EP4260099A1

EP4260099A1 - X-ray detector having increased resolution, arrangement, and corresponding methods

Info

Publication number: EP4260099A1
Application number: EP21839025.0A
Authority: EP
Inventors: Philipp Fischer; Geert Heilmann
Original assignee: Smiths Detection Germany GmbH
Current assignee: Smiths Detection Germany GmbH
Priority date: 2020-12-08
Filing date: 2021-12-08
Publication date: 2023-10-18
Also published as: CN117280250A; WO2022122824A1; US20240219323A1; DE102020132705A1

Abstract

The invention relates to an arrangement (10) consisting of an X-ray detector (20) and a shielding element (30) that shields X-rays (RX) and is intended for increasing the spatial resolution of the X-ray detector (20), wherein the X-ray detector (20) comprises at least one detector array (22) having at least one detector element (24) which is arranged along the detector array (22), the shielding element (30) comprises one or more regions (31) that are opaque to X-rays (RX) and at least one region (32) that is transparent to X-rays (RX), the shielding element (30) is arranged above the reception surface (23) for the X-rays (RX) of the at least one detector element (24), and the shielding element (30) and the at least one detector element (24) are movable relative to one another such that the effective reception surface for X-rays (RX) of the at least one detector element (24) can be changed accordingly. The invention also relates to an X-ray inspection system (100) comprising the arrangement (10), as well as to methods for increasing the spatial resolution of the X-ray detector (20) arranged in the arrangement (10), and to a processing apparatus (300) for carrying out the methods, and to a system (400) consisting of the X-ray inspection system (100) and the processing apparatus (300).

Description

X-ray detector with increased resolution, arrangement and method therefor

technical field

The disclosure relates generally to an improvement in terms of increasing the spatial resolution of an X-ray detector in imaging non-destructive inspection of objects to find targets using X-ray radiography, and more particularly to an arrangement and a method for increasing the spatial resolution of an X-ray detector.

background

The following introductory background information on the present disclosure is only intended to provide a better understanding of the relationships described below and only represents the prior art to the extent of the content of a named document that was publicly available at the time of filing.

It is known to scan an object to be inspected non-destructively (inspection object) line by line using electromagnetic radiation emitted by a radiation source, with the intensities of the radiation not absorbed by the inspection object being recorded by a detector arrangement assigned to the radiation source and then using known algorithms in a computer Generation of an X-ray image of the object are evaluated.

In X-ray inspection systems, in which an inspection object is passed through the X-ray fan at a predetermined transport speed through a scanning arrangement, which consists of a detector line arranged transversely to the transport direction and an X-ray fan directed onto the detector line, for line-by-line scanning of the inspection object, is the (physical) resolution of an X-ray image generated is essentially determined by the area of the individual detector elements, each corresponding to a picture point (pixel), and their number per unit length or per unit area of the detector line, as well as the ratio of the transport speed of the inspection object in the transport direction and the readout frequency of the detector elements.

The conventional x-ray inspection systems have two-dimensional x-ray detectors with a spatial resolution that is limited by a pixel size in the range of 0.6 to 1.2 mm. In this case, for example, 800 pixels are arranged on a detector line; the detector line can consist of several sections, each of which is formed by an associated detector unit. Small details of an X-ray image can only be perceived as blurred due to the spatial size of the image point. In particular, very fine structures, such as thin wires, can hardly be resolved and are therefore difficult to recognize.

In order to obtain a higher spatial resolution transversely to the transport direction (in the sense of higher than the physical resolution of the detector) in the X-ray image generated, one could increase the number of Increase detector elements per unit length or area accordingly. However, this results in a corresponding increase in system cost for the detector and, since increasing the density of detector elements requires a corresponding reduction in the area of each detector element, a degradation in the signal-to-noise ratio of the detected detector data.

Regardless of the spatial resolution transverse to the transport direction, the spatial resolution of the x-ray image in the scanning direction corresponding to the transport direction could be achieved by a reduced transport speed and/or an increased readout frequency. The first has a negative effect on the throughput of the inspection objects checked on the X-ray inspection system, the second again worsens the signal-to-noise ratio.

JP 2007-215929 A1 shows a medical X-ray device with a moveable bucky grid over the detector. The bucky grating is moved alternately in a first direction and in a second direction opposite to the first direction, ensuring that the position at which the speed of movement of the grating becomes zero, i.e. the reversal point of the movement, is always at a different position to avoid image distortions due to the grid in the position of the reversal point. An arrangement for the same purpose is shown in FR 2 869 789 A1, which also relates to a medical X-ray device, wherein at least two Bucky disks, consisting of a circumferential sequence of alternating X-ray opaque sectors and X-ray transparent sectors, coaxial with the focal length of the X-ray radiation, positioned between the X-ray source and a patient and between the X-ray table and the detector in the beam path, respectively, and rotated about its axis in a synchronized manner will.

US 2009/0285353 A shows an X-ray device called array CT scanning system for scanning objects with multiple X-ray fans. A conveyor belt is configured to transport baggage as inspection objects through a tunnel. A plurality of x-ray sources are provided and configured to irradiate the tunnel with different x-ray fans, each having detectors positioned to detect the fan beams. An image processing system is configured to generate 3D images of a scanned inspection object by interpolating the scan data depending on the information received from the detectors. An operator can manipulate the image data and rotate the inspection object in order to recognize objects located therein.

Summary of Revelation

It is a possible task, the spatial resolution of an X-ray detector in terms of a

Increasing the resolution compared to the physical resolution of the X-ray detector improve without having to increase the number of detector elements of the detector per unit length or area.

For example, it would be an improvement for an X-ray detector (hereinafter referred to as "detector") if, with the same number of detector elements, an X-ray image with a higher spatial resolution in the image direction orthogonal to and/or along the scanning direction could be produced from the detector data acquired with the detector can be derived.

The above object can be achieved with the features of independent claim 1 relating to an arrangement for increasing the spatial resolution of an X-ray detector. Further exemplary embodiments and developments are defined in the dependent claims.

The following explanations should be preceded by the fact that even if X-rays are always mentioned within the scope of the present disclosure and the individual embodiments explained thereto, these only serve as an example for electromagnetic or ionizing radiation; i.e. it is clear to the person skilled in the art that the principles presented here can also be applied to radiation other than X-ray radiation.

