The present disclosure relates generally to laminography inspection systems and, more particularly, to laminography inspection systems with stationary multiple focal spot x-ray sources.
Many industrial applications rely on radiological inspection techniques to determine the quality of industrial parts, such as pipes, pipe arrays, fan blades, wind blade spar caps, and so forth. Such inspection techniques may also be utilized to determine one or more features of an object, such as to determine the wall thickness of a pipe. Since these industrial applications often require inspection of an entire object for quality control purposes, the x-ray sources typically employed in such applications are associated with a mechanical gantry. Each time the mechanical gantry moves the x-ray source to a new location, another image is taken, and a series of such images is typically used to determine the presence or absence of a defect in the part.
Unfortunately, the gantries associated with these single spot x-ray sources are often complex and slow, thus reducing efficiency by increasing the amount of time required to accept or reject a manufactured object. Additionally, the complexity of such systems may lead to downtime associated with necessary repairs and malfunctions. Furthermore, such complex systems may be associated with a high monetary cost and a limited field of view. Accordingly, there exists a need for improved laminography inspection systems and methods that overcome such drawbacks.
In one embodiment, an imaging system includes a multiple focal spot x-ray source adapted to generate at least two x-ray beams and to project each of the generated x-ray beams at a different angle, one at a time, toward an object without substantial rotation or translation of the multiple focal spot x-ray source. The multiple focal spot x-ray source is disposed on a first side of the object. The imaging system also includes a detector disposed on a second side of the object opposite the first side. The detector is adapted to receive at least a fraction of the projected x-ray beams from each of the different angles after being attenuated by the object and to produce at least two x-ray projection images of the object corresponding to each of the different angles. Each of the x-ray projection images are adapted to be shifted with respect to one another and added to reconstruct a plane of the object.
In another embodiment, a laminography inspection method includes providing an object to an inspection area, irradiating the object with at least two x-ray beams from at least two different angles, one at a time, to generate a series of angularly displaced images of the object. The x-ray beams are generated by a stationary multiple focal spot x-ray source. The method also includes shifting each of the angularly displaced images with respect to one another, adding each of the shifted images together to reconstruct an image of a plane of the object, and inspecting the reconstructed image plane to identify the presence or absence of a defect in the object.
In another embodiment, a laminography inspection system includes a multiple focal spot x-ray source adapted to irradiate an object with a series of angularly displaced x-ray beams, one at a time, without substantial rotation or translation of the multiple focal spot x-ray source. The multiple focal spot x-ray source is disposed on a first side of the object. The laminography inspection system also includes a detector adapted to receive at least a fraction of the angularly displaced x-ray beams after being attenuated by the object to produce at least two x-ray projection images of the object. The detector is disposed on a second side of the object opposite the first side. The laminography inspection system also includes a processor adapted to shift and add the at least two x-ray projection images to bring at least two planes of the object into focus, one at a time.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As described in detail below, embodiments of imaging systems including a substantially stationary multiple focal spot x-ray source that generates angularly displaced x-rays that irradiate an object before being detected by a detector are provided. Such systems may be capable of remaining substantially stationary while obtaining a complete set of planar images of an object over an arc; the set of planar images may be utilized to reconstruct slices at different planes in the object. For example, in one embodiment, a processor of a laminography inspection system may utilize the set of planar images to reconstruct slices of a pipe, determine a wall thickness of a pipe, and determine the presence and location of a defect in the pipe. Further, in some embodiments, the slices of the object (e.g., a pipe) may be reconstructed via a shift-and-add procedure and, subsequently, mathematical deblurring techniques may be used to improve the image quality and slice sensitivity profile.
The foregoing features of embodiments of the present invention may offer advantages over existing single focal spot x-ray source inspection systems. For example, the use of a multiple focal spot x-ray source may increase the speed of the inspection process. That is, multiple focal spot x-ray sources are capable of rapidly obtaining multiple images by activating each focal spot, one at a time, in rapid succession, thereby eliminating the need for gantry movement time. Each of the focal spots in such an x-ray source is electronically addressable in a specific manner, thus allowing each focal spot to be activated and deactivated quickly (e.g., within 1 microsecond, within 100 microseconds, within 1000 microseconds, etc.). Such features may reduce the length of time necessary to detect and characterize a defect in an industrial product.
Furthermore, the systems disclosed herein may offer additional advantages over single spot x-ray sources, such as the scalability of the generated power. For instance, in one embodiment, each focal spot of the multiple focal spot x-ray source may have an average power of approximately 600 Watts and, accordingly, a ten focal spot x-ray source may have a total power of approximately 6000 Watts. Such a total power may be approximately six times greater than many typical single spot x-ray sources. Indeed, such multiple focal spot x-ray sources may offer many distinct advantages over traditional single spot systems.
Turning now to the drawings,
During operation, the multiple focal spot source 14 generates the x-ray beam 26 from the first focal spot 16. The x-ray beam 26 is projected onto the object 12, which attenuates the beam 26 before it reaches the detector 20. As such, the detector 20 receives a fraction of the projected x-ray beam 26 after being attenuated by the object 12. In the illustrated embodiment, the detector 20 is a flat panel digital detector that digitizes the received converted x-ray energy and exports such digitized data to the image control and processing system 22. The image control and processing system 22 is adapted to convert the digitized data into a first projection image and to store the first projection image to the memory 24 for future retrieval and/or processing. In some embodiments, the image control and processing system 22 may process the first projection image before storing it to memory.
