Device for conducting an examination of an object using X-rays

Abstract

The invention relates to a device for conducting an examination of an object using X-ray radiation, - wherein the device comprises a functional element arranged in the radiation area so as to be movable in one direction of movement, which has an electrically and / or magnetically conductive area, and a position sensor, - wherein the position sensor has an electrical coil arrangement for detecting the conductive area and for providing a total voltage depending on the detection of the conductive area, - wherein the coil arrangement comprises an excitation coil for providing an alternating magnetic field and two detection coils connected in series for detecting at least a part of the alternating magnetic field, wherein the detection coils and the excitation coil are arranged such that the sum voltage across the two detection coils depends on a position of the functional element relative to the position sensor, - wherein the device is configured to determine a position signal relating to the position of the functional element relative to the position sensor, depending on the total voltage.

Description

[0001] The invention relates to a device for conducting an examination of an object using X-rays, comprising an X-ray source for emitting X-rays, an X-ray detector for detecting at least a portion of the X-rays emitted by the X-ray source, a radiation zone formed between the X-ray source and the X-ray detector, a specimen carrier that can be arranged in the radiation zone to hold the object for conducting the examination, an evaluation unit coupled to the X-ray detector for evaluating a radiation signal from the X-ray detector, in particular for examining the object, a functional element arranged in the radiation zone to be movable in a direction of movement, which has an electrically and / or magnetically conductive area, and a position sensor, in particular for detecting a position of the functional element.

[0002] The invention further relates to a method for conducting an examination of an object using X-rays, wherein an X-ray source emits the X-rays at least partially to a radiation zone formed between the X-ray source and an X-ray detector, wherein the X-ray detector detects at least a portion of the X-rays emitted by the X-ray source and emits a radiation signal depending on the detected X-rays, wherein the object is held by a slide which is arranged in the radiation zone for conducting the examination, wherein the radiation signal of the X-ray detector is evaluated by means of an evaluation unit coupled to the X-ray detector, and wherein a functional element having an electrically and / or magnetically conductive area is moved in a direction of movement within the radiation zone.in particular a position signal, which relates to a position of the functional element relative to a position sensor, is determined.

[0003] The following are considered state of the art: DE 31 26 285 A1, EP 3 073 891 B1, US 2019 / 0 216 412 A1, DE 37 27 265 A1, EP 0 182 085 A2 and US 2009 / 0 086 830 A1.

[0004] Devices of this type, used to examine objects using X-rays, as well as methods of this type, are extensively known in the prior art, so that, in principle, a separate written reference is not required. Devices of this type, such as computed tomography scanners, X-ray machines, or the like, serve to perform an examination of the object in order to determine at least part of its structure. Such examinations are frequently used in materials testing, but also in the field of medical diagnostics, for example, in making diagnoses of biological material, living organisms, or the like. The object can therefore be, for example, an item resulting from an industrial manufacturing process, but also a mining byproduct, the body of a living organism, or the like.

[0005] Tomography is, among other things, an imaging technique capable of providing, for example, a layer-by-layer representation of an object. Within the framework of tomography, internal spatial structures of the object can be determined, and cross-sectional images can be created. Computed tomography (CT) is a particularly important imaging technique used in radiology. X-rays are frequently employed for this purpose. For example, the X-rays are directed at the object from different directions and detected by an X-ray detector. By evaluating the radiation signals, absorption values ​​of the X-rays by the object can be determined, which makes it possible to ascertain the object's structure. The evaluation unit can be integrated into the device or connected to it as a separate unit.The evaluation may result in, for example, imaging of the object's structure.

[0006] The functional element allows the device's function to be influenced, particularly during the examination. Accordingly, the functional element can be, for example, a collimator or similar device to influence the X-ray radiation within the radiation field. However, the functional element can also serve to record examination parameters during the examination, such as the object's temperature, scattered radiation, and / or the like. The functional element is typically exposed to the X-ray radiation within the radiation field, at least partially, during the examination. To allow the functional element's effect to be adjusted as needed, it is movable in a direction of movement, preferably longitudinal.For this purpose, a separate drive can be provided, which can be controlled in a suitable manner by means of a control unit of the device, so that the functional element can be moved to the desired position.

[0007] To determine the position of the functional element, the device includes a position sensor that serves to detect the position of the functional element and transmit a corresponding position signal to the control unit. In many applications, this results in the position sensor also being at least partially exposed to X-rays. Therefore, the design of the position sensor must meet specific requirements to ensure high radiation resistance, particularly to X-rays, while simultaneously achieving the highest possible accuracy in position detection. In this context, for example, DE 10 2022 206 622 A1 discloses a device for receiving a beam path component for X-rays and a method for providing position information.

[0008] Especially when the functional element includes, for example, a filter, a collimator, or similar components, its positioning within the radiation field must be highly accurate to achieve the most precise test results possible. In particular, the current position of the functional element must be monitored to detect any unwanted changes or variations, even without radiation. Typically, the functional element is driven in the direction of movement by one or more stepper motors. Their position can be determined by approaching one or more end stops and thus calibratable coding. End stop detection in a stepper motor can be achieved, for example, by sensing the motor current or by using appropriate coding devices, light barriers, switches, and / or similar mechanisms.Conventional coding devices operate, for example, using slotted discs and light barriers or magnetic discs and Hall effect sensors. However, such position sensors have proven to have only limited resistance to X-rays and are also generally sensitive to mechanical tolerances, which can arise, for example, from rotation during a computed tomography (CT) scan or during assembly or adjustment during manufacturing. Furthermore, the use of electronic circuit arrangements, especially program-controlled computer units, proves to be limited in terms of reliability and lifespan due to X-ray exposure. Therefore, in the prior art, position sensors often need to be shielded from X-rays, as also disclosed in DE 10 2022 206 622 A1.

