Patent Description:
Some inspection techniques, such as non-destructive testing, foreign object detection, non-line-of-site examination, etc., are employed when destruction of a part to be inspected is not desirable. Certain x-ray inspection techniques provide a penetrating scan or examination of a part. Such x-ray inspection techniques are used in a variety of applications, such as homeland security, oil and gas mining and refining, pipeline inspection, transportation, automotive, aerospace, marine, mining, shipping, and storage, among others.

Some inspection techniques utilize the detection of x-rays that pass through a part from one side of the part to the opposite side of the part. However, in other inspection techniques, such as x-ray backscattering techniques, the x-rays reflected back from the part (e.g., backscattered x-rays) are detected and then used to produce images or an analysis of the part. The pattern and intensity of the backscattered x-rays depends upon the materials and organization of the part. Accordingly, the pattern and intensity of the backscattered x-rays can be used to generate an image, which is relied upon to determine a quality, characteristic, or flaw of the part.

Traditionally, the quality of the image generated by x-ray backscattering techniques corresponds with the power density of the x-rays at the location where the x-rays impact the part to be inspected. For example, higher power densities generally lead to higher image quality. However, according to conventional techniques, an increase in the power density of x-rays at the point of impact with a part usually corresponds with an increase in potentially undesirable effects, such as an increase in heat generation, energy consumption, weight, and component and operating costs, among others.

<CIT> describes an imaging system that can form an image of an item under inspection using scattered radiation. A pencil beam of radiation is steered over the item under inspection and scattered radiation is detected. Regions of the item under inspection form which radiation is scattered are resolved in three dimensions using two-dimensional coordinates to which the pencil beam is steered. The third dimension is resolved using time of flight from the source. Because the inspection system is located on one side of an item under inspection, an item is imaged from a long distance and the imaging system is mounted on a moving vehicle, making the imaging system well suited for use in many security inspection systems to detect explosives and other contraband items. The radiation emanating from a point may be focused by a Fresnel zone plate into a beam of collimated rays.

<CIT>describes a system provided for inspecting a first internal characteristic of a sealed article such as a lithium-ion battery. The system includes an X-ray source, one or more X-ray detectors, one or more actuators that control the location on the article at which the X-rays are emitted, a stationary shield, a movable shield and a processing apparatus that receives X-ray detection data from the one or more X-ray detectors. The processing apparatus uses the X-ray detection data to form an X-ray backscattering image that shows the first internal characteristic. The first internal characteristic is an electrolyte level within the lithium-ion battery or a material consistency within the lithium-ion battery.

An x-ray backscatter apparatus for non-destructive inspection of a part is defined by the independent claim <NUM>. A method of non-destructive inspection of a part by x-ray backscatter is defined by the independent claim <NUM>. Preferred embodiments are defined in the appended dependent claims.

In order that the advantages of the subject matter may be more readily understood, a more particular description of the subject matter briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the subject matter and are not therefore to be considered to be limiting of its scope, the subject matter will be described and explained with additional specificity and detail through the use of the drawings, in which:.

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. Similarly, the use of the term "implementation" means an implementation having a particular feature, structure, or characteristic described in connection with one or more embodiments of the present disclosure, however, absent an express correlation to indicate otherwise, an implementation may be associated with one or more embodiments.

Referring to <FIG>, an x-ray backscatter apparatus <NUM> is shown. The x-ray backscatter apparatus <NUM> includes an x-ray emitter <NUM> to produce an incident x-ray emission <NUM>, an inspection filter <NUM>, with a plurality of filter apertures <NUM> to produce a filtered x-ray emission <NUM>, and a base <NUM>.

The x-ray emitter <NUM> is coupled to the base <NUM>. The x-ray emitter <NUM> generates the incident x-ray emission <NUM> and projects the incident x-ray emission <NUM> onto the inspection filter <NUM> proximate a filter aperture <NUM>. Only a portion (i.e., the filtered x-ray emission <NUM>) of the incident x-ray emission <NUM> passes through the filter aperture <NUM>. The filtered x-ray emission <NUM> is then used to inspect a part or other target. As shown in the depicted embodiment, the filtered x-ray emission <NUM> is a relatively small percentage of the incident x-ray emission <NUM> generated by the x-ray emitter <NUM>. As such, the power density of the filtered x-ray emission <NUM>, which is the power density of the x-rays impacting the part and available for inspection of the part, is less than the power density of the incident x-ray emission <NUM>. Accordingly, in some cases, the majority of the incident x-ray emission <NUM> generated by the x-ray emitter <NUM> is lost at the inspection filter <NUM>. To compensate for the loss of power density, in some cases, the x-ray emitter <NUM> generates an incident x-ray emission <NUM> with a power density that is much greater than is required at the part, which contributes to reduced efficiency.

