Arrangement and method for irradiating an object with electromagnetic radiation

Abstract

Arrangement (10) for irradiating an object with electromagnetic radiation, in particular for object irradiation in a production line or in connection with a production line, comprising: - a radiation source (12), - a detector device (16), - a shielding device (28), and - a control device, wherein the radiation source (12) is configured to irradiate electromagnetic radiation through an object receiving area (14) of the arrangement (10) onto the detector device (16), wherein the detector device (16) has a plurality of detector surfaces (20, 22), wherein the detector device (16) is configured to detect electromagnetic radiation incident on the detector surfaces (20, 22) to generate an object irradiation image, wherein optionally at least one of the detector surfaces (20, 22) can be shielded against the electromagnetic radiation by the shielding device (28).while at least one other of the detector areas (20, 22) is available for image acquisition, wherein the detector areas (20, 22) have the same resolution, wherein the control device is configured to perform the shielding according to a regeneration state and / or a degeneration state of at least one of the detector areas (20, 22), and to determine the regeneration state and / or degeneration state of the detector area (20, 22) based on at least the following quantity: - a dark current of the detector area (20, 22).

Description

The present invention relates to an arrangement and a method for radiating an object, in particular a workpiece, with electromagnetic radiation. In particular, the invention relates to an arrangement and a method in which a detector device generates a transmission image of at least one workpiece which originates directly or via an intermediate store for receiving a plurality of the workpieces from a production installation for producing the workpiece and / or machining the workpiece, i.e. the arrangement can be connected to a production line, for example, via a transport device and / or the intermediate store.For industrial workpiece inspection, transmission arrangements and methods are used to check, for example, the dimensional accuracy of a workpiece or the presence of internal defects. In particular, solutions from the field of computed tomography (CT) are used for this purpose, which are based on electromagnetic radiation in the range of extreme ultraviolet radiation and / or X-ray radiation. Such radiation is also referred to as invasive radiation. X-ray radiation is usually generated by accelerating (decelerating) primary radiation particles such as electrons, for example in a target of an X-ray radiation source. The spectral range of the electromagnetic radiation usable in the context of the invention is not restricted by specific wavelengths.In CT apparatuses and methods, a workpiece is irradiated with X-ray radiation from different incident directions to acquire a plurality of X-ray images. From these, a three-dimensional representation of the irradiated workpiece is then calculated, in particular by a computer. This is also referred to as a reconstruction.For generating the transmission images, use is made, for example, of detector devices having a plurality of detector elements, each detector element being configured to generate an image element of the transmission image. In particular, detector matrices are used in which the detector elements are arranged in rows and columns and which have a scintillator and a sensor element (in particular a photodiode) per matrix element. In particular, the detector devices can be designed as so-called (X-ray) flat-panel detectors.It is also known to irradiate the workpieces directly within a production line (so-called inline CT scanning) or to irradiate them adjacent to a production line. In particular, a temporal clocking of the production line can be provided, so that the object broadcasts must also be carried out in the production clock. Furthermore, the corresponding object transmission arrangement can be automatically loaded and / or unloaded, which can likewise take place at the production cycle or only with respect to a partial number of the manufactured workpieces. The arrangements and methods described within the scope of the present disclosure can be provided and / or designed in particular for object transmission within a (in particular time-clocked) production line or connected to a production line.In order to ensure an adequate quality of the object transmission within the usually short production cycle, high radiation doses may be required, in particular in order to reduce the required measurement time.However, it has been found that the reliability and in particular the useful life of detector devices can decrease in the case of high irradiation doses and / or narrow-cycle irradiation processes. This relates, for example, to properties of the detector such as the dark signal (in particular the dark current which flows through the individual sensor elements when no radiation from the radiation source is incident on the detector), the homogeneity of the signals which the individual sensor elements of the detector supply, or the sensitivity of the detector elements of the detector device. For example, if a dose of radiation per image acquisition is between 10 and 150 kGy or more, the dark current may be significantly higher and the detector sensitivity may be significantly lower than a new-factory detector. This has a negative effect on the image quality and may require premature replacement of the detector device. In addition, at high radiation doses of, for example, 100 kGy or more, defects can occur in the electronics of the detector device.Reducing the radiation dose in order to conserve the detector device can, however, mean a longer measurement time and thus a less close timing of the transmission processes. This is disadvantageous in particular for the workpiece transmission within a production line or in conjunction with a production line. In such a case, an irradiation and / or regeneration duration of the detector device (i.e. the rest time between two irradiation processes) generally cannot be adapted to the properties of the detector device either. Instead, the timing of the transmission operations is often determined by other parameters, such as the charging and discharging times of the transmission device or the general clock time of the production line.US 2015 / 0276 626 A1 shows an X-ray inspection apparatus in which a detector device can be partially shielded. JP H08-266 531 A teaches an X-ray CT system in which a detector is irradiated only locally.There is thus a need to increase the reliability and in particular the useful life of detector devices in object transmission.The inventors have generally recognized that the reliability and in particular the useful life of the detector device can increase if at least a part of the detector device, namely at least one detector surface thereof, is made possible to regenerate during a phase without an incidence of invasive electromagnetic radiation or during an incidence of electromagnetic radiation with a low radiation flux density.For this purpose, a plurality of detector surfaces are provided and it is preferably switched between the detector surfaces in such a way that at least one of them can regenerate, while at least one other is available for image acquisition. The detector surfaces have the same resolution and are preferably also of the same size.The resolution is to be understood in particular as the number of detectable image points per detector area or, in other words, of detector pixels per detector area, wherein a respective image point corresponds in particular to a signal which is or can be supplied by a sensor element (in particular a photodiode) explained above.By providing the same resolution, it can be achieved that a change of the detector surface used for image acquisition is possible with little effort and under certain circumstances without substantial adaptations of the operating variables of the arrangement to be set for image acquisition. In particular, a calibration of the arrangement can be valid, regardless of which of the detector surfaces is currently used for the image acquisition, since the detector surfaces are substantially or completely of the