[0009] A further disadvantage is that, in the prior art, an absolute or reference position of the position sensor cannot be directly determined, and potential deviations can lead to complex errors in test results that may be difficult to correct. Furthermore, the reliability of the position sensor is limited, particularly with regard to aging.

[0010] The invention is based on the objective of further developing a device and a method in such a way as to improve the radiation resistance of the position sensor and / or reduce radiation-induced aging of the position sensor.

[0011] A device and a method according to the independent claims are proposed as a solution. Advantageous further developments result from features of the dependent claims. Regardless of the grammatical gender of a particular term, persons of male, female, or other gender identities are included.

[0012] With regard to a generic device, it is particularly proposed that the position sensor comprises an electrical coil arrangement for detecting the conductive area and for providing a position signal depending on the detection of the conductive area, wherein the coil arrangement comprises an excitation coil for providing an alternating magnetic field and two detection coils connected in series for detecting at least a part of the alternating magnetic field, wherein the detection coils and the excitation coil are arranged such that a sum voltage across the two detection coils depends on a position of the functional element relative to the position sensor, wherein the device is configured to determine a position signal relating to the position of the functional element relative to the position sensor, depending on the sum voltage.

[0013] With regard to a generic method, it is particularly proposed that the conductive area is detected by means of an electrical coil arrangement of a position sensor, and that a sum voltage is provided depending on the detection of the conductive area, wherein an alternating magnetic field is provided by means of an excitation coil of the coil arrangement, wherein at least a part of the alternating magnetic field is detected by means of two detection coils of the coil arrangement connected in series, wherein the detection coils and the excitation coil are arranged such that the sum voltage across the two detection coils depends on a position of the functional element relative to the position sensor, and wherein a position signal relating to the position of the functional element relative to the position sensor is determined depending on the sum voltage.

[0014] The solution is based, among other things, on the idea that position detection can be reliably achieved using a position sensor without the need for any moving parts. This has the advantage that, for example, mechanical wear of the position sensor is essentially eliminated during normal operation over its predicted service life. Furthermore, using the coil arrangement for the position sensor proves advantageous because the coil arrangement can be easily implemented to be particularly radiation-resistant. At the same time, using the magnetic field as the medium for position detection allows for physical decoupling from X-rays, so that the position sensor achieves a position detection result that is essentially unaffected by X-rays.By utilizing the coil arrangement, it is possible to design the position sensor in such a way that only the coil arrangement needs to be located within the radiation field. This allows all other components of the position sensor, required for the operation of the coil arrangement and for determining the position, to be located essentially outside the radiation field. Therefore, separate, complex shielding of these position sensor components can be reduced or eliminated entirely.

[0015] At the same time, the coil arrangement enables reliable detection of the functional element's position because the total voltage depends on the element's position, particularly the electrically and / or magnetically conductive area. Therefore, no mechanical contact between the functional element and the position sensor is required. Furthermore, reaching an end stop is unnecessary, as the current position of the functional element can be reliably determined from the total voltage alone. The conductive area influences the geometry of the alternating magnetic field, which is detected by the sensing coils. This allows for a clear correlation between the total voltage, which depends on the induced voltages of the sensing coils, and the functional element's position.

[0016] Preferably, the detection coils are arranged side by side along the direction of movement. The detection coils can preferably be essentially identical in their geometric dimensions. The detection coils are preferably designed as flat coils and each has a winding with at least one, preferably several, turns. Particularly preferably, the windings of the detection coils have the same number of turns. For example, the detection coils can be designed essentially as Archimedean coils. The cross-section of the detection coils and / or the excitation coil can be essentially round or rectangular. The coils can be designed as cylindrical coils, flat coils, Archimedean coils, and / or the like. In particular, the excitation coil can have a geometry that differs from that of the detection coils.

[0017] The position sensor can have a single coil arrangement. However, depending on the device design, it is also possible for the position sensor to have multiple coil arrangements. The coil arrangements can be positioned essentially adjacent to each other along the direction of movement of the functional element. This makes it possible to detect even particularly large movement paths using the position sensor.

[0018] The conductive area can be made of an electrically conductive material such as metal, a metal alloy, and / or the like. Alternatively or additionally, the conductive area can also comprise a magnetizable material, such as ferrite, a magnetizable metal, a magnetizable alloy, and / or the like. The conductive area is preferably connected to the functional element as a separate component. However, it can also be formed integrally with the functional element. The conductive area is preferably arranged in the device such that it can be exposed to the alternating magnetic field emitted by the excitation coil. Accordingly, the sensing coils can detect the alternating magnetic field of the excitation coil.For this purpose, the excitation coil is supplied with a substantially constant alternating voltage or a substantially constant alternating current, so that the excitation coil provides the corresponding alternating magnetic field.

