EP4176290A1 - Détecteur à double énergie et procédés de traitement de données de détecteur - Google Patents

Détecteur à double énergie et procédés de traitement de données de détecteur

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Publication number
EP4176290A1
EP4176290A1 EP21739112.7A EP21739112A EP4176290A1 EP 4176290 A1 EP4176290 A1 EP 4176290A1 EP 21739112 A EP21739112 A EP 21739112A EP 4176290 A1 EP4176290 A1 EP 4176290A1
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EP
European Patent Office
Prior art keywords
detector
data
ray
energy
real
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21739112.7A
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German (de)
English (en)
Inventor
Eric J. RIEHN
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Smiths Detection Germany GmbH
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Smiths Detection Germany GmbH
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Publication date
Application filed by Smiths Detection Germany GmbH filed Critical Smiths Detection Germany GmbH
Publication of EP4176290A1 publication Critical patent/EP4176290A1/fr
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • 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
    • G01V5/224—Multiple energy techniques using one type of radiation, e.g. X-rays of different energies
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/06—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption
    • G01N23/083—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and measuring the absorption the radiation being X-rays
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/50—Detectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/643—Specific applications or type of materials object on conveyor

Definitions

  • the present disclosure relates generally to the spatial resolution of X-ray images in the imaging, non-destructive inspection of objects to find target objects by means of dual-energy X-ray radiography, in particular measures to increase the spatial resolution of an X-ray image generated in the process.
  • the disclosure relates in particular to a dual-energy X-ray detector with improved spatial resolution, an X-ray inspection system with such a detector and a method for processing detector data acquired with the detector.
  • the resolution of an x-ray image generated in the process is essentially dependent on the area of the individual detector elements corresponding to a respective image point (pixel) and their number per unit length or per unit area of the detector line as determined by the ratio of the readout frequency of the detector elements and the transport speed of the inspection object in the transport direction.
  • the spatial resolution of the X-ray image in the scanning direction corresponding to the transport direction could be achieved in the above-mentioned X-ray inspection systems by a reduced transport speed or an increased readout frequency.
  • the former has a disadvantageous effect on the throughput of the inspection objects checked on the X-ray inspection systems, while the latter again worsens the signal-to-noise ratio.
  • US 8433 036 B2 shows methods, systems and detector arrangements for scanning an object moving in a first direction, a first detector area with a thickness of at least 2 mm and a second detector area with a thickness of at least 5 mm being provided, the second detector area is arranged to receive radiation that has passed through the first detector area.
  • US 9 329 301 B2 shows a radiation detection device for a foreign body inspection using a subtraction method, wherein a first radiation detector detects radiation in a first energy range that passes through a sample, and a second radiation detector detects radiation in a second energy range that is higher than the radiation in the first energy range, and wherein the thickness of a first scintillator layer of the first radiation detector is less than the thickness of a second scintillator layer of the second radiation detector, and wherein a first area of each pixel in a first pixel portion of the first radiation detector is smaller than a second area of each pixel in a second pixel section of the second radiation detector.
  • US 10 386 502 B2 shows a dual energy detector and a radiation testing system.
  • the dual energy detector comprises: a detector module holder and a plurality of detector modules.
  • a detector module comprises a detector field with higher energy and a detector field with lower energy, which are arranged next to one another on the detector module holder in order to be irradiated independently of one another.
  • US 2019/0 179 038 A1 shows an X-ray image sensor with two or more energy fields, which is implemented as pixel arrays arranged next to one another on a planar and monolithic semiconductor substrate as part of an X-ray object detector.
  • Each pixel array in this monolithic side-by-side arrangement is designed to respond to a specific range of x-ray energy or a specific x-ray spectrum.
  • the number of detector elements of the detector per unit length or area should preferably not be increased and / or the scanning speed of the inspection object by the X-ray inspection system should not be reduced.
  • the above-mentioned object can be achieved with the features of claim 1 relating to a dual-energy X-ray detector. Further exemplary embodiments and developments are defined in the subsequent dependent claims.
  • the inventor has recognized that a defined effective offset between the still overlapping active surfaces of the Hi (gh) detector elements of a Hi detector line and the Lo (w) detector elements of a Lo detector line, of which a conventional dual Energy X-ray detector, a Hi and a Lo detector element are assigned to exactly one and the same pixel, can be used advantageously to improve the spatial resolution.
  • the effective offset can be directed in the direction of the detector line and / or orthogonal to the detector line; the possibilities that can be achieved are explained below.
  • the spatial resolution of the detector can thus be increased accordingly in the direction of the detector line and / or orthogonally to the detector line without increasing the total number of detector elements.
  • offset in connection with the present disclosure is intended to mean that the offset is not only an actual local offset between the working surfaces of the Hi detector elements of the Hi detector line and the Lo detector elements of the Lo detector line, but alternatively or additionally by a targeted alignment of the detector consisting of the Hi-detector line and the Lo-detector line, which do not have to be spatially offset to one another, can be effected in relation to the X-rays directed at the detector during operation. Of course, these measures can also be used in combination.
  • the core idea of the cell-shaped dual-energy X-ray detector proposed here is to design the detector structure and / or to arrange the detector rows of the detector in relation to one another and in relation to the X-ray source so that in operation with reference to the beam path from an X-ray source to the X-rays emitted from the detector, the projections of the Hi-detector elements of the Hi-detector line and of the Lo-detector elements of the Lo-detector line in the direction of a reference x-ray beam are offset from one another in an overlapping manner;
  • the “reference x-ray” can be, for example, the x-ray that runs through the centroid of the detector line or a reference detector element of the detector line;
  • a detector element in the center of the detector line can be used as the reference detector element, so that it is essentially at the same distance from all edges of the detector line.
  • centroid of the detector line or the reference detector element of the detector line can be determined in the case of the detector lines, which in practice usually have a rectangular shape, as the intersection of the straight lines bisecting the area of the detector line in the longitudinal and width directions, or can generally be calculated mathematically by integration.
  • the inventor has recognized that the detector data missing due to the effective offset of the no longer 1: 1 one of the assignable hi and lo detector elements for each individual real detector data of a type can be supplemented with virtual detector data of the other type calculated for this point . That is, based on the predetermined effective overlapping offset between the Hi detector elements of the Hi detector line and the Lo detector elements of the Lo detector line, virtual detector data can be calculated with sufficient accuracy as replacement for the locations of the missing detector elements.
  • the calculation has proven to be surprisingly easy to implement and the x-ray images derived from the real and virtual detector data have proven to be a practical improvement.
  • a cell-shaped dual-energy X-ray detector (hereinafter referred to as detector for short) for use in an X-ray inspection system (for example an X-ray inspection system according to the second aspect described below), which is used to carry out a method for dual-energy X-ray radiography of an inspection object is set up.
  • cell-shaped should initially be understood as meaning that the detector is used to acquire detector data for a large number of image points in the longitudinal direction of the detector and for a smaller number of image points, but at least for one image point, orthogonal to the longitudinal direction is set up.
  • the detector thus has two detector rows each with an equal number of Hi (gh) and Lo (w) detector elements in the longitudinal direction, each of which has a single Hi and a single Lo detector element orthogonally.
  • the detector can also have several high and low detector elements in the direction orthogonal to the longitudinal direction; the principles proposed here can then be applied accordingly.
  • the cellular detector proposed here has at least: a first detector line with first detector elements and a second detector line with second detector elements arranged parallel thereto.
  • the detector lines are configured to capture the spectrum to address the X-rays in different spectrally selective ways.
