Patent Application
20090274264
1. Technical Field
The disclosure generally relates to non-destructive inspection of components.
2. Description of the Related Art
Computed tomography (CT) involves the use of X-rays that are passed through a target. Based on the amount of X-ray energy detected at an array of detectors located downstream of the target, information about the target can be calculated. By way of example, representations of target shape and density in three dimensions can be determined.
Computed tomography systems and related methods involving localized bias are provided. In this regard, an exemplary embodiment of a computed tomography system for analyzing a target is operative to determine, with a biased density value differing from an average density value for the target, a location of an interface of the target.
An exemplary embodiment of a computed tomography method comprises: directing X-rays at a target; determining an amount of attenuation of the X-rays attributable to the target; calculating target data representative of dimensions of the target based, at least in part, on the amount of attenuation determined; and biasing the target data using a bias value, the bias value corresponding to local image density of a portion of a displayed image generated from the target data.
Another exemplary embodiment of a computed tomography method comprises: determining a location of an interface of a target subjected to computed tomography using a density value other than an average density value for the target.
Other systems, methods, features and/or advantages of this disclosure will be or may become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features and/or advantages be included within this description and be within the scope of the present disclosure.
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
Computed tomography systems and related methods involving localized bias are provided, several exemplary embodiments of which will be described in detail. In this regard, some embodiments use a bias value (e.g., a localized computed density value) for a portion of a target to refine measurements corresponding to that portion of the target. This is in contrast conventional CT systems that commonly form a point cloud describing surface locations of an inspected target using an average density of the entire target. That is, edges of the target are typically identified as locations that exhibit density values of one-half the difference between the average density of the target and the density of air. By using potentially different bias values for different portions of a target that modify the value for average density of the target locally, target edge locations can be more accurately determined. This potentially results in more accurate measurements.
In this regard,
Turntable 106 is a representative apparatus used for positioning a target, in this case, target 108. In the embodiment of
Detector array 110 is positioned downstream of the turntable. The detector array is operative to output signals corresponding to an amount of X-rays detected. In this embodiment, the array is a linear array, although various other configurations can be used in other embodiments. Notably, the X-rays emitted by source 102 can be collimated upstream and/or downstream of the target in some embodiments.
The detector array generally includes an array of scintillators that emit light responsive to receiving X-rays. The intensity of the light emitted corresponds to the intensity for the X-rays received. The light emitted by the scintillators is directed to another array (e.g., an array of photo-multipliers), which converts the light into electrical signals that include information corresponding to the amount of X-rays detected.
Image processor 112 receives the information corresponding to the amount of X-rays detected (i.e., target data) and uses the information to compute image data corresponding to the target. The image data is provided to display/analysis system 114 to enable user interaction with the information acquired by the detector array.
In
In contrast,
Beam hardening manifests as a reduction of image density that can vary in its effects across an image generated by a CT system. Notably, beam hardened portions of an image (such as area 150) can lead to inaccurate measurements of a target. By way of example, the presence of area 150 can make an accurate thickness measurement of target 108 along line 154 indeterminate. This is oftentimes the case because in a conventional CT system that uses an average density value of the entire target for determining target-air interfaces (e.g., edges), beam hardening of a portion of the target causes the CT system to incorrectly locate the local interface.
In this regard,
As an example, assume that the image density of area 142 of image 140 (
Responsive to determining that an area exhibits beam hardening, a bias can be applied to modify calculations associated with the identified area (block 188). For instance, a bias value can be used to modify the computation of the location of any interfaces (e.g., material-material or material-air interfaces) associated with the area. In some embodiments, the bias value corresponds to the local image density of an image generated by the CT system, thus, the product of the bias value and the average density value provides a local density value. In block 190, one or more measurements can be obtained using refined computations that incorporate the bias. By way of example, the measurements can include, but are not limited to, interior dimensions of the target. In some embodiments, the target can be a formed of metal. Additionally or alternatively, the target can be a gas turbine engine component, such as a turbine blade.
It should be noted that a computing device can be used to implement various functionality, such as that attributable to the image processor 112, display/analysis system 114 and/or the flowcharts of
The processor may be a hardware device for executing software, particularly software stored in memory. The processor can be a custom made or commercially available processor, a central processing unit (CPU), an auxiliary processor among several processors associated with the computing device, a semiconductor based microprocessor (in the form of a microchip or chip set) or generally any device for executing software instructions.
The memory can include any one or combination of volatile memory elements (e.g., random access memory (RAM, such as DRAM, SRAM, SDRAM, VRAM, etc.)) and/or nonvolatile memory elements (e.g., ROM, hard drive, tape, CD-ROM, etc.). Moreover, the memory may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory can also have a distributed architecture, where various components are situated remotely from one another, but can be accessed by the processor.
The software in the memory may include one or more separate programs, each of which includes an ordered listing of executable instructions for implementing logical functions. A system component embodied as software may also be construed as a source program, executable program (object code), script, or any other entity comprising a set of instructions to be performed. When constructed as a source program, the program is translated via a compiler, assembler, interpreter, or the like, which may or may not be included within the memory.
The Input/Output devices that may be coupled to system I/O Interface(s) may include input devices, for example but not limited to, a keyboard, mouse, scanner, microphone, camera, proximity device, etc. Further, the Input/Output devices may also include output devices, for example but not limited to, a printer, display, etc. Finally, the Input/Output devices may further include devices that communicate both as inputs and outputs, for instance but not limited to, a modulator/demodulator (modem; for accessing another device, system, or network), a radio frequency (RF) or other transceiver, a telephonic interface, a bridge, a router, etc.
When the computing device is in operation, the processor can be configured to execute software stored within the memory, to communicate data to and from the memory, and to generally control operations of the computing device pursuant to the software. Software in memory, in whole or in part, is read by the processor, perhaps buffered within the processor, and then executed.
It should be emphasized that the above-described embodiments are merely possible examples of implementations set forth for a clear understanding of the principles of this disclosure. Many variations and modifications may be made to the above-described embodiments without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the accompanying claims.