[0019] The X-ray detector serves, in particular, to detect secondary X-ray radiation that is at least partially transmitted, partially absorbed, and / or at least partially scattered by the object during the examination, and to provide a detector signal as a radiation signal depending on the detected secondary X-ray radiation. The detector signal can be evaluated by the evaluation unit in order to at least partially determine the structure of the object. X-ray detectors, such as those that can be used in X-ray machines and generic methods, are disclosed, for example, by MH Yaffe and HA Rowlands in "X-Ray Detectors for Digital Radiography," in Phys. Med. Biol. 42 (1997), pages 1 to 39.

[0020] Devices of this type, particularly X-ray machines, can have a wide variety of designs. An X-ray machine suitable for X-ray tomography is particularly advantageous, as it generates digital cross-sectional images from the absorption values ​​of X-rays by the object, which, for example, act upon the object from different directions. These images reveal the object's structure. Conventional X-ray methods typically involve exposing the object to X-rays, receiving the secondary X-ray radiation with an X-ray detector, and evaluating the radiation signal using an X-ray evaluation unit. The radiation signal is preferably an electrical signal, such as an analog or digital electrical signal. The evaluation unit can comprise an electronic hardware circuit and / or a program-controlled computer unit for the evaluation process.The X-ray evaluation unit may also have interfaces for providing the evaluation and / or output devices for printing the evaluation.

[0021] Furthermore, in computed tomography, absorption profiles of the object can be created from multiple spatial directions. The object's structure can also be determined from these profiles. Using computer-aided image reduction, for example, a specific absorption coefficient can be determined for a particular volume element of the object, thus revealing its spatial structure. X-ray tomography is an imaging technique that can be used, for example, to visualize a layer within the object under investigation.

[0022] It is further proposed that each winding of the sensing coils be selected such that the induced voltages of the series-connected sensing coils cancel each other out in a predetermined reference position of the functional element relative to the position sensor. This can be achieved, for example, by inverting the winding direction of the sensing coil windings relative to each other. This allows the induced voltages to cancel each other out when the sensing coils are subjected to the same magnetic flux of the alternating magnetic field. This can be implemented at a specific position of the functional element. Alternatively, it is also possible that the induced voltages are not completely canceled out. The cancellation can also be determined by a local minimum of the total voltage. Preferably, the total voltage is therefore essentially zero in the reference position.However, it may also only exhibit a local minimum in the area of ​​the reference position.

[0023] Furthermore, it is proposed that the detection coils be arranged adjacent to each other in a plane parallel to the direction of movement. This makes the function of the position sensor particularly easy to implement, because two adjacent detection coils can be subjected to the same alternating magnetic field. Preferably, the excitation coil is also arranged in the same plane.

[0024] The excitation coil can also be designed as a flat coil, with the excitation coil preferably enclosing the detection coils.

[0025] It is particularly advantageous if the series-connected detection coils are coupled to a detection-side capacitor to form a detection-side resonant circuit. The detection-side capacitor can be connected to the series circuit, or it can be connected to each detection coil individually. With multiple coil arrangements, the resulting resonant circuits preferably have the same resonant frequency. This significantly increases the sensitivity of the position sensor. The capacitor is preferably a ceramic capacitor, which has proven to be particularly resistant to X-rays.In principle, however, the capacitor can also be formed by corresponding conductive surfaces that can be arranged opposite each other on a circuit carrier in order to provide the corresponding electrical capacitance.

[0026] Furthermore, it is proposed that the detection coils be arranged on a circuit carrier that provides a connection area located outside the radiation range, with the coil arrangement preferably being at least partially located within the radiation range. This allows the detection coils to be implemented in a particularly simple manner. The circuit carrier can, for example, be a printed circuit board or another plate-like insulating material on which the detection coils can be arranged. The detection coils can, for example, be designed as conductive traces on the circuit carrier.

[0027] The circuit carrier can be made of a suitable material, such as plastic or ceramic, in particular FR4. It is also particularly advantageous to arrange the excitation coil on the circuit carrier. In this way, the entire coil assembly can be provided as a single, easily handled unit. The circuit carrier is preferably designed such that the coil assembly can be positioned within the radiation zone. At the same time, the circuit carrier can provide the connection area, which is preferably located outside the radiation zone. Thus, other components of the position sensor that are to be connected to the coil assembly can be positioned outside the radiation zone, thereby reducing or eliminating the need for separate shielding against X-rays.

[0028] Preferably, the excitation coil can also be connected to an excitation-side electrical capacitor, so that an excitation-side resonant circuit can be formed. The resonant frequency of the excitation-side resonant circuit preferably corresponds to the resonant frequency formed by the sensing coils and their capacitor.

[0029] In particular, it may be provided that the detection coils are arranged in a planar configuration on a flat circuit carrier. The flat circuit carrier can, for example, be a printed circuit board.

[0030] It is particularly advantageous if the detection coils are arranged on a first surface of the circuit carrier and the excitation coil is arranged on a second surface of the circuit carrier, which is different from the first surface and opposite it. In this way, galvanic isolation between the detection coils and the excitation coil can be achieved. At the same time, the circuit carrier, especially if it is very thin, can ensure reliable functionality with regard to the application of the alternating magnetic field to the detection coils. Preferably, the inner diameter of the excitation coil is selected such that the detection coils can be positioned within this inner diameter.

