Patent Description:
Pipelines of the type used to convey gas, oil, or other fluids over long distances are typically formed of metallic sections. These may be joined together with welds or more specifically girth welds. In many situations, the pipelines are constructed by adding sections sequentially, one section after another. When a section is added it is welded to the immediately preceding section, to build a pipeline. Because the end of the newly added section is open, may be possible to inspect the new weld from both sides, that is, from the inside and outside, which may be done using x-ray penetration of the weld and a suitable detection system such as x-ray sensitive film or a semiconductor detector substrate, for example. In some situations, internal access to the pipeline is difficult to obtain. For example, where a pipeline has already been built and needs to be inspected for wear, the pipeline may be in use, or at least partly clogged, during inspection. Therefore, a system of inspection completely external to the pipeline is of interest.

A weld in pipelines could also be longitudinal, that is, in the direction of the pipeline or a weld in a T-shaped connection or any other relevant shape. The term weld also refers to other welds in containers, tanks, automobiles or other constructions where such technology would be suitable and is thus not limited to pipelines.

Conventionally, such welds have been inspected by using a high strength, broad beam radioactive source, such as an x-ray or gamma-ray source, to penetrate both walls of the pipeline and to expose an x-ray sensitive film plate on the opposite side of the pipeline to the x-ray source. In general, in the present document the expression x-rays is employed to refer to high-energy photons.

Using semiconductor detector substrates in x-ray imaging provides benefits in that digital processing of x-ray images is faster and more versatile, and the detector substrates are more sensitive to incoming high-energy photons than film.

Document <CIT> discloses a video radiographic process, wherein a weld inspection is carried out by obtaining, using plates and video cameras, radiographic images which are compared to previously recorded flawless welds. A lack of identity in the images indicates a flaw. Document <CIT> discloses a method to test a technical body, such as a pipe, using a x-ray source and detector which are arranged to rotate about the technical body. Document <CIT> discloses an external pipeline weld inspection arrangement, wherein plural x-ray detectors may be illuminated using a fan-shaped x-ray beam. Finally, document <CIT> discloses a planar laminography method, wherein higher speed is obtained over conventional laminography by using an electronically scanned system.

illustrative examples not forming part of the invention are presented for aiding in understanding the background and advantages of the invention.

An inspection method is described herein, which increases the amount of usable information that can be obtained from a weld inspection, such that weld sections are imaged more than once during the inspection, with different x-ray angles of incidence, to enable building a more detailed understanding of an internal structure of the weld. The weld may be a circumferential, longitudinal or T-shaped weld, for example. The weld may be a pipeline weld, for example the circumferential or longitudinal weld may be a pipeline wed. Further examples of weld types include a cryogenic tank, such as liquid natural gas (LNG) section weld, and an automotive part weld.

Although two-dimensional (2D) radiographic imaging of a weld typically produces adequate results, it fails in some cases where the orientation of a defect, such as a crack, along the pipe makes it difficult to observe it. X-rays may be generated using various suitable methods, such as linear accelerators, synchrotrons, x-ray tubes or isotope sources, for example. X-ray energies may fall in the range of <NUM> kilo electronvolt (keV), <NUM> keV - <NUM> keV or even <NUM> mega electronvolt (MeV), for example.

The x-ray beam is used to illuminate the active area (or the area with pixels) of a detector, or part of it. In case only part of the active area is illuminated, system performance may be optimized by cropping the produced image data to exclude non-illuminated areas. The non-illuminated areas might receive scattered x-rays, so they may also be used to measure or estimate the amount of scattering in the object.

<FIG> illustrates an example system for inspecting a circumferential or girth weld in accordance with at least some embodiments of the present invention. Some elements of the system are not illustrated for clarity. Pipe <NUM> consists of segments, which are attached in a sequential manner using welds, such as circumferential or girth weld <NUM>. In the figure, a weld inspection process is ongoing with x-ray source <NUM> and x-ray detector <NUM> arranged externally to pipe <NUM>, about weld <NUM>. X-ray detector <NUM> may comprise a semiconductor substrate detector, for example, based on direct conversion semiconductor technology such as cadmium telluride (CdTe) or cadmium zinc telluride (CdZnTe or CZT). X-ray detector <NUM> is on the reverse side of the pipe (or opposite side of the pipe to the x-ray source <NUM>) in the perspective drawing, wherefore its outline is produced in dotted line in <FIG>. The location of an x-ray detector <NUM> is not limited to any particular position but shall always be such that the weld section or in general the object to be imaged is between the x-ray detector <NUM> and the x-ray source <NUM>.