  • the detector rows are arranged parallel to one another in the row direction.
  • the detector rows are arranged one behind the other in the direction of the X-rays to be detected that the projection of the first and second detector rows in the direction of one of the X-rays to be detected as a reference X-ray are offset from one another in an overlapping manner.
  • the projection of the first and the second detector lines can take place in the direction of one of the X-rays to be detected, which runs through the center of gravity of a reference detector element of the first or the second detector line.
  • the reference X-ray beam can be the X-ray beam running through the centroid of the total area of the active surfaces of the detector elements of the foremost detector row in relation to the X-rays to be detected, or the X-ray beam running through the center of gravity of the working surfaces of a reference detector element, the foremost detector row running in relation to the X-rays to be recorded Be x-ray.
  • the first detector line can have associated first or Lo (w) detector elements for the primary detection of low-energy X-rays and the second detector line can have associated second or Hi (gh) detector elements for the primary detection of high-energy X-rays.
  • the Lo and Hi detector elements can be configured to generate respective associated Lo detector data or Hi detector data.
  • the Lo and Hi detector elements could be essentially the same, if only because a Lo detector element is usually closer to the X-ray source and therefore absorbs more low-energy quanta than an underlying Hi detector element.
  • the arrangement on top of one another results in a (albeit small) splitting of the X-ray spectra which the Lo and Hi detector elements capture.
  • a filter material for hardening i.e. filtering of the low-energy X-rays
  • filter material for hardening i.e. filtering of the low-energy X-rays
  • the first row of detectors and the second row of detectors are offset from one another in the row direction by a first (local) offset.
  • the spatial resolution of the X-ray images to be derived can be increased in the line direction (i.e. transverse to the scanning direction).
  • the first detector row and the second detector row are offset from one another by a second (local) offset orthogonally to the row direction.
  • an increase in the spatial resolution of the X-ray images to be derived can be achieved orthogonally to the line direction (ie in the scanning direction).
  • the spatial resolution of the X-ray images to be derived can be increased in the scanning direction without having to reduce the transport speed or the ratio of transport speed and scanning frequency for the inspection object.
  • the transport speed or the ratio of transport speed and scanning frequency for the inspection object and, accordingly, the throughput of the x-ray inspection system can be increased accordingly. Combinations of both effects are also possible with the appropriate configuration.
  • the first and the second embodiment can be used alternatively or in addition to one another, i.e. at the same time.
  • the first and second detector rows can also be inclined at a corresponding angle of inclination with respect to the reference X-ray beam be inclined to achieve the effective offset.
  • the desired effective offset can also be achieved in this way with a conventional detector in which the first and second detector elements can be clearly assigned 1: 1 - that is, they are not spatially offset from one another. It is of course possible to use the third version in combination with the first and / or the second version in order to achieve the same effect as the other version; that is, the third embodiment can be used to achieve the effect of both the first and second embodiments.
  • the first and second detector rows are usually arranged one behind the other in such a way that a connection line between a Lo detector element and the associated Hi detector element exactly on the focal point of the associated X-ray generator aligned with the detector indicates. Since the Lo and Hi detector elements, which are arranged one behind the other, have a predetermined distance (for example, about 1 cm) from the X-ray generator, the whole detector can easily be tilted at a suitable angle (for example by 5 ° -6 °) Be inclined with respect to the reference X-ray in the direction of the longitudinal direction of the detector and / or orthogonally thereto.
  • a suitable angle for example by 5 ° -6 °
  • the connecting line between the centroids of a pair of a Hi and a Lo detector element runs past the X-ray generator.
  • the inclination can be set in such a way that the connecting line between the centroid of a Lo detector element and the gap between two adjacent Hi detector elements points to the X-ray generator.
  • the inclination in the case of an inclination orthogonal to the longitudinal direction of the detector, the inclination can be set in such a way that the connecting line between the centroid of a Lo detector element and the edge of a Hi detector element located behind it points to the X-ray generator.
  • any required effective offset between the first and second detector elements can be sufficient to achieve one of the above-described effects or a combination thereof.
  • the effective offset can be set so that in operation with detector pairs formed from a real and a calculated virtual detector element, the connecting line through the associated focal points of the two detector elements is aligned on the X-ray generator, ie on the The focal spot of the generator is focused.
  • an I-, L- or U-shaped detector line in an X-ray inspection system can be formed from a large number of individual cell-shaped detectors, each of which is individually related to a reference X-ray beam each assigned X-ray generator of the system are aligned.
  • the projections of the first and second detector lines along the reference x-ray beam in the third embodiment are in practice already shifted from one another at least at the detector line ends due to the geometry (by approx. 14-15%). It is therefore recommended that the overlap between the detector elements of the first and the second detector line be a maximum of 80% and at least 20%.
  • the first detector elements and the second detector elements can have essentially the same cross-sectional shape and the same in the direction of the X-rays to be detected Have cross-sectional area (effective area).
  • a first detector element and a second detector element for a conventional arrangement can be arranged one behind the other and brought into congruence.
  • the “working area” of a detector element is understood here to mean the effective area of the detector element on which the X-rays to be detected, which have passed through the inspection object, are incident in the intended arrangement.
  • the first detector elements and the second detector elements each have a length in the row direction and a width orthogonally thereto.
  • the first offset in the line direction corresponds to half the length of the first and second detector elements.
  • the preferred first embodiment provides a detector with twice the spatial resolution in the line direction.
  • the second offset is determined based on the readout frequency f in [1 / s] for reading out the detector data from the detector elements and the transport speed b in cm / s of an inspection object compared to the dual-energy X-ray detector according to of the formula (1):
  • the preferred second embodiment provides a detector with twice the spatial resolution perpendicular to the line direction with an unchanged ratio of the transport speed of the inspection object past the detector and the readout frequency of the detection elements.
  • the scanning speed for inspection objects in the X-ray inspection system with the detector could be correspondingly reduced, possibly halved, with the spatial resolution remaining the same.
  • higher belt speeds with constant image quality or improved spatial resolution with constant belt speed are optionally possible.
  • the ratio of tape speed to scanning frequency can be adjusted as required. If, in the particularly preferred second embodiment, the tape speed and the scanning frequency are left the same, the spatial resolution is improved with the new detector.
  • the preferred second embodiment thus offers a particularly high level of flexibility with which systems can be designed for different requirements.
  • the spatial resolution, as described above, can be doubled in the conveying direction, since intermediate values are generated at a distance As / 2.
  • the value pairs are of the form ((L0 1 , vHii), (vLoi, Hii), (Lo 2 , vHi 2 ), (vLo 2 , Hi 2 ) ..., (LON, VHIN), (VLON, THERE)).
  • this means that detector data are still in the order L0 1 , Hii, Lo 2 , Hi 2 , Lo n , Hi n , ...
  • LON, HIN are generated, but now L0 1 and Hi 2 are spatially congruent.
  • the measured values can now be combined accordingly, for example in the form ((Lo 2 , Hii), (L0 3 , Hi 2 ), ..., (LON, H ⁇ N-I)), so that a calculation of Intermediate values can be dispensed with. That is, with such a use of the preferred second embodiment, the spatial offset between the associated first and second detector data due to the serial readout can be compensated for by the clever combination of spatial offset of the detector elements orthogonal to the line direction and the ratio of readout frequency and belt speed.
  • the two particularly preferred embodiments can (depending on the objective) be used independently of one another or in combination.
  • the third embodiment can be used as an alternative or in addition to the first and / or second embodiment with the effects and possible uses explained above.
