Patent Description:
For industrial applications, a CT system can include an emitter, or source of radiation, a rotatable stage, and a detector. To scan an inspection part, the inspection part can be rigidly mounted to the stage, and the stage can be rotated about an axis. As the part is rotated, the emitter can emit radiation (e.g., X-rays), and a portion of the radiation can travel through the inspection part. As the radiation travels through the inspection part, the radiation can be attenuated to varying degrees, depending on its travel path through the inspection part as well as material(s) that it travels through. Therefore, intensities of the radiation that travel through thick portions of the inspection part can be more attenuated than intensities of the radiation that travel through thinner portions of the inspection part. The detector can detect the radiation, including the portion that traveled through the inspection part, and the detector can deliver data characterizing the detected radiation to a computer. The computer can use the data to generate a projected image, or projectional radiograph, of the inspection part. With a sufficient number of projectional radiographs corresponding to known angles of rotation, the computer can generate cross-sectional (tomographic) images of the inspection part, as well as a <NUM>-dimensional reconstruction of the inspection part, using tomographic reconstruction techniques.

While imaging, as the inspection part rotates, the stage can experience some off-axis mechanical wobble, which can transfer to the inspection part. In some cases, mechanical wobble can include tilting of the stage such that there is a deviation between an expected axis of rotation, or reference axis, and a true axis of rotation of the inspection part. Therefore, the true axis of rotation can differ from the expected axis of rotation. The mechanical wobble can introduce noise, or artifacts, into tomographic images if it is unaccounted for prior to, or during, tomographic reconstruction. In some cases, mechanical wobble can be mitigated by using high precision bearings within the stage. Additionally, prior to scanning the inspection part, the system can be calibrated using a calibration part that has a known geometry. The calibration part can be scanned, and the computer can determine an average axis of rotation of the calibration part. The inspection part can then be scanned. After the inspection part is scanned, data characterizing the average axis of rotation can be applied within tomographic reconstruction to reduce noise within the tomographic images of the inspection part. However, the inspection part may wobble in a different manner than the calibration part, which can reduce the effectiveness of the calibration. Additionally calibration does not provide real-time data that can be used to account for unexpected wobble (e.g., due to external forces) that can occur while scanning the inspection part.

Systems, devices, and methods are provided for determining a position and an orientation of an inspection part relative to a detector of a CT system. A system is provided that includes an emitter configured to emit radiation, and a stage assembly having a stage positioned at a first angle relative to a first reference axis. The stage is configured to couple to an inspection part and to rotate the inspection part about a first rotation axis. The stage assembly includes a first sensor coupled to the stage. The first sensor is configured to measure the first angle. The system includes a detector positioned at a second angle relative to a second reference axis. The detector is configured to detect at least a portion of the radiation emitted by the emitter. The system also includes a second sensor coupled to the detector. The second sensor is configured to measure the second angle.

The system includes an analyzer configured to receive measurement data characterizing the first angle and the second angle from the first sensor and the second sensor, respectively. The analyzer includes at least one data processor configured to generate one or more images of the inspection part based on the received measurement data. The at least one data processor of the analyzer is configured to compensate for a tilt angle of one or more of the stage and the detector using the received measurement data. Based on the
compensation, the at least one data processor of the analyzer generates the one or more images. In addition, based on the compensation, the at least one data processor of the analyzer can perform an image correction operation on the one or more images.

In certain embodiments, the first sensor can be configured to measure an orientation of the stage relative to the first reference axis. The first sensor can also be configured to measure movement of the stage in a first plane and movement of the stage in a second plane perpendicular to the first plane. Additionally, the first sensor can be disposed on a surface of the stage.

In certain embodiments, the second sensor can be configured to measure an orientation of the detector relative to the second reference axis. The second sensor can also be configured to measure movement of the detector in a first plane and movement of the detector in a second plane perpendicular to the first plane. Additionally, the second sensor can be disposed on a surface of the detector.

In certain embodiments, the analyzer can be configured to receive data from the first sensor. The first sensor can be configured to detect a change in position thereof with respect to an initial position of the first sensor, and the analyzer can include at least one data processor that is configured to calculate the first angle based on the detected change in position of the first sensor. The analyzer can also be configured to receive data from the second sensor. The second sensor can be configured to detect a change in position thereof with respect to an initial position of the second sensor, and the analyzer can include at least one data processor that is configured to calculate the second angle based on the detected change in position of the second sensor.

In certain embodiments, the first angle can correspond to a tilt angle of the stage relative to the first reference axis, and the second angle can correspond to a tilt angle of the detector relative to the second reference axis.