The inventors have recognized that a change over time in the effective receiving area of a detector element for X-rays and a corresponding scanning (reading) of these receiving areas, which are different from one another, can be advantageously used to improve the spatial resolution. The inventors have found that the spatial resolution of the detector can thus be increased in the direction of the detector row and/or orthogonally to the detector row without increasing the total number of detector elements.

The core idea of the solution proposed here consists in the minimal design in an arrangement of a detector element and an associated shielding element, by means of which the effective receiving surface of the detector element for X-rays is shielded by the shielding element shielding the X-rays by a time-varying shadowing (e.g. through absorption or reflection) of the receiving surface can be changed. The effective spatial resolution of the detector element can thus be increased. In particular, the shielding element is designed in such a way that it can be used to change the effective receiving area of the detector element for incident X-rays; the shielding element thus has the function of a dynamic screen.

According to a first aspect, an arrangement of an X-ray detector and an X-ray shielding shielding element for use in an X-ray inspection system (for example one according to the second aspect described below) that is set up for carrying out a method for X-ray radiography of an inspection object is provided. In this case, the X-ray detector has at least one detector line with at least one (preferably a large number of) detector element(s) arranged along the detector line.

It should be noted that the detector row can also consist of several sections, each consisting of a corresponding sub-detector row.

In connection with the arrangement proposed here, “line-shaped” is initially understood to mean that the detector is used to acquire detector data for a large number of pixels in the longitudinal direction of the detector (i.e. orthogonally to the scanning or transport direction of the inspection object) and for a smaller number of pixels , but at least for one pixel, is set up orthogonally to the longitudinal direction (i.e. in the scanning or transport direction of the inspection object).

In the simplest embodiment, the detector thus has a line with a certain number N of detector elements in the longitudinal direction of the line (e.g. N=n) and has a number M=1 orthogonal to the line, i.e. exactly one single detector element is wide. That is, the detector line is a special case of a detector matrix with NxM detector elements, where N=n and M=1.

In principle, the detector can also have more than one detector element in the direction orthogonal to the longitudinal direction (i.e. in the scanning direction or transport direction of the inspection object) with M>1, i.e. the detector is then a detector matrix with NxM detector elements. The principles proposed here using a detector line (N=n and M=1) can be used correspondingly for a matrix detector (N=n and M=m with m<>1) and can further increase the spatial resolution there.

The shielding element is arranged (in the direction of an incident X-ray beam) in front of the X-ray receiving surface of the at least one detector element and has one or more X-ray opaque areas and at least one X-ray transparent area. A region impermeable to X-rays can be achieved, for example, by the material of the shielding element absorbing and/or reflecting incident X-rays.

In the arrangement proposed here, the shielding element and the at least one detector element can be moved relative to one another, so that the effective receiving area for the X-rays of the at least one detector element can be changed accordingly over time. As a result, the shielding element, together with the relative movement, acts as a dynamic aperture for the detector element.

With the arrangement according to the first aspect, the shielded area of the receiving surface of the detector element and thus the active (effective) receiving surface of the detector element can be changed over time, so that scanning different areas of the surface of the same detector element is possible. Since the intended time-varying shading effective receiving area of the detector element is smaller than the actual maximum receiving area of the detector element, the resolution that can be achieved with the detector element increases accordingly.

Theoretically, almost any resolution of the X-ray detector can be achieved with the proposed arrangement by coordinating the readout frequency of the detector element, the relative movement between the detector element and the shielding element, and the movement of the inspection object.

The "(maximum) reception area" is understood here to mean the maximum area of a detector element on which the X-rays impinge and generate an associated irradiance there, from which an intensity value associated with the received X-rays can be determined by measurement or calculation.

The “effective receiving surface” of a detector element is understood here to mean the surface of the detector element on which the X-rays to be detected, which have passed through the inspection object, are incident in the proposed arrangement due to the shading caused by the shielding element. In other words, the “effective reception area” of the detector element corresponds to the partial area of the (maximum) reception area that is currently not shielded by the shielding element. Therefore, the “effective receiving area” can be less than or equal to the (maximum) receiving area of the detector element.

It goes without saying that a "relative movement" between the shielding element and the at least one detector element can be achieved in various ways, for example by the shielding element being stationary and the detector being moved, or by the shielding element being moved and the detector being stationary, or by moving both the shielding element and the detector relative to each other.

In the intended arrangement when scanning an inspection object with X-rays, the detector of the arrangement proposed here of the first aspect with the line direction is preferably arranged orthogonally to the scanning direction of the inspection object so that the inspection object can be scanned line by line. It is preferred that there is no movement of the inspection object in the direction of the increase in resolution that is brought about.

The shielding element can have one or more areas that are opaque to X-rays (hereinafter referred to as “opaque area”) and one or more areas that are transparent to X-rays (hereinafter referred to as “transparent area”). The shielding element thus exhibits at least one alternation between at least one impermeable area and at least one permeable area. According to the overlap of permeable area and receiving surface of the detector element, it is possible for the X-rays to pass through to the detector element and thus a corresponding detection of incident X-rays is possible.

In principle, the permeable area(s) of the shielding element can have any desired shape and size. For example, the shielding element can have a regular or an irregular pattern, which is formed by the permeable and impermeable areas. For example, an irregular pattern could be a random pattern.

At any point in time, the intersection of the shape and size of the transparent area of the shielding element and the shape and size of the receiving area of the detector element together determine the current effective receiving area of the detector element.

Preferably, the opaque portion(s) of the shielding member is made of a material which is opaque to, i.e. absorbs, X-rays. For example, an impermeable area may be made of a higher density material such as metals such as lead.

In the simplest embodiment, the permeable area(s) can be a recess in the impermeable area of the shielding element. As already described above, the shielding element can have a single recess or a plurality of recesses.

If the shielding element has a plurality of recesses, these can all have the same shape or also different shapes; that is, the cavities may all be the same or of different sizes and shapes. The multiple recesses can be arranged regularly or irregularly on the shielding element. In other words, a plurality of recesses on the shielding element can form a regular or irregular (for example random) recess pattern.

