The master clock and/or position signal modulation may be performed by selecting the modulation producing an image of a layer of interest. This can be either specified as a physical dimension, such as depth in the weld, or by, for example, finding the layer of maximum sharpness, contrast or other measure calculated from the image frame data. Finding maximum sharpness may involve methods similar to optical photography where the focusing distance is adjusted by analysing the image. Other possibilities, for example, include image processing means such as maximizing the response of edge detection filters such as the Sober filter or difference of Gaussian (DoG) filter. The master clock modulation may also be calculated by actively following a feature or features in in the reconstructed image. In case the feature becomes less sharp, the modulation can be adjusted slightly to either direction. If the resulting sharpness is better, the modulation is accepted. On the other hand, if the resulting sharpness is worse, the opposite direction may be tried.

In use, the x-ray source 110 may be positioned to illuminate the weld section 101B closest to the x-ray detector 120, while directing beam 111 past the weld closest to the x-ray source 110. In other words, beam 111 may be slightly angled to only illuminate one section of the weld. In other words, in a pipeline embodiment, the x-ray beam 111 may be aligned so as to traverse the circumferential weld 101 only once, at the side closest to x-ray detector 120.

The x-ray beam 111 may also be directed through both the weld on the x-source side and the weld on the x-ray detector side. These two welds would both appear superpositioned in the image frames or image data, but the reconstruction method could selectively reduce or eliminate the image of either one of them.

The x-ray source may be collimated to a narrow fan beam, for example. This directs the beam substantially at the area of the weld, also thereby reducing the scattering of unused x-rays. Scattered x-rays could hit detector pixels from random directions, causing undesired graininess or noise in images.

FIG. 1B illustrates a pipe built of different sections than the pipe of the upper part of the figure, namely bent panels. Joining such panels involves longitudinal welds 102, which may have T-shaped or X-shaped intersections with each other.

FIGS. 4A-4D illustrate ways of imaging a weld section more than once. The illustrated planes comprising the weld sections 101B are curved to suggest a pipe, however, more generally these planes may be non-curved where the weld inspection does not involve a pipe. As an example, in FIG. 4A, a single x-ray detector 120 is used with a single x-ray source 110, such that beam 111 illuminates weld section 101B more than once. In detail, the x-ray detector 120 is moved tangentially to the surface (for example, back and forth, in an oscillating movement), arrows 210, while moving it along an overall circumferential (or in the direction of the weld or along the axis defined by the weld if the weld is not circumferential) trajectory during the scan of the pipe (for example, circumferential modulation, parallel modulation or movement 470 in a direction substantially parallel to the overall direction of the weld, as shown in FIG. 5B). Thus, one imaging of weld section 101B is obtained moving x-ray detector in one direction, generating one set of imaging information or a first imaging data set, and another imaging of the same weld section 101B is obtained moving x-ray detector 120 in another direction, generating a second set of imaging information or a second imaging data set, and/or again in the same direction. The x-ray source may be moved between the imaging positions, such that the x-ray source is not in the same place during the acquisition of the two imaging data sets, thus changing the angle of arrival of x-ray beam 111 upon x-ray detector 120 and the angle of incidence at section of the weld 101B. The movement of the detector may thus resemble the back-and-forth oscillating motion of a vacuum cleaner head on a carpet, while the carpet is being vacuumed. A plot of the circumferential angle phi against time is plotted in FIG. 4B. Therefore, in this option, a smaller-amplitude back-and-forth (oscillating or sine wave) circumferential movement is superimposed on the broader, overall circumferential movement 120A (slope of the sine wave) about the weld.

In some variants, a second back-and-forth (oscillating) movement, substantially transverse to the circumferential movement (for example, perpendicular modulation or movement 460 in a direction substantially perpendicular to the overall direction of the weld, as shown in FIG. 5B), is also, or alternatively, used to obtain more imaging information of weld section 101B. This combination of uni-directional circumferential (or along the weld) direction and either circumferential or perpendicular modulation allows more depth information to be collected either on the whole weld of selected section of the weld. The direction along the weld is not limited to exactly follow the weld nor the perpendicular direction to be exactly perpendicular to the weld, but either of the directions may differ up to ±15°, ±30°, ±45° or even ±65°. The angle of at least one x-ray source or at least one x-ray detector to the surface of weld can be up to ±15°, ±30°, ±45° or even ±65° in a transverse direction 460 to the overall direction of the weld and/or the angle of at least one x-ray source or at least one x-ray detector to the surface of weld can be up to ±15°, ±30°, ±45° or even ±65° in parallel direction 470 to the overall direction of the weld. Having an orientation other than the perpendicular direction may be useful due to space constraints. For example, in industrial facilities pipes may be laid out close to each other, restricting freedom of movement. The proposed system and method are able to perform both types of imaging (that is movement oscillating across the weld and movement along the weld) in single scan through the weld.