In certain embodiments, the first sensor can be disposed on the stage such that the first sensor is configured to rotate during rotation of the stage. Alternatively, the first sensor can fixedly mounted such that the first sensor is configured to remain stationary during rotation of the stage. In this regard, the stage assembly can further include: a base; a bracket fixed to the base, the bracket having an opening formed therethrough; and a rotatable drive shaft extending through the opening of the bracket, the drive shaft configured to effect the rotation of the stage. The first sensor can be mounted to a portion of the bracket.

In certain embodiments, the first and second sensors can be digital inclinometers.

In certain embodiments, the stage assembly can further include a rotation sensor configured to measure an angle of rotation of the stage.

A method of using the system is provided that includes operations of rotating a stage about a first rotation axis, the stage being positioned at a first angle relative to a first reference axis and coupled to an inspection part; emitting radiation toward the inspection part by an emitter; measuring the first angle using a first sensor coupled to the stage; detecting at least a portion of the radiation emitted by the emitter using a detector positioned at a second angle relative to a second reference axis; and measuring the second angle using a second sensor coupled to the detector.

The method further includes operations of receiving measurement data characterizing the first angle and the second angle from the first sensor and the second sensor, respectively; compensating for a tilt angle of one or more of the stage and the detector using the received measurement data; and generating one or more images of the inspection part according to the compensation.

Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems, devices, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings.

Tomography can refer to techniques that display cross-sectional representations through a body. Computed tomography (CT) is one example of tomography that can use radiation (e.g., X-rays) to produce <NUM>-dimensional representations of a scanned object, including internal and external features of the object. Because CT can be utilized for imaging the object without damage, it has been utilized in industrial applications as a non-destructive test technique for quality assurance (e.g., flaw detection, failure analysis, geometric tolerances, etc.). A CT system can include an emitter, or source of radiation, a rotatable stage, and a radiation detector. This can allow for flexible solutions for loading and unloading of an inspection part with a higher number of degrees of freedom for fast and flexible inspection while remaining cost-effective. To scan an inspection part, the inspection part can be rigidly mounted to the stage, and the stage can be rotated about an axis. The emitter can emit radiation (e.g., X-rays), and a portion of the radiation can travel through the inspection part. The detector can detect the radiation, including the portion that traveled through the inspection part, and can deliver data characterizing the detected radiation to a computer, which can use the data to generate a projected image, or projectional radiograph, of the inspection part. With a sufficient number of projectional radiographs corresponding to known angles of rotation, the computer can generate cross-sectional (tomographic) images of the inspection part, as well as a <NUM>-dimensional reconstruction of the inspection part, using tomographic reconstruction techniques.

As described above, mechanical wobble of the stage can cause the part to become misaligned from its expected axis of rotation during the computed tomography (CT) scanning process can introduce false information, referred to as noise or artifacts, into cross-sectional (tomographic) images and <NUM>-dimensional reconstructions of the inspection part, and/or cause the loss of true information if it is unaccounted for (e.g., prior to, or during, tomographic reconstruction). Systems, methods, and devices are thus provided for determining a position and/or an orientation of an inspection part and a detector of a CT system.

In some cases, data from inclinometers (e.g., tilt sensors) can be used to determine the position and/or the orientation of the inspection part relative to the detector of the CT system. For example, a first inclinometer can be coupled to the stage and a second inclinometer can be coupled to the detector. Data from the inclinometers can be used to determine misalignment (e.g., variations in the position of the inspection part and/or the detector as a result of wobble) between the stage and the detector. As an example, data from the inclinometers can be used to adjust values associated with projections of the inspection part in the projectional radiographs to correct for the mechanical wobble of the stage. The use of position and/or orientation data acquired by the inclinometers to correct for mechanical wobble of the stage and/or the detector can reduce artifacts within, and unsharpness of, tomographic images and <NUM>-dimensional reconstructions of the inspection parts. In some applications, the embodiments disclosed herein may be used for simple, inaccurate manipulator systems or robot systems, where the compensation method may have significant influence.

<FIG> shows an exemplary embodiment of a CT system <NUM> that can be configured to generate <NUM>-dimensional reconstructions of an inspection part <NUM>. As an example, the inspection part <NUM> can be any structure that interacts with (e.g., attenuates) the radiation passing therethrough while also providing sufficient transmittance of the radiation for detection. In one aspect, the inspection part <NUM> can be a casting, such as a pressure die casting.

