Method and device for determining at least one geometric parameter of elongated object having periodic structure

Abstract

The invention relates to a method for determining at least one geometric parameter of an elongated object having a periodic structure, in particular of a corrugated pipe comprising a corrugated layer having a periodic corrugated shape, x-rays diverging transversely to the longitudinal direction of the object irradiate the object, and the X-rays after transmission through the object are detected by a spatially resolved X-ray detector as spatially resolved measurement signals transversely to the longitudinal direction of the object. A measurement section of the object extending in the longitudinal direction of the object is irradiated with the X-rays, and the X-ray detector detects a plurality of spatially resolved measurement signals transversely to the longitudinal direction of the object for the X-rays transmitted through the measurement section. Combining the measurement signals into an evaluation signal which is spatially resolved transversely to the longitudinal direction of the object, in which evaluation signal layer transitions within the object and / or between the object and a medium surrounding the object are detected at a plurality of locations of the measurement section, and determining at least one geometric parameter of the object based on the identified layer transition. The invention also relates to a corresponding device.

Description

TECHNICAL FIELD

[0001] The invention relates to a method for determining at least one geometric parameter of an elongated object having a periodic structure, in particular a bellows, the bellows comprising a bellow layer having a periodic bellow shape, wherein the object is irradiated with X-rays diverging transversely to the longitudinal direction of the object and the X-rays after transmission of the object are detected by a position-resolved X-ray detector as a measurement signal position-resolved transversely to the longitudinal direction of the object.

[0002] The invention also relates to a device for determining at least one geometric parameter of an elongated object having a periodic structure, in particular a bellows, the bellows comprising a bellow layer having a periodic bellow shape, the device comprising an X-ray source configured to irradiate the object with X-rays diverging transversely to the longitudinal direction of the object and comprising a position-resolved X-ray detector configured to detect the X-rays after transmission of the object as a measurement signal position-resolved transversely to the longitudinal direction of the object. BACKGROUND

[0003] Bellows are available in different variants, shapes and sizes, for example. They have a wave layer having a periodic bellow shape, for example with sinusoidal bellows or with other periodic structures, for example box-shaped profiles, trapezoidal profiles, etc. The bellows can be composed of the wave layer. The bellows can also have an inner layer which in shape, for example, corresponds to the shape of a smooth tube, on which the wave layer having a periodic bellow shape is arranged. Usually the bellows are made of plastic. But electrically conductive and / or magnetic materials are also possible.

[0004] In a bellows having an inner layer and a wave layer arranged thereon, for example, the material layers of the inner layer and the wave layer are distinguishable in the region of the peaks of the periodic bellow shape, since the inner layer and the wave layer in this region are separated from one another by air or another medium. In contrast, in the valleys the inner layer and the wave layer are essentially directly on top of one another, so that there is only one total layer. In particular when the inner layer and the wave layer are made of the same material, it is hardly possible to divide the wall thickness into the wave layer and the inner layer in the valleys.

[0005] There is in principle an interest in detecting geometric parameters, such as layer thicknesses, of elongated objects having a periodic structure on a measurement-technical basis. Layer transitions between a plurality of corrugation layers, between a corrugation layer and air and / or between an inner layer and air can be detected, for example, when measuring a corrugated tube. The radius and the midpoint position of the respective layer can be described trigonometrically by means of the layer transitions. The respective layer thickness (wall thickness) can be determined therefrom. In order to determine the layer transitions technically, it is known from practice to emit X-rays onto the layer transitions and to detect the X-rays after transmission of the corrugated tube using an X-ray detector. The X-rays diverge perpendicular to the longitudinal direction of the corrugated tube, and the X-ray detector records an absorption image of the X-rays with position resolution perpendicular to the longitudinal direction of the corrugated tube. The layer transitions of the corrugated tube to air can be inferred from the change curve of the measurement signal, and the geometric parameters, such as the layer thickness of the corrugated tube, can be inferred therefrom.

[0006] For example, the corrugated tube is usually conveyed through the measurement region along the longitudinal axis of the corrugated tube during the measurement, especially when the measurement should be carried out shortly after the corrugated tube has been manufactured, which is desirable in view of the early recognition of production defects and thus the minimization of rejects. The problem of motion blurring of the X-ray measurement arises therefrom, especially since the scan rate of the X-ray sensor device is generally relatively low. Thus, the X-ray detector detects a measurement signal of the X-rays, which transmits different sections of the corrugated tube and thus different regions of the period of the corrugated shape. This makes a conventional evaluation of the measurement signal for determining the layer transitions difficult. In order to solve this problem, attempts are made to minimize the blurring of the X-ray recording, so that in the best case only one cross-sectional position of the corrugated tube is recorded by the X-ray detector, from which the measurement signal of the X-ray detector should then be evaluated exactly in the usual approach. For example, attempts have been made to operate the X-ray detector in a so-called TDI mode (time delay and integration), in which the read speed of the X-ray detector, which is constructed, for example, as a line sensor, is synchronized with the conveying speed of the corrugated tube. Ideally, a clear recording of the absorption signal is thus achieved by one line of the X-ray detector. However, this synchronization is technically costly and has to be readjusted each time the production conditions of the corrugated tube change. It is also proposed to arrange the detector, for example for terahertz radiation, on a support that can be moved in the longitudinal direction of the corrugated tube, which moves with the corrugated tube synchronously with the conveying speed of the corrugated tube. The goal is again to record the detector as clearly as possible. However, this measure is also very costly in terms of construction and prone to errors in practice. A costly adjustment is again required each time the production speed changes. SUMMARY

[0007] Starting from the state of the art set out, the task of the present application is to provide a method and a device of the type mentioned at the outset with which at least one geometric parameter of an elongate object having a periodic structure can be determined reliably and precisely in a structurally simple manner.