same design.Specifically, an arrangement and method according to the appended independent arrangement and method claims are proposed. Advantageous further developments are defined in the dependent claims.The invention proposes an arrangement for radiating an object (in particular a workpiece or a plurality of workpieces) with electromagnetic radiation, in particular for object radiation in a production line or in conjunction with a production line, wherein the arrangement comprises a radiation source, a shielding device (for example shielding device at least attenuating the radiation and preferably attenuating it, in particular by at least 80% with respect to the radiation flux density) and a detector device. The radiation source is configured to direct electromagnetic radiation through an object receiving region of the arrangement onto the detector device, i.e. to radiate it during operation. The detector device has a plurality of detector surfaces, wherein the detector device is configured to detect electromagnetic radiation impinging on the detector surfaces for generating an object transmission image. In this case, at least one of the detector surfaces can be selectively shielded from the electromagnetic radiation by the shielding device, while at least one other is available (i.e. not shielded) for image acquisition. The at least one unshielded detector surface can therefore detect radiation from the radiation source, which radiation is radiated through the object receiving region onto the unshielded detector surface. The shielded radiation can comprise direct radiation components (i.e. components running in a straight line from the radiation source) and / or scattered radiation components.Furthermore, the detector surfaces have the same resolution.The optional shielding here means that in principle all of the detector surfaces can be shielded (for example one after the other, but not necessarily simultaneously) and there is a possible selection as to which of the detector surfaces is currently to be shielded (for example either a first or a second) and / or which is not to be shielded. Thus, there is also the possibility that that detector surface which is to be shielded can be changed and in particular replaced by a detector surface which was shielded beforehand.Accordingly, a development provides that the arrangement can be operated in such a way that a detector surface which is initially not shielded and used for image generation (i.e. generation of an object transmission image) is shielded and is replaced for image generation by a detector surface which is initially shielded.According to a preferred embodiment of the arrangement and the method, when there is no object to be transmitted in the object receiving region and said object is, for example, empty or radiation can pass through it without substantial absorption, electromagnetic radiation radiated from the radiation source through the object receiving region onto a shielded detector surface can have a first radiation flux density. An electromagnetic radiation radiated from the radiation source through the object receiving region onto a non-shielded detector surface can, on the other hand, have a second radiation flux density, wherein the first radiation flux density (striking the shielded detector surface) is less than 20% of the second radiation flux density (striking the non-shielded detector surface).As mentioned, it is intended to allow parts of the detector to regenerate. Ideally, the radiation flux density of the electromagnetic radiation radiated onto the shielded detector surface is therefore zero. In particular due to scattered radiation and the fact that materials of the shielding device which absorb the electromagnetic radiation with a high degree of absorption do not completely absorb the radiation, this ideal case is generally not achievable.Nevertheless, within the scope of the present disclosure, a shielded detector surface can be referred to as non-irradiated or non-irradiated. This is to be understood on the basis of the non-ideal shielding explained in the sense of an approximately or substantially unexposed state of the detector surface. This is to be understood in particular in the context of the aforementioned reduced radiation flux density (less than 20%), which describes a state that is accordingly approximately unexposed. On the other hand, unshielded detector surfaces can be referred to as being emittable, wherein this is to be understood in the sense of direct emission (without shielding between radiation source and detector surface), for example, through a workpiece in the object receiving region.It is therefore proposed that the first radiation flux density is less than 20% of the second radiation flux density. It has been found that detector surfaces can regenerate at a radiation flux density reduced by 80% and more. Preferably, the first radiation flux density is less than 15%, and particularly preferably less than 10%, of the second radiation flux density.In particular, the first radiation flux density is the greatest radiation flux density of the radiation flux density distribution of the electromagnetic radiation radiated onto the first detector surface. In this case, the second radiation flux density is the greatest radiation flux density of the radiation flux density distribution of the electromagnetic radiation radiated onto the second detector surface. Alternatively, the first radiation flux density is an average value of the radiation flux density distribution of the electromagnetic radiation radiated onto the first detector surface. In this case, the second radiation flux density is an average value of the radiation flux density distribution of the electromagnetic radiation radiated onto the second detector surface.Features of an arrangement for radiating an object of the invention are described below, which can optionally be realized individually or in any combination even if the first radiation flux density should be not less than 20% of the second radiation flux density.In particular, the detector device can comprise a first detector surface and a second detector surface and irradiate these alternately. "irradiation" means that the X-ray beam (for example a diverging beam in an approximately conical spatial region) emanating from the radiation source is incident on the first detector surface at a given point in time, but not on the second detector surface, or vice versa. The edge surfaces of an x-ray beam emanating from the radiation source are often defined by a diaphragm at the exit from the x-ray source (for example an x-ray tube). Viewed from a focal spot of the X-ray source, in this case all parts of the detector lie in the irradiated spatial region which can be connected by a straight line from the focal spot to the respective part of the detector which extends through the aperture opening. However, any parts of the detector which are located behind a shielding device, for example of lead or tungsten or a combination thereof, as seen from the focal spot, are not irradiated. As already mentioned, it cannot be completely prevented that electromagnetic radiation with a corresponding radiation flux density nevertheless impinges on the non-irradiated detector surface. "Irradiation" therefore means that the respective detector surface is directly irradiated without shielding on a straight line between focal spot and detector surface, and "unexposed" means that shielding shields the detector surface from the electromagnetic radiation.This does not exclude that, in addition to the first detector surface and the second detector surface, there is also at least one third detector surface which likewise forms a portion of an overall detector surface of the detector device and which is likewise available for detecting the radiation radiated onto the detector device through the object receiving region, in particular if the third detector surface and the radiation source are positioned relative to one another such that radiation impinges on the third detector surface.The arrangement can be used in particular within a production line or connected to a production line, wherein the production line can be clocked in time according to the introductory statements. In particular, the workpiece can be transported from the manufacturing plant to the arrangement directly or