In the illustrated example, the CT system <NUM> includes an emitter <NUM>, a stage assembly <NUM> including a stage <NUM>, a detector <NUM>, and an analyzer <NUM>. The emitter <NUM> can include an emitting element <NUM> that can be configured to emit a radiation beam <NUM>, which can be, e.g., an X-ray beam. The inspection part <NUM> can be rigidly mounted to the stage <NUM> using a mechanical constraint (e.g., a clamping, suction, and/or adhesive mechanism), and the stage <NUM> can be positioned between the emitter <NUM> and the detector <NUM> such that the inspection part <NUM> extends into the radiation beam <NUM>. In the absence of mechanical wobble, the stage <NUM> can be configured to rotate about an axis A1 ("first reference axis"). The axis A1 can be a reference axis that can characterize a desired, or expected, position and/or orientation of the stage <NUM> and the inspection part <NUM>. In some cases, wobble can include tilting of the stage <NUM> such that there is a deviation between an expected axis of rotation (e.g., A1), or reference axis, and a true axis of rotation of the inspection part <NUM>. The stage assembly <NUM> can include a rotation sensor (not shown) configured to measure angles of rotation of the stage <NUM>.

The detector <NUM> can include a detection element <NUM> that can detect the radiation emitted by the emitter <NUM>. The detector <NUM> can be positioned such that the detection element <NUM> faces toward the emitting element <NUM>. The detection element <NUM> can extend along an axis B1 ("second reference axis"). The axis B1 can be a reference axis that can characterize an expected alignment, position, and/or orientation, of the detector <NUM> and/or the detection element <NUM>. Axes A1, B1 can be used as reference axes which can, respectively, characterize expected positions and/or orientations of the stage <NUM> and the detector <NUM>.

The analyzer <NUM> includes at least one data processor, and can be coupled to the detector <NUM> and to the stage assembly <NUM>. In some embodiments, the analyzer <NUM> can be configured to control operation of the stage assembly <NUM> and/or detector <NUM>. The analyzer <NUM> can be configured to receive data from the detector <NUM> and from the rotation sensor of the stage assembly <NUM>, and to use the data to generate cross-sectional (tomographic) images of the inspection part <NUM>, as well as a <NUM>-dimensional reconstruction of the inspection part <NUM>, using tomographic reconstruction techniques. The data from the detector <NUM> can characterize projected images, or projectional radiographs, of the inspection part <NUM>. The data from the rotation sensor of the stage assembly <NUM> can characterize a rotation angle θ of the stage.

To scan the inspection part <NUM>, the stage <NUM> can be rotated about the axis A1. Because the inspection part <NUM> is substantially rigidly coupled to the stage <NUM>, aligning a longitudinal axis of the inspection part <NUM> with the axis A1 can also result in corresponding rotation of the inspection part <NUM> about axis A1. After the inspection part <NUM> is rotated to a desired position, the emitter <NUM> can emit the radiation beam <NUM> (e.g., X-rays). A portion of the radiation beam <NUM> can travel through the inspection part <NUM>. The detector <NUM> can detect the radiation beam <NUM>, e.g., via the detection element <NUM>, including the portion of the radiation beam <NUM> that traveled through the inspection part <NUM>. The detected radiation can characterize a projected image, or projectional radiograph, of the inspection part <NUM>. The detector <NUM> can provide data to the analyzer <NUM> characterizing the projectional radiograph. The rotation sensor coupled to the stage assembly <NUM> can measure the rotation angle θ during scanning, and the rotation sensor can provide data to the analyzer <NUM> characterizing the measured rotation angles θ. Therefore, absent mechanical wobble, each projectional radiograph can correspond to a known rotation angle θ about the expected rotation axis A1. The analyzer <NUM> can use the projectional radiographs, including the corresponding rotation angles θ, to generate cross-sectional (tomographic) images of the inspection part <NUM>, as wells as a <NUM>-dimensional reconstruction of the inspection part <NUM>, using tomographic reconstruction techniques.

<FIG> shows an example of a projectional radiograph <NUM> that can be generated using the CT system <NUM> in the absence of mechanical wobble. The projectional radiograph <NUM> includes a projection <NUM> of the inspection part <NUM> and can correspond to a known angle of rotation θ of the stage <NUM>. In the illustrated example, the stage <NUM> is aligned as expected with regard to the axis A1, and the projection <NUM> of the inspection part extends along a projected axis A1'. The projected axis A1' can be a projection of the expected rotation axis A1. Similarly, the detector <NUM> is aligned as expected with regard to axis B1, and a frame <NUM> of projectional radiograph <NUM> extends along axis B1'. The axis B1' can be a projection of axis B1.