As an alternative to a material recess, a permeable area on the shielding element can consist of a material permeable to X-rays. For example, a low density material such as plastic, glass or wood could be used for this.

For example, one or more material recesses in the shielding element can be filled with an X-ray transparent material. In this case, the shielding element consists of a compact composite material with at least two different materials, one material being transparent to X-rays and the other material being opaque to X-rays.

The shielding element itself can have almost any geometric shape. In any case, the shielding element should be relative to the detector and thus to the detector elements can be arranged that by means of a defined relative movement between the detector and the shielding a corresponding time-defined change in the effective receiving area of the detector element can be achieved.

For example, the X-ray opaque portion of the shielding member may be comb-shaped, i.e. in the form of a comb having a longitudinal portion on which a number of regular or irregular teeth are arranged. The gap between the prongs then corresponds to the X-ray permeable area(s) of the shielding element. When this comb-shaped shielding element is placed with its longitudinal direction in the direction of the row direction of the detector with the tines above the detector, the tines of the comb form the impermeable areas and the gaps between the tines form the transmissive areas of the shielding element.

Alternatively, the shielding element may be disc-shaped, i.e. in the form of a disc having an outer peripheral portion which may be provided with tines similar to the portion of the comb referred to above, the tines being directed substantially radially outwards from the center of rotation of the disc. For this purpose, a disk-shaped shielding element can have a plurality of marginal permeable areas in the form of recesses which are arranged uniformly or unevenly along the circumference of the disk, ie at the edge. For example, the shielding element could be a coding disk or a spiral disk.

Alternatively, the shielding element may be band-shaped, i.e. in the form of a band. One or more transmissive areas can be arranged as recesses in the belt along the longitudinal direction of the belt. Here, too, the permeable areas can always have the same shape or different shapes and can be arranged regularly or irregularly in the longitudinal direction of the belt.

Alternatively, the shielding element may be tubular, i.e. in the form of a tube. The tubular shielding element can be arranged to encompass the row of detectors in its longitudinal direction. Similar to the band-shaped shielding element, one or more permeable areas with the same or different shape can be arranged in the casing of the pipe. Alternatively, a permeable area can also run spirally around the pipe in the longitudinal direction in the pipe jacket. For example, the tube can be cylindrical in the simplest case, but any other tube cross-sections are also possible.

The relative movement between the shielding element and the detector can be achieved by rotation, translation and/or a combination of rotational and translational movement of the shielding element and/or the detector. The relative movement between the shielding element and the detector can be a periodic movement, for example an oscillating movement.

For example, the above-mentioned comb-shaped shielding element can be arranged in a plane defined by the teeth of the comb, parallel to the receiving surfaces of the detector elements of the detector and can be reversibly shifted between two end positions. The relative movement between a first end position and a second end position can be an oscillating movement. As a result, the effective receiving area of the detector elements is changed cyclically.

For example, the above-mentioned disc-shaped shielding element can be arranged to rotate about an axis orthogonal to the receiving surfaces of the detector elements of the detector or to oscillate over a certain angular range relative to the detector.

For example, the above-mentioned tubular shielding element can be arranged to rotate about an axis parallel to the longitudinal axis of the detector or, alternatively, to oscillate over a certain angular range relative to the detector.

The way in which the relative movement between the shielding element and the detector is configured, in particular with regard to the movement speed, determines the dynamic change in the effective receiving area of the detector elements of the detector that is caused thereby.

The transmissive portion of the shielding element may have a graded profile with respect to a detector element and the configured relative motion between shielding element and detector.

The feature "stepped profile" is understood here in relation to the configured relative movement in which the transmissive region for a particular detector element is configured such that when the shielding element and the at least one detector element are moved relative to one another, the effective X-ray receiving area of the at least one Detector element can be changed accordingly in predetermined stages.

Based on each corresponding step, the associated detector element is partially shielded or exposed to X-rays, with the effective receiving area being stepwise variable by a specified percentage. For example, the profile of the transmissive region can be stair-stepped with regular or irregular steps.

For example, the stair shape can have four equal steps, so that the effective reception area can be changed by 20% each time, from 0% permeability through 20%, 40% and 60% to 80% in succession. A state in which the detector is completely covered or shielded is also possible. An irregular graduation would also be conceivable. In order to enable the relative movement between the shielding element and the at least one detector element, the shielding element can be coupled to a first actuator and/or the detector line can be coupled to a second actuator. Mechatronic drive elements can be used as actuators, for example piezoelectric crystal actuators or electromagnetic actuators.

To generate the relative movement, the first actuator and/or the second actuator can be coupled to a control unit, which controls both actuators or one of the actuators accordingly.

The shielding element can also be designed in such a way that it can be moved from its shielding position to a storage position or parking position, so that the detector elements are no longer shielded. This position of the shielding element can be used to enable conventional X-ray inspection of an inspection object, i.e. with a low resolution but with a higher scanning speed.

A second aspect provides an X-ray inspection system with the arrangement according to the first aspect.

The x-ray inspection system is set up for transporting an inspection object in a transport direction through the x-ray inspection system. The line direction of the detector is preferably arranged orthogonally to the transport direction, i.e. the scanning direction of the inspection object, so that the transport direction corresponds to the scanning direction for the inspection object. The x-ray inspection system is configured to provide intensity values for x-rays of the respective effective receiving area for x-rays of the at least one detector element for different times when scanning an inspection object.

With the X-ray inspection system of the second aspect, imaging X-ray radiography can be performed for non-destructive inspection of the inspection object. The intensity values provided are based on the detection of the X-rays penetrating the inspection object with the detector of the arrangement of the first aspect.

A third aspect of the present disclosure relates to a method for increasing the spatial resolution of an x-ray detector with at least one detector line with at least one detector element. In particular, the at least one detector element and a shielding element arranged above the X-ray receiving surface of the at least one detector element are movable relative to one another, whereby the effective X-ray receiving surface of the at least one detector element can be changed. Preferably uses the method of the third aspect the arrangement of the first aspect in an X-ray inspection system of the second aspect. The method of the third aspect has the following steps:

A first step with a first reading of the at least one detector element at a first point in time t, during which a first effective area of the at least one detector element was irradiated by X-rays.

A second step of reading out the at least one detector element a second time at a second point in time t+1 during which a second effective area of the at least one detector element was irradiated by X-rays.