via an intermediate store. Alternatively or additionally, the arrangement can be automatically loaded and / or unloaded. The duration of the object transmission processes can be matched to the general production cycle (i.e. the production cycle is not exceeded in time). However, only a part of the production products can also be supplied to the arrangement.The electromagnetic radiation can be generated in the form of X-ray radiation or other invasive electromagnetic radiation from the radiation source of the arrangement. The radiation source (for example in the form of an X-ray tube) can be designed to emit the electromagnetic radiation, in particular in the form of X-ray radiation, in the direction of the object receiving region in which the object to be received is located. The emitted radiation can move from the radiation source through the object receiving region of the arrangement. The object receiving area can comprise, for example, a turntable, a platform, a holder or another suitable means for receiving and optionally moving the object and thus allowing transmission of radiation from different directions. The object may be a workpiece, a plurality of workpieces, or another industrial product.The detector device can comprise a plurality of detector surfaces sensitive to the electromagnetic radiation and can generally be configured to generate a two-dimensional image corresponding to the electromagnetic radiation impinging on the detector surface. As discussed in the introduction, the detector device can comprise at least one flat-panel image detector and can preferably be configured for CT image acquisition. In particular, any detector surfaces of the detector device can in principle be configured to generate a transmission image of the object, which is preferably only possible, however, or is only possible with a desired minimum quality if these are not shielded. The first and the second detector surface can each have dimensions of, for example, 40 cm by 40 cm or 20 cm by 20 cm. In particular, therefore, the two detector surfaces or generally at least two of the plurality of detector surfaces can be of the same size.In particular, the detector device and the radiation source are positioned facing each other and / or on both sides of the object receiving region. In particular, they enclose the object receiving area between them. Furthermore, the arrangement may be operable in the manner of a CT scanner in order to generate a three-dimensional image of the object. For this purpose, a relative movement and in particular a relative rotation of object and detector device can also be provided.In order to leave the detector surfaces at least partially unexposed and to shield them more precisely, i.e. to leave at least one of the detector surfaces unexposed and in particular to irradiate them with a radiation flux density which is less than 20% of the second radiation flux density, the detector device can be positioned or positionable accordingly within the arrangement, for example relative to the radiation source or an optional shielding device explained below. In other words, the detector device or at least two detector surfaces of the detector device can be movable relative to the radiation source and / or the shielding device, for example in order to position at least one of the detector surfaces behind the shielding device in each case.In particular, a first part of the detector device can have a first detector surface and a second part of the detector device can have a second detector surface. In this case, a partial arrangement consisting of the first part and the second part and optionally at least one further part of the detector device with a further detector surface can be movable and can also be moved in order to bring the first part or the second part into a position in which the respective part is no longer irradiated. The movement can be a straight-line movement. In this case, for example, the first part is moved in a rectilinear manner-and in particular in a direction perpendicular to a propagation direction of the electromagnetic radiation of the radiation source impinging on the detector device-in order to position the first detector surface in a spatial region which is not reached directly and / or only after passing through the shielding device by the electromagnetic radiation passing through the object receiving region.However, the movement is not limited to a rectilinear movement. Instead, alternatively or additionally, a rotational movement can take place in order to bring the first part or the second part into a position in which the respective part is no longer irradiated.In particular, the at least first and second parts can be moved simultaneously in the same manner (i.e. in the same direction and / or at the same speed). This is possible in particular when the at least first and second parts are mechanically connected to one another, for example are supported by a common carrier.If it is a rotational movement, the at least first and second parts can be rotated, for example, about an axis of rotation which runs perpendicular to a propagation direction of the radiation impinging on the detector device.Because the total detector surface has at least one portion unexposed to the electromagnetic radiation during object transmission, it can regenerate at least partially. Therefore, it is provided that, in the case of object transmission, not the entire detector device is irradiated, but a portion thereof (i.e. at least one detector surface) is left unexposed. The irradiation of the entire detector surface can thus be interrupted or paused at least partially, so that a regeneration can take place in the corresponding unexposed portion, for example by a diffusion of electrons and holes within the sensor elements of a sensor matrix of the detector. This can reduce the above-explained quality losses of the detector device, in particular in comparison with a permanent or closely clocked and full-surface irradiation. In particular, the occurrence of aging effects such as dark current rise or sensitivity loss can at least be slowed down. The irradiated portion of the total detector surface, on the other hand, is still available for image acquisition and thus ensures the operability (or operability) of the arrangement with respect to image acquisition.As explained below in connection with a specific embodiment, the described arrangement can also be used to increase the radiation dose in order to shorten the measurement time (for example for use in a time-clocked production line). An alternative possibility for correcting the so-called ghosting effect can likewise be provided, which will be discussed in more detail below.According to the invention, the screening takes place according to a regeneration state and / or a degeneration state of at least one of the detector surfaces. With respect to different detector surfaces and more precisely with respect to an arrangement with a shielded and with an imageable detector surface, the degeneration state of the imageable detector surface and the regeneration state of the shielded detector surface can change synchronously and in particular proportionally to one another. That is, as the degeneration state of the irradiated detector surface increases, the regeneration state of the shielded detector surface may correspondingly increase, and vice versa. On the other hand, it can be provided that for one and the sameThe detector surface has an opposite relationship between the regeneration state and the degeneration state and, in particular, an anti-proportional relationship (i.e., when the degeneration state of a detector surface increases, the regeneration state of the same detector surface may decrease in a corresponding manner, and vice versa).More specifically, in this context, it can be provided that a detector surface is shielded at least until it has reached a predetermined regeneration state, and / or that a detector surface is shielded at the latest when it has reached a predetermined degeneration state. The predetermined regeneration or degeneration state can be defined by a threshold value for one of the variables explained below.In general, within the scope of this disclosure, the regeneration state and / or degeneration state can be measured, for example on the basis of a variable which specifies