In some cases, the stage <NUM> of the CT system <NUM> can wobble such that the inspection part <NUM> rotates about, and/or extends along, an unknown axis. <FIG> and <FIG> show examples of projectional radiographs <NUM>, <NUM> that can be generated by the CT system <NUM> if the stage <NUM> wobbles during scanning. If the stage <NUM> wobbles during scanning, the true axis of rotation can be different from the expected rotation axis A1. Referring to <FIG>, the projectional radiograph <NUM> includes a projection <NUM> of the inspection part <NUM>. The projectional radiograph <NUM>, including the projection <NUM>, corresponds to a known angle of rotation θ = θ3 of the stage <NUM>, shown in an inset <NUM>. However, the projection <NUM> of the inspection part <NUM> extends along an axis C3', which can be a projection of a true axis of rotation of the inspection part <NUM>. As shown in the illustrated example, the axis C3' does not coincide with the projected axis A1', and there can be some angle α3' between the axes A1', C3'. The true axis of rotation of the inspection part <NUM> can be unknown. Therefore, the orientation of the inspection part, which resulted in the projection <NUM> can be unknown.

Referring to <FIG>, the projectional radiograph <NUM> includes a projection <NUM> of the inspection part <NUM>. The projectional radiograph <NUM>, including the projection <NUM>, corresponds to a known angle of rotation θ = θ4, shown in an inset <NUM>, where θ4 can be different than θ3. The projection <NUM> of the inspection part <NUM> extends along an axis C4', which can be a projection of a true axis of rotation of the inspection part <NUM>. As shown in the illustrated example, the axis C4' does not coincide with the projected axis A1', and there can be some angle α4' between the axes A1', C4'. The true axis of rotation of the inspection part <NUM> can be unknown. Therefore, the orientation of the inspection part, which resulted in the projection <NUM> can be unknown. As shown in <FIG> and <FIG>, axes C3' and C4' can be different. Therefore, the orientations of the inspection part <NUM> during scanning that resulted in the projections <NUM>, <NUM>, can be different.

In the projectional radiographs <NUM>, <NUM> shown in <FIG> and <FIG>, the detector <NUM> is aligned as expected, and frames <NUM>, <NUM> of the projectional radiographs <NUM>, <NUM> extend along axis B1'. In some cases, the detector <NUM> can move during scanning of the inspection part <NUM>. Movement of the detector <NUM> during scanning can result in conditions similar to those described above with regard to <FIG> and <FIG>. <FIG> shows an example of a projectional radiograph <NUM> that can be generated by the CT system <NUM> if the detector <NUM> moves, or wobbles, during scanning. The projectional radiograph <NUM> includes a projection <NUM> of the inspection part <NUM>. The projectional radiograph <NUM>, including the projection <NUM>, corresponds to a known angle of rotation θ = θ5, shown in an inset <NUM>, where θ5 can be different than θ3 and θ4. In the illustrated example, the stage <NUM> is aligned as expected, and the projection <NUM> of the inspection part <NUM> extends along the projected axis A1'. A frame <NUM> of the projectional radiograph <NUM> extends along axis D5', which can be a projection of an alignment axis of the detection element <NUM>. As shown in the illustrated example, the axis D5' does not coincide with the projected axes A1', B1' which can indicate that the detector <NUM> was misaligned during scanning. There can be some angle β5' between the axes D5', B1'.

During tomographic reconstruction, projectional radiographs (e.g., projectional radiographs <NUM>, <NUM>, <NUM>) corresponding to known angles of rotation can be used to generate cross-sectional (tomographic) images of the inspection part, as well as a <NUM>-dimensional reconstruction of the inspection part (e.g., inspection part <NUM>). However, tomographic reconstruction can rely on the ability to identify and characterize relationships between projections (e.g., projections <NUM>, <NUM>, <NUM>) of the inspection part. In some cases, knowing the orientations of the inspection part that resulted in the projections can improve the process of identifying and characterizing relationships between projections of the inspection part. Unknown variations in the orientation of the inspection part across the radiographs can introduce noise, or artifacts, into tomographic images and/or <NUM>-dimensional reconstructions if the variations in the orientation are unaccounted for during tomographic reconstruction.

<FIG> shows an exemplary embodiment of a CT system <NUM> that can be configured to generate <NUM>-dimensional reconstructions of an inspection part <NUM>. In the illustrated example, the CT system <NUM> includes an emitter <NUM>, a stage assembly <NUM> including a stage <NUM>, a detector <NUM>, and an analyzer <NUM>. The CT system <NUM> can be similar to the CT system <NUM> shown in <FIG>, but can include sensors <NUM>, <NUM> (e.g., digital inclinometers) coupled to the detector <NUM> and the stage <NUM>, respectively. The sensors <NUM>, <NUM> can be configured to measure and/or facilitate determining tilt of the detector <NUM> and the stage <NUM>, respectively, as discussed in more detail below. The emitter <NUM> can include an emitting element <NUM> that can be configured to emit a radiation beam <NUM>, which can be, e.g., an X-ray beam. The inspection part <NUM> can be rigidly mounted to the stage <NUM>, and the stage <NUM> can be positioned between the emitter <NUM> and the detector <NUM> such that the inspection part <NUM> extends into the radiation beam <NUM>. The stage <NUM> can be configured to rotate about an axis A1 ("first reference axis") to position the inspection part at various angles θ. The stage assembly <NUM> can include a rotation sensor configured to measure the rotation angle θ of the stage <NUM>. The axis A1 can be an axis about which the inspection part <NUM> is expected to rotate.