  • the high-energy high-energy and low-energy low-energy detector elements are effectively shifted by half a detector element compared to the conventional arrangement.
  • the ratio of readout frequency and belt speed and, accordingly, the effective offset in the transport or scanning direction can be set as required, as noted above.
  • the Hi and Lo detector elements are configured to respond differently (spectrally selective) to the incident X-rays to be detected, due to the defined effective offset of the Hi and Lo detector elements in the line direction and / or orthogonal to the line direction, as well as The known ratio of readout frequency and belt speed, if necessary, the missing Hi detector data for a real Lo detector element can be calculated as virtual Hi detector data based on the detected neighboring real Hi and / or real Lo detector data. Possibilities for a specific procedure are explained below in connection with the method according to the third aspect for processing first and second detector data obtained with the detector of the first aspect.
  • the first and second detector elements can be constructed in a manner known per se for the required spectral selectivity for a spectrum of X-rays used.
  • the first and second detector elements can each have a photodiode, in front of which a scintillator material is arranged with respect to the incident X-rays to be detected.
  • the scintillator material can be selected for setting the required spectrally selective sensitivity for X-rays of the spectrum used and / or dimensioned accordingly in the thickness to be traversed by the X-ray radiation.
  • YAG yttrium aluminum garnet
  • YGAG yttrium-gadolinium-aluminum-garnet
  • GOS gadolinium oxysulfide
  • layer thicknesses in the order of magnitude less than 1 mm are preferably set, and for a high-energy scintillator, second layer thicknesses in the order of magnitude greater than 1 mm are preferably set.
  • the light quanta generated by the incident X-rays in the respective scintillator material are detected by the associated photodiode and converted into an output voltage that depends on the time interval after which the output signal generated by the photodiode is read out.
  • the output signals regularly read out in this way correspond to the associated detector data.
  • a filter for hardening the incident X-rays for example made of copper, titanium, aluminum or the like, can also be arranged, which attenuates low-energy X-rays particularly strongly, so that the second detector elements predominantly from high-energy X-rays can be achieved and thus are Hi-detector elements.
  • the first and the second detector elements can be arranged to form the detector proposed here on the same side of a carrier in accordance with one of the said first and second embodiments or a combination thereof.
  • the first detector elements can be located on one side of the carrier and the second detector elements on the other side of the carrier.
  • a printed circuit board PCB
  • a carrier on which the conductor tracks and possibly functional electronics for contacting and reading out the detector elements are located.
  • the predetermined effective overlapping offset proposed here between the high and low detector elements lying one behind the other in the direction of the X-rays to be detected achieves numerous advantages with the same system costs.
  • the dual energy detector proposed here achieves a higher spatial resolution without having to increase the number of Hi and Lo detector elements per unit length or unit area.
  • the dual-energy detector proposed here has a better signal-to-noise ratio compared to a structure with detector elements with a smaller effective area to increase the number of high and low detector elements per unit length or area.
  • the dual energy detector proposed here is particularly simple. In principle, no extensive changes to existing detectors are necessary to put the concept into practice. In principle, the high and low detector elements have to be shifted by the desired predetermined effective overlapping relative offset, for example preferably by half a length and / or width of a detector element.
  • a second aspect of the present disclosure provides an X-ray inspection system with the cellular dual-energy X-ray detector (detector) according to the first aspect.
  • the X-ray inspection system is set up for a transport of an inspection object in a transport direction through the inspection system.
  • the line direction of the dual-energy x-ray detector is preferably arranged orthogonally to the transport direction, so that the transport direction corresponds to the scanning direction for the inspection object.
  • the X-ray inspection system provides acquired first detector data in the form of Lo detector data and second detector data in the form of Hi detector data of the inspection object.
  • an imaging dual-energy X-ray radiography can be carried out for a non-destructive inspection of the inspection object and Lo and Hi detector data describing the inspection object can be provided.
  • the Lo and Hi detector data are based on detecting the X-rays penetrating the inspection object with the dual-energy X-ray detector of the first aspect.
  • the inspection object is scanned at a predetermined or optionally set transport speed through a scanning arrangement, consisting of the cell-shaped detector arranged orthogonally to the transport direction and an X-ray fan aligned to the detector line, for the corresponding line-by-line scanning with a likewise predetermined or optionally set readout frequency of the detector elements through the X-ray fan passed through.
  • a scanning arrangement consisting of the cell-shaped detector arranged orthogonally to the transport direction and an X-ray fan aligned to the detector line, for the corresponding line-by-line scanning with a likewise predetermined or optionally set readout frequency of the detector elements through the X-ray fan passed through.
  • the relationship between the belt speed and the readout frequency can be adjusted appropriately as required (high throughput or higher spatial resolution).
  • the detector data acquired with the detector and made available are indexed via a position variable n, which runs in the direction of the row of the detector starting at one end.
  • the first detector elements ie the Lo detector elements, acquire first real detector data, ie real Lo detector data L01, L02, Lo n , ..., LO N of the inspection object, where 1 ⁇ n ⁇ N and N is the number of Lo- Detector elements in the row direction of the detector is.
  • the second detector elements ie the Hi detector elements, detect corresponding second real detector data, ie real Hi detector data Hii, H12, H, ..., HI N of the inspection object, where 1 ⁇ n ⁇ N and N is the number of detector elements is in the row direction of the detector.
  • the inventor has also found that a similar effect on the spatial resolution achieved or the ratio of transport speed and readout frequency of the detector elements, as with the second or corresponding third embodiment of the detector according to the first aspect, also in an X-ray inspection system with a conventional detector by means of a certain readout patterns for the Hi and Lo detector data can be achieved on the conventional dual-energy X-ray detector. That is, the readout method below uses a dual-energy X-ray detector line with a high-energy Hi detector element and a low-energy Lo detector element per pixel, which are arranged essentially congruently one above the other in the direction of the X-rays to be detected.
  • the inventor has found that with a readout sequence in which all detector elements of one type (Hi or Lo) are read out first along the position variable n and then all other detector elements of the other type along the position variable n, i.e. all Hi detector data first Hii, Hh, H, .... HIN, and then all Lo detector data L01, L02, L03, .... LO N (or vice versa) the same result can be achieved as with the shift of the first and the second Detector row to each other can be achieved according to the second embodiment.
  • the above readout method is thus an equivalent software solution to the hardware solution with Hi and Lo detector elements that are effectively offset to one another in an overlapping manner, according to the second and / or appropriately configured third embodiment of the first aspect.
  • the readout method comprising: reading out the Hi and Lo detector elements in such a way that initially all detector elements of one type are read out along the position variable n and then all other detector elements of the other type are read out along the position variable n.
  • a third aspect of the present disclosure relates to a method for processing the Lo detector data and Hi detector data provided by the x-ray inspection system of the second aspect or the above-described x-ray inspection system with a conventional detector and the read-out method described above, so that an x-ray image with a improved spatial resolution can be derived.
  • the missing Hi detector data for a real Lo detector element as a virtual Hi detector data and correspondingly to a real Hi Detector element allows the missing Lo detector data to be calculated as virtual Lo detector data.
  • the method of the third aspect basically comprises: calculating a respective virtual Lo detector data at the position of a real Hi detector element. It goes without saying that, as an alternative or in addition, a respective virtual Hi detector data item can also be calculated at the position of a real Lo detector element.
  • the calculation of a virtual Lo detector data at the position of a real Hi detector element can include: Calculating the virtual Lo detector data based on a specific first number of neighboring real Lo detector data and a specific second number of neighboring real Hi detector data.