this state or is at least indirectly dependent thereon. However, it is also possible to perform estimates and / or simulations explained below in order to at least indirectly draw conclusions about the present regeneration state and / or degeneration state. For these estimates, variables such as the time durations and dose values explained below can be considered. These can be based not or only partially on direct measurements of physical variables of the arrangement during its operation, but can be estimated, for example, on the basis of measurement parameters of the arrangement that are predetermined for the object transmission.According to the invention, the regeneration state and / or degeneration state of a detector surface (in particular not shielded) is determined based on at least the dark current of the detector surface. The determination can additionally be made based on at least one of the following variablesa sensitivity of the detector surface;an image homogeneity that can be achieved with the detector surface;purely optionally: a shielding time period or an irradiation time period of the detector surface;an irradiation dose value of the detector surfaceThe first three listed quantities can be measured and used to quantify a regeneration condition. The last two listed examples, on the other hand, can be used for estimating a corresponding state and, in particular, the dose value can itself be based on an estimation made, for example, on the basis of operating parameters of the arrangement.The dark current of a detector surface, which is discussed in the introduction, can decrease with increasing regeneration and increase with increasing degeneration. The dark current can also be referred to as an offset value and specify an output signal of a detector surface (added up for example over a predetermined time interval) in the absence of an input signal. An output signal of a detector surface can generally be a measurement signal, whereas an input signal can be defined by the electromagnetic radiation and in particular its radiation flux density.Additionally or alternatively, the sensitivity of the detector surface can be viewed. This can be defined as a ratio of an output signal of the detector surface to a (current) input signal. Likewise, the sensitivity may be defined as a signal-to-noise ratio in the output signal.Alternatively or additionally, the image homogeneity that can be achieved with the detector surface can be considered. This can vary depending on the response behavior of the individual detector pixels, in particular relative to their immediate neighbors. Here, response behavior can be understood to mean a profile of the measurement signal of a detector pixel and / or a maximum value of the measurement signal of a detector pixel for a specific input signal. In order to achieve a high image homogeneity, the detector pixels should have as much as possible the same response behavior for an input signal that is essentially the same for all detector pixels (for example when irradiating the detector surface without object in the object receiving region). Whether this is the case can be checked, for example, during a change of the workpiece to be illuminated by recording an image without an object in the object recording region (in other words by recording a bright image). The achievable image homogeneity can then be determined for this image.In general terms, the response behavior of the detector surface and, in particular, an at least local distribution of the response behavior within the detector surface (i.e., of its individual detector pixels) can thus also be considered as a variable for ascertaining the regeneration state and / or degeneration state.Furthermore, it is possible to estimate or simulate the regeneration state and / or degeneration state on the basis of at least one variable which relates only indirectly to such a state or is dependent thereon.For this purpose, it is possible in particular to determine an irradiation time period which specifies how long an unshielded detector surface has already been irradiated, for example, during a continuous (but possibly clocked, i.e. possibly also briefly interrupted) measurement operation. This can thus be a cumulative time duration.Likewise, a shielding time period can be determined which indicates how long a detector surface is already shielded.Furthermore, an irradiation dose of a (unshielded) detector surface can be estimated. An actual measurement of this dose would also be theoretically conceivable. The irradiation dose can be defined as an accumulated irradiation dose during the ongoing measurement operation and in particular clocked measurement operation. The value of the irradiation dose can be estimated from the operating variables of the arrangement. For this purpose, at least one of the following operating variables can be considered: an emitted irradiation dose, a duration of a single irradiation process (for example in the form of a cycle duration), a number of irradiation processes carried out, a (radiation) degree of absorption of the workpiece to be illuminated.Preferably, a degeneration threshold value can be defined on the basis of or for any(s) of the variables explained above (if they relate to an unshielded state) and, for example, if this threshold value is exceeded, an unacceptable degeneration state can be concluded. This can mean that the detector surface concerned can no longer be used for image acquisition, but must be shielded.Conversely, a regeneration threshold may be defined based on or for all (r) of the above-discussed quantities (if they relate to a shielded state), and if this is reached, an acceptable regeneration state may be inferred, for example. This can mean that the detector surface concerned has regenerated sufficiently and can be used for image acquisition (i.e. no longer has to be shielded). Said threshold values may define a predetermined regeneration state mentioned above.To establish such threshold values, test measurements can be carried out with the arrangement or with an arrangement of identical construction. A high level of relevance can be achieved if such a test measurement is carried out with the actually used arrangement and / or a workpiece to be illuminated actually, since the degree of absorption of the workpiece also determines the radiation dose which the detector surface actually reaches.Examples of a degeneration threshold value, which is preferably not to be exceeded, are:an absolute value of the dark current, in particular an absolute portion of a (theoretically) possible maximum value. The latter may be indicated as a so-called maximum digital value (e.g. 65535 (i.e. 16 2) with a 16 bit output of an A / D converter of a detector device);an increase (for example percent) in dark current within a predetermined time period;a (for example percent) decrease of a modulation from a starting value (for example calculated as median over all pixel values), wherein the modulation applies to a maximum expected radiation dose. The reaching of the maximum expected radiation dose can be checked by means of a dosimeter and / or can be at least approximately achieved by using always identical settings of the radiation source. To check changes in the modulation, the same maximum expected radiation dose should always be assumed;a size of contiguous bad pixel clusters, for example when the detector pixels of the detector surface are checked for linearity, stability or the achievable absolute measurement value. In this case, bad pixels may be defined as those which do not meet a correspondingly predetermined minimum set value. Such clusters suffer in particular from image homogeneity.Examples of a regeneration threshold value, which preferably indicates a minimum value to be reached, are:an absolute value of the dark current according to the above definition, which typically decreases during the regeneration and for the determination of which no image acquisitions are required;a decrease (for example percent) in the dark current within a predetermined time period;a size of contiguous bad pixel clusters as defined above, which size typically decreases during regeneration and can be checked, e.g., by means of test image acquisitions.It is also possible in principle to check a regeneration threshold value in an irradiated state and / or to define