X-ray source <NUM> on the obverse side is arranged on a mounting 100a. Likewise, x-ray detector <NUM> on the reverse side is arranged on a mounting 100c of its own. The mountings 100a, 100c are separately controllable to enable moving the x-ray source <NUM> and the x-ray detector <NUM> about the weld independently of each other, using a motor arrangement 100b, 100d, for example. The mountings 100a, 100c may also be mechanically coupled with each other and there may be additional manipulators on the mountings, such as electric actuators, which allow moving the x-ray source or the x-ray detector relative to each other. There may also be multiple manually adjustable positions for the x-ray source and/or the x-ray detector, such as adjustment knobs. The motor arrangement 100b, 100d may comprise an electric motor arrangement, for example. The mountings may comprise motorized buggies, rails, or combinations thereof, for example. A rail or rails may be attached around pipe <NUM> at the weld <NUM> location to inspect the weld. There may be more than one x-ray source <NUM> and/or there may be more than one x-ray detector <NUM>. A movement 110A of the x-ray source <NUM> is schematically illustrated in <FIG>, and likewise a movement 120A of x-ray detector <NUM> is schematically illustrated in <FIG>.

A circumferential movement is a movement along the pipe which aims to directly move around the pipe without movement in the direction of the length of the pipe. In a two-dimensional coordinate representation, the outer surface of the pipe may be represented by coordinates (<NUM>, phi), where <NUM> is a distance from a beginning of the pipe and phi is an angle from a reference orientation of the pipe. For example, phi = <NUM> may be selected as the direction directly upward from a centre of the pipe. Thus, as an example, if a device is placed on top of the pipe and it is moved circumferentially to the bottom of the pipe without moving it along the length of the pipe, phi increases from zero to <NUM> degrees and <NUM> remains constant. In this sense, phi is a circumferential angle. Angle phi is illustrated in <FIG> at the end of the visible pipe segment.

In use, x-ray source <NUM> emits a beam of x-rays with a central ray <NUM>, which may be generated according to processes known in the art. The central ray <NUM> of the beam of x-rays is the portion of the beam with the highest energy level. The beam may be a fan shaped beam or a cone shaped beam, for example. The beam may be directed by a control device 100e of the inspection system to illuminate a section of the weld 101B, and the detector <NUM> behind the weld section 101B. Thus, an image of the weld section 101B may be obtained on the detector. Although the coupling is not shown in <FIG> for sake of clarity, the control system can be coupled to at least one of the motor arrangement 100b, 100d, at least one of the additional manipulators on the mountings 100a, 100c, at least one of the x-ray sources <NUM>, and at least one of x-ray detectors <NUM>. For ease of illustration, reference is made to the section of the weld 101B or the weld section 101B, but the referenced section 101B can be any pipe feature or other object that can be imaged using x-rays with the pipe feature or other between the x-ray source <NUM> and the x-ray detector <NUM>. The section of the weld 101B refers to a portion of the weld, the pipe, or other feature that can be captured into one or more images. Multiple sets of imaging information or imaging data sets may be used to generate one or more images of the weld section 101B. As used herein, sets of imaging information and imaging data sets may be used interchangeably. As the x-ray source and x-ray detector move substantially along the direction of the weld, or in the case of a pipeline girth weld, circumferentially about the pipe, multiple imaging data sets of the entire weld may thus be obtained, for example. Movement profiles, which may comprise speeds and locations, of the x-ray source and the x-ray detector, influence the layer of the weld which are in focus. Therefore adjustment of the profiles may be used to select the layer to be in focus in the resulting image or images. The process of forming, from the imaging information or imaging data sets, a set of resulting images is called the imaging process or merely imaging.

The imaging information may comprise pixel data originating from the at least one x-ray detector <NUM>. The imaging information may further comprise position data indicating, directly or indirectly, where the at least one x-ray source <NUM> and the at least one x-ray detector <NUM> were when the pixel data was obtained in the at least one x-ray detector <NUM>. The imaging information is usable in the generation of images of the weld and/or sections 101B thereof.