A third step of calculating associated X-ray intensity values for the first effective area at the first point in time t and the second effective area at the second point in time t+1.

If a permeable area of the shielding element is designed in such a way that it is already small enough, i.e. has the desired partial detector element size, the intensity values read out correspond directly to these desired effective active areas (i.e. partial areas) of the detector element for the desired increased resolution.

If required, the size of the partial detector elements can additionally or alternatively be further reduced by determining intensity values for virtual small effective areas, which are determined as intermediate values between successive readings of the detector elements. For this purpose, the method can have a further, i.e. fourth, step, in which the intensity values calculated in the third step (chronologically consecutive) are subtracted in order to obtain a virtual intensity value of the X-ray radiation for a partial area of the at least one detector element based on the subtraction in the third step to determine. As a result, by means of the fourth step, an additional intensity signal for a virtual (smaller) pixel can be determined by the above-mentioned subtraction of the detected intensities from the real intensity values of the two consecutive sampling times t and t+1. The second area and the first area should overlap or overlap at least in a partial area.

The change in the relative arrangement between the shielding element and the at least one detector element can be synchronized with the reading and exposure of the associated detector element to x-rays. This is particularly advantageous when the permeable area of the shielding element has a stepped profile.

The exposure of a detector element requires a specific exposure time. Two movements take place during this exposure time: The relative movement between the detector (element) and the shielding element and the movement of the inspection object to be scanned on the Detector aligned X-ray fan. Ideally, these two movements are negligible (slow) compared to the exposure time. Movements that are too fast could lead to blurring in the fluoroscopy image derived from the intensity data. With slow relative movement and slow object movement or high sampling frequency, this problem is negligible.

In order to reduce a negative effect of the relative movement, even with longer exposure times, the above-mentioned shielding element with stepped, profiled passage areas has proven itself. The effective exposure areas of the detector elements to be exposed are kept constant over a long period of time and then changed by a predetermined step within a short period of time (i.e. like a step function). The X-ray exposure can then be synchronized with the phases in which the effective exposure area of the detector element is constant. As a result, possibly only a movement of the inspection object then remains as a negative effect.

A fourth aspect relates to a processing device for preparing the intensity values provided by the x-ray inspection system of the second aspect, the processing device being set up to carry out the method of the third aspect. In a specific embodiment, the processing device can be integrated into the arrangement of detector and shielding element, so that the detector data provided by the detector corresponds to that of a detector with a correspondingly higher physical resolution. Alternatively, the processing device can also be integrated into a control unit of an X-ray inspection system, so that the detector or image data supplied by the system for evaluation also already have the higher spatial resolution.

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 intensity values based on the scanning of an inspection object to the processing device and to the processing device for corresponding data communication connected is.

A sixth aspect of the present disclosure relates to a computer program product or a data carrier with the computer program product, the computer program product having a computer program and the software means for performing a method of the third aspect when the computer program is run on a computer, such as the processing device of the fourth aspect .

A seventh aspect of the present disclosure relates to a data stream with electronically readable

Control signals that can interact with a programmable computer in such a way that when the computer executes the electronically readable control signals, the computer executes a method of the third aspect.

Brief description of the drawing figures

Further advantages, features and details of the solution(s) proposed here arise from the following description, in which exemplary embodiments are described in detail with reference to drawings. The features mentioned in the claims and in the description can each be essential individually or in any combination. Likewise, the features mentioned above and those further explained here can each be used individually or together in any combination. Parts or components that are functionally similar or identical are sometimes provided with the same reference symbols. The terms “left”, “right”, “above” and “below” used in the description of the exemplary embodiments refer to the drawings in an orientation with a normally legible figure designation or normally legible reference symbols. The embodiments shown and described are not to be understood as final, but have an exemplary character to explain the solution proposed here. The detailed description is provided for the convenience of those skilled in the art, and therefore well-known structures and methods are not shown or discussed in detail in the description to avoid obscuring the understanding of the description.

FIG. 1a is a simplified perspective representation of the structure of an arrangement for increasing the spatial resolution of an X-ray detector by means of a dynamically variable aperture.

Figure 1b is a cross-sectional view through the xy plane of the assembly of Figure 1a.

Figure 1c is a functional block diagram of the arrangement for increasing the spatial resolution of the X-ray detector of Figures 1a and 1b.

Figure 2 is a simplified perspective view of the structure of an embodiment of the arrangement proposed here.

FIG. 3a is a simplified perspective representation of the structure of a further exemplary embodiment of the arrangement proposed here.

FIG. 3b illustrates a detail of the representation of FIG. 3b.

FIG. 3c is a simplified representation for the determination of a virtual intensity value of the X-ray radiation of a partial area of a detector element in the exemplary embodiment in FIG. 3a.

FIG. 4 is a simplified perspective illustration of the structure of a further exemplary embodiment of the arrangement proposed here.

FIG. 5 is a simplified perspective illustration of the structure of a further exemplary embodiment of the arrangement proposed here.

FIG. 6 is a simplified perspective illustration of the structure of a further exemplary embodiment of the arrangement proposed here.

FIG. 7a is a simplified perspective representation of the structure of a further exemplary embodiment of the arrangement proposed here.

FIG. 7b is a simplified representation of the determination of a virtual intensity value of detected X-ray radiation of a partial area of the detector elements according to the exemplary embodiment in FIG. 7a. Figure 8a is a block diagram of a system including x-ray inspection equipment and processing apparatus.

Figure 8b is a simplified side view of an x-ray inspection system having an arrangement contemplated herein, such as an arrangement of Figures 2-7a.

Figure 9 illustrates a method for dynamically increasing the spatial resolution of the x-ray detector.

Detailed description of exemplary embodiments

FIGS. 1a and 1b show an arrangement 10 for increasing the spatial resolution of an X-ray detector 20 in a simplified representation.

The description of Figures 1 a and 1 b should be preceded by the fact that an xyz coordinate system is shown in the figures for orientation and mutual reference, according to which the longitudinal direction of the detector rows shown always runs in the x direction, while the direction from to the detector elements incident X-rays RX to be detected (represented in simplified form as a bundle of arrows) in the y-direction and ultimately when using the detector lines, a 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 is shown in simplified form in FIG. 8, for example). 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.