it with respect to the irradiated state. For example, sufficient regeneration may be assumed when any of the above degeneration thresholds is not yet exceeded in an irradiated state.It should again be noted that such variables can be measured directly (i.e. online) in the measurement mode. Preferably, however, these are determined in a test mode, which can also be carried out with another but structurally identical arrangement, and an irradiation time period, a shielding time period and / or an irradiation dose are determined at which the corresponding threshold values are reached. During operation of the arrangement (i.e. in particular during measurement operation), it is then possible to estimate by monitoring or ascertaining the corresponding time periods and / or dose values whether a predetermined regeneration or degeneration state has been reached without renewed measurements of the stated variables being required.As already indicated above, according to a further development of the arrangement and the method, it can be provided that the detector surfaces are of the same size. In particular, the detector surfaces can have the same base surface or a same surface spanned or filled by their detector pixels.The detector device can have an overall detector surface for detecting incident electromagnetic radiation, wherein at least parts of the overall detector surface can be formed by a first detector surface and a second detector surface. A development of the method and of the arrangement provides that the first detector surface and / or the second detector surface each form at least one quarter to one half of the total detector surface. The unshielded portion of the total detector surface, on which electromagnetic radiation from the radiation source can directly impinge during operation of the arrangement, is available for image acquisition. This can form one half to three quarters of the total detector area.In particular, only the data of the detector device can be further processed, which are assigned to the unshielded portion of the total detector surface on which electromagnetic radiation impinges. In other words, the shielded part of the detector device can also generate data which forms the detector surface not irradiated by the electromagnetic radiation. However, this data is not important for the examination of the object. If only the data corresponding to the irradiated detector area is processed, processing time can be saved and the amount of data can be limited.According to a further embodiment of arrangement and method, an area size of a shielded and / or an area size of an unshielded portion of the total detector area (which is composed of the plurality of detector areas of the arrangement) is / are variable, in particular between two object transmission processes. An object transmission process can be understood to mean an object-specific complete transmission process, i.e. a process which includes the recording of a single transmission image or of a plurality of transmission images required for a reconstruction of the object by means of the detector device. In particular, the size of the non-irradiated portion of the total detector surface can be variable or varied between the transmission processes of two different objects.The variation may be performed continuously, stepwise and / or after predetermined time intervals or reaching thresholds, such as a predetermined number of object transmission operations. Alternatively or additionally, the variation of the size of the non-irradiated portion can be achieved, for example, by suitable movement of at least one of the following components of the arrangement: radiation source, detector device or a shielding device explained below. As a result, the detector device can be adapted to different sizes of a workpiece to be transmitted.The relative movement of the radiation source and the detector device has already been mentioned above in general, and in particular the movement of the detector device or of parts of the detector device. Alternatively or additionally to a movement of the detector device or of parts of the detector device, the radiation source can be moved. The detector device can therefore be movable and the radiation source can remain substantially stationary (or vice versa). It is also possible to move both the detector device and the radiation source in order to bring the first part (for example a first detector surface) or the second part (for example a second detector surface) into a position in which the respective part is no longer irradiated.The relative movement of detector device and radiation source can also enable the above-explained variation of the size of the shielded portion of the total detector surface. In particular, at least a portion of the total detector surface can be positionable outside radiation emitted by the radiation source and in particular behind a shielding device from the perspective of the radiation source in such a way that this portion remains substantially unexposed during object transmission. The corresponding movements can take place linearly and / or rotationally and are preferably made possible by actuator devices of the arrangement. In particular, at least one drive motor (for example an electric motor) can be provided, which drives the movement.The detector surfaces of the detector device can be configured continuously and in particular can be formed by at least one single detector module. The detector module can be a structural unit. The detector module can be irradiated for the purpose of generating a single coherent transmission image, wherein only a non-shielded part of the detector module is irradiated at one time. In particular, the detector module can in principle be configured to generate a (preferably complete and / or complete) image of the object and / or to provide the signals or data required for this purpose in the event of an unshielded irradiation with the electromagnetic radiation. The unexposed, since shielded, portion of the total detector surface or of the detector module can, on the other hand, be ignored or define a corresponding dark image area in the transmitted image obtained.The contiguous formation of the detector surfaces can generally comprise the provision of a substantially closed or uniform detector surface, such that a continuous or substantially continuous detection of the electromagnetic radiation is possible, which may only depend on a local resolution of the detector device.Alternatively, it can be provided that the total detector surface of the detector device is formed in multiple parts or, in other words, is divided, for example into the individual detector surfaces and / or into individual detector modules, each of which comprises at least one detector surface. The total detector surface can be spatially, mechanically and / or electrically divided. Each portion of the total detector surface is configured to acquire a separate and / or complete transmission image of the object. Each portion may be a single detector surface.In particular, a first detector surface can be formed by a first detector module and at least one further detector surface by at least one further detector module. According to the above explanations, the detector modules can be configured to respectively acquire individual and / or complete transmission images. The non-irradiated portion of the total detector surface can in this context be at least one at least partially or even completely non-irradiated, since shielded detector module. The remaining detector module or modules, on the other hand, cannot be shielded for image detection and can consequently be irradiated. In particular, it can be provided that a previously unshielded irradiated detector module is no longer irradiated and instead a previously unshielded detector module is irradiated for the purpose of image acquisition. The (unshielded) irradiation with the electromagnetic radiation can consequently change between the detector modules, at least one being partially or completely shielded and thus remaining (at least approximately) unexposed.The shielding device can comprise material which strongly weakens electromagnetic radiation, such as lead. In particular, it can be designed in a plate-shaped and / or ring-shaped manner. In general, the shielding device can be positioned