[0008] The task is solved by the independent claims 1 and 15. Advantageous design solutions emerge from the dependent claims, the description and the figures.

[0009] For a method of the type mentioned at the outset, the task is solved by the present application in that an object is irradiated with X-rays in a measurement section of the object which extends in the longitudinal direction of the object, a plurality of position-resolved measurement signals of the X-rays transmitted through the measurement section are detected by an X-ray detector transversely to the longitudinal direction of the object, the measurement signals are combined into an evaluation signal which is position-resolved transversely to the longitudinal direction of the object, layer transitions within the object and / or between the object and a medium, for example air, surrounding the object are identified in the evaluation signal at a plurality of positions of the measurement section, and at least one geometric parameter of the object is determined on the basis of the identified layer transitions.

[0010] For a device of the type mentioned at the outset, the task is solved by the present application in that the X-ray source is also configured to irradiate an object in a measurement section of the object which extends in the longitudinal direction of the object with X-rays, and the X-ray detector is also configured to detect a plurality of position-resolved measurement signals of the X-rays transmitted through the measurement section transversely to the longitudinal direction of the object, the device also comprises evaluation means which are configured to combine the measurement signals into an evaluation signal which is position-resolved transversely to the longitudinal direction of the object, to identify layer transitions within the object and / or between the object and a medium, for example air, surrounding the object in the evaluation signal at a plurality of positions of the measurement section, and to determine at least one geometric parameter of the object on the basis of the identified layer transitions.

[0011] According to the application, at least one geometric parameter of an object, in particular of a bellows, is determined, for example the radius and the midpoint of two layers, and thus the layer thickness. The object has a periodic structure. When the object is a bellows, the bellows has at least one bellows layer with a periodic bellows shape, which can be configured, for example, sinusoidal or box contour or trapezoidal or otherwise periodic. In the peak and valley of the bellows shape, for example in the case of a box contour configuration, there can be flat regions. The object can be configured, for example, strip-shaped, in particular tube-shaped. It can be made, for example, of plastic. But other materials are also conceivable, for example electrically conductive and / or magnetic materials. If it is a bellows, the bellows can consist of the bellows layer. But it can also have an inner layer, on which the bellows layer is arranged. The inner layer can be configured, for example, cylindrical or otherwise. It can be, for example, cylindrical. The inner layer can have the form of a smooth tube. The periodic shape of the object consists of alternating peaks and valleys, between which ascending and descending flanks are arranged. If there is an inner layer in the case of a bellows, the bellows layer generally lies directly on the inner layer in the region of the valleys. The inner layer and the bellows layer can be made of the same material. But different materials can also be involved.

[0012] For determining the at least one geometric parameter, according to the application, a layer transition within the object, for example between the bellows layers of a bellows, and / or between the object and a medium surrounding the object, in particular between the bellows layer of a bellows and the surrounding medium and / or between the inner layer of a bellows and the surrounding medium, is determined. The surrounding medium is generally a gaseous medium, in particular air. But it can also be a liquid medium. The surrounding medium can also be, for example, between the inner layer and the bellows layer at the peak of the bellows layer of a bellows.

[0013] First, similar to in the prior art, the object is irradiated with X-rays at least transversely to the longitudinal direction of the object, preferably in the (main radiation) direction transversely to the longitudinal direction of the object, and the X-rays after transmission through the object are detected by an X-ray detector which is position-resolved at least transversely to the longitudinal direction of the object as a position-resolved measurement signal. As set out at the outset, in the prior art measures are taken at great expense to avoid a positional blur or motion blur of the measurement signal recorded by the X-ray detector. In contrast to the teaching of the prior art, the present application not only tolerates a positional blur and / or motion blur of the measurement signal of the X-ray detector, but rather exploits it precisely for the measurement and evaluation according to the application. To this end, a measurement section of the object extending in the longitudinal direction of the object is irradiated with X-rays, and the X-ray detector detects a plurality of measurement signals which are position-resolved at least transversely to the longitudinal direction of the object for the X-ray beam transmitted through the measurement section. These measurement signals, which arise due to the positional blur and / or motion blur, are combined into an evaluation signal which is position-resolved at least transversely to the longitudinal direction of the object. In said evaluation signal, layer transitions within the object and / or between the object and the surrounding medium at a plurality of positions of the measurement section are identified. On the basis of the identified layer transitions, at least one geometric parameter of the object is determined, for example also at a plurality of positions of the measurement section. Said measurement section has an extension in the longitudinal direction of the object. Said extension may, for example, be at least 10% of the period of a periodic structure of the object, for example of the corrugation shape of the corrugation layers of a bellows.

[0014] As long as the currently mentioned direction transversely to the longitudinal direction of the object, this includes not only a direction perpendicular to the longitudinal direction of the object, but also a direction inclined to the longitudinal direction of the object. If the X-rays are incident in a main radiation direction perpendicular to the longitudinal direction of the object and the measurement signal is position-resolved perpendicular to the longitudinal direction of the object, the evaluation of the measurement signal according to the application is simplified.