[0031] It is further proposed that the series-connected detection coils are coupled with a detection-side electrical capacitor to form a detection-side resonant circuit, wherein the excitation coil is supplied with an alternating current and / or an alternating voltage by a frequency generator coupled to the excitation coil, wherein a frequency of the alternating current or the alternating voltage essentially corresponds to a resonant frequency of the detection-side resonant circuit.

[0032] This allows for a particularly high sensitivity of the position sensor with regard to detecting the position of the functional element.

[0033] It has proven particularly advantageous to choose a resonant frequency in the range of approximately 800 kHz to approximately 1.6 MHz. It has been shown that interference is particularly low in this frequency range, thus further improving the function of the position sensor.

[0034] The invention provides that the position signal and a processing signal, which has a processing frequency that is particularly higher than the resonant frequency, are mixed by means of a first mixing unit to provide an intermediate frequency signal. The provision of the intermediate frequency signal enables improved signal processing, particularly with regard to the accuracy of detecting the position of the functional element. The processing frequency is a predefinable frequency that can, for example, be fixed for a specific application. It can also be provided that the predefining of the processing frequency is changed or varied depending on a specific event. Although the processing frequency can, in principle, be chosen to be lower than the resonant frequency, it can preferably be higher than the resonant frequency.Particularly advantageous is the ability to predefine the processing frequency as dependent on the resonant frequency. This makes it possible to provide the intermediate frequency signal with a substantially fixed frequency, allowing subsequent signal processing units to be specifically adapted to the intermediate frequency signal. This improves signal processing, enabling both upmixing and downmixing.

[0035] According to an alternative version of the invention, the intermediate frequency signal is filtered using an intermediate frequency bandpass filter to provide an intermediate frequency filter signal. This allows interference and unwanted influences to be filtered out particularly effectively, thus further improving the reliability and function, especially with regard to the accuracy of the position sensor. It is particularly advantageous if the intermediate frequency signal can be provided at a substantially constant frequency. This allows the intermediate frequency bandpass filter to be specifically tailored to this frequency, thereby improving the desired filtering effect.

[0036] It is further proposed that the intermediate frequency signal, the intermediate frequency filter signal, and / or the sum voltage be sampled discretely in time. This makes it possible to feed the intermediate frequency signal, the intermediate frequency filter signal, or the sensor signal into digital signal processing. The digital signal processing can be performed using a program-controlled computing unit, such as a digital signal processor (DSP), an FPGA, an ASIC, and / or the like. If the sensor signal is already sampled discretely in time, the subsequent signal processing can be almost entirely digitalized.

[0037] The invention provides that the intermediate frequency signal or the intermediate frequency filter signal, on the one hand, and a differential frequency signal, on the other hand, are mixed by means of a second mixing unit to provide a baseband signal, wherein one frequency of the differential frequency signal essentially corresponds to a difference between the frequencies of the position signal and the processing signal. This method achieves a type of demodulation that makes it possible to provide the baseband signal, which can then serve as a position signal with virtually no changes. Naturally, the position signal can be provided depending on the baseband signal, and further additional processing steps may be included, depending on the requirements and design of the device or the implementation of the method.

[0038] It is further proposed that the difference frequency signal has a frequency of approximately 8.5 kHz to approximately 50 kHz. This frequency range has proven to be particularly advantageous for signal processing in the context of position detection.

[0039] It is further proposed that the baseband signal be filtered using a low-pass filter to provide the position signal. This can achieve a further improvement in the accuracy and reliability of the position signal.

[0040] The advantages and effects specified for the device according to the invention also apply equally to the method according to the invention, and vice versa. In particular, method features can therefore also be formulated as device features and vice versa. The features and combinations of features specified above in the description, as well as the features and combinations of features mentioned in the following description of exemplary embodiments and / or shown in the figures alone, are usable not only in the combinations specified but also in other combinations. Thus, embodiments are also encompassed by the invention or are considered disclosed that are not explicitly shown and explained in the figures but can be derived and generated from the explained embodiments by separate combinations of features.

[0041] The features, functions, and / or effects illustrated by the exemplary embodiments can each, considered independently, represent individual features, functions, and / or effects of the invention, each of which further develops the invention independently. Therefore, the exemplary embodiments are intended to include combinations other than those described in the embodiments. Furthermore, the described embodiments can also be supplemented by additional features, functions, and / or effects of the invention already described.

[0042] They show: Fig. 1 a schematic representation of an X-ray machine, Fig. 2 in a schematic sectional view a section of a first embodiment of a position sensor of the device according to Fig. 1, Fig. 3 in a schematic top view a section of a second embodiment of the position sensor of the device according to Fig. 1, Fig. 4 a schematic circuit diagram of the position sensor according to Fig. 3, Fig. 5 a schematic diagram representation of a sum voltage of two series-connected detection coils of the coil arrangement according to Fig. 4 depending on a position of a collimator of the device according to Fig. 1, and Fig. 6 a schematic block diagram representation of the position sensor according to Fig. 3.

[0043] In Fig. Figure 1 shows a schematic representation of an X-ray device 10 as a device for performing an examination of an object using X-rays, which in this case is designed as an X-ray computed tomography (CT) scanner. The X-ray device 10 serves, for example, to perform an X-ray examination on a patient. However, the X-ray device 10 is not limited to use on patients and can, in principle, be used on any object, for example in materials testing or the like.