  • the alternative calculation of a virtual Hi detector data at the position of a real Lo detector element can include: Calculating a virtual Hi detector data based on a certain first number of neighboring real Hi detector data and a certain second number of neighboring real Lo detector data.
  • the inventor has found that different approaches are possible for the calculation of the virtual high and / or low detector data, which can be used alone or in combination.
  • a virtual Lo or Hi detector data can be calculated based on a mean value or median from neighboring Hi and / or Lo detector data.
  • the missing Hi detector data for a Lo detector element can be calculated as a virtual Hi detector data according to a first approach as follows: Based on a certain first number (e.g. two) of immediately adjacent real Hi detector data (ie the detector data, for example of the two Hi detector elements that overlap with the Lo detector element, i.e. are adjacent to it in the line on the left and right) and a certain second number (e.g. three) of the next real Lo detector data (i.e. the detector data of the Lo detector element under consideration as well as the two adjacent Lo detector elements on the left and right).
  • a virtual Lo detector data can be calculated taking into account the course of the values of the Hi detector data and / or a virtual Hi detector data can be calculated taking into account the course of the values of the Lo detector data.
  • the approaches mentioned above can be implemented using a machine learning algorithm.
  • the virtual hi or lo detector data can be generated based on the provided lo and hi detector data using a deep learning algorithm.
  • the inventor has surprisingly found that an approach from the field of processing the image data of a digital image sensor with a so-called Bayer color filter is suitable for calculating the virtual detector data.
  • the missing color information at the point of an image point can be calculated using a so-called demosaicking algorithm (i.e. an algorithm for removing mosaics).
  • demosaicking algorithm i.e. an algorithm for removing mosaics.
  • Such an algorithm is described, for example, in: “Color filter array demosaicking using high-order interpolation techniques with a weighted median filter for Sharp color edge preservation” by J. S. J. Li and S. Randhawa, IEEE Transactions on image Processing, Vol. September 9, 2009; for reference, the document is abbreviated in the following as Li / Randahawa and its content is incorporated by reference.
  • the filter elements for the primary colors red, green and blue of the color filter are arranged as a so-called Bayer matrix (or Bayer pattern) (cf. are arranged, whereby 50% of the filter elements are green and 25% of each of the filter elements are red and blue.
  • Bayer matrix or Bayer pattern
  • the “Bayer matrix” and the “Bayer filter” are named after their inventor, Bryce E. Bayer, and are described in US Pat. No. 3,971,065 A, for example.
  • the detector data recorded and provided with the dual-energy X-ray detector of the first aspect are indexed via the above-mentioned position variable n, which runs in the row direction of the dual-energy X-ray detector starting at one end, in such a way that the Lo detector elements Detect real Lo detector data L01, L02, ..., Lo n , ..., LON of the inspection object and the Hi detector elements corresponding real Hi detector data Hii, H12, ..., Hi n , ..., Detect HIN of the inspection object, where 1 ⁇ n ⁇ N and N is the number of Hi and Lo detector elements in the line direction of the dual-energy X-ray detector.
  • the real Hi and Lo detector elements of the dual energy X-ray detector are read out in pairs in the order Hii, L01, Hb, L02, ..., Hi n , Lo n , ..., HIN, LON, with several being read out in this way Sequences form a two-dimensional Hi / Lo matrix. Ever after how the offset has actually been implemented in relation to the readout direction of the detector elements, the above sequence can also begin with the element L01 and then end with the element HIN.
  • the virtual hi and / or lo detector data can be calculated using an adapted demosaicking algorithm, for example the algorithm described in Li / Randhawa.
  • the demosaicking algorithm for example the algorithm described in Li / Randhawa, the three-color Bayer pattern on which the algorithm described there is based is first reduced to a two-color chessboard pattern and the one color of the chessboard is reduced to the hi-detector data and the other color of the chessboard is assigned to the Lo detector data.
  • the demosaicking algorithm adapted to the checkerboard pattern is then applied accordingly to the two-dimensional hi / lo matrix rotated by 45 ° with the recorded real hi and lo detector data in order to calculate virtual detector data associated with a real detector data.
  • a fourth aspect of the present disclosure relates to a processing device for processing the Lo detector data L01, L02, L03, ..., LON and Hi detector data Hii, H12, H, ..., HIN provided by the X-ray inspection system of the second aspect , wherein the processing device is set up to carry out a method of the third aspect.
  • a fifth aspect of the present disclosure relates to a system consisting of an x-ray inspection system of the second aspect and the processing device of the fourth aspect, the x-ray inspection system being set up to provide the high and low detector data based on the scanning of an inspection object to the processing device and for this purpose with the Processing device is connected for a corresponding data communication.
  • a sixth aspect of the present disclosure relates to a computer program product that has software means for performing a method of the third aspect when the computer program is executed on a computer, such as the processing device of the fourth aspect. That is to say, a computer program product which comprises instructions which, when the computer program is executed by a computer, in particular a processing device (300) according to the fourth aspect, cause the computer to execute the method according to the third aspect.
  • a seventh aspect of the present disclosure relates to a computer-readable data carrier with a computer program product of the sixth aspect.
  • An eighth aspect of the present disclosure relates to a data stream with electronically readable control signals which can interact with a programmable computer in such a way that, when the computer executes the electronically readable control signals, the computer carries out a method of the third aspect. That is, a data carrier signal that the computer program product of the sixth aspect carries.
  • FIG. 1a is a simplified perspective illustration of the structure of a conventional dual-energy detector.
  • FIG. 1b is a cross-sectional view of the section through the xy plane of the detector of FIG. 1a.
  • FIG. 2a is a simplified perspective illustration of the structure of a first exemplary embodiment according to the first embodiment of the dual-energy X-ray detector proposed here.
  • FIG. 2b is a cross-sectional view of the section through the xy plane of the detector of FIG. 2a.
  • Figure 2c is a side view of a detector according to the first embodiment with the first and second detector rows spaced from one another.
  • FIG. 3 is a simplified perspective illustration of the structure of a second exemplary embodiment based on the second embodiment of the dual-energy X-ray detector proposed here.
  • FIG. 4 is a simplified perspective illustration of the structure of a third exemplary embodiment based on a combination of the first and the second embodiment of the dual-energy X-ray detector proposed here.
  • FIG. 5 is a side view of an inclined detector according to an exemplary embodiment of the third embodiment, in which an effective offset is achieved, as in the exemplary embodiment according to the first embodiment that is illustrated in FIG. 2c.
  • FIG. 6 is a simplified side view of an X-ray inspection system with a dual-energy X-ray detector proposed here, such as, for example, a detector from FIGS. 2a-5.
  • FIG. 7 illustrates the readout situations of the detector data with a detector of FIGS. 1a and 1b as reference (FIG. 7 above) and FIGS. 2a and 2b (or 5) according to the first embodiment (FIG. 7 below).
  • FIG. 8 illustrates the readout situations of the detector data with a detector of FIGS. 1a and 1b as reference (FIG. 8 above) and FIG. 3 with a dual-energy X-ray detector according to the second embodiment (FIG. 8 below).
  • FIG. 9 illustrates the readout situations of the detector data with a detector of FIGS. 1a and 1b as a reference (FIG. 9 above) and, like a readout situation similar to the representation shown in FIG Hi and Lo detector elements can be achieved (Fig. 9 below).
  • FIG. 10 illustrates the readout situations of the detector data with a detector of FIGS. 1a and 1b as a reference (FIG. 10 above) and FIG. 3 as a second reference (FIG. 10 middle) and additionally FIG Offset of the pixels in the z-direction corresponds to twice the offset of that shown in FIG.