[0015] The extension of the field of view of the X-ray detector over the measurement section extending in the longitudinal direction of the object according to the application can be achieved by a movement of the object along its longitudinal axis during the measurement and / or by a positional resolution of the X-ray detector in the direction of the longitudinal axis of the object and / or by an adjustment of the exposure time of the X-ray detector. There is a duality between positional blur and temporal blur. The X-rays are at least divergent transversely to the longitudinal direction of the object. It can also be divergent in the longitudinal direction of the object, that is to say, for example, have a conical radiation characteristic. It is then possible to irradiate the measurement section extending in the longitudinal direction of the object simultaneously with X-rays. It is also possible, however, to irradiate the measurement section successively with X-rays, in particular when the object is conveyed along a conveying direction which can in particular be identical to its longitudinal axis during the measurement. With X-rays which are also divergent in the longitudinal direction of the object or the conveying direction and a conveying of the object through the measurement region along its longitudinal axis or the conveying direction, a combined measurement can also be achieved.

[0016] The X-ray detector is position-resolved at least transversely to the longitudinal direction of the object. It can also be position-resolved in the longitudinal direction of the object. The X-ray detector can comprise a scintillator and at least one optical sensor array, for example a one- or two-dimensional CCD array. If the X-ray detector is also position-resolved in the longitudinal direction of the object, it can directly and, if necessary, simultaneously detect the X-rays of different regions of the transmission measurement section. It is also conceivable, however, that the X-ray detector detects the X-rays of different regions of the transmission measurement section sequentially, in particular when the X-ray detector is only position-resolved transversely to the longitudinal direction of the object, that is to say with a line sensor having only one sensor row.

[0017] Unlike the prior art set out at the outset, the application is based on the insight that the blurring recorded by the X-ray detector, in the case of which there is an overlap of different regions of the object along the measurement section in the absorption image, simplifies or first of all enables the recognition of the characteristic features for determining the geometric parameters. By allowing the X-ray detector to record blurring in the longitudinal direction of the object, the requirements on the sensor device are significantly reduced and simplified compared to the prior art. At the same time, more information about the geometric shape of the object is provided overall in the evaluation signal which is merged from the measurement signals of the different regions along the measurement section in accordance with the application than in the case of a clear recording of only one unique region of the object. The geometric parameters of the object can therefore also be determined reliably and accurately compared to the prior art. As a result of the blurring recorded by the X-ray detector which is deliberately used in accordance with the application, significantly more portions of an oscillation period are detected by the X-ray detector. It is thereby possible to increase the proportion of the evaluated tube section which has information. As a result, regions of the oscillation period which are not visible in the case of a clear detector recording can also be detected. This acquires particular relevance in the case of the often small (for example 1 to 10 Hz) scan rates of such X-ray systems in order to increase the possible measurement points. Furthermore, an improved representation of the characteristic features in the evaluation signal for determining the geometric parameters can be achieved in accordance with the application. In particular, the contribution of different regions of the periodic structure (for example the corrugation shape of the corrugation layers of the bellows, for example peak regions and trough regions) is increased by the blurring and the respective features are represented more strongly in the absorption variation curve of the evaluation signal.

[0018] As already mentioned, the object, for example the bellows, is conveyed in the conveying direction during the X-ray transmission in accordance with one design variant. The conveying direction can correspond to the longitudinal axis of the object. The device according to the application can comprise a conveying device which is configured for this purpose.

[0019] As already explained, X-rays irradiating an object can also diverge along the object's longitudinal direction. X-ray detectors can also be position-resolved along the object's longitudinal direction, for example, comprising a two-dimensional sensor array (e.g., a two-dimensional CCD array) along with a scintillation counter, particularly a two-dimensional scintillation counter layer. The scintillation counter or scintillation counter layer converts the received X-rays into electromagnetic radiation that can be detected by optical sensors (e.g., CCD sensors), such as light in the visible or invisible wavelength range.

[0020] As further explained, detecting multiple regions of an object, such as the corrugation shape of a bellows layer, along a measurement section in a measurement technique improves the information content of the evaluation signal used to determine the at least one geometric parameter. Accordingly, according to one design, it is feasible for the measurement section to extend over at least 20%, preferably at least 40%, of the period of the periodic structure (e.g., the corrugation shape of a bellows layer). Here, it is particularly advantageous for the evaluation according to the invention to detect different segments of the period. Accordingly, according to another design, the measurement section can be specified to extend over at least a portion of the crests and troughs of the periodic structure (e.g., the corrugation shape of a bellows layer) and along the sides between the crests and troughs. With the above-described design of the X-ray detector's field of view, on the one hand, multiple layer transitions within the object and / or between the object and the surrounding medium can be identified at multiple locations within the measurement section. On the other hand, the characteristic features of the layer transitions are more strongly expressed in the evaluation signal.

[0021] According to the invention, it is further recognized that excessively large measurement segments, especially excessively large regions covering periodic structures, may degrade the evaluation signal used in the evaluation according to the invention. For example, when adjacent peaks are detected outside the peaks detected by the measurement segment attached to the periodic structure, it may lead to a deterioration in the characterization of the evaluation signal with respect to the layer transition and thus distortion in the determination of geometric parameters. Furthermore, it can be inferred that if the extension of the measurement segment or field of view of the X-ray detector exceeds one period, the quality of the non-interference characterization of the layer transition in the evaluation signal will be significantly degraded. Accordingly, according to another design, it can be specified that the measurement segment extends over no more than 100%, preferably no more than 75%, of the period of the periodic structure (e.g., the corrugated shape of the corrugated layer of a bellows). It can also be specified that the measurement segment extends over no more than one peak and one trough of the periodic structure and on the side between the peak and the trough of the periodic structure.