The analyzer <NUM> can include at least one data processor, and can be coupled to, and/or configured to receive data from, the detector <NUM>, the stage <NUM>, and the sensors <NUM>, <NUM>. The analyzer <NUM> can be configured to receive data from the detector <NUM>, the rotation sensor of the stage assembly <NUM>, and the sensors <NUM>, <NUM>, and to use the data to generate cross-sectional (tomographic) images of the inspection part <NUM>, as well as a <NUM>-dimensional reconstruction of the inspection part <NUM>, using tomographic reconstruction techniques. In some embodiments, the analyzer <NUM> can be configured to control operation of the stage assembly <NUM> and/or detector <NUM>.

<FIG> show magnified views of the detector <NUM>. The detector <NUM> can include a detection element <NUM> that can detect the radiation emitted by the emitter <NUM>. In some cases, during scanning, the detector <NUM> can rotate, or tilt. For example, as shown in <FIG>, the detector <NUM> can rotate about an axis E6 such that the detector <NUM> is positioned at an angle δ relative to a plane defined by axes B1, E6. Alternatively and/or additionally, the detector <NUM> can rotate about an axis F6 such that the detector <NUM> is positioned at an angle γ relative to a plane defined by axes B1, F6, as shown in <FIG>. The sensor <NUM> can be configured to measure the angles δ, γ and determine an orientation of the detector <NUM> relative to the axis B1. The axes B1, E6, F6 can be reference axes that can identify a desired, or expected, position of the detector <NUM>. The positions and orientations of axes B1, E6, F6 can be known.

As shown in <FIG> and <FIG>, the plane defined by axes B1, E6 and the plane defined by axes B1, F6 can be perpendicular to each other. Thus, the sensor <NUM> can be configured to measure movement of the detector <NUM> in a first plane (e.g., the plane defined by axes B1, E6) and also to measure movement of the detector <NUM> in a second plane (e.g., the plane defined by axes B1, F6) that is perpendicular to the first plane.

In some embodiments, the sensor <NUM> can be disposed on a surface of the detector <NUM>, such as the top or upper surface thereof. In additional embodiments, the sensor <NUM> can be at least partially embedded into the surface of the detector <NUM>.

<FIG> show magnified views of the stage <NUM> and the inspection part <NUM>. In some cases, during scanning, the stage <NUM> can rotate, or tilt. For example, as shown in <FIG>, the stage <NUM> can rotate about an axis R6 such that the inspection part <NUM> is positioned at an angle φ relative to a plane defined by axes A1, R6. Alternatively, and/or additionally, the stage <NUM> can rotate about an axis T6 such that the inspection part <NUM> is positioned at an angle ε relative to a plane defined by axes A1, T6, as shown in <FIG>. The sensor <NUM> can be configured to measure the angles φ, ε and determine an orientation of the stage <NUM> relative to the axis A1. The axes A1, R6, T6 can be reference axes that can identify a desired, or expected, position and orientation of the stage <NUM> and the inspection part <NUM>. The positions and orientations of axes A1, R6, T6 can be known. The tilt angles φ, ε can define a position and/or orientation of an axis of rotation of the inspection part <NUM> that can be different than the reference axis A1.

As shown in <FIG> and <FIG>, the plane defined by axes A1, R6 and the plane defined by axes A1, T6 can be perpendicular to each other. Thus, the sensor <NUM> can be configured to measure movement of the stage <NUM> a first plane (e.g., the plane defined by axes A1, R6) and also to measure movement of the stage <NUM> in a second plane (e.g., the plane defined by axes A1, T6) that is perpendicular to the first plane.

In some embodiments, the sensor <NUM> can be disposed on a surface of the stage <NUM>, such as the top or upper surface thereof. In additional embodiments, the sensor <NUM> can be at least partially embedded into the surface of the stage <NUM>.