[0044] The X-ray machine 10 has a patient positioning device 46, which in turn has a traversing table 48 and a patient table 50 that is traversable in a longitudinal direction 52 relative to the traversing table 48 and serves as a support for the object, in this case a patient. By means of the patient positioning device 46, the patient 12, positioned on the patient table 50, can be positioned longitudinally 52 in a through-opening of a gantry 54. The gantry 54 is a ring-shaped support structure in which the through-opening is tunnel-shaped, allowing an examination area 30 of the patient 12 to be inserted into the through-opening for the X-ray examination.By means of the traversing table 48 the patient can be positioned in the passage opening of the gantry 54 in a predetermined manner so that the examination area 30 can be well exposed to the X-ray radiation 14 on the one hand and secondary X-ray radiation 20 can be well detected by means of the X-ray detector 18 on the other hand.

[0045] In a ring area surrounding the through-hole of the gantry 54, an X-ray source 16 is arranged, which serves to emit the X-ray radiation 14.

[0046] Radially opposite, in the ring area, is the X-ray detector 18. The function, arrangement, and construction of a suitable X-ray detector are described, for example, in DE 10 2008 050 838, for which further reference is made to the explanations therein.

[0047] As from Fig. As can be seen in Figure 1, the X-ray device 10 also has a control unit 56 which provides a control signal 58 by means of which the patient table 50 can be positioned in the gantry 54. In addition, the control unit 56 provides a control signal 60 which is used, among other things, to control the X-ray source 16 and the X-ray detector 18 in the gantry 54.

[0048] The X-ray device 10 also has a user interface 62, which can be used to at least partially specify the control signals 58, 60. The user interface 62 can, for example, include a joystick, a computer mouse, a keyboard, combinations thereof, and / or the like.

[0049] The examination area 30 of the patient 12 is examined by sliding the patient 12 longitudinally 52 into the gantry 54 using the patient table 50. During this movement, the X-ray source 16 and the X-ray detector 18 preferably move synchronously in a circular motion around the patient 12. The X-ray source 16 emits X-rays 14, which penetrate the examination area 30 of the patient 12. The X-rays 14 are partially absorbed, scattered, and / or deflected within the examination area 30 of the patient 12, so that secondary X-rays 20 emerge on the opposite side of the examination area 30. The secondary X-rays 20 can be detected by the X-ray detector 18.The X-ray detector 18 provides corresponding detector signals 22 as radiation signals, which are fed to the X-ray evaluation unit 24. This unit performs a corresponding evaluation of the detector signals 22 and transmits the evaluated data to the control unit 56. In the control unit 56, this data can be further processed, for example, to convert projection images into image information 64. The image information 64 can be transmitted from the control unit 56 to a display unit 66, which provides a graphical visual display for a user of the X-ray device 10.

[0050] A radiation zone 36 is formed between the X-ray detector 18 and the X-ray source 16. The examination area 30, for example, is located within this radiation zone 36. A collimator 26, which is movable in a direction 32, is also arranged within this radiation zone 36 as a functional element. For this purpose, the collimator 26 is coupled to a linear drive (not shown) which can be controlled by the control unit 56. The linear drive allows the collimator 26 to be moved to a desired position within the radiation zone 36. The collimator 26 can be used to influence the X-ray radiation within the radiation zone 36.

[0051] Since information about the position of the collimator 26 is important for carrying out the examination of the patient 12, the X-ray device 10 has a position sensor 28 which detects the position of the collimator 26 in the radiation area 36 and transmits a corresponding position signal 34 to the control unit 56.

[0052] Fig. Figure 2 shows a schematic circuit diagram of a section of a first embodiment for the position sensor 28. Fig. Figure 2 shows that the position sensor 28 has an electrical coil arrangement 40 which serves to detect a conductive area 38 of the collimator 26. The coil arrangement 40 also serves to provide the total voltage 68 depending on the detection of the conductive area 38.

[0053] In the present embodiment, the collimator 26 is mechanically connected via an unnamed connecting rod to a ferrite body, which forms the conductive area 38. This creates, in particular, a magnetically conductive area. In alternative embodiments, for example, an electrically conductive area or an electrically and magnetically conductive area may be provided.

[0054] Out of Fig. Figure 2 further shows that the coil arrangement 40 has an excitation coil 42, which in this case is designed as a cylindrical coil and is connected to a generator 70, so that the excitation coil 42 can be supplied with an alternating current in normal operation, which has essentially a constant amplitude and a constant frequency. The generator 70 is controllable by the control unit 56, so that at least the amplitude or the frequency of the alternating current can be adjusted. However, it is also possible to supply the excitation coil 42 with a corresponding alternating voltage.

[0055] Out of Fig. Figure 2 further shows that detection coils 44 are arranged axially adjacent to the axial ends of the excitation coil 42. The detection coils 44 are also designed as cylindrical coils and have essentially the same inner diameter as the excitation coil 42. The detection coils 44 are positioned coaxially to the excitation coil 42. The detection coils 44 are electrically connected in series and, in this case, have the same number of turns but with a winding direction inverted relative to each other. This results in a total voltage 68 across both detection coils 44, which, particularly with respect to its amplitude, corresponds to a difference in the voltages induced in the individual detection coils. The excitation coil 42 provides an alternating magnetic field due to the application of the alternating current, which, among other things, flows through the detection coils 44.