[0022] According to a particularly practical design, in order to combine measurement signals into an evaluation signal that is position-resolved in the longitudinal direction of the object, an average value of the measurement signals detected in the measurement section can be formed. Therefore, the individual measurement signals detected in the measurement section, which are position-resolved in the longitudinal direction of the object, are averaged into an evaluation signal, which is itself position-resolved in the longitudinal direction of the object. The position resolution in the longitudinal direction of the object is not lost during averaging. Averaging is performed only in the direction of the measurement section. For example, if an X-ray detector that is also position-resolved in the longitudinal direction of the object is used, averaging can be simply performed on the sensor pixels in the longitudinal direction of the object. Therefore, integration is performed with respect to the rows of the X-ray detector in the longitudinal direction of the object.

[0023] According to another design, layer transitions within an object and / or between the object and the surrounding medium, particularly between multiple corrugated layers of a bellows and / or between the corrugated layers of a bellows and the surrounding medium, and / or between the inner layer of a bellows and the surrounding medium, can be identified by means of minimum and / or maximum values ​​and / or slope variations and / or discontinuities in the evaluation signal. In particular, characteristic and well-distinguishable features for the layer transition to be identified are identified in the curve variations of the position-resolved evaluation signal. By selecting a suitable, particularly sufficiently large but not excessively large, measurement segment, at least two, preferably at least three, more preferably at least four, e.g., five minimum and / or maximum values ​​and / or slope variations and / or discontinuities can be identified in the evaluation signal according to the invention for determining layer transitions. Here, the identified layer transitions exist at different locations along the measurement segment of the object, as described.

[0024] According to another design approach, layer transitions can be identified using machine learning algorithms, preferably when using artificial neural networks, by leveraging the minimum and / or maximum values ​​and / or slope variations and / or discontinuities in the evaluation signal. This so-called artificial intelligence algorithm is capable of explicitly and reliably identifying the aforementioned characterizing features even in evaluation signals with real-world interference.

[0025] As already mentioned, the layer thickness of an object, particularly the corrugated layer and / or inner layer of a bellows, can be determined as at least one geometric parameter, for example, at multiple locations within the measurement section. Layer thickness is of particular interest for evaluating the production quality of the manufactured object. If an unacceptable deviation of the layer thickness from the nominal value is identified, this can be displayed, for example, as a warning notification via the evaluation device. Intervention in the production equipment used to manufacture the object, such as the extrusion direction, is also conceivable.

[0026] In principle, it is also conceivable to set up multiple X-ray sources and X-ray detectors, which transmit X-rays through the object from two mutually perpendicular directions. Accordingly, it can be specified that the object is irradiated by X-rays diverging from two directions transverse to the longitudinal direction of the object, preferably in the main radiation direction transverse to the longitudinal direction of the object, and the X-rays after transmission through the object are detected by at least two position-resolved X-ray detectors as measurement signals at least transverse to the longitudinal direction of the object. This is wherein measurement sections extending in the longitudinal direction of the object are irradiated by X-rays from the two directions respectively, wherein the X-ray detectors detect multiple measurement signals at least transverse to the longitudinal direction of the object for the X-rays transmitted through the measurement sections, and wherein the measurement signals detected by the X-ray detectors are combined into evaluation signals at least transverse to the longitudinal direction of the object. In these evaluation signals, layer transitions within the object and / or between the object and the medium surrounding the object are identified at multiple locations within the measurement section, and at least one geometric parameter of the object is determined based on the identified layer transitions.

[0027] This provides another measurement axis for the X-ray system. The design of the X-ray source and X-ray detector, as well as the evaluation of the measurement signal, can be performed as described above and below. This provides additional information about the layer geometry. In particular, other geometric parameters, such as radius and midpoint position, can be easily determined in this way, and the wall thickness can be determined based on these, as further explained below. Thus, for example, the midpoint position of each layer can be determined using two measurement axes. Once at least two layer transitions have been determined, the radius can be derived from this, and the wall thickness can be derived based on this. Of course, more than two measurement axes can also be constructed according to the invention. With more than two measurement axes, when the layers have different radii, for example, along the circumference of the tube, the elliptical shape can be determined more accurately.

[0028] Based on the divergence of X-rays and the spaced arrangement of the X-ray source, object, and X-ray detector, the layer transitions identified in the evaluation signal must be trigonometrically converted into the corresponding geometric parameters of the respective layers, such as layer thickness, taking into account the known distances (especially between the X-ray source and the X-ray detector, and, if necessary, the object). This is known in itself. Therefore, according to one design, it is possible to calculate the midpoint position and radius of the corresponding layer at the identified layer transition in order to determine at least one geometric parameter, such as the layer thickness. After extracting the characteristic features of the layer transition from the evaluation signal, target values, such as the midpoint position and radius of the corresponding layer, can be calculated, and subsequently, the layer thickness can be calculated. Here, the midpoint position and radius are determined for each layer transition. For each layer transition, two positions must be found for each measurement axis of the X-ray measurement system, two positions on each side of the object (e.g., a bellows), for example, on each side of two mutually perpendicular measurement axes. To do this, the angle between the measurement axis and the direct connection between the measurement axis and the corresponding detector value of the characteristic feature from the point-like X-ray source to the X-ray detector can first be determined. The center of the object (e.g., a bellows) lies on the beam between the X-ray source and the X-ray detector, which may be at an angle to the measurement axis. The midpoint of the corresponding layer is calculated, taking into account the geometry of the measurement axis, particularly the distance between the X-ray source and the X-ray detector. For the radius of the layer, the half-angle between each connection of the point-like X-ray beam and the position of the characteristic feature on the X-ray detector is determined. If the midpoint and radius of the transition between the two layers of the corresponding layer have been determined, the layer thickness or wall thickness can then be calculated. For this, simply subtract the radii from each other, taking into account possible eccentricities.