Thus, in this embodiment, one or two smaller-amplitude back-and-forth (oscillating) movements are superposed on the overall movement along the length of the weld. Where two such smaller-amplitude back-and-forth movements are involved, an overall corkscrew (spiral) type movement may be generated as an example, which is illustrated in FIG. 5B.

The superimposed smaller-amplitude movement comprises translations and/or rotations of the x-ray source and/or the x-ray detector. Such translations and/or rotations are not necessarily completely aligned with the broader overall movement along the weld. The superimposed movement may be at least in part simultaneous with the broader overall movement along the weld. The benefit of having simultaneous movement is a more stable system with less vibrations which would normally be caused by accelerations and decelerations. The system may also be faster for the same reason as the average imaging movement speed may be higher. The combination of multiple movement components, illustrated in FIG. 5B, allows increasing the range of angles of incidence of x-rays 111 at the section of the weld, as illustrated in FIG. 3B. This may result in better depth resolution in the weld or section thereof.

In FIG. 4C, another way to obtain plural imaging data sets of weld section 101B is illustrated. In this case, there are two x-ray detectors 120, which are moved circumferentially about the weld. A single x-ray source 110 illuminates weld section 101B first for a first detector, and then x-ray source 110 illuminates weld section 101B for the other detector. X-ray source 110 may move or rotate in between the imaging positions, to provide a separate imaging information sets with different angles of incidence of the x-ray beam 111 upon the x-ray detector 120, via the weld section 101B.

In FIG. 4D, there are two x-ray sources 110, and one x-ray detector is moved along the length of the weld, obtaining one imaging by illuminating the detector by the x-ray source and a second imaging by illuminating the detector by the second x-ray source. In this example, the x-ray sources 110 are separated by a nonzero distance (e.g., not co-located in the same place). As shown, the angles of incidence of x-ray beams 111 are different. Thus, again, two imaging data sets are obtained, with different x-ray source locations, which is here caused by having two distinct x-ray sources. The two x-ray sources may illuminate different parts of the detector or they can be toggled on and off in a synchronous manner so that the frames corresponding to the separate x-ray source illuminations can be separated. More than two detector-x-ray source pairs can be included for better image quality and/or faster scan speeds. One benefit of using multiple x-ray sources is that in a typical weld inspection application, the cooling capacity of an individual x-ray source can be limited and thus using multiple sources allows a longer operational time. The part of the active area of the detector illuminated by the x-ray sources can vary from one x-ray source to another.

In general, for a pipeline weld inspection, the movement of the at least one x-ray detector and the at least one x-ray source may be non-circular to obtain the differing angles of incidence for the imaging data sets generated for the respective section(s) of the weld.

An effect similar to the movement of the one or more x-ray sources may also be achieved by moving the beam collimation, adjusting possible monochromator or diffractor angle or by focusing the x-ray beam by changing the x-ray source control signals, voltages and parameters such as the anode angle. A monochromator is a device installed between the x-ray source and object to adjust the spectrum of the x-ray beam. Any of these means may be used to redirect, that is, change the direction of, the x-ray beam which allows, for example, illuminating more than one detector from a single x-ray source.

FIGS. 6A-6B illustrate an effect of moving a collimator 710. In FIG. 6A, collimator 710 is in a first position relative to the x-ray source 110, causing post-collimator beam 720 to fall on the detector 120 in a first way, and in FIG. 6B the collimator 710 is in a second position relative to the x-ray source 110, causing post-collimator beam 720 to fall on the detector 120 in a second way, as illustrated. A similar effect may be obtained by moving the focal spot of the x-ray tube or source 120 is moved electrically or mechanically.