[0056] According to the design of the detection coils 44 and the electrical wiring, the following results in the Fig. At the position of the conductive area 38 shown in Figure 2, a total voltage 68 is generated, which is essentially zero. The voltages induced in each of the individual detection coils 44 thus cancel each other out. As soon as the collimator 26 and, consequently, the conductive area 38 move in the direction of movement 32, the coupling of the detection coils 44 with respect to the excitation coil 42 changes, so that the amplitudes of the voltages induced in each of the individual detection coils 44 differ from one another, and consequently, a total voltage 68 that deviates significantly from zero is generated. An amplitude of the total voltage 68 and / or a phase angle with respect to the alternating current of the generator 70 can be assigned to a position of the conductive area 38 and thus also to the position of the collimator 26.This makes it possible for the position signal 34, which is determined depending on the total voltage 68, to contain precise position information with respect to the conductive area 38 and thus with respect to the collimator 26.

[0057] The coil arrangement 40 is located near the collimator 26, i.e., within the radiation zone 36. A connection area 72 is also provided, at which the total voltage 68 is supplied. The connection area 72 is located outside the radiation zone 36. This allows a corresponding circuit arrangement 80 for processing the total voltage 36 to also be located outside the radiation zone 36. The present design of the position sensor 28 has the advantage that no mechanically moving parts are required. Furthermore, the design of the position sensor 28 proves to be particularly radiation-resistant. At the same time, the position of the collimator 26 can be detected with high accuracy.

[0058] Fig. Figure 3 shows a second embodiment for a position sensor 28, which in principle can also be used in place of the position sensor 28 in the X-ray device 10 according to Fig. 1. Regarding this configuration, reference is made to the explanations of the previous configuration. In the following, only the differences to the first configuration of the position sensor 28 are explained.

[0059] As from Fig. As can be seen in Figure 3, two coil assemblies 40 are arranged adjacent to each other on the circuit board 76 in the direction of movement 32 of the conductive area 38. The coil assemblies 40 are essentially identical in design. Fig. Figure 4 shows a schematic circuit diagram of the position sensor 28.

[0060] In the present embodiment, the coil arrangement 40 is formed on the printed circuit board 76 by conductive traces. This allows the coil arrangement 40 to be implemented in a particularly flat, space-saving, and cost-effective manner. The coils 42 and 44 are arranged essentially in the same plane, which is defined by the printed circuit board 76. The coil arrangement 40 includes an excitation coil 42 to which an excitation-side capacitor 82 is connected in parallel. The excitation coil 42 and the excitation-side capacitor 82 thus form an excitation-side resonant circuit, which in this case has approximately the same resonant frequency, essentially corresponding to the frequency of the alternating current supplied by the generator 70.In the present embodiment, it can optionally be provided that the excitation coil 42 and the detection coils 44 of the respective coil arrangement 40 are formed on different opposing surfaces of the circuit board 76.

[0061] Furthermore, how from Fig. As can be seen in Figure 4, the two detection coils 44 of the coil arrangement 40 are connected in series, with the detection coils 44 having the same number of turns but an inverted winding direction. The detection coils 44 are formed within an inner diameter of the excitation coil 42. The detection coils are arranged adjacent to each other in the direction of movement 32. In the present embodiment, it is provided that all detection coils 44 as well as the excitation coils 42 are arranged adjacent to each other parallel to the direction of movement 32.

[0062] The total voltage 68 drops across the two sensing coils 44 of the coil arrangement 40. This total voltage 68 can be supplied to the circuit arrangement 80 of the position sensor 28 via a connection area 72, which can optionally be formed on the circuit board 76. The circuit arrangement 80 evaluates the total voltage 68 and provides the position signal 34 accordingly.

[0063] The excitation coil 42 is also connected to the generator 70, so that the excitation coil 42 can be supplied with alternating current. In this embodiment, two excitation coils 42 are connected in parallel to the generator 70.

[0064] In this embodiment, the conductive area 38 is located in the direction of movement 32 within the area of ​​one of the coil arrangements 40, so that the position of the conductive area 38, and thus also the position of the collimator 26, can be precisely determined from the total voltage 68 of the corresponding coil arrangement 40. The adjacent arrangement of coil arrangements 40 is determined by the direction of movement 32. Using the two position sensors 28 on the same circuit board 76, for example, two end positions of the collimator 26 along the direction of movement 32 can be detected.

[0065] From the second embodiment of the position sensor 28, it is further evident that a number of coil arrangements can be selected depending on the stroke of the conductive area 38. Naturally, the dimensions of the coil arrangements 40 themselves can also be adapted as required. The geometry of the respective coils 42, 44 can also be varied as required; for example, the coils 42, 44 can be circular, angular, in particular rectangular, or the like. The sensing coils 44 can also be designed as Archimedean coils.

[0066] According to another embodiment, two opposing aperture jaws can be provided, between which an aperture slit for the X-ray radiation 14 is formed and which are movable relative to each other along the direction of movement 32 to adjust the width of the aperture slit. Then, one of the two position sensors 28, which are arranged on the same circuit board 76, detects the position of one of the two aperture jaws, and the other of the two position sensors 28, which are arranged on the same circuit board 76, detects the position of the other of the two aperture jaws.