[0029] The apparatus according to the invention can be configured for implementing the method according to the invention. Accordingly, the method according to the invention can be implemented using the apparatus according to the invention. Attached Figure Description

[0030] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The drawings schematically illustrate:

[0031] Figure 1 The device according to the invention is shown in a first view.

[0032] Figure 2 A partial cross-sectional view of a bellows with a schematic sensor field for an X-ray detector according to the invention is shown.

[0033] Figure 3 Show Figure 1 A magnified description of a portion,

[0034] Figure 4A graph is shown to illustrate the measurement signals of the X-ray detector.

[0035] Figure 5 Other graphs are shown to illustrate the measurement signals from the X-ray detector.

[0036] Figure 6 A graph illustrating the generation of evaluation signals according to the method of the present invention is shown, and

[0037] Figure 7 A device according to another embodiment of the invention is shown in a first view. Detailed Implementation

[0038] Unless otherwise stated, the same reference numerals in the accompanying drawings denote the same objects.

[0039] exist Figure 1 The apparatus shown for determining at least one geometric parameter of the bellows 10 includes a substantially point-like X-ray source 12, which in... Figure 1 At least in the plane spanned by the x-axis and y-axis of the Cartesian coordinate system shown, diverging X-rays are emitted, such as in Figure 1 As illustrated by the dashed lines, the X-ray source can also be located in the longitudinal direction of the bellows 10, i.e., in... Figure 1 The bellows 10 emits diverging X-rays in a plane spanning the x and z axes. The longitudinal axis of the bellows 10 is located in... Figure 1 The bellows 10 extends in the z-axis direction, i.e., into the drawing plane. During measurement, the bellows 10 can be conveyed through the measurement area of ​​the device along the conveying direction, where the conveying direction corresponds to the longitudinal axis of the bellows 10. Figure 1 Therefore, it extends in the z-direction. For this purpose, the device may include a corresponding conveying mechanism.

[0040] In the example shown, the bellows 10 is irradiated by X-rays emitted from the X-ray source 12, which diverge perpendicularly to its longitudinal axis in the xy plane. As long as the X-rays are in… Figure 1The X-rays also diverge in the xz plane, so the bellows 10 is also irradiated in the longitudinal direction of the bellows. X-rays are transmitted through the bellows 10 and detected by a position-resolved X-ray detector 14 after transmission of the bellows 10, as a position-resolved measurement signal in the direction perpendicular to the longitudinal direction of the bellows 10, and in this case, in the y-axis direction. The position-resolved X-ray detector 14 is position-resolved at least in the y-direction in this example. It can also be position-resolved in the z-direction, i.e., along the longitudinal axis of the bellows 10. The X-ray detector 14 may include a two-dimensional scintillation counter layer having a two-dimensional sensor array (e.g., a CCD array) disposed downstream. The measurement signal from the X-ray detector 14 is present on an evaluation device 16, which processes it in a manner that will be described in detail below to determine the geometric parameters of the bellows 10.

[0041] In the example shown, the bellows 10 includes an inner layer 18 in the form of a smooth tube and a corrugated layer 20 with a periodic corrugated shape disposed on the inner layer 18. Figure 2 The corrugated pipe 10 is shown in partial longitudinal sectional view. Here, approximately two cycles of the corrugated shape of the corrugated layer 20 can be seen. Specifically, it can be seen that the corrugated layer 20 rests directly against the inner layer 18 in the region of the trough 22, while in the region of the crest 24, there is a distance between the corrugated layer 20 and the inner layer 18, said distance being filled with air. Thus, in the region of the trough 22, there are two layer transitions to air, one on the outside of the corrugated layer 20 and the other on the inside of the inner layer 18 and the air. In the region of the crest 24, there are four layer transitions, two between the corrugated layer 20 and the air and two between the inner layer 18 and the air. According to the invention, these layer transitions should be determined, thereby allowing geometric parameters, such as the layer thickness (wall thickness) of the inner layer 18 and / or the corrugated layer 20, to be determined in a manner known to those skilled in the art. Furthermore, in Figure 2 The two-dimensional sensor array of the X-ray detector 14 can be seen, where, in the example shown, 2000 pixels in the y-direction and 128 pixels in the z-direction are shown. If the bellows 10 is transported along its longitudinal axis, i.e., in the z-direction, during operation, the sensor array of the X-ray detector 14 thus alternately detects X-rays at the transmission troughs 22 and crests 24, along with the sides located between them. Figure 1 In the cross-sectional view of the bellows 10, the crest 24 can be seen precisely, thus creating a distance between the inner layer 18 and the corrugated layer 20.