  • FIGS. 11-13 illustrate an exemplary embodiment of an approach for processing the detector data acquired with a dual-energy X-ray detector proposed here, based on a demosaicing algorithm.
  • FIGS. 14-17 illustrate methods for processing and preparing real detector data acquired with the dual-energy X-ray detectors shown in FIGS. 1a-5 for the additional provision of required virtual detector data.
  • Dual-energy X-ray radiography is based on the fact that the attenuation coefficient is a material property of the material being irradiated.
  • the attenuation coefficient is a material property of the material being irradiated.
  • Organic materials largely have an atomic number of around 10 or less and metallic materials have an atomic number of over 10.
  • the materials in an inspection object can thus be classified and based on the determined effective atomic number for optical material discrimination, the pixels in a displayed X-ray image are colored accordingly.
  • This principle is used, for example, for the visual evaluation of X-ray images of baggage at airport control points, by providing the operating personnel with displayed X-ray images for optical material discrimination at inspection systems with predominantly organic compounds orange, with predominantly metallic material blue and a mixture of organic and metallic colored green.
  • FIGS. 1a to 6 should be preceded by the fact that an xyz coordinate system is plotted in the figures for orientation and mutual reference.
  • the longitudinal direction of the detector lines is always in the x-direction, while the direction of the X-rays RX (shown in simplified form as a bundle of arrows) incident on the detector elements in the y-direction and, when the detector lines are used, one of the The direction corresponding to the scanning direction runs orthogonally to the detector line in the z-direction.
  • the scanning direction usually corresponds to the transport direction TD of an inspection object past the detector line and through an X-ray inspection system (as shown in simplified form in FIG. 6). That is, the longitudinal direction (x-direction) of the detector proposed here is usually arranged transversely to the scanning direction (z-direction) in the application.
  • the representation of the detector used here is a simplification compared to the U- or L-shaped detector lines usually used in practice.
  • the detector line does not run exclusively in the transport plane of the inspection objects.
  • the legs of the detector line are always orthogonal to the X-rays he captured and also orthogonal to the transport or scanning direction z.
  • the considerations outlined here for an I-shaped detector line running only in the xz plane can be transferred without problems to the U- and L-shaped detector lines used in practice.
  • Figures 1a and 1b illustrate the structure of a conventional dual-energy X-ray detector 1 (hereinafter referred to as detector 1) in the form of a section from a detector line 2.
  • detector 1 a conventional dual-energy X-ray detector 1
  • Figure 1a is a simplified perspective view of the detector 1 and Figure 1b is, To illustrate the structure, a projection of a detector 1 from FIG. 1a onto the xy plane.
  • the detector line 2 consists of dual-energy detector elements 3 arranged next to one another; for the sake of clarity, only four such elements are shown, the number being in reality it is usually higher (e.g. 1,000).
  • Each detector element 3 consists of low-energy Lo (w) detector elements 4 and high-energy Hi (gh) detector elements 5, which are superimposed in a sandwich-like manner with respect to the X-ray radiation RX to be detected, with an intermediate filter layer 6 (e.g. made of copper) are arranged.
  • the Lo detector elements 4 generate Lo detector data, which are mainly due to low-energy X-rays RX
  • the Hi detector elements 5 generate Hi-detector data which are due to high-energy X-rays RX.
  • the detector 1 thus has at least two output channels: one on which the Hi detector data are provided, and one on which the Lo detector data are provided.
  • the effective area A4 of the Lo detector elements 4 and the effective area A5 of the Hi detector elements 5 are essentially the same size.
  • the effective surfaces of the Lo detector elements 4 and the Hi detector elements 5 have a length L in the direction of the row (i.e. longitudinal direction of the detector row 2) and a width W orthogonally to it.
  • the effective area of a detector element can be 0.8 mm (length L in the line direction) by 0.8 mm (width W transverse to the line direction).
  • a typical detector line can, for example, be 80 cm in total in the direction of the line, so that the line consists of approximately 1,000 detector elements. In principle, the dimensions of the detector elements in a technically meaningful range and the length of the detector line can be freely selected.
  • the detector line 2 is usually arranged transversely to a transport direction TD for an inspection object, so that the inspection object can be scanned line by line with the X-rays RX.
  • the detector 1 can in principle consist of several detector rows 2. That is, with the detector 1 of Figures 1a and 1b, by means of a single line-by-line scan of an inspection object, a low-energy X-ray image based on radiation with low-energy X-rays and a high-energy X-ray image based on radiation with high-energy X-rays can be captured at the same time.
  • FIG. 1b additionally illustrates the real Hi detector data Hii, Hh, H, .... HI N and Lo detector data L01, L02, L03, .... LON made available by means of the individual detector elements 4 and 5.
  • N for the respective position of the associated detector element in the detector row 2, where 1 ⁇ n ⁇ N and N is the number of detector elements of the associated type (Hi or Lo) in the row direction.
  • N 8
  • the detector line 2 consists of 8 Hi detector elements and Lo detector elements arranged along the detector line.
  • the usual read-out for providing the Hi and Lo detector data recorded with the detector 1 is illustrated in the left-hand part of FIGS. 6-8 in the direction of movement of the position variable n along the detector line and over time t.
  • FIGS. 2a-4 each show a specific exemplary embodiment of the dual-energy X-ray detector 100 proposed here, which essentially consists of a first detector line 110 with first detector elements 111 and a second detector line 120 with second detector elements 122 arranged parallel thereto.
  • the two detector rows 110 and 120 are configured to respond to a spectrum of the X-rays RX to be detected in a differently spectrally selective manner.
  • associated first detector elements 111 in the form of Lo detector elements for the primary detection of low-energy X-rays are arranged next to one another in the first detector line 110 and associated second detector elements 122 in the form of Hi-detector elements for the primary acquisition of high-energy X-rays are arranged next to one another.
  • the two detector lines 110 and 120 are arranged parallel to one another in the line direction and arranged one behind the other in the direction of the X-rays to be detected RX so that the detector lines 110 and 120 are offset from one another in an overlapping manner.
  • each Hi and each Lo detector element has the same length L and the same width W orthogonally to the line direction, i.e. the longitudinal direction of the detector 100.
  • the lengths LHI and Li_ 0 and the widths WH and W Lo the same size, ie the effective areas of the Hi and Lo detector elements 111 and 122 are the same size.
  • FIG. 2a shows a simplified perspective illustration of a first exemplary embodiment based on the first embodiment of the dual-energy X-ray detector 100 proposed here to illustrate the basic structure.
  • FIG. 2b is a cross-sectional view through the xy plane of a detector 100, as is shown in detail in FIG. 2a.
  • the first detector row 110 and the second detector row 120 are arranged offset from one another by a first offset Dc in the row direction.
  • FIG. 2b illustrates (similarly to FIG. 1b) the real Hi detector data Hii, HL, Hh, .... HI N and Lo detector data L01, L02, L03,. ... LON.
  • N 8 applies, ie the detector line consists of 8 Hi detector elements and Lo detector elements arranged along the detector line.
  • a Lo detector element 115 is shown, which provides a Lo detector data L0 4.
  • a virtual Lo detector data vLo # or Hi detector data vHi # can be calculated based on the mean value or median of neighboring Hi and / or Lo detector data.
  • the Hi detector data missing from the real detector data L0 4 which is recorded and provided by the Lo detector element 113, can be calculated as virtual Hi detector data vHL as follows:
  • the virtual Hi detector data vHL can be calculated.
  • the course of the values of the Lo detector data can be taken into account by means of the values L03, L04 and L05.