Subsequently, while remaining substantially stationary, the multiple focal spot x-ray source 14 generates additional x-ray beams, one at a time, from distinct focal spots disposed over a predefined arc. That is, without substantial rotational or translational movement, the multiple focal spot x-ray source projects x-ray beams at a variety of different angular positions. As before, each of the x-ray beams originate from a focal spot in the substantially stationary x-ray source 14, project through the object 12, and impinge the detector 20, where they are each converted to a separate projection image acquired at a different angle about the predefined arc. The generated set of planar images obtained over the arc may then be utilized by the image control and processing system 22 to reconstruct slices of the object 12 at different planes.
For example, in one embodiment, the digital projection images acquired at distinct angular positions are shifted and then summed a desired number of times to bring multiple depths of the object into focus, one at a time. In this embodiment, different shift distances may be utilized to reconstruct different planes in the volume of the object 12. For example, by adding the acquired projection images without applying a shift distance, the focal plane of the object 12 that is coincident with the focal plane of the scan may be reconstructed by the image processing system 22. For further example, by shifting each image by another set of first distances, which are determined based on the system geometry, and subsequently adding the shifted images, a second focal plane of the object 12 may be brought into focus. Using this approach, the image processing system 22 may reconstruct all the planes of interest in the acquisition volume. Subsequently, the processing system 22 may apply one or more mathematical deblurring techniques to each of the reconstructed planes to improve the image quality by removing image artifacts from out of focus planes. As described in more detail below with respect to
In some embodiments, after a set of projection images are acquired over the predefined arc, the object 12 may be translated, as indicated by arrow 26, and the described procedure may be repeated at the next location along the length of the object. In further embodiments, the multiple focal spot x-ray source 14 may be translated, as indicated by arrow 28, to another location along the length of the object, and the described procedure may be repeated. That is, a second set of images may be acquired over the given arc at the next lengthwise position of the object 12 and the additional image set may be used to reconstruct additional slices at distinct planes in the object. However, each time the multiple focal spot x-ray source 14 is positioned to image the object, the source 14 remains stationary (i.e., does not rotate or translate) while acquiring a complete set of projection images over the desired angular range.
During operation, the x-ray source 14 is adapted to selectively activate each of the focal spots to obtain a set of projection images of the pipe 30. For example,
In the illustrated embodiment, the three acquired projection images form a single set of images acquired over a single arc that may be utilized to reconstruct multiple planes of interest in the acquisition volume of the pipe 30. It should be noted, however, that in further embodiments, any desired number of focal spots may be provided in the stationary x-ray source 14 and activated to produce any desired number of images over the given arc range. For example, in the illustrated embodiment, each of the seven focal spots may be activated to produce seven projection images in a single acquisition set. Further, the images may be acquired over any desired angular range (e.g., 20 degrees, 30 degrees, 40 degrees, etc.). However, as described in detail above, a shift-and-add procedure may be performed on each acquisition set to reconstruct the desired planes within the pipe 30.
During operation, the x-ray source 14 selectively activates each of the focal spots to obtain a set of projection images of the pipe array 48. For example,
During operation, the plurality of cathodes 66 emit electrons into the vacuum chamber 72, and the electrons are collected by the plurality of anodes 68, thus establishing electron beams 104, 106, 108, 110, and 112 through the x-ray tube 14. As the electrons originate from the plurality of cathodes 66 and collide with the plurality of anodes 68, energy is generated and emitted as x-rays, for example, in a direction perpendicular to the electron beams 104, 106, 108, 110, and 112. The high voltage and oil feedthrough 70 accelerates the electrons as they flow through the x-ray tube. The controller 64 controls each of the anodes individually to control x-ray generation such that the previously described sets of projection images may be acquired.
In the illustrated method, the object is subsequently translated (block 126) and again irradiated at a plurality of angles to obtain another set of projection images at the second lengthwise location along the length of the object (block 128). However, it should be noted that during acquisition of the set of projection images, the multiple focal spot x-ray source remains substantially stationary with respect to rotational and translational movement. The acquired x-ray data along the length of the object is then processed (block 130), and a determination is made as to whether the object is accepted, rejected, or flagged (block 132). That is, the object is inspected for the presence or absence of a defect, such as stress corrosion on a pipe.
In one embodiment of the above method, if the object fits within the boundary of the source detector active regions, there may be no movement of the object necessary to obtain laminographic data and to reconstruct planes of the object. In such embodiments, the virtual motion of the source may substitute for the motion of the object. As such, certain embodiments may be substantially stationary in that no moving parts are necessary, thus possibly reducing the complexity and monetary expense associated with making and operating the disclosed imaging systems.
Technical effects of embodiments of the invention include an increased inspection speed as compared to traditional systems. That is, the multiple focal spot x-ray systems disclosed herein are capable of electronically addressing each of the focal spots in a specific manner, thus allowing each focal spot to be activated and deactivated quickly (e.g., within 1 microsecond). Such features may reduce the length of time necessary to detect and characterize a defect in an industrial product. Further, the systems disclosed herein may offer additional technical advantages over single spot x-ray sources, such as the scalability of the generated power. The total power capable of being generated by embodiments of present invention may be substantially greater than many typical single spot x-ray sources. Additionally, in embodiments in which an object size fits within the active regions of the source detector configuration, movement of the x-ray source, the object, or the detector may not be necessary, thus possibly reducing or eliminating motion blur.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.