FIGS. 6A-6D illustrate an effect of moving a monochromator 750. In FIG. 6C, monochromator 750 is in a first position, receiving polychromatic beam 730 from the x-ray source 110 and directing a monochromatic beam 740 onto a first part of the detector 120. In FIG. 6D, monochromator 750 is in a second position, being tilted with respect to the first position, receiving polychromatic beam 730 from the x-ray source 110 and directing a monochromatic beam 740 onto a second part of the detector 120.

The one or more x-ray sources and one or more detectors may be used in a synchronous way to increase the image quality. The source-detector sub-systems (each containing one or more x-ray sources and one or more detectors) can be operated in such a way that the x-rays emitted by a sub-system are not detected by any other sub-systems. Reducing x-ray interference from between sub-systems may be achieved by not collecting data in a detector of another subsystem when an x-ray source of a subsystem is active, for example. For example, minimizing the scattered x-rays from one sub-system can reduce the degradation of the image quality of a second sub-system. This decoupling of the systems may be performed by adequate collimation of the x-ray beams, synchronized movement sub-systems to minimize overlap of the x-ray beams or scattered x-rays, or by temporal synchronization in which the one or more of the sub-systems are toggled on and off to reduce the effect of neighbouring sub-systems.

The plural imaging data sets may be used to enhance the understanding the inspection gains of the weld, for example, the plural imaging data sets may be focused at different depths in the weld to generate a three-dimensional model of the weld, and/or the imaging data sets may be used to average out noise and effects of x-ray scattering.

FIG. 3A illustrates x-ray imaging geometries in accordance with at least some embodiments of the present invention. Illustrated is an arrangement similar to those in FIGS. 4A-4D, with two positions of x-ray source 110 and two positions of x-ray detector 120 depicted. The figure may also be interpreted as depicting two x-ray sources and two x-ray detectors, to similar effect. The object of the imaging of FIG. 3A is marked with an “x” in the weld section 101B. Two imaging positions are thus illustrated in FIG. 3A, with different imaging geometries.

The angle α indicates an angle between x-ray beam 111 of the two imaging positions concerning a specific point in the weld. The larger is angle α, the better is a depth resolution in the overall imaging process which relies on compiling imaging information from more than one imaging of the same section of the weld. The x-ray weld inspection apparatus may be configured to image at least some sections of the weld more than once, during a single x-ray scan along the direction of the weld, such that α between the imaging positions correspond to at least half a detector width (or the width of the x-ray beam at the detector in case it is narrower) in the imaging geometry used. The angle α may be defined in 3D space and is thus not tied to any particular 2D projection. Thus, the term detector width means effectively the size of the x-ray beam in the chosen direction. For example, sin(α)>(x)/(2d) may be satisfied, where x is the size of the x-ray beam inside the active area of the x-ray detector in the any direction of α and d the distance between x-ray source and x-ray detector.

In an aspect, a scan refers to an imaging process during which a substantially entire weld is imaged, from a starting point to an ending point, allowing for a range of movements along the way. Alternatively or additionally, a scan refers to an imaging process the x-ray weld inspection apparatus performs based on a configuration without user intervention. During the scan, the at least one x-.ray source may continuously emit x-rays, or may alternatingly emit and not emit x-rays. Likewise the at least one x-ray detector may be continuously active, or alternatingly active and inactive. The x-ray weld imaging apparatus may further be configured to autonomously modify at least one movement profile of x-ray source(s) and/or x-ray detector(s) during the scan, for example responsive to machine vision determinations.

The angle of arrival ω of x-rays x-ray detector 120 may vary between imaging positions of a same section of the weld. By the angle of arrival it is meant the primary arrival angle of an x-ray beam from an x-ray source. For example, the angle of arrival may be determined at a specific phase of a data collection period, such as a midpoint or start point of the data collection period of the imaging of the section of the weld. Using different ω between imaging positions enhances the diversity of imaging data obtained of the weld section, improving the quality of the resulting image.