  • the values H and HU can be averaged and used as a base value for the virtual Hi detector data vHU.
  • This approach can also be used as the basis for a machine learning algorithm, e.g. a deep learning algorithm.
  • the detector rows 110 and 120 are offset in the row direction by the effective offset Dc in an overlapping manner.
  • the X-rays RX impinging on the detector 100 and passing through the detector elements run essentially orthogonally to the first and second detector rows 110, 120.
  • FIG. 3 shows an exemplary embodiment in accordance with the second embodiment of the dual-energy X-ray detector 100 proposed here.
  • the first detector line 110 and the second detector line 120 are now arranged orthogonally to the line direction offset from one another by a second offset Ay.
  • the provided detector data can be processed in a similar way as explained in FIGS. 2a and 2b by calculating an associated virtual detector data vLo # or vHi # for each real detector data Hi # or Lo #.
  • FIG. 5 is a side view of the conventional detector 1 from FIG. 1, as an example of the use of a conventional detector by means of an arrangement according to the third embodiment of the present disclosure to achieve an effective offset.
  • a desired effective offset between the Lo detector elements 4 and the Hi detector elements 5 - for example like that in the detector 100 of FIG. 2c - but can be achieved by means of the third embodiment of the present disclosure in that the detector line 2 is inclined by an angle a with respect to the incident X-rays RX.
  • FIG. 5 shows in a greatly simplified manner that the desired effective offset can be achieved solely by means of this inclined arrangement of a conventional detector line 2 with respect to the X-rays RX incident thereon, as is achieved, for example, in the exemplary embodiment for the first embodiment of FIG. 2c.
  • a normal N which runs through the centers of the two lines formed by the associated Hi and Lo detector elements, is entered in FIG.
  • a reference X-ray RXref of the X-rays RX incident on the detector 1 is plotted, which strikes the point of the detector 1 through which the normal N extends.
  • the angle of inclination a is thus formed between the normal N and the reference X-ray ray RXref.
  • the angle of inclination ⁇ is set in such a way that the desired effective offset Ax results between the Lo and Hi detector elements 4, 5.
  • the same offset is thus effectively achieved as in the corresponding exemplary embodiment of the first embodiment in FIG. 2c.
  • the principle of the third embodiment, which is thus illustrated in FIG. 5, can accordingly also be transferred to the second embodiment.
  • the third version can also be combined with the first and / or second version.
  • the effect of the combined first and second embodiment can also be achieved by means of the third embodiment alone.
  • FIG. 6 shows a system 400 which essentially consists of an X-ray inspection system 200 and a processing device 300.
  • the highly simplified X-ray inspection system 200 has radiation protection curtains 202, 204, one of which is arranged at an input 206 and an output 208 of a beam tunnel 210 of the X-ray inspection system 200.
  • a Strahlungsbe rich 212 within the radiation tunnel 210 with at least one radiation source 214, for example an X-ray tube with a collimator to generate an X-ray fan 215, which is aligned with the dual-energy X-ray detector 100 proposed here.
  • a transport device 218, for example a sliding belt conveyor is used, which conveys the inspection objects in the transport direction TD through the radiation region 212.
  • the cell-shaped detector 100 is L-shaped or U-shaped and is arranged with its longitudinal direction orthogonal to the transport direction TD, so that the transport direction TD corresponds to the scanning direction of the inspection object 216.
  • the processing device 300 is essentially set up to carry out at least one of the methods proposed here for processing the high and low detector data acquired with the dual energy x-ray detector proposed here.
  • the dual-energy X-ray detector 100 is, for example, one of the kind shown in simplified form in FIGS. 2a-5.
  • the detector data provided by the dual-energy x-ray detector 100 and processed by the processing device 300 can be used to generate an x-ray image of the inspection object 216 colored based on material classes, which is displayed to an operator on a screen (not shown) in a manner known per se will.
  • the processing device 300 can be part of a control device 220 of the X-ray inspection system 100.
  • the processing device 300 can in principle also be located completely separate from the X-ray inspection system 200, for example at a central location where the raw detector data from several inspection systems 200 converge and are processed there centrally. This makes no difference to the proposed measures for processing the detector data.
  • the processing unit 300 can also be part of the detector 100, so that the detector data generated by the detector 100 are already processed on the detector 100 in accordance with the measures proposed here.
  • the detector 100 proposed here can in principle be made compatible with existing X-ray inspection systems with conventional detector units. That is, as a result, with an X-ray inspection system that is otherwise sufficiently structurally identical, an embodiment of the new detector 100 proposed here with integrated processing of the detector data could be used with lower system costs with a constant image quality. Alternatively, the spatial resolution of an existing X-ray inspection system could be increased while the system costs remain almost the same.
  • FIGS. 2b and 7-10 a particularly preferred approach for processing the high and low detector data provided with a dual-energy x-ray detector 100 proposed here is now presented.
  • a wide variety of approaches are conceivable for calculating virtual detector data for the detector elements missing due to the offset.
  • the essential finding of the suggested improvement lies in the overlapping and mutually offset hi and lo detector elements of the dual-energy x-ray detector 100, as illustrated, for example, in FIGS. 2a-5.
  • FIG. 2b The task on which the preparation of the provided real hi and lo detector data is based is first illustrated using FIG. 2b.
  • the detector structure illustrated in FIG. 2a with mutually overlapping, offset Hi and Lo detector lines 110 and 120 leads to the problem that not every real Lo detector data, for example the Lo detector data L0 4 , exactly one Hi detector data - and vice versa - can be assigned.
  • the respective detector data of the other type belonging to a specific real detector data of the one type (Hi or Lo) must therefore be supplemented in a suitable manner as a virtual detector data by calculation or determined in some other way.
  • the virtual detector data vHL is shown in FIG. 2b.
  • a “real detector data” is understood here to mean an intensity value for measured x-rays that is actually detected with a specific detector element physically present on the detector 100.
  • a “virtual detector datum” is understood here to mean a virtual intensity value generated by calculation or otherwise for a detector element that is physically missing at a specific location on a detector 100.
  • the associated Hi detector datum can assume values from x to x + a, depending on the material irradiated through.
  • the difference a would be very small, i.e. the Hi detector data vHL and the Lo detector data L04 would be approximately identical.
  • the difference in a would be considerable. It is precisely this fact that is used - as explained above - for material detection by means of dual-energy radiography. That is to say, in order to be able to distinguish steel from plastic or aluminum at a location, the information from the Hi and Lo channels of the dual-energy X-ray detector 100 is required for this location. If the value of the associated Lo detector data could be inferred directly from a Hi detector datum, no two different spectrally selective measurements would be necessary.
  • the inventor has found that, instead of a real Lo or Hi detector data, the associated missing value can be determined as a virtual vLo or vHi detector data with sufficient accuracy. For practicality, it is desirable to achieve a result that is as close as possible to reality with as little computing power as possible.
  • a simple approach would be to calculate, for example, the missing real Hi detector data for the real Lo detector data L04 as the mean value of the two adjacent real Hi detector data HU and His. However, this simple approach does not achieve the required accuracy.
  • the inventor has further found that the course of the Hi detector data in the Hi channel and the course of the Lo detector data in the Lo channel of the detector 100 are similar. In other words, if the signal drops in the Hi channel, under real conditions it also drops in the Lo channel and vice versa. Depending on the irradiated material, stronger or less strong. This means that the course of the detector data in the Lo channel, i.e. the Lo detector line 110, can be used when determining the virtual Hi detector value vHU. For example, as mentioned elsewhere, a deep learning algorithm could be used that is trained to calculate the missing virtual high and low detector data.