or positionable in a beam path of the electromagnetic radiation (for example within a beam cone of the electromagnetic radiation). In particular, the shielding device can be positioned at least partially between the detector device and the radiation source and / or the object receiving region (e.g. viewed along a beam axis originating from the radiation source and extending to the detector device).Additionally or alternatively, the shielding device can be positioned or positionable in such a way that the electromagnetic radiation impinges on the shielding device, but does not penetrate it or does not completely penetrate it and consequently also does not arrive at the shielded portion of the detector surface or only reaches it in a significantly attenuated manner. In other words, the shielding device can at least partially cover the detector surface in order to achieve the shielding. The shielding device can be formed in one part or in multiple parts. In one variant, it comprises shielding surfaces positioned on both sides of the beam axis.In this context, it can also be provided that the total detector surface is defined by a plurality of individual detector modules and the shielding device is configured to shield at least one of the detector modules, while at least one other of the detector modules can be irradiated by the electromagnetic radiation. The shielded detector module can correspondingly form the unexposed, as shielded portion of the total detector surface. In particular, it can be provided that at least one of the detector modules is completely or substantially completely shielded, while at least one other of the detector modules is completely or substantially completely uncovered (i.e. not shielded) for the purpose of irradiation with electromagnetic radiation. In a variant, it is provided that the total detector surface is defined by at least two detector modules, at least one of which can be shielded, while at least one other is left free for irradiation by the electromagnetic radiation. In other words, the at least two detector modules can be mutually shielded and left free, so that one can regenerate, while the other is available for generating transmission images and thus ensures operability of the arrangement.According to a further development of arrangement and method, the detector device and the shielding device are movable relative to one another. In general, movability can be made possible in such a way that the selective shielding of at least one portion of the detector device and / or the release of another portion of the detector device for the purpose of irradiation can be achieved. Furthermore, the movability can enable the above-explained changing of the shielded portion of the total detector surface and / or the alternating leaving free and shielding of a plurality of detector modules. All movements can take place linearly and / or rotationally and are preferably made possible by actuator devices (in particular at least one drive motor) of the arrangement.In one variant, the shielding device is installed in a fixed position and the detector device is movable, in particular orthogonally to the beam axis. In particular, it can be provided that the detector device comprises a plurality of detector modules and, as part of a movement of the detector device, at least one of the detector modules can be brought into a shielding overlap with and / or a shielding relative arrangement to the shielding device. By contrast, at least one other detector module can be / are arranged (for example by arranging in a beam course of the electromagnetic radiation or by arranging in an overlapping manner with a beam axis) such that electromagnetic radiation from the radiation source impinges on the other detector module and is detectable.According to one embodiment of arrangement and method, the unexposed portion of the total detector area is ignored when detecting the electromagnetic radiation. In particular, it can be provided that a shielded detector module is ignored in a plurality of detector modules. The not-taken-into-consideration can comprise at least partially switching off the detector surface or a detector module and / or the at least partially placing the detector device in a state that does not detect or evaluate the radiation. By means of this embodiment, the energy consumption of the arrangement can be reduced. Furthermore, a regeneration of the shielded portion of the detector surface can be accelerated, since the ignored portion does not have to be kept in a standby mode. In particular, therefore, not only in this embodiment can the sensor elements of the detector device, which are assigned to the shielded detector surface and / or not used for the image recording, be electrically switched off, i.e. no more electrical voltage is present at the sensor elements. This also contributes to a regeneration of the detector elements and thus of the detector surface.A further development provides that the shielding device comprises lead. For example, the shielding device can comprise a lead-containing alloy or consist of such an alloy. In principle, however, the use of other shielding materials is also provided, in particular materials which make possible shielding from X-rays.In all of the above embodiments relating to movability of certain components, elements may further be provided for mechanically controlling the respective movements. In particular, guide devices such as guide rails or slide rails can be provided in order to guide a movement of the detector device or shielding device, for example. Additionally or alternatively, at least one stop can be provided in order to spatially limit the movement of at least one moved component. As a result, for example, irradiation of the detector device can be reliably achieved in a predefined part of the total detector area.The invention further relates to a method for radiating an object (in particular a workpiece) with electromagnetic radiation (in particular X-ray radiation), comprising the steps:shielding at least one of a plurality of detector surfaces of a detector device from electromagnetic radiation that can be radiated onto the detector device through an object receiving region, wherein at least one other detector surface is not shielded;irradiating the electromagnetic radiation onto the detector devicedetecting at least that electromagnetic radiation which impinges on the unshielded detector surface,wherein the detector surfaces have the same resolution.The method can be carried out with an arrangement described in this description. The method may generally comprise any further feature and step to perform / provide all of the modes, interactions and effects discussed above and below. In particular, the method can have a step of changing between the shielded and unshielded detector surfaces, a step of shielding a single detector module while leaving another detector module exposed (and / or changing between the shielded and left exposed detector modules) or a step of not leaving an unexposed, as shielded, portion of the detector surface unexposed. Furthermore, the method can be carried out within the scope of object transmission in a production line or in conjunction with a production line, in particular within the scope of a temporal clocking of the production line (see inline CT scanning, as discussed above, or by transport directly or indirectly from the production line to the arrangement).An embodiment of the invention is explained below with reference to the attached schematic figures. They represent: FIG. 1 shows an arrangement according to the embodiment of the invention in an operating phase in which one of two detector modules is shielded; and FIG. 2 shows an arrangement according to the embodiment of the invention in another operating phase, in which the other is shielded by two detector modules.FIG. 1 shows an arrangement 10 according to an embodiment of the invention in a first operating phase. The arrangement 10 is designed to carry out a method for radiating an object with electromagnetic radiation. The arrangement 10 comprises a radiation source 12 in the form of an X-ray radiation source. The radiation source 12 is configured to emit an x-ray beam (i.e. electromagnetic radiation) along a beam axis A indicated by dashed lines. The electromagnetic radiation propagates from the