Figures 1a and 1b illustrate the structure of an arrangement 10 with an X-ray detector 20 (hereinafter simply detector 20) in the form of a section from a detector line 22. Figure 1a is a simplified perspective view of the arrangement 10 and Figure 1b is, for Illustration of the structure, a projection of an arrangement 10 of Figure 1 a on the xy plane.

The detector line 22 consists of detector elements 24 arranged next to one another; For reasons of clarity, only four such elements are shown, with the number in reality not being limited in principle. The detector elements 24 are preferably located on a carrier element 25.

Although not shown in the figures, each detector element 24 for use in the known dual-energy radiography can each consist of a low-energy X-ray selective low-detector element and a high-energy X-ray selective high detector element, which with respect to detecting X-ray radiation RX are sandwiched one above the other with an intermediate filter layer (e.g. made of copper).

During the scanning of an inspection object, the detector elements 24 generate detector data that are based on the x-rays RX detected in each case. The detector 20 has at least one output channel at which the detected detector data is provided. During use, the detector line 22 is usually arranged transversely to a transport direction TD for an inspection object (eg 116, FIG. 8b) so that the inspection object can be scanned line by line with the x-ray beams RX.

As already noted elsewhere, the detector 20 can in principle also consist of a plurality of detector rows 22 arranged one behind the other in the transport direction, which then form a two-dimensional detector matrix or a two-dimensional matrix detector; the statements and measures that are explained here using the example of a detector line can be directly transferred to a matrix detector.

The assembly 10 further includes a shielding member 30 disposed over the top surface of the detector 20 . The upper surface of the detector 20 is formed by the receiving surfaces 23 of each of the detector elements 24 . The shielding element 30 consists of an area 31 that is impermeable to the X-rays RX, in which the X-rays RX are reflected and/or absorbed there, and an area 32 that is permeable to the X-rays RX, in which the X-rays RX pass through the shielding element with as little influence as possible and onto the receiving surface of the Detector 20 impinge. It should be noted that in FIGS. 1a and 1b there is only one permeable region 32 in the shielding element 30 for a simple explanation of the principle proposed here.

The area of the detector element 24 that is hit by the X-rays RX defines the effective receiving area 23'. Since the shielding element 30 and the detector 20 or the detector elements 24 can be moved relative to one another (see the double arrow in FIG. 1a), the effective reception area 23' can be dynamically changed by means of this arrangement. The permeable area 32 of the shielding element 32 thus functions as a dynamic diaphragm for one or more detector elements 24.

In FIG. 1a, one permeable area 32 is configured as a rectangular recess 34. FIG. When the arrangement 10 is operated as intended, the shielding element 30 is displaced relative to the detector elements 24 orthogonally to the beam direction (for example oscillating in the line direction). The effective receiving surface 23' thus corresponds to the parallel projection of the X-rays RX on the upper surface of the detector 20 or on the receiving surface of the detector elements 24. In other words, the shape of the effective receiving surface 23' corresponds to the profile or the clear surface of the recess 34.

FIG. 1c illustrates the arrangement 10 for increasing the spatial resolution of the detector 20 as a block diagram.

The arrangement 10 has the shielding element 30 and the detector 20 which consists of a plurality of detector elements 24 . A control unit 40 controls a first actuator 42 and/or a second actuator 44 to control the relative movement between the shielding element 30 and the detector 20 to be carried out in a particularly deterministic manner. In this case, the first actuator 42 is coupled to the shielding element 30 and the second actuator 44 to the detector 20 . In principle, the intended relative movement can also only be achieved by means of one of the two actuators 42, 44. In a particularly preferred embodiment, there is only the first actuator 42, which moves the shielding element 30 as a dynamic screen. A piezoelectric actuator or actuator (piezoelectric actuator), for example, can be used as the actuator 42 and/or 44 .

FIG. 2 shows a first embodiment of the arrangement 10 of FIG. 1c. In this case, the shielding element 30 is comb-shaped, i.e. has the shape of a comb which can be moved in an oscillating manner in the line direction of the detector (arrow RB) relative to the detector 20 and thus to the detector elements 24 . For this purpose, the shielding element 30 oscillates between a first position P1 and a second position P2.

The comb-shaped shielding element 30 is designed in such a way that the teeth or tines of the comb each correspond to an impermeable area 31 and the recesses 34 (i.e. the spaces between the teeth) correspond to the permeable areas 32, with the impermeable areas 31 always being a partial region of the receiving surface of each detector element Shield 24 and the permeable areas 32 are arranged over the rest of the partial region, so that the difference between these two partial regions corresponds to the effective reception area 23' (cf. FIG. 1a).

Figures 3a and 3b illustrate a second embodiment of the arrangement 10 of Figure 1c, wherein the shielding element 30 has the shape of a disc. The face of the disc defines a plane parallel to the receiving faces 23 of the detector elements 24 and configured such that the transmissive areas 32 are located as regular recesses 34 extending radially outward from the pivot point along the edge of the disc. The alternation between the areas 31 opaque to X-rays RX and the transparent areas 32 is achieved by rotating (or alternatively oscillating over a certain angular range) the disc about an axis orthogonal to the receiving surfaces 23 of the detector elements 24 .

FIG. 3c shows a section of a simplified top view of the disk-shaped shielding element 30 of FIGS. 3a and 3b to illustrate a development of the principle proposed here, by means of which the spatial resolution of the detector can be additionally increased. FIG. 3c only shows the edge of the disk-shaped shielding element 30 in detail, on which impermeable areas 31 and permeable areas 32 alternate, with a relative movement of two recesses 34 arranged at the edge being illustrated over three detector elements 24 of the detector. For example, the detector element 24 arranged in the center is read out at a first point in time t, during which a first (partial) area 24' is irradiated by x-rays RX. The irradiated (partial) area 24' corresponds to the current effective reception area of this detector element 24.

The same detector element 24 is then read out at a next, i.e. subsequent, second point in time t+1, during which a second (partial) area 24" is irradiated by x-rays RX. Due to the relative movement between the shielding element 30 and the detector elements 24, the first area 24' does not correspond to the second area 24". The two (partial) areas 24' and 24" overlap.