  • FIGS. 7-10 the time sequence of a readout process on a greatly simplified dual-energy X-ray detector 100 (detector 100 for short) is shown in the left part of the figure, as shown, for example, in FIG. 2a and its Hi and Lo Detector lines each have only 4 associated real detector elements.
  • the real Hi detector elements are shown as empty / white circles and the real Lo detector elements as filled / black circles.
  • FIGS. 1a and 1b the readout situation for the conventional detector 1 is illustrated, which is shown in FIGS. 1a and 1b.
  • the Hi detector data Hin of the first Hi detector element is read out, followed by the Lo detector data Lon of the first Lo detector element; then the Hi detector data H ⁇ 21 of the second Hi detector element is read out, followed by the Lo detector data L021 of the second Lo detector element; etc. If the Lo detector data Lo ni of the last Lo detector element has been read out, the process starts again with the first Hi detector element and the Hi detector data H112 is read out there.
  • FIGS. 7-10 each shows a two-dimensional matrix M #, the fields of which are each assigned to the recorded real Hi and Lo detector data.
  • Each field of the matrix M # with the associated detector data corresponds to a respective pixel from one of the de- X-ray image to be derived from tector data. Therefore, the effect achieved by the proposed modification of the associated detector 100 on the spatial resolution of the X-ray image derived from the respective detector data can be seen directly from the matrix M # of the respective FIGS. 6-9.
  • the upper right half of each image with the matrix MO provided by means of the conventional detector 1 in FIGS. 1a and 1b serves as a reference for the matrices M6-M10 in FIGS. 7-10.
  • the read-out situation in the case of a detector 100 according to the first embodiment of FIGS. 2a and 2b is illustrated.
  • the Hi detector line is offset in an overlapping manner to the Lo detector line in the line direction and thus perpendicular to the transport direction TD (FIG. 6) by an offset Dc which corresponds to half a length L of a detector element.
  • the real high and low detector data are read out in the same order as for detector 1 (upper half of FIG. 7).
  • the readout situation in FIG. 7 shows that a Lo detector data and vice versa can no longer be assigned to every real Hi detector data.
  • FIG. 8 shows the readout situation for a detector 100 according to the second embodiment of FIG an offset Ay, which corresponds to half a width W of the detector elements, offset from one another in an overlapping manner. If the real Hi and Lo detector elements are read out sequentially in the same order as in FIG. 7, the readout situation illustrated in FIG. 8 arises.
  • the matrix M7 of FIG. 8 shows, however, that the spatial resolution in an x-ray image that can be derived from the detector data is improved, namely doubled, in the scanning direction (or in the transport direction TD, FIG. 6).
  • the readout situation in FIG. 8 is interesting if either the spatial resolution of the derived X-ray image increases in the scanning direction or in the transport direction (TD, FIG. 6) or, with the same resolution, the transport speed for the inspection objects through the X-ray inspection system increases with a corresponding setting of the ratio of readout frequency and belt speed shall be.
  • the spatial resolution in the scanning direction or orthogonal to the line direction of the detector can be increased by increasing the readout frequency f.
  • FIG. 9 a further clever consideration by the inventor is illustrated.
  • the inventor has recognized that a similar effect on the spatial resolution achieved (or, alternatively, the transport speed or scanning speed to be set), as practically hardware-wise with the second embodiment of the detector 100, also in an X-ray inspection system with a conventional detector 1, as shown in FIG 1a and 1b can be achieved by means of a modified readout pattern (ie readout sequence) for the Hi and Lo detector data on the conventional dual-energy X-ray detector 1 of FIGS. 1a and 1b.
  • a modified readout pattern ie readout sequence
  • the readout sequence on the detector 100 is modified so that first all detector elements of one type (Hi or Lo) along the position variable n of the detector line and then all detector elements of the other type along the position variable n of the detector line can be read out. That is to say, for example, as shown in FIG. 9, first all Hi detector data Hii, Hh, H, .... HIN, and then all Lo detector data L01, L02, I_q3, .... LO N read out (or vice versa).
  • the comparison of the matrices M7 and M8 shows that with the modified readout sequence of Figure 9, the same result can be achieved as is achieved with the displacement of the first detector line 110 and the second detector line 120 to each other in the detector 100 according to the second embodiment.
  • the readout method of FIG. 9 is thus an equivalent software solution to the hardware solution of FIGS. 3 and 8, with high and low detector elements offset from one another in an overlapping manner.
  • the Hi and Lo detector lines 110, 120 on the detector are not offset from one another in the scanning direction, but the readout order of the Hi and Lo detector elements is appropriately changed, the same effect on the spatial resolution is obtained achieved as with the detector line 100 of FIGS. 3 and 8.
  • the spatial resolution in the transport direction or the scanning direction is also improved in this case.
  • the read-out situation in FIG. 9 is elegant, since essentially no modifications to a conventional detector 1 (cf. FIGS. 1a and 1b) are required. In order to implement the modified chronological readout sequence, a redesign of the circuit board of the detector 1 or a redesign of the readout chip could be necessary. If a readout chip connected to the detector 1 is able to internally change the time sequence of the readings of the individual real hi and lo detector elements as required, the readout situation in FIG. 9 can be implemented without major measures.
  • An offset Az (mb) / (2 f) can be calculated for a specific pair of values (bi, T), which leads to a situation as shown in the middle of FIG. 10 and in which missing values have to be calculated. Since X-ray systems are often integrated into a complex system of conveyor systems, it can sometimes be desirable to adapt the belt speed to these framework conditions.
  • the inventor has recognized that the structure of the matrices M6-M10, which are provided with the detectors 100 proposed here (FIGS. 2a-6, and 7-8) or the modified readout method (FIG. 9), with regard to the hi and Lo-detector data can possibly be processed similarly to the processing of the image data captured with an image sensor with Bayer-CFA.
  • the two different color information items must be supplemented by a suitable calculation for each pixel.
  • a virtual detector data of the other type must be calculated for the real detector data of one type (Hi or Lo).
  • the inventor proposes to modify a CFA demosaicing used in digital image sensors for processing the real detector data of the detectors 100 proposed here. Since there are numerous known implementations for CFA demosaicing, the basic principle of adaptation should be sufficient here to explain. Namely, the present disclosure is in no way limited to any particular single or particular implementation.
  • CFA demosaicing The core idea of CFA demosaicing is to calculate the two missing colors for each pixel of a Bayer pattern from the known, actually recorded colors in the immediate vicinity.
  • FIG. 11 initially shows a comparison of the Bayer pattern BAYER (FIG. 11, left) with the Hi / Lo detector data matrix M6 * (FIG. 11, right), as it is, for example, in the readout situation of FIG. 7 with the detector of Figures 2a and 2b results.
  • the Bayer pattern BAYER (FIG. 11, left)
  • the white boxes stand for blue pixels
  • the hatched boxes for green pixels and the crosshatched boxes for red pixels.
  • the matrix M6 * FIG. 11, right
  • the Lo detector data are shown by hatched boxes
  • the Hi detector data are shown by crosshatched boxes.
  • FIG. 13 compared to FIG. 12, only the matrix BAYER * was rotated 45 ° clockwise in order to illustrate a suitable assignment of the data of the matrix M6 * to the data of the modified Bayer pattern BAYER **.
  • FIG. 13 further illustrates that the modified Bayer pattern BAYER ** and the matrix M6 * have a similar, alternating structure.
  • the pixels in the marked areas in the modified Bayer pattern BAYER ** can be assigned to the detector data in the marked areas of the matrix M6 *.