During operation, the position of the sensor <NUM> can change when the stage <NUM> is rotated. Therefore, measurements from the sensor <NUM> can be based on the position of the sensor <NUM> with respect to an initial position thereof. For example, the sensor <NUM> can measure tilt angles φ', ε', as shown in <FIG>. The tilt angles φ', ε' can correspond to rotation about axes R6', T6', respectively. The axes R6', T6' can intersect the axis A1. The tilt angle φ' can be a measure of tilt of the stage <NUM> relative to a plane defined by axes A1, R6'. The tilt angle ε' can be a measure of tilt of the stage <NUM> relative to a plane defined by axes A1, T6'. The positions of axes R6', T6' can vary with the position of the sensor <NUM> as the stage <NUM> is rotated. Therefore, tilt angles φ', ε' can correspond to a position of the sensor <NUM>, which can be characterized by the rotation angle θ of the stage <NUM>. The tilt angles φ', ε' and the rotation angle θ can be used (e.g., by the analyzer <NUM>) to determine the tilt angles φ, ε using, e.g., trigonometric relationships based on the position of the sensor <NUM> relative to the axis A1.

The sensor <NUM> can measure the tilt angles δ, γ of the detector <NUM> in a similar manner. Particularly, the position of the sensor <NUM> can change when the detector <NUM> is rotated. Therefore, measurements from the sensor <NUM> can be based on the position of the sensor <NUM> with respect to an initial position thereof. Tilt angles δ', γ' can correspond to a position of the sensor <NUM>, and the measured tilt angles δ', γ' can be used (e.g., by the analyzer <NUM>) to determine the tilt angles δ, γ using, e.g., trigonometric relationships based on the position of the sensor <NUM> relative to the axis B1.

<FIG> illustrates a flow chart of an exemplary method <NUM> of using data from sensors <NUM>, <NUM> to determine misalignment between the inspection part <NUM> and the detector <NUM>. In some cases, misalignment can be characterized by changes in the positions/orientations of the inspection part <NUM> and the detector <NUM> relative to known reference positions. At step <NUM>, the stage can be rotated to an angle θ = θx such that the inspection part is at a desired orientation. At step <NUM>, the sensor <NUM> can measure tilt angles δ, γ. At step <NUM>, the sensor <NUM> can measure tilt angles φ', ε'. The sensors <NUM>, <NUM> can provide data to the analyzer <NUM> characterizing the measured angles δ, γ, φ', ε'. The rotation sensor coupled to the stage can also provide data to the analyzer <NUM> characterizing a measured angle of rotation θx, as shown at step <NUM>.

At step <NUM>, the analyzer <NUM> can translate data from the sensor <NUM> to a value corresponding to an absolute coordinate system (e.g., using a vector calculation). For example, the analyzer <NUM> can use data characterizing the tilt angles φ', ε' and the rotation angle θx to determine tilt angles φ, ε. Therefore, the analyzer <NUM> can determine a position of the inspection part <NUM> relative to the reference axis A1. At step <NUM>, the analyzer <NUM> can calculate a deviation, or change, between the position of the detector <NUM> and the stage <NUM> and/or the inspection part <NUM>. For example, as described above the tilt angles δ, γ can define an orientation of the detector <NUM> relative to reference axes B1, E6, F6. Similarly, the tilt angles φ, ε can define an orientation of the inspection part <NUM> relative to the reference axes A1, R6, T6. Since the positions and orientations of the reference axes B1, E6, F6, A1, R6, T6 are known, the analyzer <NUM> can determine changes between the positions of the inspection part <NUM> the detector <NUM>. Therefore, the analyzer <NUM> can determine a total deviation of the position of the inspection part <NUM> relative to the detector <NUM>. Additionally, the positions and orientations of the detector <NUM> and the inspection part <NUM> can be determined with respect to an absolute, or global, coordinate system. At step <NUM>, data characterizing the positions of the detector <NUM> and the inspection part <NUM> can be stored (e.g., in memory of the analyzer).

At step <NUM>, an image (e.g., a projectional radiograph) can be acquired. For example the emitter <NUM> can emit a radiation beam <NUM>, and a portion of the radiation can travel through the inspection part <NUM>. The detector <NUM> can detect the radiation, e.g., via the detection element <NUM>, including the portion of the radiation that traveled through the inspection part <NUM>. The detected radiation can be, or can characterize, a projected image, or projectional radiograph, of the inspection part <NUM>. The detector <NUM> can provide data characterizing the projectional radiograph to the analyzer <NUM>. At step <NUM>, the analyzer <NUM> can perform image correction to the projectional radiograph using, e.g., filtering algorithms, to reduce noise, or artifacts, within the projectional radiograph. At step <NUM>, data characterizing the positions of the detector <NUM> and the inspection part <NUM> can be combined with data characterizing the filtered projectional radiograph. Steps <NUM>-<NUM> can be repeated until a desired number of projectional radiographs are obtained.