[0042] With the help of Figure 1 The enlarged partial view should be obtained by using Figure 3 And refer to Figure 4The position-resolved absorption signal generated on the X-ray detector 14, perpendicular to the longitudinal axis of the bellows 10, is described in detail. Figure 4 The absorbed signals obtained are shown in three graphs for three positional states of the bellows 10 relative to the X-ray detector 14, where the static record of the stationary bellows 10 is shown. Therefore, due to the two-dimensional extension of the X-ray detector 14, especially when averaging along the z-direction of the X-ray detector 14, only positional ambiguity exists. Figure 4 The axis diagram in the topmost chart is explained as follows: Figure 2 The middle involves corresponding to Figure 1 X-ray detector 14. In Figure 4 In the three charts below, the intensity in arbitrary units is plotted on the pixels of the sensor array of the X-ray detector 14 in the y-direction, that is, the longitudinal axis perpendicular to the bellows 10.

[0043] Figure 4 The bottom chart in corresponds to in Figure 4 The position shown in the upper right corner indicates that X-ray detector 14 receives only X-rays from the transmission trough 22. Figure 4 The second chart from the bottom is shown in Figure 4 The position shown above in the middle indicates that the X-ray detector 14 receives X-rays transmitted through the sides between trough 22 and crest 24, as well as short segments of trough 22 and crest 24. Figure 4 The second chart from the top shows... Figure 4 The position shown in the upper left corner indicates that the X-ray detector 14 receives only the X-rays transmitted from the peak 24. This position is also... Figure 3 As shown in [the image]. Figure 4 In the ideal state shown in the upper left and upper right, positional ambiguity does not affect the signal because the bellows 10 does not change its shape in the observed area.

[0044] exist Figure 3 For illustrative purposes, the six beamlines 0 to 5 of the diverging X-rays emitted by X-ray source 12 are marked with dashed lines. Between beamlines 0 and 1, the X-rays pass freely beside the bellows 10. Accordingly, no absorption occurs, which... Figure 4 The second chart from the top reflects this as a constant maximum intensity in region A. The transition between each layer of air and the corrugated pipe 10 initially causes a decrease in intensity, as in... Figure 4 As shown at point B in the second chart from the top. Figure 3 Between beamlines 1 and 2, the chord length increases due to the plastic of the corrugated layer 20, and correspondingly, the absorption of X-rays increases, which leads to... Figure 4In the second graph from the top, the intensity value decreases between points B and C. Figure 4 The middle corresponds to Figure 3 The maximum chord length for the corrugated layer 20 is reached at point C of the beamline 2, which leads to... Figure 4 The local minimum of the intensity change curve is plotted at point C in the second graph from the top. Next... Figure 3 Between beamlines 2 and 3, the intensity increases again due to the decrease in the two transmitted string portions of the corrugated layer 20 until it reaches beamline 3. From this beamline, in addition to the contribution of the two strings of the corrugated layer 20 to the absorption, the material of the inner layer 18 now additionally contributes to the absorption of X-rays. From beamline 3, the received intensity decreases accordingly, as in... Figure 4 As shown at point D in the second chart from the top. Due to the increased chord length of the inner layer 18, the intensity level decreases until... Figure 3 The beamline 4 in the image is used to obtain the intensity variation curve. Figure 4 The absolute minimum value is plotted at point E in the second chart from the top. From beamline 4 until... Figure 3 In the beamline 5, due to the decrease in the chord length involved by the inner layer 18 and the corrugated layer 20, the absorption increases again until... Figure 4 The local maximum value at F is plotted in the second graph from the top. Further, ideally for bellows 10... Figure 4 The other half, not shown, yields a symmetrical intensity variation curve.

[0045] exist Figure 4 In the case shown in the bottommost chart, where X-ray detector 14 receives only X-rays from transmission trough 22, the intensity variation curves visibly exhibit fewer characterizing features than in the cases discussed earlier. Specifically, there are only two layer transitions present here, as explained at the beginning. Figure 4 The minimum absolute intensity E, plotted in the second chart from the top, can also be found in... Figure 4 The positional state shown in the bottom chart is identified in the intensity change curve. However, particularly characteristic features B, C, and D in the curve changes are... Figure 4 Not visible in the bottommost chart. Another characteristic feature G can be identified in this regard: when X-rays are incident on the layer transition between the outer side of the corrugated layer 20, which is directly attached to the inner layer 18, and the air. Accordingly, in Figure 4 The characteristic feature G cannot be seen in the second chart from the top.

[0046] exist Figure 4 The second chart from the bottom shows the results for... Figure 5The topmost graph shows the intensity variation curve of the positional state in the middle, where X-ray detector 14 receives X-rays that are transmitted through the sides and portions of trough 22 and peak 24. It can be seen that the signal detected by X-ray detector 14 contains two additional [unclear phrase - likely referring to specific parameters or conditions]. Figure 4 All characteristic features A to G of the intensity change curve plotted in the image are shown. Figure 2 Compared to the two other intensity variation curves, some features, especially features C, G, and D, are relatively difficult to identify, particularly due to the lateral influence between trough 22 and peak 24. Therefore, the manifestation of these features is relatively small, but still identifiable.