As already explained elsewhere, the increase in the physical resolution of a detector element that can be achieved by means of the arrangement proposed here is directly dependent on the size of the regions 32 in the shielding element 30 that are transparent to X-rays. If a further reduction in the area of a pixel is desired, this can be achieved with the subtraction of successively detected real intensity values already described here in the general part in order to determine an intensity value for a virtual (smaller) pixel.

For this purpose, the associated intensity values of the X-rays RX detected at times t and t+1 for the first (partial) area 24' and the second (partial) area 24" are first recorded or calculated (if, for example, an integration over a scanning period he follows). The two intensity values are then subtracted from one another in order to use them to determine the virtual intensity value for x-rays RX of the (smaller) partial area 24'' of the detector element 24.

It should be noted that the development of the method described above for determining a virtual intensity value of detected x-rays RX can be applied to each of the exemplary embodiments for the arrangement 10 presented here in order to further increase the spatial resolution.

FIG. 4 shows a third exemplary embodiment of the arrangement 10 from FIG. The shielding element 30 has a slit running spirally in the longitudinal direction of the tube and in the jacket of the tube, which is transparent to X-rays RX, while the remaining jacket of the tube is opaque to X-rays RX. Thus, in the arrangement 10 of FIG. 4, impermeable areas 31 and permeable areas 32 regularly alternate in the longitudinal direction of the detector line 22. The desired relative movement between the shielding element and the detector and the associated change in the effective receiving areas of the detector elements is achieved by rotating the tube about its axis, which is arranged parallel to the line direction of the detector line 22, and thus about the detector line 22. FIG. 5 illustrates a fourth exemplary embodiment of the arrangement 10 from FIG. 1c, the shielding element 30 being wheel-shaped, ie having the shape of a wheel. Unlike the shielding element 30 of Figures 3a-3c, the shielding element 30 of Figure 5 is designed in such a way that the wheel can be rotated about an axis parallel to the receiving surfaces 23 of the detector elements 24 and consists of a plurality of teeth or tines (similar to those of the crest of Figure 2) extending orthogonally from the plane defined by the wheel from the edge of the wheel. The tines again form the impermeable areas 31 and the spaces between two adjacent tines form the permeable areas 32. Rotation of the wheel about its axis or oscillation of the wheel through a certain angular range about the axis produces the desired relative movement of the tines over the receiving surfaces 23 of the Detector elements 24, so that a corresponding change over time in the effective receiving area of the detector elements is achieved again.

FIG. 6 illustrates a fifth exemplary embodiment of the arrangement 10 from FIG. 1c, the shielding element 30 having the shape of a band with a large number of rectangular recesses 34 arranged regularly in the direction of the band. The alternation between the impermeable areas 31 and the permeable areas 32 is achieved by moving the belt around two pulleys 36 . The shielding element 30 can preferably run steplessly in one direction or change the running direction at certain points in time, ie it can also oscillate between two positions. In this arrangement, the detector row 22 is arranged under the belt and between the rollers 36 .

FIG. 7a shows a sixth exemplary embodiment of the arrangement 10 from FIG. 1c, the shielding element 30 being tubular in a manner similar to that in FIG. In contrast to the shielding element 30 shown in Figure 4, the tube in Figure 7a does not have a spiral slot as the area transparent to X-rays, but consists of several sub-elements 33 arranged next to one another in the longitudinal direction and shielding X-rays RX, which in the circumferential direction of the tube have a stepped profile such that the area of the transmissive region for an associated detector element can be changed by rotating the tube. If the tubular shielding element 30 is rotated about its axis, which is arranged parallel to the line direction of the detector line 22, each partial element 33 changes the receiving surface of an associated detector element 24 gradually or in steps. The effective reception area of each detector element 24 is changed accordingly in steps. The sub-elements 33 shielding X-rays RX thus correspond to the impermeable areas 31 and are arranged next to one another in such a way that the permeable areas 32 themselves also have a graded profile. Figure 7b illustrates a gradual or stepped change in the effective receiving area 23 'of a detector element 24 when using an arrangement 10 with a shielding element 30 similar to the shielding element 30 shown in Figure 7a X-ray opaque area shown with five levels each.; of course, more or fewer levels, but also an irregular (eg random) gradation are possible.

In FIG. 7b, for each detector element 24 there is a correspondingly graded opaque area 31 with five equal gradations. The space between the impermeable areas 31 arranged next to one another corresponds to the respective permeable area 32 of the shielding element 30.

During the relative movement RB (cf. Figure 7a) of the shielding element 30 relative to the detector elements 24 (here the rotation of the tubular shielding element 30 about an axis of rotation which runs parallel to the row direction of the detector row 22), each detector element 24 is partially or finally completely shielded and the effective receiving area 23' changes again and again over time by a set percentage (shown here as 20% for illustration) by means of the graded profile.

It should be noted that the stepped profile of the impermeable region 31 shown in FIG. 7b can be arranged exactly once or several times in a row along the jacket of the tubular shielding element 30 (cf. FIG. 7a).

For the discussion of Figure 7b, it is assumed that there are exactly six different time segments (l)-(VI) during one revolution of the shielding element 30 (cf. Figure 7a), in the sequential course of which the opaque area 31 covers the effective receiving area of the associated detector element 24 gradually changed (in 16.7% steps) from not shielded (0%) to almost completely shielded (83.3%).

In the first period of time (I), the opaque area 31 of the shielding element 30 is not yet arranged over the receiving surface of the detector element 24 . Thus, the receiving surface of the detector element 24 is completely irradiated by x-rays RX.

As soon as the shielding element 30 moves in the direction of the detector element 24 (in FIG. 7b this corresponds to a movement of the unrolled lateral surface from FIG. 7a to the left), the impermeable area 31 begins to shield the detector element 24 by 16.7%. At period (II), the 16.7% step of the opaque region 31 shields the detector element 24 accordingly. Thus, the size of the effective receiving area 23' is reduced by 16.7% corresponding to the size of the first stage. Moving further to the left, the 33.3% level of the opaque area 31 begins to shield the detector element 24 accordingly for the third time period (III) as soon as the 33.3% level of the opaque area 31 moves the detector element 24 by 33, 3% shielded.