FIG. 3B illustrates angles of incidence β₁and β₂. The beam geometry is similar to that in FIG. 3A, in that two x-ray beams 111 are incident on a specific point in the weld. The specific point is in the origin of a coordinate system comprised of a tangential axis 301 and a normal axis 302, which are orthogonal to each other. Angle β₁is an angle of incidence of a first one of the x-ray beams 111, and angle β₂is an angle of incidence of a second one of the x-ray beams 111. In other words, the angle of incidence may be defined as an angle between a normal axis and the x-ray. Normal in this sense refers to perpendicular to the tangent, and applies also to welds which are on a flat surface.

FIG. 5A illustrates an example detector substrate in accordance with at least some embodiments of the present invention. The system of FIG. 5A is a weld imaging system. The weld imaging system may comprise an x-ray/gamma-ray imaging system, for example. The system of FIG. 5A is arranged to image radiation 401 incident from an x-ray source to detector substrate 410 from the top. Detector substrate 410 is arranged to convert the incident radiation 401 to a plurality of electrical signals, each such signal representing a value of a pixel 416 of detector substrate 410. The electric signals can be charges, voltages, currents or digital values related to the deposited x-ray dose at the pixels. The electric signals may also be one or more digital numbers corresponding to the number of photons received by the detector with one or more energy thresholds. The electric signals are collected by detector circuits 440 and output to a processing device 420 as the imaging data sets. The processing device may be comprised in or as the control device 100e (FIG. 1A), for example. The processing device 420 may perform, selectably, operations on information encoded in the electrical signals from detector circuit 440, to result in a digital image 430. In the example illustrated in FIG. 5A, this image comprises an image of an object 432, which may comprise a weld defect, for example.

The incident radiation may be x-ray or gamma radiation, for example. Detector substrate 410 may comprise CdTe substrate, CZT substrate, a gallium arsenide (GaAs) substrate, a silicon (Si) substrate, a selenium (Se) substrate or a mercury (II) iodide (HgI₂) substrate, for example. The detector substrate 410 may also be of indirect conversion type and consist of a scintillating layer which converts the x-rays to light such as cesium iodide (CsI) substrate, cadmium tungstate (CdWO₄or CWO) substrate or gadolinium oxysulfide (Gd₂O₂S) substrate, and a complementary metal-oxide-semiconductor (CMOS), charge-coupled device (CCD) or thin-film transistor (TFT) layer converting the incident light to electricity. The operations performed in processing device 420 may comprise calibration, noise reduction, edge detection, auto-focusing, sharpness evaluation, feature tracking and/or contrast enhancement, for example. The imaging system may be furnished with information characterizing the individual pixels such as dark currents of the detector substrate or pixel specific tuning values such as gain and/or offset values, for example, each detector circuit 440 interfaced with detector substrate 410 may have a memory with such information relating to the pixel 416 linked to the particular detector circuit, or the information may otherwise be stored in or for detector circuit 440.

FIG. 5B illustrates a corkscrew (spiral) movement of superimposed component movements. Direction 450 is the overall direction of the weld, which may be a circumferential direction where a pipe is being inspected, or a linear weld, for example, depending on the application at hand. Back-and-forth (oscillating) movement 470 is in a direction substantially parallel to the overall direction of the weld, while back-and-forth (oscillating) movement 460 is in a direction substantially perpendicular to the overall direction of the weld. When these three movements are superimposed in a scanning movement, an overall corkscrew (spiral) movement 480 is generated, moving along the direction of the weld. This movement enables multiple imaging data sets of weld sections, with differing angles of incidence and angles of arrival. The movement 480 may be a path of motion of an x-ray detector, for example. In general, the angle of incidence may be defined in accordance with an x-ray beam direction, in at least one point of the beam intersecting with the section of the weld.

FIG. 7 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in by the weld inspection apparatus described herein above, for example.

Phase 510 comprises controlling a motor arrangement to move at least one x-ray source and at least one x-ray detector during an x-ray weld scan substantially along the direction of a weld, the motor arrangement configured to move, using first and second mountings, respectively, the at least one x-ray source and the at least one x-ray detector. In phase 520 at least one section of the weld is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, wherein an angle of incidence of x-rays at the at least one section of the weld is different for the imaging data sets. One set of imaging information may be generated per each imaging. Each of the at least one x-ray source and the at least one x-ray detector may be moved along spline trajectories.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, that is, a singular form, throughout this document does not exclude a plurality.

According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims.