The x-ray detector may comprise an x-ray sensitive sensor configured to output two-dimensional image frames, or other imaging information, corresponding to the pixels on the active area of the x-ray detector, and one or more communication links, such as Ethernet, WiFi, wireless local area networking (WLAN) links, Universal Serial Bus (USB) or other suitable technologies, to transfer the collected imaging information to a computer or to other type of equipment used to view, process and/or analyze the imaging information. The imaging apparatus overall may further comprise components, such as at least one processor or processing core, to reconstruct an image from the imaging information. The image can be reconstructed either on the x-ray detector, a dedicated processing unit, a central processing unit (CPU), a computer, a graphical processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a microcontroller, a programmable logic array (PLA), device such as a field programmable logic controller (PLC), a field-programmable gate array (FPGA), or on another suitable processing device. The imaging apparatus may likewise comprise memory (for example volatile memory, like dynamic random-access memory (DRAM) or electronic solid-state non-volatile computer storage) configured to store computer program instructions arranged to control the functioning of the imaging apparatus, when these instructions are executed by the processor or processing core. The memory can include volatile memory, such as dynamic random-access memory (DRAM), or electronic solid-state non-volatile computer storage, such as flash memory. The x-ray detector assembly may be cooled to a constant temperature to ensure stable operation. The x-ray detector used has resolution and contrast capabilities which are sufficient for imaging as disclosed herein, as the skilled person will understand. In some applications different sensitivities may be used. The x-ray detector may be sufficiently sensitive to be able to collect x-ray quanta at a sensitivity which is several orders of magnitude better than what conventional x-ray film plates are able to detect.

The detector may be configured to operate in a frame output mode in which consecutive collected image frames may have overlap with respect to the section of weld 101B being imaged. The image frames output from the detector correspond to at least part of the two-dimensional spatial representation of the values of the physical pixels on the detector. The values of the physical pixels are related to the incident x-ray photons arriving to the corresponding pixels and thus may either correspond to the charge deposited by the photons or the number of the photons with possibly one or more energy discriminating circuits. The image frames or parts of the image frames may then be used as imaging information to reconstruct a final image using a time delayed integration (TDI) method either digitally or in analog domain. Alternatively, the image frames may be used to reconstruct the final image of three-dimensional voxel volume by using another reconstruction method, such as, for example, tomosynthesis, computed laminography or computer tomography (CT). In the TDI reconstruction method, the consecutive image frames are shifted one or two-dimensionally according to the movement profile of the x-ray detector along the weld, and values of the pixels are added to the values of the pixels in the final image. The shifting can be over either an integer number of pixels or over an arbitrary number, in which case the addition would be performed using a form of filtering such as finite impulse response (FIR) or infinite impulse response (IIR) filters or interpolation such as linear interpolation, spline interpolation or wavelet interpolation or by using a transform such as the Fourier transform, for example.

The x-ray detector has a two-dimensional pixel matrix with dimensions, for example, of <NUM> millimeter (mm) x <NUM> or <NUM> x <NUM>. Where the longer dimension is typically, but not necessarily perpendicular to the weld and the short dimension along the weld. The detector may have a pixel size of <NUM> micron (µm or micrometer), <NUM>, <NUM> or <NUM>, for example. A preferred pixel size is <NUM> or less or even <NUM> or less. The thickness of the converter material, such as CdTe, in the x-ray detector may be <NUM>, <NUM> - <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM> for example. Preferably the thickness of the of the converter material is more than <NUM> or <NUM> or even <NUM> or more.

The x-ray detector electronics may be synchronized to the scanning mechanism via a master clock such that data from the x-ray detector is sampled each time the detector has advanced by a predefined distance. The master clock can be generated by the processing device <NUM>, the x-ray source <NUM>, the x-ray detector <NUM>, by other components in the system or by an external component or device in which case it is transmitted using a wire or wireless connection to the system.

The x-ray detector electronics may be asynchronous to the movement of the scanning mechanism. In such a case, the imaging apparatus may comprise or use additional position information or signals generated by the scanning mechanism, an optical encoder, an optical position sensor producing image data, a gyroscope, an accelerometer or other device configured to measure movement and/or position. The image data used for the additional position information may be distinct from the final x-ray images produced using the x-ray weld inspection apparatus. The position and/or speed profile can also be estimated from the output data of the detector by either tracking prominent features in the weld, such as defects or changes in thickness, or by tracking artificial fiducial markers. The artificial fiducial markers may be printed, etched, painted, ground or otherwise manufactured markers on the surface on or near the weld. The artificial fiducial markers may be part of the mechanical manipulators or other features of the system or part of an object containing a pattern of the markers. This position information or signals may be used to record the location of the x-ray detector and/or the x-ray source and/or other components in the system to thereby contribute to the imaging information, and may be used by the reconstruction algorithm to align the measured image frames to produce the desired results. This additional position information may also be used as the master clock in the synchronous mode.

This additional position information may contain translation and/or rotation information and may therefore be used to rotate, scale, warp or otherwise transform the imaging information output from the x-ray detector before the reconstruction is performed. One-or two-dimensional TDI reconstruction may be employed, for example to x-ray detector output transformed based on the additional position information. Frame output mode may be used instead of, or in addition to, TDI reconstruction. Outputted image frames may be used in other reconstruction techniques, for example to compile three-dimensional images.