[0067] Out of Fig. Figure 4 further shows that the two detection coils 44 of a coil arrangement 40 are connected in series and in parallel to a detection-side capacitor 86. This results in a detection-side resonant circuit whose resonant frequency is tuned to the resonant frequency of the excitation coil 42 with the capacitor 82. This arrangement allows for high sensitivity.

[0068] In the present embodiment, the frequency of the alternating current from generator 70 is approximately 1 MHz. Despite this comparatively high frequency, the position sensor shown achieves high sensitivity and resolution of the position.

[0069] Fig. Figure 5 shows a possible curve for the position signal 34, represented here by an electrical voltage, when the conductive area 38 is moved in the direction of movement 32. The voltage curve is labeled with a graph 84. When the conductive area 38 is outside the detection coils 44, a voltage U2 is established. As soon as the conductive area 38 enters the area of ​​a first detection coil of the respective coil arrangement 40, the voltage drops to a value U3. At this point, the conductive area 38 has reached approximately the midpoint of the first detection coil 44. If the conductive area 38 is moved further, the voltage increases until the conductive area 38 reaches the midpoint of the second detection coil 44 of the coil arrangement 40. In this position, the voltage is U1.If the conductive area 38 is moved further, the voltage drops from the value U1 to the value U2, at which the conductive area 38 has left the coil arrangement 40 again.

[0070] The coil arrangement 40 proves to be particularly sensitive in an area 88 located between the two detection coils 44. In this area, the position of the conductive area 38 can be detected with particularly high accuracy.

[0071] Fig. Figure 6 shows a schematic block diagram of the construction of the circuit arrangement 80, which is connected to the connection area 72.

[0072] Out of Fig.Figure 6 shows that the generator 70 includes an oscillator 90. The oscillator 90 provides an alternating voltage, which is reduced to a desired partial frequency by means of a frequency divider 92. The desired frequency, which in this case is approximately 1 MHz, is set by means of a selector unit 94. If necessary, however, the frequency can also be varied in steps of approximately 50 kHz from 800 kHz down to 1.5 MHz. An amplifier 96 provides a corresponding alternating current at the terminal 72 for the excitation coil 42.

[0073] The total voltage 68 is supplied via the connection area 72 to a first mixing unit 98 of the circuit arrangement 80. The first mixing unit 98 mixes the total voltage 68 with a processing signal 100. The processing signal 100 is supplied to the circuit arrangement 80 from the AC voltage of the oscillator 90 by means of a frequency divider 102. The processing signal 100 has a frequency that is approximately 10 kHz higher than the frequency of the AC current of the generator 70. Consequently, the mixing by the first mixing unit 98 results in an intermediate frequency signal 104, which has a frequency of approximately 10 kHz.

[0074] The intermediate frequency signal 104 is amplified by means of an amplifier 106 of the circuit arrangement 80. The intermediate frequency signal 104 is then filtered by means of a bandpass filter 108 of the circuit arrangement 80. After the bandpass filter 108, or the intermediate frequency bandpass filter, an intermediate frequency filter signal 122 is present, which is fed to an analog-to-digital converter 110 of the circuit arrangement 80. During the analog-to-digital conversion, the intermediate frequency signal is sampled using oversampling. Further signal processing is performed digitally.

[0075] The signal digitized in this way is subjected to down-sampling at 112, whereby the signal generated in this way is fed to a second mixing unit 114 of the circuit arrangement 80.

[0076] The second mixing unit 114 is further supplied with a differential frequency signal 124, which is generated from the alternating voltage provided by the oscillator 90 by supplying this alternating voltage via a further frequency divider 116 of the circuit arrangement 80 and a delay unit 118 of the circuit arrangement 80. The frequency of the differential frequency signal 124 essentially corresponds to approximately a difference between the frequencies of the sum voltage 68 and the processing signal 100. Here, it is intended that the differential frequency signal 124 has a frequency of approximately 10 kHz. However, depending on requirements, the frequency can also vary, for example, from approximately 8.5 kHz to 11.5 kHz.

[0077] The second mixing unit 114 provides a baseband signal 126 as a result of the mixing. Finally, the baseband signal 126 is filtered by means of a low-pass filter 120 of the circuit arrangement 80, so that the position signal 34 is provided.