  • the CFA demosaicing algorithm for the Bayer pattern can be applied to the detector data of the matrix M6 *.
  • the inventor has found that the results are somewhat worse because the detector data are further apart in the horizontal and vertical directions than the pixels in the Bayer pattern. However, this can be compensated for by the fact that the vertical detector data series can still be viewed with the M6 * matrix, which does not exist with the Bayer BAYER ** sample.
  • an interpolated value for the missing pixel is determined for a certain number of spatial directions, based on a Taylor series development of the measured data in the immediate vicinity.
  • a gradient is then calculated for each of these spatial directions, which is a measure of how much the signal changes in the respective direction.
  • the weighted mean value is formed from all interpolated values in a final step.
  • the matrices of the detector data provided by the detectors 100 proposed here deliver surprisingly good results with an unexpectedly low computational effort.
  • FIGS. 14-17 illustrate various aspects of the method proposed here for processing the real Lo and Hi detector data that have been detected by an inspection object by means of one of the detectors 100 described here.
  • FIG. 14 illustrates the basic structure of a method 1300 for processing the Lo detector data L01, L02, L03, ..., LO N and Hi detector data Hii, H12, H, ..., HI provided by, for example, the X-ray inspection system 200 of FIG N
  • the method has the following basic steps: a step S1 for calculating a respective virtual Lo detector data vLo at the position of a real Hi detector element 122 (see, for example, FIG. 2b); and a step S2 for calculating a respective virtual Hi detector data vHi at the position of a real Lo detector element 111 (cf., for example, FIG. 2b).
  • the step S1 for calculating a virtual Lo detector data vLo at the position of a real hi detector element 122 has: a step S11 for calculating the virtual Lo detector data based on a specific first number Real Lo detector data adjacent to the real Hi detector element 122 and a specific second number of real Hi detector data adjacent to the real Hi detector element 122.
  • the step S2 for calculating a virtual Hi detector data vHi at the position of a real Lo detector element 111 has: A step S21 for calculating a virtual Hi detector data based on the determined first number of the real Lo- Detector element 111 adjacent real Hi detector data and the determined second number to the real Lo detector element 111 adjacent real Lo detector data.
  • Step S11 has a step S12 for calculating the virtual Lo detector data as a mean value from neighboring Hi and Lo detector data.
  • Step S21 has a step S22 for calculating the virtual Hi detector data as a mean value from neighboring Hi and Lo detector data.
  • FIG. 15 illustrates a modified method 1400, with step S1 a step S14 for calculating the virtual Lo detector data taking into account the course of the values of the Hi detector data and step S2 a step S24 for calculating the virtual Hi detector data taking into account the course which has values of the Lo detector data.
  • the mentioned calculation steps for the virtual Hi or Lo detector data can be implemented based on the Lo and Hi detector data provided using a deep learning algorithm (DLA)
  • DLA deep learning algorithm
  • FIG. 16 illustrates a method 1500 as a special embodiment of the method 1300 of FIG. 14.
  • the Lo detector elements detect real Lo detector data L01, L02, ..., Lo n , ..., LO N of the inspection object and the Hi detector elements detect corresponding real Hi detector data Hii, H12, ..., Hin, ..., HIN of the inspection object, where 1 ⁇ n ⁇ N and N is the number of Hi and Lo detector elements in the row direction of the dual energy X-ray detector (100).
  • the method 1500 of FIG. 15 has the following steps:
  • a step S33 for calculating the virtual hi and / or lo detector data using an adapted demosaicking algorithm consist of the following steps:
  • the required virtual (i.e. missing) detector data is calculated by means of the adapted demosaicking algorithm in a similar way to that for a photo sensor chip with BAYER color filter, which can be calculated for the other two basic colors missing for a certain pixel.
  • FIG. 17 illustrates a readout method 1600 for reading out Hi and Lo detector elements of a dual-energy X-ray detector 1, as shown, for example, in FIG. 1b and, for example, can be installed in an X-ray inspection system 200 of FIG.
  • the dual-energy X-ray detector 1 has at least: a dual-energy X-ray detector line 2 with a high-energy Hi detector element 5 and a low-energy Lo detector element 4 per pixel, which are essentially congruent in the direction of the X-rays to be detected RX over- which are arranged.
  • the readout method 1600 of FIG. 17 essentially comprises a step S4 for reading out the Hi and Lo detector elements, in which all detector elements of one type, i. E.

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Abstract

L'invention se rapporte à un détecteur de rayons X à double énergie (100) comprenant un premier réseau de détecteurs (110) doté de premiers éléments détecteurs (111) et un second réseau de détecteurs (120) disposé parallèlement au premier réseau et doté de seconds éléments détecteurs (122). Les réseaux de détecteurs (110, 120) sont disposés parallèlement les uns par rapport aux autres dans la direction de réseau et sont disposés les uns derrière les autres dans la direction des rayons X (RX) à détecter, de telle sorte que les projections des premier et second réseaux de détecteurs (110, 120) dans la direction de l'un des rayons X (RX) à détecter, ledit rayon X passant à travers le centroïde de la zone d'un élément détecteur de référence du premier ou du second réseau de détecteurs (110, 120), se chevauchent et soient décalées selon un décalage effectif (Δx ; Δy). En outre, l'invention se rapporte à un système d'inspection à rayons X (200) doté dudit détecteur (100) et à des procédés de traitement de données de détecteur fournies au moyen du détecteur (100).
EP21739112.7A 2020-07-02 2021-07-01 Détecteur à double énergie et procédés de traitement de données de détecteur Pending EP4176290A1 (fr)

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DE102020117484.5A DE102020117484A1 (de) 2020-07-02 2020-07-02 Dual-energie-detektor und aufbereitungsverfahren für detektordaten
PCT/EP2021/068274 WO2022003141A1 (fr) 2020-07-02 2021-07-01 Détecteur à double énergie et procédés de traitement de données de détecteur

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WO2024013671A1 (fr) * 2022-07-15 2024-01-18 Raytec Vision S.P.A. Installation et procédé d'inspection de produits
CN116735631B (zh) * 2023-08-09 2024-02-23 同源微（北京）半导体技术有限公司 一种x射线成像检测单元、模块和装置

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US3971065A (en) 1975-03-05 1976-07-20 Eastman Kodak Company Color imaging array
EP0176314B1 (fr) * 1984-09-21 1992-06-10 Picker International, Inc. Appareil de radiographie
WO1997042877A1 (fr) * 1996-05-13 1997-11-20 University Of Massachusetts Medical Center Systeme d'imagerie radiographique quantitative
AU8759898A (en) 1997-08-06 1999-03-01 Eg&G Astrophysics Side-by-side detector array for dual energy x-ray imaging system
GB0803640D0 (en) 2008-02-28 2008-04-02 Rapiscan Security Products Inc Scanning systems
JP5467830B2 (ja) 2009-09-18 2014-04-09 浜松ホトニクス株式会社 放射線検出装置
US10067239B2 (en) * 2012-05-31 2018-09-04 Minnesota Imaging And Engineering Llc Detector systems for radiation imaging
CN106483153A (zh) 2016-12-23 2017-03-08 同方威视技术股份有限公司 双能探测器及辐射检查系统
CN110034136B (zh) 2017-12-08 2022-12-16 X-Scan映像股份有限公司 基于集成并排式像素阵列传感器的多能量x射线检测器
US10191160B1 (en) * 2018-08-31 2019-01-29 David Edward Newman Staggered detector array for locating radioactive sources

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