The positioning signal may indicate, for example, the actual relative or absolute movement and/or position profile of the x-ray detector and/or the x-ray source. The movement and/or position profile may be expressed, for example, in terms of a distances, <NUM>-D or <NUM>-D coordinates, angular or arbitrary expressions characterizing the movement and/or place as a function of time.

<FIG> illustrates an example of a movement profile of the x-ray detector and/or an x-ray source. <FIG> is in Cartesian coordinates x, y and z, and a movement from a position at time instant t<NUM> (shown as a circle) to time instant t<NUM> (shown as a triangle) is expressed in terms of the Cartesian coordinates is illustrated. The overall movement consists of sub-trajectories s<NUM>, s<NUM> and s<NUM>. Alternatively to Cartesian coordinates, a different coordinate basis could be employed, such as, for example, polar or cylindrical coordinates.

At least some sections of the weld may be imaged more than once using different movement and/or position profile in the respective images. Where a certain section of the weld is imaged using more than one geometry, featuring, for example, different angles of incidence, an enhanced understanding of the weld may be obtained in the depth direction. Here, the angle may correspond to an angle of incidence of the x-ray beam on the section of the weld and/or an angle of arrival of an x-ray beam on a detector surface. The angle of incidence (i.e., angles β<NUM> and β<NUM>) will be described herein below in connection with <FIG>, and the angle of arrival (i.e., angle ω) will be described in connection with <FIG>. The angle may be in any coordinate system and is not limited to any coordinate system used in or by the apparatus or components thereof. An obtained depth resolution of a section of the weld is proportional to a range of angles at which said section is imaged. In general, increasing the range of used angles may increase the depth resolution. The angular range can also be optimized to certain directions if there exists knowledge of the direction of a possible defect, or of other structures of interest.

The master clock and/or the position signal may also be modulated during the inspection process. In case the positioning signals are recorded, for example in the imaging information, the positioning signals may be used to vary the alignment of the collected image frames after the inspection. If the TDI method is used, this enables varying the shift between the consecutive image frames which in turn results in a different layer (depth) to be focused. Multiple images can be reconstructed by this method with different position signal modulations, which provides more information of the weld at different depths. These images can also be combined to provide a 3D representation of the weld.

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

The x-ray beam <NUM> 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> 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 <NUM>, which may have T-shaped or X-shaped intersections with each other.

<FIG> 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>, a single x-ray detector <NUM> is used with a single x-ray source <NUM>, such that beam <NUM> illuminates weld section 101B more than once. In detail, the x-ray detector <NUM> is moved tangentially to the surface (for example, back and forth, in an oscillating movement), arrows <NUM>, 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 <NUM> in a direction substantially parallel to the overall direction of the weld, as shown in <FIG>). 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 <NUM> 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 <NUM> upon x-ray detector <NUM> 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>. 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 <NUM> in a direction substantially perpendicular to the overall direction of the weld, as shown in <FIG>), 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 ±<NUM>°, ±<NUM>°, ±<NUM>° or even ±<NUM>°. 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 ±<NUM>°, ±<NUM>°, ±<NUM>° or even ±<NUM>° in a transverse direction <NUM> 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 ±<NUM>°, ±<NUM>°, ±<NUM>° or even ±<NUM>° in parallel direction <NUM> 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>.

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>, allows increasing the range of angles of incidence of x-rays <NUM> at the section of the weld, as illustrated in <FIG>. This may result in better depth resolution in the weld or section thereof.

In <FIG>, another way to obtain plural imaging data sets of weld section 101B is illustrated. In this case, there are two x-ray detectors <NUM>, which are moved circumferentially about the weld. A single x-ray source <NUM> illuminates weld section 101B first for a first detector, and then x-ray source <NUM> illuminates weld section 101B for the other detector. X-ray source <NUM> 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 <NUM> upon the x-ray detector <NUM>, via the weld section 101B.

In <FIG>, there are two x-ray sources <NUM>, 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 <NUM> 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 <NUM> 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.

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

<FIG> illustrate an effect of moving a monochromator <NUM>. In <FIG>, monochromator <NUM> is in a first position, receiving polychromatic beam <NUM> from the x-ray source <NUM> and directing a monochromatic beam <NUM> onto a first part of the detector <NUM>. In <FIG>, monochromator <NUM> is in a second position, being tilted with respect to the first position, receiving polychromatic beam <NUM> from the x-ray source <NUM> and directing a monochromatic beam <NUM> onto a second part of the detector <NUM>.