According to a first aspect of the present disclosure, there is provided an x-ray weld inspection apparatus comprising at least one x-ray source 110 attached on a first mounting 100a, at least one x-ray detector 120 attached on a second mounting 100c, a motor arrangement 100b, 100d configured to move, using the first 100a and second mountings 100c, respectively, the at least one x-ray source 110 and the at least one x-ray detector 120 substantially along a weld, and a control device 100e comprising memory and at least one processing core, configured to control the motor arrangement 100b, 100d to move the at least one x-ray source 110 and the at least one x-ray detector 120 during an x-ray weld scan substantially along the direction of the weld, wherein at least one section of the weld 101B is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and wherein an angle of incidence of x-rays at the at least one section of the weld 101B is different for the imaging data sets.

According to a second aspect of the present disclosure, there is provided a method of x-ray weld inspection comprising controlling, 510, a motor arrangement 100b, 100d to move at least one x-ray source 110 and at least one x-ray detector 120 during an x-ray weld scan substantially along the direction of the weld, the motor arrangement 100b, 100d configured to move, using first 100a and second 100c mountings, respectively, the at least one x-ray source 110 and the at least one x-ray detector 120, wherein, 520, at least one section of the weld 101B is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and wherein an angle of incidence of x-rays at the at least one section of the weld 101B is different for the imaging data sets.

According to a third aspect of the present disclosure, there is provided an apparatus comprising means for controlling, 100e, a motor arrangement 100b, 100d to move at least one x-ray source 110 and at least one x-ray detector 120 during an x-ray weld scan substantially along the direction of the weld, the motor arrangement 100b, 100d configured to move, using first 100a and second 100c mountings, respectively, the at least one x-ray source 110 and the at least one x-ray detector 120, wherein at least one section of the weld 101B is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and wherein an angle of incidence of x-rays at the at least one section of the weld 101B is different for the imaging data sets.

According to a fourth aspect of the present disclosure, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least control, 510, a motor arrangement 100b, 100d to move at least one x-ray source 110 and at least one x-ray detector 120 during an x-ray weld scan substantially along the direction of the weld, the motor arrangement 100b, 100d configured to move, using first 100a and second 100c mountings, respectively, the at least one x-ray source 110 and the at least one x-ray detector 120, wherein, 520, at least one section of the weld 101B is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and wherein an angle of incidence of x-rays at the at least one section of the weld 101B is different for the imaging data sets.

According to a fifth aspect of the present disclosure, there is provided an x-ray weld inspection apparatus comprising at least one x-ray source 110 attached on a first mounting 100a and at least one x-ray detector 120 attached on a second mounting 100c, a motor arrangement 100b, 100d configured to move, using the first 100a and second 100c mountings, respectively, the at least one x-ray source 110 and the at least one x-ray detector 120 substantially along a weld, and a control device 100e comprising memory and at least one processing core, configured to control the motor arrangement 100b, 100d to move the at least one x-ray source 110 and the at least one x-ray detector 120 during an x-ray weld scan substantially along the direction of the weld, and compile imaging information from the at least one x-ray detector, such that at least one part of the image is reconstructed based on additional position information estimated from image data.

Technical Clauses

Clause 1. An x-ray weld inspection apparatus comprising:

- at least one x-ray source attached on a first mounting;
- at least one x-ray detector attached on a second mounting;
- a motor arrangement configured to move, using the first and second mountings, respectively, the at least one x-ray source and the at least one x-ray detector substantially along a weld; and
- a control device comprising memory and at least one processing core, configured to:
  - control the motor arrangement to move the at least one x-ray source and the at least one x-ray detector during an x-ray weld scan substantially along the direction of the weld;
  - wherein at least one section of the weld is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and
  - wherein an angle of incidence of x-rays at the at least one section of the weld is different for the imaging data sets.

Clause 2. The weld inspection apparatus according to Clause 1, wherein the control device is configured to image the at least one section of the weld at least two times by moving at least one of the at least one x-ray detector in an oscillating movement substantially along the direction of the weld while moving the at least one x-ray detector substantially along the direction of the weld during the scan of the weld.

Clause 3. The weld inspection apparatus according to Clause 2, wherein the control device is configured to image the at least one section of the weld at least two times by further moving the at least one x-ray detector in an oscillating movement in a direction substantially perpendicular to the movement along the weld.