<FIG> illustrates an x-ray emitter <NUM> of the x-ray backscatter apparatus <NUM> of <FIG>. The x-ray emitter <NUM> includes an x-ray shield <NUM>. Moreover, the x-ray shield <NUM> includes an emission aperture <NUM>. The x-ray shield <NUM>, with the exception of the emission aperture <NUM>, encloses a vacuum tube <NUM>. The vacuum tube <NUM> encloses a cathode <NUM> and an anode <NUM>. The cathode <NUM> and anode <NUM> are connected to a voltage supply via leads <NUM>. The cathode <NUM> is further connected to a filament supply line <NUM> and is selectively operable to generate an electron emission that is received at the anode <NUM>. The anode <NUM> receives the electron emission, from the cathode <NUM>, and generates a hard x-ray stream. The hard x-ray stream is directed towards the emission aperture <NUM> of the x-ray shield <NUM>. A portion of the hard x-ray stream from the anode <NUM> passes through the emission aperture <NUM> while a separate portion of the hard x-ray stream is blocked by the x-ray shield <NUM>. The portion of the hard x-ray stream that passes through the emission aperture <NUM> is the incident x-ray emission <NUM>.

In the illustrated representation, the anode <NUM> of the x-ray emitter <NUM> is a rotating anode. However, in other representations, the anode <NUM> of the x-ray emitter <NUM> does not rotate. The anode <NUM> can be a tungsten anode coupled to a rotor <NUM>. The rotor <NUM> is supported by a rotor support <NUM> and can be coupled to the rotor support <NUM> with bearings or other structures that facilitate relative rotation between the rotor <NUM> and the rotor support <NUM>. The rotor <NUM> is driven by a motor <NUM>. A magnetic field created by applying an electrical signal to the motor <NUM> applies a force to the rotor <NUM> to turn the rotor <NUM> and the anode <NUM>.

In the illustrated embodiment, the incident x-ray emission <NUM> then reaches the inspection filter <NUM> as described in associated <FIG>. Due to the relatively unfocused nature of the incident x-ray emission <NUM> and the relatively small size of the filter aperture <NUM>, only a portion of the incident x-ray emission <NUM> that reaches the inspection filter <NUM> passes through the filter aperture <NUM>. In other words, the portion of the incident x-ray emission <NUM> that passes through the filter aperture <NUM> (i.e., the filtered x-ray emission <NUM>) is small relative to the incident x-ray emission <NUM> and even smaller compared to the x-rays generated by the anode <NUM> before exiting the emission aperture <NUM>.

<FIG> is a schematic cross-sectional view of an x-ray backscatter apparatus <NUM>. The x-ray backscatter apparatus <NUM> includes features analogous to features of the x-ray backscatter apparatus <NUM> of <FIG>, with like numbers referring to like features. However, the x-ray backscatter apparatus <NUM> of <FIG> provides advantages over the x-ray backscatter apparatus <NUM> of <FIG>. For example, the x-ray backscatter apparatus <NUM> includes a zone plate <NUM> interposed between the x-ray emitter <NUM> and the filter aperture <NUM> of the inspection filter <NUM>. The zone plate <NUM> receives the incident x-ray emission <NUM> from the x-ray emitter <NUM> and focuses the incident x-ray emission <NUM> into a focused x-ray emission <NUM>. The focused x-ray emission <NUM> is directed, by the zone plate <NUM>, toward the filter aperture <NUM> of the inspection filter <NUM>. A portion of the focused x-ray emission <NUM> passes through the filter aperture <NUM> to define the filtered x-ray emission <NUM>. By first focusing the incident x-ray emission <NUM> into a focused x-ray emission <NUM>, before passing through the filter aperture <NUM> of the inspection filter <NUM>, a higher amount or concentration of x-rays, and thus a higher power density of x-rays, passes through the filter aperture <NUM> and impacts the part to be inspected. Accordingly, the portion of the incident x-ray emission <NUM> converted into the filtered x-ray emission <NUM> is greater with the x-ray backscatter apparatus <NUM>, because of the zone plate <NUM>, than with the x-ray backscatter apparatus <NUM>.