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> illustrates x-ray imaging geometries in accordance with at least some embodiments of the present invention. Illustrated is an arrangement similar to those in <FIG>, with two positions of x-ray source <NUM> and two positions of x-ray detector <NUM> 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> is marked with an "x" in the weld section 101B. Two imaging positions are thus illustrated in <FIG>, with different imaging geometries.

The angle α indicates an angle between x-ray beam <NUM> 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 <NUM> 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> illustrates angles of incidence β<NUM> and β<NUM>. The beam geometry is similar to that in <FIG>, in that two x-ray beams <NUM> 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 <NUM> and a normal axis <NUM>, which are orthogonal to each other. Angle β<NUM> is an angle of incidence of a first one of the x-ray beams <NUM>, and angle β<NUM> is an angle of incidence of a second one of the x-ray beams <NUM>. 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> illustrates an example detector substrate in accordance with at least some embodiments of the present invention. The system of <FIG> is a weld imaging system. The weld imaging system may comprise an x-ray/gamma-ray imaging system, for example. The system of <FIG> is arranged to image radiation <NUM> incident from an x-ray source to detector substrate <NUM> from the top. Detector substrate <NUM> is arranged to convert the incident radiation <NUM> to a plurality of electrical signals, each such signal representing a value of a pixel <NUM> of detector substrate <NUM>. 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 <NUM> and output to a processing device <NUM> as the imaging data sets. The processing device may be comprised in or as the control device 100e (<FIG>), for example. The processing device <NUM> may perform, selectably, operations on information encoded in the electrical signals from detector circuit <NUM>, to result in a digital image <NUM>. In the example illustrated in <FIG>, this image comprises an image of an object <NUM>, which may comprise a weld defect, for example.

The incident radiation may be x-ray or gamma radiation, for example. Detector substrate <NUM> may comprise CdTe substrate, CZT substrate, a gallium arsenide (GaAs) substrate, a silicon (Si) substrate, a selenium (Se) substrate or a mercury(II) iodide (HgI<NUM>) substrate, for example. The detector substrate <NUM> 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 (CdWO<NUM> or CWO) substrate or gadolinium oxysulfide (Gd<NUM>O<NUM>S) 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 <NUM> 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 <NUM> interfaced with detector substrate <NUM> may have a memory with such information relating to the pixel <NUM> linked to the particular detector circuit, or the information may otherwise be stored in or for detector circuit <NUM>.

<FIG> illustrates a corkscrew (spiral) movement of superimposed component movements. Direction <NUM> 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 <NUM> is in a direction substantially parallel to the overall direction of the weld, while back-and-forth (oscillating) movement <NUM> 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 <NUM> 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 <NUM> 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> is a flow graph of a method. The phases of the illustrated method may be performed in by the weld inspection apparatus described herein above, for example.

Phase <NUM> 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 <NUM> 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.

In the following some illustrative aspects not forming part of the invention are presented.

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 <NUM> attached on a first mounting 100a, at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM> 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, <NUM>, a motor arrangement 100b, 100d to move at least one x-ray source <NUM> and at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM>, wherein, <NUM>, 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 <NUM> and at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM>, 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, <NUM>, a motor arrangement 100b, 100d to move at least one x-ray source <NUM> and at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM>, wherein, <NUM>, 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 <NUM> attached on a first mounting 100a and at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM> 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 <NUM> and the at least one x-ray detector <NUM> 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.

Claim 1:
An x-ray weld inspection apparatus comprising:
- at least one x-ray source (<NUM>) attached on a first mounting (100a);
- at least one x-ray detector (<NUM>) attached on a second mounting (100c);
- a motor arrangement (100b) configured to move, using the first and second mountings (100a, 100c), respectively, the at least one x-ray source (<NUM>) and the at least one x-ray detector (<NUM>) substantially along a weld (<NUM>), the weld (<NUM>) being a pipeline weld; and
- a control device (100e) comprising memory and at least one processing core, configured to:
▪ control the motor arrangement (100b) to move the at least one x-ray source (<NUM>) and the at least one x-ray detector (<NUM>) during an x-ray weld scan substantially along the direction of the weld (<NUM>);
▪ wherein at least one section of the weld (<NUM>) is imaged at least twice during a single x-ray scan by moving at least one of the at least one x-ray detector (<NUM>) in an oscillating movement substantially along the direction of the weld (<NUM>), the oscillating movement superimposed on movement of the at least one x-ray detector (<NUM>) substantially along the direction of the weld (<NUM>) during the scan of the weld (<NUM>), 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 (<NUM>) is different for the imaging data sets.