[0047] Based on the understanding described above, this invention is based on the following concept: Ambiguity in the longitudinal direction of the bellows 10, particularly positional ambiguity and / or motion ambiguity, in the intensity record of the X-ray detector 14—that is, the superposition of X-ray beams from different regions of the transmitted bellows 10—can improve the identification of characterizing features for the layer transition to be identified in the intensity signal of the X-ray detector 14. Figure 1 The diagram shows the change in intensity curves received by X-ray detector 14 as the measurement segment reflecting blurring increases (X-ray detector 14 receives X-rays after transmission bellows 10 for this measurement segment), the change being shown as a percentage of the detected period of the corrugated shape of the corrugated layer 20 in the current case. Here, the intensity in arbitrary units at the sensor pixels of the sensor array is shown in the direction perpendicular to the longitudinal axis of the bellows 10, i.e., the y-direction. It can be seen that the number of evaluable characterizing features for layer transition in the intensity signal increases with increasing field of view of the X-ray detector 14, i.e., the measurement segment. This is particularly applicable in the example shown from the measurement segment extending at 25% of the period of the corrugated layer 20. Provided that crests 24 and troughs 22, along with the sides located between them, are sufficiently identified, five characterizing features of the layer transition between the air and the corrugated layer 20 or the inner layer 18—namely features B, C, D, E, and G—can be identified as minimum and / or maximum values ​​and / or slope variations and / or discontinuities in the intensity variation curve, as shown in... Figure 6 As illustrated in the drawing. Increasing the measurement segment further to more than 25% of the period of the corrugated layer 20 results in an improved representation of these characterizing features, which further improves the evaluation. Conversely, once an additional adjacent side of the corrugated shape of the corrugated layer 20 flows into the measurement segment, it leads to a deterioration in the feature representation. If the measurement segment extends over more than one period of the corrugated shape of the corrugated layer 20, it can be inferred that the feature no longer possesses uninterrupted quality.

[0048] Such as usingFigure 6 As shown, the X-ray detector 14 is located in the longitudinal direction of the bellows 10, in... Figure 7 The sensor also has positional resolution in the z-direction. For example, the sensor could have 128 rows in this direction. ​ In the diagram, the measured values ​​are shown as a group of gray intensity variation curves, position-resolved perpendicular to the longitudinal direction of the bellows 10, in, for example, 128 rows along the longitudinal direction of the bellows 10, as the measurement signal 26 of the X-ray detector 14. This measurement signal 26 received by the X-ray detector 14 is combined by the evaluation device 16 into a similarly position-resolved curve perpendicular to the longitudinal direction of the bellows 10. ​ The evaluation signal 28, shown as a solid black line, is combined in this example by averaging over the group 26 of measurement signals. In the evaluation signal 28, the characterizing features described above, particularly the five minimum and / or maximum values ​​and / or slope variations and / or discontinuities B, C, D, E, and G, can now be identified by the evaluation device 16 as layer transitions between the bellows 10, particularly the inner layer 18, and the bellows layer 20, and the air. The identification of these features, and therefore the layer transitions, can be simplified by using machine learning algorithms, particularly artificial neural networks. With the layer transitions thus identified, and considering the geometric relationships, particularly the distance between the X-ray source 12 and the X-ray detector 14, and, if necessary, the position of the bellows 10, the layer thicknesses, i.e., the wall thicknesses, of the inner layer 18 and the bellows layer 20 can be calculated trigonometrically as geometric parameters, as described above and as is known in principle to those skilled in the art.

[0049] ​ An apparatus according to the invention, according to another embodiment, is shown, in which another measurement axis is formed by a second X-ray source 12' and a second X-ray detector 14', the second X-ray detector being oriented perpendicular to the measurement axis formed by the first X-ray source 12 and the first X-ray detector 14. The second X-ray source 12' and the second X-ray detector 14' can, in particular, be constructed in the same manner as the first X-ray source 12 or the first X-ray detector 14. The measurement signal received by the second X-ray detector 14' can also be evaluated by the evaluation device 16 in the same manner as the measurement signal from the first X-ray detector 14. As explained above, the midpoint position of the corresponding layer can be determined, for example, by using the two measurement axes. Once at least two layer transitions have been determined, the radius can be derived from this, and the wall thickness can be derived based on it.

[0050] Although the invention has been described with reference to an embodiment of a bellows, other elongated objects with periodic structures may also be involved instead of bellows. Of course, the bellows may also have additional corrugated layers, as described at the beginning.

[0051] List of reference numerals

[0052] 10 corrugated pipe

[0053] 12X-ray source

[0054] 12' X-ray source

[0055] 14 X-ray detector

[0056] 14' X-ray detector

[0057] 16 Evaluation Devices

[0058] 18 inner layers

[0059] 20 corrugated layers

[0060] 22 troughs

[0061] 24 peaks

[0062] 26 Measurement Signals

[0063] 28 Evaluation Signals

Claims

1. A method for determining at least one geometric parameter of an elongated object (10) having a periodic structure, particularly a bellows (10), the bellows comprising a corrugated layer (20) having a periodic corrugated shape, wherein, The object (10) is irradiated with X-rays that diverge laterally in the longitudinal direction of the object, and the X-rays after passing through the object (10) are detected by a position-resolved X-ray detector (14) as a position-resolved measurement signal in the longitudinal direction of the object (10). The invention is characterized in that, the X-ray irradiates a measurement section of the object (10) extending in the longitudinal direction of the object (10), the X-ray detector (14) detects multiple measurement signals (26) that are positionally resolved in the longitudinal direction of the object (10) for the X-rays that penetrate the measurement section, the measurement signals (26) are combined into an evaluation signal (28) that is positionally resolved in the longitudinal direction of the object (10), the evaluation signal (28) identifies layer transitions within the object and / or between the object (10) and the medium surrounding the object (10) at multiple locations in the measurement section, and at least one geometric parameter of the object (10) is determined based on the identified layer transitions.

2. The method according to claim 1, characterized in that, The object (10) is transported along the transport direction during X-ray transmission.

3. The method according to any one of the preceding claims, characterized in that, The X-rays irradiating the object (10) are also divergent in the longitudinal direction of the object (10), and / or the X-ray detector (14) is also position-resolved in the longitudinal direction of the object (10).