radiation source, in particular within a beam cone. This is achieved, for example, by a not-illustrated aperture of the radiation source 12. The beam axis can be, in particular, the central axis of the beam cone. The beam axis A and thus the X-ray radiation passes through an object receiving region 14, which is likewise indicated by dashed lines. An object to be passed through can be positioned in the object receiving region 14 (for example an industrially produced workpiece).At an end of the beam axis A remote from the radiation source 12, a detector device 16 is arranged. This includes an overall detector surface 18 sensitive to x-rays, which is composed of two individual detector surfaces 20, 22. The individual detector surfaces 20, 22 are formed by separate detector modules 24, 26 or are each formed as surfaces of such a detector module 24, 26 facing the radiation source. Specifically, the detector device 16 comprises a first detector module 24, which can be irradiated by the radiation source 12 in the operating phase shown in FIG. 1, and a second detector module 26, which is shielded from the electromagnetic radiation by a shielding device 28, which is explained below, in the operating phase shown in FIG. 1.The detector modules 24, 26 are each configured to capture a transmission image of the object to be transmitted upon irradiation with the electromagnetic radiation and to provide this image, for example in the form of an image file, for further evaluation. Each detector module 24, 26 can generate its own and preferably complete transmission image of the object.The shielding device 28 comprises two shielding elements 30, which are shown in plate form and are positioned on both sides of the beam axis A in the embodiment shown. In principle, it can also be provided that a single and, for example, annular shielding element 30 is provided. The shielding surfaces illustrated in FIG. 1 would in this case represent a cross section through such an annular shielding element 30 or, in other words, in each case a cross section through a circumferential region of the annular shielding element 30.The shielding elements 30 are each made of lead, tungsten, an alloy containing lead and / or tungsten and / or a sandwich material with at least one layer of lead and / or tungsten and are substantially opaque to the electromagnetic radiation, i.e. the attenuation of the invasive radiation by the shielding elements 30 is very high. In the exemplary embodiment shown, the shielding elements 30 are installed in a fixed position within the arrangement 10. In another embodiment, the detector device 16 can be configured to be stationary or both the shielding elements 30 and the radiation source 12 can be arranged to be movable. Viewed along the beam axis A, the shielding elements 30 in the exemplary embodiment shown are furthermore positioned between the radiation source 12 and the detector device 16 and also between the object receiving region 14 and the detector device 16. In particular, the shielding elements 30 are positioned in such a way that a region lying behind them from the perspective of the radiation source 12 is shielded from the electromagnetic radiation.More precisely, a beam emitted by the radiation source 12 propagates along the beam axis A, for example in the sense of a beam cone, and thus also impinges on the shielding elements 30 (not shown separately). However, since these have a high degree of absorption for the incident electromagnetic radiation, a region behind them is shielded. This thus relates in each operating phase to a region in which a proportion of the total detector surface 18 (i.e. the first detector surface 20 and the second detector surface 22) of the detector device 16 is arranged.In particular, it can be seen in FIG. 1 that the detector modules 24, 26 are positioned within the arrangement 10 in such a way that the second detector module 26 can be irradiated for image detection, while the first detector module 24 is shielded from the electromagnetic radiation. This is achieved in that the first detector module 24 is positioned behind the upper shielding element 30 in FIG. 1 from the perspective of the radiation source 12, while the beam axis A impinges on the second detector module 26 and the second detector module 26 is uncovered.By masking and thus shielding one of the detector modules 24, 26, the total detector surface 18 of the detector device 16 is partially masked. The concealed first detector module 24 is thus kept radiation-free and can regenerate. The first detector module 24 also forms an unexposed portion of the total available detector area 18. However, the operability of the arrangement 10 is still ensured by providing the second unshielded detector module 26.As already indicated in FIG. 1 by the arrow P, the detector device 16 is furthermore movable relative to the beam axis A and is displaceable orthogonally to the beam axis A in the exemplary embodiment shown. This can be effected via an actuator device of the arrangement 10, not shown separately, and in particular driven by a drive motor. In particular, the detector device 16 is displaceable in such a way that either the first or the second detector module 24, 26 can be selectively irradiated by the radiation source 12. At the same time, the detector device 16 is displaceable in such a way that the respective other (or non-irradiated) detector module 24, 26 is shielded from the shielding device 28 and can consequently regenerate.This results from a consideration of FIG. 2, in which the detector device 16 has been displaced according to the arrow P from FIG. 1. As shown, in the corresponding second operating phase illustrated in FIG. 2, the first detector module 24 can be irradiated with the electromagnetic radiation, while the second detector module 26 is covered by the shielding device 28. In this state, the second detector module 26 can consequently regenerate, while the operability of the arrangement 10 is still ensured in the sense of a still existing possibility for image acquisition.It is understood that a return movement from the second operating phase shown in FIG. 2 and counter to the arrow P is also provided for reaching the first operating phase according to FIG. 1. These movements can likewise be guided by guide devices, not shown. The end positions of the movements of the detector modules 24, 26 in the respective operating phases can furthermore be defined via stop elements, so that a position relative to the radiation source 12 is substantially reproducible and at least for this reason no repeated measurement and if necessary alignment of the detector modules 24, 26 is required.In summary, the arrangement 10 of the embodiment shown in FIGS. 1 and 2 is configured to alternately irradiate the first or the second detector module 24, 26 for the purpose of image acquisition, while the respective other of the first or the second detector module 24, 26 can regenerate as a result of shielding by the shielding device 28.Using separate detector modules 24, 26 is optional. Alternatively, it can also be provided to use a single detector module which is displaceable analogously to the operating phases illustrated in FIGS. 1 and 2. In this case, for example, one half of the total detector surface of the detector module would be radiation-transmissive, while the other half is shielded for the purpose of regeneration. Alternatively, in each case in an operating phase, for example, three quarters of the total detector area can be shielded and one quarter of the total detector area can be irradiated with radiation from the radiation source, in particular when using a detector module with a square total detector area. In order to be able to irradiate the desired quarter of the total detector surface in each case, i.e. to be able to use it as a detector surface, the detector device can be movable, for example, not only in one direction transverse to the beam axis A but in two different directions transverse to the beam axis A. Alternatively, the detector device can be rotatable about an axis of rotation which, for example, extends parallel to the beam axis A but offset with respect to the beam axis A.The time duration or the time of the change between the operating phases illustrated in FIGS. 1 and 2 can be selected, for example, depending on properties of the detector device 16 derived