The movement of the shielding element 30 continues accordingly until finally the sixth period (VI), in which the effective receiving area 23' is correspondingly shielded from the last 83.3% stage.

Since the shielding element 30 is actually tubular as shown in Figure 7a, the method would start again at the first point in time (I) with the 0% step of the step-shaped profiled opaque area 31.

Alternatively, the shielding element can also be set up for an oscillating rotational movement between the first and sixth profile sections, so that the process described above would be run through backwards after time section (VI) back to time section (I).

In a preferred development, in order to increase the degree of accuracy of the spatial resolution of the detector 10, the movement of the shielding element 30 is synchronized with the irradiation of the detector elements with x-rays RX. The checkered areas shown on the time line t of Figure 7b illustrate the synchronized activation of the irradiation or exposure of the detector elements 24. Thus, the intensity values are accurately measured in the predetermined time intervals (I) to (VI). That is, whenever, for example, a certain profile step of the opaque area 31 shields the receiving surface 23 of the detector element 24 in such a way that the effective receiving surface is constant for the period of time. During the transition phase from one profile stage to the next, the exposure is switched off electronically (for example by switching off the radiation source or closing an associated collimator - see Figure 8b).

FIG. 8a illustrates a system 400, which essentially consists of an x-ray inspection system 100 and a processing device 300. The processing device 300 interacts with the x-ray inspection system 100 according to the principles described here via a communication connection 410 in order to enable one of the methods presented here for determining the effective spatial resolution of the detector 20 arranged in the x-ray inspection system 100 .

In FIG. 8b, an X-ray inspection system 100 is shown in a much simplified manner as an example. The x-ray inspection system 100 has two radiation protection curtains 102, 104, one of which is arranged at an entrance 106 and an exit 108 of a radiation tunnel 110 of the x-ray inspection system 100. Between the radiation protection curtains 102, 104 is within the radiation tunnel 110 a radiation area 112 in which at least one radiation source 114 for ionizing radiation is arranged; for example, an X-ray tube 114a with a collimator 114b for generating an X-ray fan 115 which is aligned with an X-ray detector 20. The x-ray fan can be turned on and off by activating and deactivating x-ray tube 114a and/or shuttering collimator 114b.

The X-ray inspection system 100 also has one of the arrangement 10 proposed here in different exemplary embodiments according to the principle explained in FIGS.

Without establishing a prioritization, the arrangement 10 according to the principle of FIG. 2 is shown in FIG. 8b solely for the purpose of illustration. In addition, only one detector subassembly 10'' is shown as a portion of the overall detector assembly 10 for ease of illustration. This also corresponds to the implementation in practice, with line or matrix-type detectors in line scanners for line-wise or matrix-wise scanning of inspection objects usually being composed of a corresponding arrangement of a plurality of detector subunits. According to this common implementation, only the detector sub-unit 10" is shown in detail in FIG. 8b as a section of the entire detector arrangement 10, which in the example shown consists of the three detector sub-units 10', 10', 10"". Furthermore, the detector 20 shown is a matrix detector which is two detector elements 24 wide in the scanning direction.

A transport device, for example a sliding belt conveyor with three sections 118-1, 118-2, 118-3, which promotes the inspection objects through the radiation area 112, is used to transport a piece of luggage 116 as an example of an inspection object in the transport direction TD through the radiation tunnel 110.

The line-shaped detector 10 is space-efficiently L-shaped or U-shaped and arranged with its longitudinal direction (i.e. line direction) orthogonal to the transport direction TD, so that the transport direction TD corresponds to the scanning direction of an inspection object.

The section of detector 10 formed by a detector subunit 10" in the illustration in Figure 8b consists of the associated matrix detector 20", which corresponds to a section of the entire (matrix) detector line 22, over which a comb-shaped shielding element 30" is arranged. The shielding element 30" is connected to an actuator 42" (for example a piezomechanical actuator), so that the actuator 42" can move the shielding element 30" reciprocally, i.e. in the row direction, as an example of one of the relative movements RB proposed here, in order to Detector elements 24 "to act as a dynamic aperture. In order to synchronize the reading of the detector elements 24" of the detector sub-unit 10" with the relative movement RB of the shielding element 30", the actuator 42" is controlled by a control unit 120 of the X-ray inspection system 100 via a corresponding control connection 120-42. The control unit 120 is set up, synchronized with the relative movement RB of the shielding element 30", to read out the respective detector elements 24" via a readout connection 120-20 and the X-ray fan 115 via a control connection 120-114 by correspondingly activating and deactivating the X-ray tube 114a and/or opening and closing of a radiation output of the collimators 114b on and off.

The processing device 300 is essentially set up to carry out at least one of the methods proposed here and to process the detector data recorded with the arrangement 10 .

It goes without saying that the arrangement 10 can alternatively also be such as is shown in simplified form in FIGS. 3-7b, or another arrangement following the principle proposed here.

The detector data provided by the X-ray detector 20 and processed by the processing device 300 can be used to generate an X-ray image of the inspection object 116 colored based on material classes with increased spatial resolution, which is displayed to an operator on a screen (not shown) in a manner known per se can.

As shown in FIG. 8 b , the processing device 300 can be part of the control device 120 of the x-ray inspection system 100 . However, the processing device 300 can also be located separately from the X-ray inspection system 100 next to it or at a remote location, for example at a central location where the raw detector data from a number of inspection systems 100 are combined and processed centrally there. The arrangement of the processing device 300 in or on the X-ray inspection system 100 or at a distance from it makes no difference to the proposed measures for processing the detector data.

The processing unit 300 can also already be part of the arrangement 10 or of the detector 20 .

The detector data generated by the detector 20 can then already be processed at the detector 20 in accordance with the measures proposed here. The arrangement 10 proposed here would thus be fundamentally compatible with existing x-ray inspection systems with conventional detector units. This means that with X-ray inspection systems that are otherwise sufficiently structurally identical, an embodiment of the new arrangement 10 proposed here with integrated processing of the detector data can achieve a constant image quality with lower system costs, or alternatively could The spatial resolution of an existing X-ray inspection system can be increased at almost the same system costs.