4. The method according to any one of the preceding claims, characterized in that, The X-ray detector (14) includes a scintillation counter and a sensor array, particularly a CCD array.

5. The method according to any one of the preceding claims, characterized in that, The measurement section extends over at least 20%, preferably at least 40%, of the period of the periodic structure of the object (10).

6. The method according to any one of the preceding claims, characterized in that, The measurement section extends over at least a portion of the crests (24) and troughs (22) of the periodic structure of the object (10) and extends along the side between the crests (24) and troughs (22) of the periodic structure of the object (10).

7. The method according to any one of the preceding claims, characterized in that, The measurement section extends over no more than 100%, preferably no more than 75%, of the period of the periodic structure of the object (10).

8. The method according to any one of the preceding claims, characterized in that, The measurement section extends on the side of the periodic structure of the object (10) at no more than one peak (24) and one trough (22) and between the peak (24) and the trough (22) of the periodic structure of the object (10).

9. The method according to any one of the preceding claims, characterized in that, In order to combine the measurement signals (26) into an evaluation signal (28) that is positionally resolved in the longitudinal direction of the object (10), the average value of the measurement signals (26) detected in the measurement section is formed.

10. The method according to any one of the preceding claims, characterized in that, Layer transitions are identified by means of the minimum and / or maximum values ​​and / or slope changes and / or discontinuities in the evaluation signal (28).

11. The method according to claim 10, characterized in that, Layer transitions are identified by means of at least two, preferably at least three, and more preferably at least four minimum and / or maximum values ​​and / or slope changes and / or discontinuities in the evaluation signal (28).

12. The method according to any one of the preceding claims, characterized in that, Layer transitions are identified by using machine learning algorithms, preferably with the help of minimum and / or maximum values ​​and / or slope changes and / or discontinuities in the evaluation signal (28), preferably with the help of artificial neural networks.

13. The method according to any one of the preceding claims, characterized in that, As at least one geometric parameter, the layer thickness of the object (10), especially the layer thickness of the corrugated layer (20) and / or inner layer (18) of the corrugated pipe (10), is determined.

14. The method according to any one of the preceding claims, characterized in that, The object (10) is irradiated by X-rays emanating from two directions in a direction transverse to the longitudinal direction of the object, and the X-rays after passing through the object (10) are detected by at least two position-resolved X-ray detectors (14, 14') as position-resolved measurement signals in the longitudinal direction transverse to the object (10). Each of the two directions irradiates a measurement segment extending in the longitudinal direction of the object (10), and each X-ray detector (14, 14') detects multiple X-rays passing through the measurement segment. A measurement signal (26) is obtained that is positionally resolved in the longitudinal direction of the object (10), and the measurement signals (26) detected by each X-ray detector (14, 14') are combined into an evaluation signal (28) that is positionally resolved in the longitudinal direction of the object (10), wherein the evaluation signal (28) identifies layer transitions within the object and / or between the object (10) and the medium surrounding the object (10) at multiple locations in the measurement section, and determines at least one geometric parameter of the object (10) based on the identified layer transitions.

15. An apparatus for determining at least one geometric parameter of an elongated object (10) having a periodic structure, particularly a bellows (10), the bellows comprising a corrugated layer (20) having a periodic corrugated shape, the apparatus comprising an X-ray source (12) configured to irradiate the object (10) with X-rays diverging transversely to the longitudinal direction of the object, and the apparatus comprising a position-resolved X-ray detector (14) configured to detect X-rays after transmission through the object (10) as a position-resolved measurement signal transversely to the longitudinal direction of the object (10). Its features are, The X-ray source (12) is also configured to irradiate the object (10) with X-rays in a measurement section extending in the longitudinal direction of the object (10), and the X-ray detector (14) is also configured to detect multiple measurement signals (26) resolved in the longitudinal direction of the object (10) for X-rays that penetrate the measurement section. The device also includes an evaluation device (16) configured to combine the measurement signals (26) into an evaluation signal (28) resolved in the longitudinal direction of the object (10), in which the evaluation signal (28) identifies layer transitions in the measurement section that are within the object and / or between the object (10) and the medium surrounding the object (10), and determines at least one geometric parameter of the object (10) based on the identified layer transitions.

16. The device according to claim 15, characterized in that, The device includes two X-ray sources (12, 12') configured to irradiate the object (10) with X-rays emanating from different directions in a longitudinal direction transverse to the object (10), and the device includes two X-ray detectors (14, 14') configured to detect X-rays after they have penetrated the object (10) as position-resolved measurement signals in a longitudinal direction transverse to the object (10), wherein the X-ray sources (12, 12') are respectively configured to irradiate a measurement segment of the object (10) extending in the longitudinal direction of the object (10) with X-rays, and the X-rays... The X-ray detectors (14, 14') are configured to detect multiple measurement signals (26) that are position-resolved in the longitudinal direction transverse to the object (10) for X-rays that transmit through the measurement section, and the evaluation device (16) is configured to combine the measurement signals (26) into evaluation signals (28) that are position-resolved in the longitudinal direction transverse to the object (10), identify layer transitions in the evaluation signals (28) that are located within the object and / or between the object (10) and the medium surrounding the object (10) at multiple locations in the measurement section, and determine at least one geometric parameter of the object (10) based on the identified layer transitions.

17. The device according to any one of claims 15 or 16, characterized in that, The device is configured to implement the method according to any one of claims 1 to 14.

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