from the image (for example, a change in a spatially and / or temporal noise component or the noise distribution). Likewise, a dependence on a number of image acquisition processes, an operating time and / or a radiation intensity can be provided. In all of these cases, the arrangement 10 can automatically effect a change between the operating phases.Examples of suitable variables for concluding a regeneration state and / or degeneration state of one of the detector surfaces 20, 22 and for initiating a change based thereon are given in the general part of the description. The determination of the value for these variables can be carried out by a control device, not shown, of the arrangement 10, which can comprise a computer device and / or a microprocessor, for example. The control device can also initiate steps in an automated manner in order to bring about the displacement according to the arrow P and / or vice versa. Additionally or alternatively, a manual change between the operating phases is also possible, wherein the control device can, for example, output suitable instructions to an operator regarding the need for the change.Because the arrangement 10 provides the possibility of an intermediate and at least partial regeneration of the detector device 16, the reliability and in particular the useful life of the detector device 16 or of its detector modules 24, 26 increases. In particular, the use of a high radiation dose, which would otherwise lead to rapid degeneration during continuous irradiation of the entire individual detector surface 20, can be compensated again at least partially by the provided regeneration possibility.Furthermore, the detector modules 24, 26 and thus their detector surfaces 20, 22 are configured generally identically in the example shown. In particular, they have the same resolution and also the same size. As a result, the object transmission can be continued substantially seamlessly even in the event of a change between shielded and unshielded detector surfaces 20, 22. In particular, it is not necessary to separately check which of the detector surfaces 20, 22 is currently being irradiated and, on the basis thereof, to carry out adaptations, for example of an image generating device which receives the measurement signals of the detector surfaces 20, 22 for generating a transmission image.In particular, this can make it possible for calibration parameters for one of the detector surfaces 20, 22 to also be valid for the other detector surface 20, 22, which reduces the calibration outlay, but also the outlay for image generation, since it is not necessary to distinguish between currently valid calibration parameters.The reliability can also be increased by providing with the arrangement 10 an alternative possibility for reducing the so-called ghosting effect, which is gentle on the detector device 16. The ghosting effect occurs above all in the case of detector materials such as highly sensitive scintillator-cesium iodide (Csl). If an object is transmitted over a longer period of time and / or without a movement, this effect can further influence the transmitted image then captured even after termination or subsequent change of the transmission. Therefore, structures of a previous measurement object or of another orientation of the same measurement object that do not correspond to the current situation can remain recognizable. In the prior art, this is often compensated for by carrying out irradiation at maximum intensity and without further object transmission after the transmission image has been acquired. However, the high radiation dose used in this case again reduces the reliability of the detector device 16.The arrangement 10 according to the embodiment shown, on the other hand, makes it possible to shield the portion of the individual detector surface 20 or 22 (or an individual detector module 24, 26) that is critical for any possible ghosting effect and to temporarily intentionally exclude it from image acquisition. The shielded portion of the individual detector surface 20 or 22 can then regenerate, decaying the ghosting effect, without having to be exposed to a high radiation dose. This also increases the reliability and in particular the useful life of the detector device 16. Instead, the image acquisition can be continued with the portion of the detector surface 20 or 22 that is not ghosted and also not shielded.

Claims

Arrangement (10) for radiating an object with electromagnetic radiation, in particular for object radiation in a production line or in conjunction with a production line, having: - a radiation source (12), - a detector device (16), - a shielding device (28), and - a control device, wherein the radiation source (12) is configured to radiate electromagnetic radiation through an object receiving region (14) of the arrangement (10) onto the detector device (16), wherein the detector device (16) has a plurality of detector surfaces (20, 22), wherein the detector device (16) is configured to detect electromagnetic radiation impinging on the detector surfaces (20, 22) for generating an object radiation image, wherein optionally at least one of the detector surfaces (20, 22) can be shielded against the electromagnetic radiation by the shielding device (28), while at least one other of the detector surfaces (20, 22) is available for image acquisition, wherein the detector surfaces (20, 22) have the same resolution, wherein the control device is configured to carry out the shielding according to a regeneration state and / or a degeneration state of at least one of the detector surfaces (20, 22), and to determine the regeneration state and / or degeneration state of the detector surface (20, 22) based on at least the following variable: - a dark current of the detector surface (20, 22).Arrangement (10) according to Claim 1, wherein, when there is no object to be transmitted in the object receiving region (14), electromagnetic radiation radiated from the radiation source (12) through the object receiving region (14) onto a shielded detector surface (20) has a first radiation flux density, and electromagnetic radiation radiated from the radiation source (12) through the object receiving region (14) onto an unshielded detector surface (22) has a second radiation flux density, wherein the first radiation flux density is less than 20% of the second radiation flux density.Arrangement (10) according to one of the preceding claims, wherein the arrangement (10) is operable in such a way that a detector surface (20, 22) which is initially not shielded and used for image generation is shielded and a detector surface (20, 22) which is initially shielded is used instead for image generation.The arrangement (10) of claim 1, wherein a detector surface (20, 22) is shielded at least until it has reached a predetermined regeneration state; or wherein a detector surface (20, 22) is shielded at the latest when it has reached a predetermined degeneration state.Arrangement (10) according to one of the preceding claims, wherein the detector surfaces (20, 22) are of the same size.Arrangement (10) according to one of the preceding claims, wherein at least two of the detector surfaces (20, 22) are formed continuously.Arrangement (10) according to Claim 6, wherein the detector surfaces (20, 22) are formed by a common detector module (24, 26).Method for radiating an object with electromagnetic radiation, comprising the steps of: - shielding at least one of a plurality of detector surfaces (20, 22) of a detector device (16) from electromagnetic radiation that can be radiated onto the detector device (16) through an object receiving region (14), wherein at least one other detector surface (20, 22) is not shielded; Irradiation of the electromagnetic radiation onto the detector device (16) - detecting at least that electromagnetic radiation which impinges on the unshielded detector surface (20, 22), wherein the detector surfaces (20, 22) have the same resolution, wherein the control device is configured to carry out the shielding according to a regeneration state and / or a degeneration state of at least one of the detector surfaces (20, 22), and to determine the regeneration state and / or degeneration state of the detector surface (20, 22) based on at least the following variable: - a dark current of the detector surface (20, 22).

Images