FIG. 9 illustrates the basic structure of a method 200 for determining the spatial resolution of the X-ray detector 20, which can be used, for example, in the arrangement of FIGS. 1a-7b. The method 200 has the following basic steps:

A step S1 for the first reading of the detector element 24 at a first point in time t, during which a first region 24' of the detector element 24 is irradiated by X-rays RX.

A step S2 for the second reading S2 of the detector element 24 at a second point in time t+1, during which a second region 24″ of the detector element 24 is irradiated by the x-rays RX.

A step S3 for calculating associated intensity values of the X-rays RX for the first area 24' and the second area 24'' for the first point in time t and the second point in time t+1.

Optionally, the method can also have a step S4, in which the intensity values calculated in step S3 are subtracted in order to calculate an intensity value for a virtual pixel with a correspondingly small area and thus further increase the spatial resolution of the detector as a result. For this purpose, in the optional step S4, the virtual intensity value of the X-ray radiation RX of a partial area 24'" of the at least one detector element 24 is calculated based on the subtraction that has taken place, with the result being that the virtual intensity value provides detector data for a correspondingly smaller virtual detector element and thus a further increase in the spatial resolution of the detector.

Claims

23 claims

1. Arrangement (10) of an X-ray detector (20) and an X-ray (RX) shielding shielding element (30) for providing detector data with a higher spatial resolution than the physical resolution of the X-ray detector (20), the X-ray detector (20) having at least one Detector line (22) with at least one detector element (24) arranged along the detector line (22), the shielding element (30) has at least one area (31) impermeable to X-rays (RX) and at least one area (32) permeable to X-rays (RX) has, the shielding element (30) is arranged in the beam direction of the X-rays (RX) in front of the receiving surface (23) of the at least one detector element (24), the shielding element (30) and the at least one detector element (24) for a relative movement (RB) relative are movable to each other, so that the effective receiving area for X-rays (RX) of the at least one detector element nts (24) can be changed dynamically accordingly.

2. Arrangement (10) according to claim 1, wherein the X-rays (RX) permeable area (32) of the shielding element (30) is a recess (34).

3. Arrangement (10) according to claim 1, wherein the x-rays (RX) permeable region (32) of the shielding element (30) consists of a material with a low attenuation for x-rays (RX), for example plastic; and/or the area (31) of the shielding element (30) which is opaque to X-rays (RX) consists of a material with a high attenuation for X-rays (RX), for example lead; wherein the transmittance for X-rays (RX) is higher in the transmissive region (32) than in the non-transmissive region (31).

4. Arrangement (10) according to any one of claims 1-3, wherein the shielding element (30) has the shape of a comb, a disc, a belt, a

wheel or a tube enclosing the detector array (22); and/or the shielding element (30) can be moved by rotation, translation or by a combination of rotational movement and translational movement for the movement (RB) relative to the detector elements (24).

5. Arrangement (10) according to any one of claims 1-4, wherein the shielding element (30) is movable by an oscillating movement between a first position and a second position for the relative movement (RB) relative to the detector elements (24).

6. Arrangement (10) according to any one of claims 1-5, wherein the X-ray (RX) transparent region (32) has a graded profile such that when the shielding element (30) and the at least one detector element (24) for the relative movement (RB) are moved relative to each other, the effective receiving area for X-rays (RX) of the at least one detector element (24) can be changed accordingly in regular or irregular steps.

7. Arrangement (10) according to any one of claims 1-6, wherein the shielding element (30) with a first actuator (42) and / or the detector line (22) with a second actuator (44) is or are coupled, wherein the the first actuator (42) and/or the second actuator (44) for the relative movement (RB) between the shielding element (30) and the at least one detector element (24) can be controlled.

8. X-ray inspection system (100) with an arrangement (10) according to any one of claims 1-7, wherein the X-ray inspection system (100) is set up for transporting an inspection object (116) in a transport direction (TD) through the inspection system (100) and the Detector line (22) of the X-ray detector (20) is arranged in a line direction, which is aligned orthogonally to the transport direction (TD), and the X-ray inspection system (100) is set up to detect intensity values of the X-rays (RX) from a scanned area of the changed effective receiving area for the x-rays (RX) of the at least one detector element (24) for different points in time.

9. Method (200) for increasing the spatial resolution of an X-ray detector (20) with at least one detector row (22) with at least one detector element (24), wherein the at least one detector element (24) and one above the receiving surface (23) for the X-rays (RX) of the at least one detector element (24) are movable relative to each other for a relative movement (RB), whereby the effective receiving surface for the X-rays (RX) of the at least one detector element (24) is changed.

10. The method (200) according to claim 9, wherein the method (200) comprises: a step S1 with a first reading (S1) of the at least one detector element (24). a first point in time t, during which a first region (24') of the at least one detector element (24) is irradiated by the X-rays (RX); a step S2 with a second reading (S2) of the at least one detector element (24) at a second point in time t+1 , during which a second region (24″) of the at least one detector element (24) is irradiated by the X-rays (RX); and a step S3 with calculation (S3) of associated intensity values of the X-rays (RX) for the first area (24') and the second area (24'') for the first point in time t and the second point in time t+1.

11 . Method (200) according to claim 10, wherein the method further comprises: a step S4 with subtracting (S4) the intensity values calculated in step (S3); and a step S5 with determining (S5) a virtual intensity value of the X-rays (RX) of a partial area (24"') of the at least one detector element (24) based on the subtraction in step S3.

12. The method (200) according to claim 11, wherein the second region (24") of the at least one detector element (24), which is irradiated by X-rays (RX), comprises at least a partial region of the first region (24') of the at least one detector element ( 24), which is irradiated by X-rays (RX), is superimposed.

13. The method (200) according to any one of claims 10-12, wherein a change in the relative arrangement of the shielding element (30) and the at least one detector element (24) with the respective irradiation of the X-ray detector (20) with X-rays (RX) is synchronized.

14. Processing device (300) for processing the intensity values of the X-ray radiation (RX) provided by the X-ray inspection system (100) according to claim 8, wherein the processing device (300) is set up to carry out a method (200) according to one of claims 9-13.

15. System (400) with an X-ray inspection system (100) according to claim 8 and a processing device (300) according to claim 14, wherein the X-ray inspection system (100) for providing the intensity values based on the scanning of an inspection object (116) to the processing device (300) is set up and to the processing device (300) for a

data communication is connected.