Clause 4. The weld inspection apparatus according to Clause 1, wherein the at least one x-ray detector comprises at least two x-ray detectors, and wherein the control device is configured to image the at least one section of the weld at least two times by moving the x-ray detectors along the direction of the weld, where the at least one weld section is imaged once by each x-ray detector.

Clause 5. The weld inspection apparatus according to Clause 4, wherein the apparatus is configured to re-direct an x-ray beam of the at least one x-ray source at least once during the scan to illuminate the at least two x-ray detectors.

Clause 6. The weld inspection apparatus according to Clause 1, wherein the at least one x-ray source comprises at least two x-ray sources and wherein the control device is configured to image the at least one section of the weld at least two times by moving the at least one x-ray detector in the direction of the weld and by imaging the at least one section of the weld by illuminating the at least one x-ray detector by each of the at least two x-ray sources.

Clause 7. The weld inspection apparatus according to Clause 6, wherein the apparatus is configured to cause the at least two x-ray sources to illuminate different parts of a same x-ray detector from among the at least one x-ray detector.

Clause 8. The weld inspection apparatus according to Clause 6, wherein the apparatus is configured to cause the at least two x-ray sources to illuminate at least partially a same part of a same x-ray detector from among the at least one x-ray detector, wherein the illumination of the at least two x-ray sources occurs at least partially during different times.

Clause 9. The weld inspection apparatus according to any of Clauses 1-8,wherein the apparatus is configured to cause the at least one section of the weld to be imaged at least two times using a time delayed integration, TDI, imaging or a three-dimensional reconstruction based on a frame sequence.

Clause 10. The weld inspection apparatus according to Clause 9, wherein the apparatus is configured to cause the at least one section of the weld to be imaged at least two times by using TDI imaging with different shifts between consecutive image frames, resulting in a different depth layer of the section of the weld to be focused.

Clause 11. The weld inspection apparatus according to any of Clauses 1-10, wherein the apparatus is configured to cause the at least one section of the weld to be imaged at least two times by producing one or more two-dimensional images of the section of the weld and one or more three dimensional images of the section of the weld.

Clause 12. The weld inspection apparatus according to any of Clauses 1-11, wherein the apparatus is configured to cause the at least one section of the weld to be imaged at least two times such that an angle α between x-ray beams between different times, corresponding to the times the section of the weld is imaged, satisfies the inequality sin(α)>(x)/(2d), where x is a size of the x-ray beam inside an active area of the x-ray detector in the direction of α and d is a distance between an x-ray source and an x-ray detector during the imaging.

Clause 13. The weld inspection apparatus according to any of Clauses 1-12, wherein the control device is configured to cause the motor arrangement to move at least one of: the at least one x-ray source and the at least one x-ray detector along the weld direction at an angle of ±45° from a normal axis of the weld in a transverse direction to the weld direction or at an angle of ±45° from a tangential axis of the weld in a parallel direction to the weld direction, during the scan.

Clause 14. A method of x-ray weld inspection comprising:

- controlling a motor arrangement to move at least one x-ray source and at least one x-ray detector during an x-ray weld scan substantially along the direction of the weld, the motor arrangement configured to move, using first and second mountings, respectively, the at least one x-ray source and the at least one x-ray detector;
  - wherein at least one section of the weld is imaged at least twice during a single x-ray scan, producing at least two imaging data sets, respectively, and
  - wherein an angle of incidence of x-rays at the at least one section of the weld is different for the imaging data sets.

Clause 15. The method according to Clause 14, comprising imaging the at least one section of the weld at least two times by moving at least one of the at least one x-ray detector in an oscillating movement substantially along the direction of the weld while moving the at least one x-ray detector substantially along the direction of the weld during the scan of the weld.

Clause 16. The method according to Clause 15, comprising imaging the at least one section of the weld at least two times by further moving the at least one x-ray detector in an oscillating movement in a direction substantially perpendicular to the movement along the weld.

Clause 17. The method according to Clause 14, wherein the at least one x-ray detector comprises at least two x-ray detectors, and wherein the method comprises imaging the at least one section of the weld at least two times by moving the x-ray detectors along the direction of the weld, where the at least one weld section is imaged once by each x-ray detector.