 30, 2, along with the drive mechanisms 32, 34, may be coupled to the control unit 40 using hardwire connections.
  • the control unit 40 includes a processing means (not shown) which is preferably adapted to interpret the data received from the detector 1 during the imaging cycles, so as produce one or more images of the sampling volume under inspection.
  • An image processing algorithm preferably implemented via software, interprets the received data so as to derive the angular shift information contained within the images.
  • the processing means is able to construct a stereoscopic representation of the sampling volume 4, which is preferably displayed as a image on an associated display monitor, or else is provided as a hardcopy.
  • the processing means can render the image for display on a suitable virtual reality headset or other ocular viewing device, which is configured to permit an operator to virtually inspect different aspects of the sampling volume by movement of the operator's head.
  • the x-ray screening apparatus 20 can be adapted to automatically determine the relative displacement and/or orientation of the source 2 0 and detector 1 with respect to each other.
  • this is achieved without the need for a complex synchronised drive mechanism, thereby maintaining portability of the apparatus and ensuring flexibility of deployment in screening environments.
  • the positions of the source and detector are typically determined by encoders attached to the drive mechanism.
  • the encoder information is provided to a control unit which is then recorded for use in subsequent image reconstruction, allowing the exact orientation of the source and detector to be derived.
  • the relative displacement and/or orientation of the source 2 0 and detector 1 can be determined automatically, without any reference to a drive mechanism or predetermined coordinate system.
  • the head assemblies 30, 2 discussed above in' relation to figure 9) can simply be deployed at the screening site, in relation to the sampling volume 4, and the subsequent source and detector positions can be determined automatically either in real-time or during an image processing stage.
  • the ability to derive accurate source and detector positions is very important in reconstructing the captured image data, since in the case of stereoscopic images, the precise viewing angles of the detector 1 relative to the source 2o must be known throughout the screening process.
  • the displacement and/or orientation of the source 2o and detector 1 can be determined relative to each other by using one or more of several complementary techniques.
  • a particular configuration may use any number of the following techniques to ensure that adequate position data is derived during a screening process.
  • the head and source assemblies 30, 2 are each respectively adapted to include at least one acoustic transmitter or at least one acoustic receiver. Either assembly may be selected to host the transmitter (or respectively, the receiver), but in practical applications it is expected that the transmitter will be associated with the x-ray source 2 0 .
  • the transmitter/receiver operate in ultrasonic wavebands, to avoid unnecessary noise disturbance for the operator within the screening environment.
  • any suitable sound wave may be used, provided a recognisable signal from the transmitter can be detected by the receiver.
  • the transmitter may form part of the source assembly 2 circuitry, or alternatively, may be a separate unit that can be attached directly to the assembly 2o- In either case, the transmitter will preferably be controlled by the operator, and will usually be activated automatically when the apparatus is in use.
  • the transmitter is arranged to transmit pulsed ultrasonic sound waves towards the detector, which are then received by the receiver attached to the detector assembly 30. Due to the separation of the source 2o and detector 1, an inherent delay in receiving the pulse will occur relative to the time of transmission. Therefore, this time-delay can be determined to provide a measurement of the relative displacement between the source 2 0 and the detector 1, having knowledge of the speed of propagation of the ultrasonic wave pulse.
  • the detector assembly 30 includes a controller, comprising a timing circuit, which is synchronised with the transmitter circuitry, so that the time- delays associated with each pulse can be calculated and used to determine the corresponding separations between the source 2o and detector 1.
  • a controller comprising a timing circuit, which is synchronised with the transmitter circuitry, so that the time- delays associated with each pulse can be calculated and used to determine the corresponding separations between the source 2o and detector 1.
  • the timing circuit can automatically calculate the relative displacement between the source 2 0 and detector 1, which can then be logged against a time stamp for use during image reconstruction.
  • the timing circuit can determine the time-delay for a pulse to be detected by each of the three receivers, and therefore having knowledge of their spatial separation (i.e. inter-receiver separation) and speed of propagation of the pulse, can calculate the angle (and hence orientation) of the detector 1 relative to the source 2 0 based on each of the displacements of the receivers relative to the source 2Q.
  • transmitters and receivers may be used in the x-ray screening apparatus 20 according to the present invention, depending on the particular application.
  • the transmitters and receivers may be spatially arranged in any suitable array structure or configuration, to provide reliable and accurate position determination for the detector 1 relative to the source 2 0 , and vice versa.
  • the above technique may also be implemented using light or radio based transmitters and receivers, and therefore is not limited to acoustic implementations.
  • the transmitter may be a light source, such as an optical or Infra-Red (IR) laser
  • the receivers may be any suitable photodetector device.
  • the timing circuit would be a high speed timing device to take the significantly faster propagation speeds into consideration.
  • Radio based implementations would use radio-frequency (RF) pulsed waveforms and receivers would be conventional radio antennae and amplifier circuitry.
  • RF radio-frequency
  • the displacement and/or orientation of the source 2 0 and detector 1 relative to each other may be determined by use of a mask device.
  • the mask device is preferably in the form of a 'shadow mask', which is a physical device which can be attached or mounted to either the detector 1 or source 2o, or both.
  • the purpose of the mask is to generate a recognisable shadow pattern in an x-ray image generated by the detector 1.
  • the relative displacement and/or orientation of the source 2 0 and the detector 1 can be calculated based on the shape, size and/or location of the shadow pattern in the captured image data.
  • the mask can be formed from any suitable x-ray opaque material or composite material, and can have any geometric shape. Preferred mask shapes are nonsymmetrical, having a unique shape defined by their outer perimeter. This allows the rotation of the detector 1 relative to the source 2oto be determined by analysis of the orientation of the shadow with respect to a part of the detector 1.
  • the mask is preferably attached directly to the detector assembly 30, and may be positioned close to the detector's surface. Alternatively, or additionally, the mask (or additional mask) can be attached to the source 2 0 , so that a shadow is formed within the emission cone of the source 2 0 .
  • a mask may alternatively include one or more shaped apertures across its surface, thereby being partially transparent to x-rays. Use of such apertures can allow unique mask shadows to be produced, which can aid identification and processing of a shadow within captured image data. It is to be appreciated that any number of masks may be used according to the present invention, depending on the particular application. Moreover, in preferred arrangements, the mask or masks may be switchable, in that they can be selectively switched into or out of the image plane of the detector 1, prior to or during image capture, after having served to determine the relative positions of the source 2 0 and detector 1 at that time.
  • the position of the shadow in the resulting captured image is dependent on the relative orientation of the source 2Q and detector 1. Therefore, there is a functional relationship between the shadow position and angular displacement of the detector 1 relative to the source 2 0 . Hence, this relationship can be pre-calibrated during fabrication of the apparatus 20 to permit the relative orientation of the source 2 0 and the detector 1 to be determined during screening.
  • the mask and detector can be arranged so that the shadow is always cast on a dedicated portion of the detector, e.g. a corner of the detector surface.
  • the shadow can be made to fall onto a non-imaging part of the detector, e.g. a border of the detector.
  • the image processing algorithms have a priori knowledge of where the shadow is expected to reside in any particular image, and therefore processing of the shadow can begin quickly, permitting rapid determination of the relative orientation of the source 2 0 and detector 1.
  • a change in the position of the shadow in the image data may take the form of a relative change in both horizontal and vertical axes of the shadow, and a change in size of the shadow would be indicative of a change in the relative displacement between the source 2o and detector 1.
  • the processing of the shadow information in the image data can be performed by a dedicated processor, which preferably forms part of the control unit 40 (discussed earlier in relation to figure 9), or alternatively, the shadow processing can form part of the processing algorithms used for image reconstruction and can be executed on an image processor. It is to be appreciated that other arrangements may alternatively, or additionally, be used in order to determine the relative displacement and/or orientation between the source and detector, all of which are consistent with the present invention, hi particular, in the transmitter/receiver based applications, the transmitter need not be mounted to the source assembly, and could instead form part of a transmitter array etc. including a plurality of transmitters disposed at specific locations within and/or around the screening environment.
  • the x-ray screening apparatus includes a remote sensing system for determining the relative position and orientation of the source and detector relative to one another either directly or by reference to in independent reference frame (e.g. some remote positioning transmitters or beacons, or even the walls or structures surrounding the screening environment etc.).
  • a remote sensing system for determining the relative position and orientation of the source and detector relative to one another either directly or by reference to in independent reference frame (e.g. some remote positioning transmitters or beacons, or even the walls or structures surrounding the screening environment etc.).
  • the X-ray screening apparatus of the present invention is ideal for inspecting baggage and luggage in airport environments and security check-in points, it will be recognised that the apparatus can be extended to other applications, including inspecting freight, cargo and small to medium size vehicles at depots, ports and terminals.