At step <NUM>, the analyzer <NUM> can reconstruct the projectional radiographs using the data characterizing the positions of the detector <NUM> and the inspection part <NUM> corresponding to each filtered projectional radiograph. For example, data from the sensors <NUM>, <NUM> characterizing tilt angles δ, γ, φ, ε can be used to adjust values associated with the projections of the inspection part <NUM> in the projectional radiographs to correct for the mechanical wobble of the stage <NUM> and/or the detector <NUM>. In some cases positions of the projections of the inspection part <NUM> can be adjusted based on the tilt angles δ, γ, φ, ε. As another example, values of intensity corresponding to various locations of the projections of the inspection part can be adjusted based on the tilt angles δ, γ, φ, ε. Data from the sensors <NUM>, <NUM> can be applied in any number of algorithms that can be used to adjust values associated with the projections of the inspection part <NUM>. The reconstructed projectional radiographs can be used to create a 3D reconstruction of the inspection part <NUM>. In some cases, data from the sensors <NUM>, <NUM> can be used to adjust values associated with projections of the inspection part <NUM> during tomographic reconstruction to generate tomographic images and <NUM>-dimensional reconstructions of the inspection part <NUM>.

By using sensor data characterizing the measured tilt angles δ, γ, φ, ε to adjust projectional radiographs, the analyzer <NUM> can perform various image correction operations to reduce artifacts within, and unsharpness of, tomographic images and <NUM>-dimensional reconstructions of the inspection part <NUM>. Reducing artifacts and unsharpness of tomographic images and <NUM>-dimensional reconstructions can result in improved quality of tomographic images and <NUM>-dimensional reconstructions.

In some embodiments, a sensor can be coupled to a stage assembly such that the sensor does not rotate with a stage of the stage assembly during scanning. The sensor can measure tilt angles of the stage directly. <FIG> shows a stage assembly <NUM> that includes a sensor <NUM> (e.g., a digital inclinometer) configured to measure tilt angles of a stage <NUM> of the stage assembly <NUM>. The stage assembly <NUM> can be used within CT systems such as, e.g., the CT system <NUM> shown in <FIG>. In the illustrated example, the stage assembly <NUM> includes the stage <NUM> coupled a base <NUM> via a drive shaft <NUM>. The stage <NUM> can be configured to receive an inspection part (e.g., inspection part <NUM>) coupled thereto. A drive element (e.g., motor) can be configured to rotate the drive shaft <NUM>, thereby rotating the stage <NUM> and the inspection part about an axis A8. The stage assembly <NUM> can include a rotation sensor configured to measure rotation angles θ of the stage <NUM>.

The sensor <NUM> can be coupled to a bracket <NUM>. The bracket <NUM> can be coupled to the drive shaft <NUM> and the base <NUM> of the stage assembly <NUM>. In the illustrated example, the drive shaft <NUM> can extend through an opening <NUM> in the bracket <NUM>. The opening <NUM> of the bracket can include a bearing that couples to the drive shaft <NUM> such that the drive shaft <NUM> can rotate relative to the bracket <NUM>. In some embodiments, the drive shaft <NUM> and the bearing can have a high concentric run-out to facilitate rotation of the drive shaft <NUM> relative to the bracket <NUM>. The sensor <NUM> can be mounted to the bracket <NUM> at a location adjacent to the opening <NUM>.

The bracket <NUM> can be coupled to the base <NUM> of the stage assembly via a biasing element <NUM>, or flexible member. The biasing element <NUM> can extend from the base <NUM> to couple to the bracket <NUM> such that the sensor <NUM> is positioned above the biasing element <NUM>.

As shown in the illustrated <FIG>, the stage <NUM> can rotate, or tilt, in two directions. For example, as shown in <FIG>, the stage <NUM> and the drive shaft <NUM> can rotate about an axis R8 such that the stage <NUM> is positioned at an angle φ relative to a plane defined by axes A8, R8. Alternatively and/or additionally, the stage <NUM> and the drive shaft <NUM> can rotate about an axis T8 such that the stage <NUM> is positioned at an angle ε relative to a plane defined by axes A8, T8, as shown in <FIG>. The axes A8, R8, T8 can be reference axes that can identify a desired, or expected orientation of the stage <NUM> and the inspection part <NUM>. The positions and orientations of axes A8, R8, T8 can be known. The tilt angles φ, ε can define a position and/or orientation of an axis of rotation of the inspection part that can be coupled to the stage <NUM>.

When the stage <NUM> and the drive shaft <NUM> tilt, the bracket <NUM> can be tilted in the same manner since the drive shaft <NUM> extends through the opening <NUM> of the bracket <NUM>. The biasing element <NUM> can allow the bracket <NUM> and the sensor <NUM> to tilt with the drive shaft <NUM> and the stage <NUM>. Therefore, the sensor <NUM> can measure tilt angles φ, ε of the stage <NUM>. The biasing element <NUM> can also provide some resistance to mitigate tilt of the drive shaft <NUM> and the stage <NUM>.