Claims

[1] Device (10) for performing an examination of an object (12) using X-ray radiation (14), - wherein the device (10) comprises an X-ray source (16) for emitting X-rays (14), an X-ray detector (18) for detecting at least a portion of the X-rays (14) emitted by the X-ray source (16), a radiation zone (36) formed between the X-ray source (16) and the X-ray detector (18), a slide (50) for holding the object (12) that can be arranged in the radiation zone (36) for carrying out the examination, an evaluation unit (24) coupled to the X-ray detector (18) for evaluating a radiation signal (22) from the X-ray detector (18), a functional element (26) arranged in the radiation zone (36) so as to be movable in a direction of movement (32) and which has an electrically and / or magnetically conductive area (38), a first mixing unit (98), a second mixing unit (114) and a position sensor (28), - wherein the position sensor (28) has an electrical coil arrangement (40) for detecting the conductive area (38) and for providing a total voltage (68) depending on the detection of the conductive area (38), - wherein the coil arrangement (40) comprises an excitation coil (42) for providing an alternating magnetic field and two detection coils (44) connected in series for detecting at least a part of the alternating magnetic field, wherein the detection coils (44) and the excitation coil (42) are arranged such that the sum voltage (68) across the two detection coils (44) depends on a position of the functional element (26) relative to the position sensor (28), - wherein the device (10) is configured to determine a position signal (34) relating to the position of the functional element (26) relative to the position sensor (28), depending on the total voltage (68), - wherein the first mixing unit (98) is configured to mix the sum voltage (68) and a processing signal (100) to provide an intermediate frequency signal (104), - wherein the second mixing unit (114) is configured to mix an intermediate frequency filter signal (122) provided by filtering the intermediate frequency signal (104) by means of an intermediate frequency bandpass filter (108) or the intermediate frequency signal (104) on the one hand and a difference frequency signal (124) on the other hand to provide a baseband signal (126), wherein a frequency of the difference frequency signal (124) corresponds to a difference of the frequencies of the sum voltage (68) and the processing signal (100). [2] Device according to claim 1, - wherein each winding of the detection coils (44) is selected such that the voltages induced in the individual detection coils (44) cancel each other out when the functional element (26) is in a predetermined reference position of the functional element (26) relative to the position sensor (28). [3] Device according to claim 1 or 2, - wherein the detection coils (44) are arranged adjacent to each other in a plane which is parallel to the direction of movement (32). [4] Device according to any one of the preceding claims, - wherein the position sensor (28) has a detection-side electrical capacitor (86), - wherein the detection coils (44) are coupled to the detection-side electrical capacitor (86) to form a detection-side resonant circuit. [5] Device according to any one of the preceding claims, - wherein the device (10) has a connection area (72), wherein the connection area (72) is electrically connected to the detection coils (44) and is configured to provide the sum voltage (68) outside the radiation area (36), - wherein the coil arrangement (40) is preferably arranged at least partially in the radiation area (36). [6] Device according to claim 5, - wherein the detection coils (44) are arranged in a planar arrangement on a flat circuit carrier (76). [7] Method for performing an examination of an object (12) using X-ray radiation (14), - wherein an X-ray source (16) emits the X-rays (14) at least partially to a radiation zone (36) formed between the X-ray source (16) and an X-ray detector (18), wherein the X-ray detector (18) detects at least a portion of the X-rays (14) emitted by the X-ray source (16) and emits a radiation signal (22) depending on the detected X-rays (14), wherein the object (12) is held by a slide (50) which is arranged in the radiation zone (36) for the purpose of carrying out the examination, wherein the radiation signal (22) of the X-ray detector (18) is evaluated by means of an evaluation unit (24) coupled to the X-ray detector (18), wherein a functional element (26) which has an electrically and / or magnetically conductive area (38) is moved in the radiation zone (36) in a direction of movement (32), - wherein the conductive area (38) is detected by means of an electrical coil arrangement (40) of a position sensor (28) and a total voltage (68) is provided depending on the detection of the conductive area (38), - wherein an alternating magnetic field is provided by means of an excitation coil (42) of the coil arrangement (40), wherein at least a part of the alternating magnetic field is detected by means of two detection coils (44) of the coil arrangement (40) connected in series, wherein the detection coils (44) and the excitation coil (42) are arranged such that the sum voltage (68) across the two detection coils (44) depends on a position of the functional element (26) relative to the position sensor (28), - wherein a position signal (34), which relates to the position of the functional element (26) relative to the position sensor (28), is determined depending on the total voltage (68), - wherein the sum voltage (68) and a processing signal (100) are mixed by means of a first mixing unit (98) to provide an intermediate frequency signal (104), - wherein an intermediate frequency filter signal (122) is provided by filtering the intermediate frequency signal (104) using an intermediate frequency bandpass filter (108), or the intermediate frequency signal (104) on the one hand and a difference frequency signal (124) on the other hand are mixed using a second mixing unit (114) to provide a baseband signal (126), wherein a frequency of the difference frequency signal (124) corresponds to a difference between the frequencies of the sum voltage (68) and the processing signal (100). [8] Method according to claim 7, - wherein the detection coils (44) are coupled to a detection-side electrical capacitor (86) to form a detection-side resonant circuit, - wherein the excitation coil (42) is supplied with an alternating current and / or an alternating voltage at a frequency which corresponds to a resonant frequency of the sensing-side resonant circuit by a frequency generator (70) coupled to the excitation coil (42). [9] Method according to claim 7 or 8, - where the resonant frequency of the detection-side resonant circuit is greater than 800 kHz and / or less than 1.6 MHz. [10] Method according to any one of claims 7 to 9, - wherein the processing signal (100) has a processing frequency that is greater than the resonant frequency of the sensing-side resonant circuit. [11] Method according to any one of claims 7 to 10, - wherein at least the intermediate frequency signal (104), the intermediate frequency filter signal (122) and / or the sum voltage (68) is sampled in a time-discrete manner. [12] Method according to any one of claims 7 to 11, - where the frequency of the difference frequency signal (124) is greater than 8.5 kHz and / or less than 50 kHz. [13] Method according to any one of claims 7 to 12, - wherein the baseband signal (126) is filtered by means of a low-pass filter (120) to provide the position signal (34).

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