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  • Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Geophysics (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Abstract

Cette invention concerne un dispositif de détection par rayons X plus particulièrement utilisé pour contrôler et inspecter des bagages dans des environnements aéroportuaires. Le dispositif de détection décrit dans cette invention comprend au moins une source de rayons X, au moins un détecteur de rayons X et un volume d'échantillonnage, par exemple, un bagage, placé entre la source et le détecteur. Le dispositif est configuré de telle sorte qu'au moins un détecteur peut recevoir un rayonnement provenant de ladite source; ce rayonnement traverse chaque élément du volume présentant une résolution spatiale à l'intérieur du volume d'échantillonnage à au moins deux angles d'incidence différents, et à l'intérieur duquel au moins deux des éléments parmi lesquels la source, le détecteur et le volume d'échantillonnage peuvent être déplacés de manière relative pour permettre un déplacement relatif totalement indépendant de chacun des éléments parmi lesquels la source, le détecteur et le volume d'échantillonnage. L'interprétation du rayonnement détecté permet de constituer des images stéréoscopique du volume d'échantillonnage, ce qui permet d'obtenir des informations précises concernant les articles se trouvant dans le volume d'échantillonnage.
PCT/GB2006/002186 2005-06-15 2006-06-15 Dispositif de detection par rayons x Ceased WO2006134362A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0512132.2 2005-06-15
GB0512132A GB2427339A (en) 2005-06-15 2005-06-15 X-ray stereoscopic screening apparatus

Publications (2)

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WO2006134362A2 true WO2006134362A2 (fr) 2006-12-21
WO2006134362A3 WO2006134362A3 (fr) 2007-02-08

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GB2427339A (en) 2006-12-20
WO2006134362A3 (fr) 2007-02-08

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