The tilt angles φ, ε can be used to adjust values associated with the inspection part in the projectional radiographs to correct for the mechanical wobble of the stage, as described herein. By using data characterizing the measured tilt angles φ, ε to adjust projectional radiographs, artifacts within, and unsharpness of, tomographic images and <NUM>-dimensional reconstructions of the inspection part can be reduced. Reducing artifacts and unsharpness of tomographic images and <NUM>-dimensional reconstructions can result in improved quality of tomographic images and <NUM>-dimensional reconstructions.

In some embodiments, the sensors (e.g., sensors <NUM>, <NUM>, <NUM>) facilitate determining positions and/or orientations of an inspection part and a detector of a CT system, without needing to be in optical or physical communication with each other. In some cases, the sensor can use forces generated by gravity to determine tilt angles of the inspection part and/or the detector. The use of gravity can contribute to robust functionality of the sensors.

Traditionally, the quality of tomographic images and/or <NUM>-dimensional reconstructions of inspection parts can be dependent upon the type, and quality, of the stage and/or stage assembly that the inspection part is mounted to. The use of position and/or orientation data acquired by sensors to correct for mechanical wobble can increase precision, or consistency, of tomographic images and/or <NUM>-dimensional reconstructions of inspection parts generated when using different stages and/or stage assemblies. Therefore, the quality of tomographic images and/or <NUM>-dimensional reconstructions can be less dependent upon the stages and/or stage assemblies used during scanning.

Exemplary technical effects of the subject matter described herein include the ability to determine positions and orientations of a detector and an inspection part of a CT system. The positions/orientations of the inspection part and the detector can each be determined relative to the other, and can be defined in an absolute coordinate system. In some embodiments, sensors coupled to a stage assembly and the detector can be used to determine the tilt angles of a stage and the detector, respectively. The positions/orientations of the detector and the inspection part can be defined, at least in part, by tilt angles (e.g., δ, γ, φ, ε) relative to reference axes (e.g., B1, E6, F6, A1, R6, T6) and/or planes defined by various combinations of the reference axes. Data from the sensors characterizing tilt angles can be used to adjust values associate with projections of the inspection part in the projectional radiographs to correct for the mechanical wobble of the stage and/or the detector. By using sensor data characterizing the measured tilt angles to adjust projectional radiographs, artifacts within, and unsharpness of, tomographic images and <NUM>-dimensional reconstructions of the inspection part can be reduced. Reducing artifacts and unsharpness of tomographic images and <NUM>-dimensional reconstructions can result in improved quality of tomographic images and <NUM>-dimensional reconstructions.

One skilled in the art will appreciate further features and advantages of the subject matter described herein based on the above-described embodiments. Accordingly, the present application is not to be limited specifically by what has been particularly shown and described.

Other embodiments are within the scope of the disclosed subject matter. Those skilled in the art will understand that the systems, devices, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

In some embodiments, sensors (e.g., sensors <NUM>, <NUM>, <NUM>) can be configured to measure tilt/rotation in three dimensions. As another example, the sensors (e.g., sensors <NUM>, <NUM>, <NUM>) can be accelerometers.

The subject matter described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed in this specification and structural equivalents thereof, or in combinations of them.

Claim 1:
A computed tomography system (<NUM>) comprising:
an emitter (<NUM>) configured to emit radiation;
a stage assembly (<NUM>) including:
a stage (<NUM>) positioned at a first angle relative to a first reference axis, the stage (<NUM>) configured to couple to an inspection part and to rotate the inspection part about a first rotation axis,
characterized by a first sensor (<NUM>) coupled to the stage (<NUM>), the first sensor (<NUM>) configured to measure the first angle; and
a detector (<NUM>) positioned at a second angle relative to a second reference axis, the detector (<NUM>) configured to detect at least a portion of the radiation emitted by the emitter (<NUM>), the detector (<NUM>) including:
a second sensor (<NUM>) configured to measure the second angle; and
an analyzer (<NUM>) configured to receive measurement data characterizing the first angle and the second angle from the first sensor (<NUM>) and the second sensor (<NUM>), respectively, the analyzer (<NUM>) including at least one data processor configured to generate one or more images of the inspection part based on the received measurement data, wherein the at least one data processor of the analyzer (<NUM>) is configured to compensate for a tilt angle of one or more of the stage (<NUM>) and the detector (<NUM>) using the received measurement data, and to generate the one or more images according to the compensation.