Therefore, to achieve the same power density of the filtered x-ray emission <NUM>, the x-ray backscatter apparatus <NUM> can generate an incident x-ray emission <NUM> with a lower energy density compared with the x-ray backscatter apparatus <NUM>, which promotes certain advantages. For example, the x-ray backscatter apparatus <NUM> promotes one or more of a wider area of x-ray imaging, a larger field of view, a larger inspection angle, an improved image resolution, an improved image sharpness, a reduced number of required transverse scans, a dynamic and instantaneous field of view, a reduced image distortion, a reduced pin-cushion effect at imaging corners, a reduced power supply requirement, a reduced cooling requirement, a reduced system weight, a reduced system size, an improved portability, an improved viability for a broader range of testing situations, and an improved component life compared with the x-ray backscatter apparatus <NUM>.

The focused x-ray emission <NUM> includes any x-ray stream in which a portion of the x-rays of the focused x-ray emission <NUM> are modified to a convergent mode from a divergent mode by the zone plate <NUM>.

In some examples, the zone plate <NUM> may provide between approximately <NUM>% and approximately <NUM>% focus of the received x-rays. More specifically, the zone plate <NUM> may provide approximately <NUM>% focus. Other embodiments of the zone plate <NUM> may focus more or less than the examples given above. In some embodiments, the zone plate <NUM> may focus the incident x-ray emission <NUM> sufficient to pass between approximately <NUM>% and approximately <NUM>% of the incident x-ray emission <NUM> through the filter aperture <NUM> as the focused x-ray emission <NUM>.

In some implementations, the zone plate <NUM> may be made wholly or partially of lead. In some embodiments, the density of the lead allows for a greater effect of the zone plate <NUM> on the incident x-ray emission <NUM>. In some embodiments, the zone plate <NUM> may include carbon nanotubes. Carbon nanotubes offer benefits in weight reduction, thermal conduction and cooling, and strength. The zone plate <NUM> may also include a surface treatment. The surface treatment may include plating, doping, hardening, coating, or some other chemical, mechanical, or thermal treatment.

The zone plate <NUM> may be positioned to receive some or all of the incident x-ray emission <NUM> from the x-ray emitter <NUM>. In the illustrated embodiment, the zone plate <NUM> is shown in a horizontal orientation. However, the zone plate <NUM> may be oriented at a zero or non-zero orientation from horizontal. In some embodiments, the zone plate <NUM> may be oriented at a zero or non-zero angle relative to the x-ray emitter <NUM>, relative to the filter aperture <NUM>, relative to the base <NUM>, or relative to some other physical or construct point of reference on or outside of the x-ray backscatter apparatus <NUM>. In some embodiments, the position and orientation of the zone plate <NUM> is adjustable. The adjustability of the zone plate <NUM> is facilitated by a frame or other mounting structure (not shown) to which the zone plate <NUM> is coupled. In other embodiments, the zone plate <NUM> is coupled to a cooling system to cool the zone plate <NUM> through conduction, convection, or radiation.

The illustrated embodiment depicts the zone plate <NUM> as located outside of the x-ray emitter <NUM>. In an alternative embodiment, multiple zone plates <NUM> are coupled to the inspection filter <NUM> to correspond with each filter aperture <NUM> individually or so that each zone plate <NUM> corresponds to multiple filter apertures <NUM> on the inspection filter <NUM>.

Referring to <FIG>, the zone plate <NUM> of <FIG> is shown relative to the x-ray emitter <NUM> of <FIG>. In the illustrated embodiment, the zone plate <NUM> is located relative to the emission aperture <NUM> of the x-ray emitter <NUM>. In this arrangement, the zone plate <NUM> receives at least a portion of the incident x-ray emission <NUM> passing through the emission aperture <NUM>. In some embodiments, the zone plate <NUM> is coaxial with the emission aperture <NUM> or is oriented at some other angle. In an alternative embodiment, the zone plate <NUM> is coaxial with the filter aperture <NUM>. In the illustrated embodiment, the zone plate <NUM> is shown between the x-ray emitter <NUM> and the inspection filter <NUM>. In some embodiments, the zone plate <NUM> is positioned closer to the x-ray emitter <NUM> or closer to the inspection filter <NUM>. In other embodiments, the zone plate <NUM> is positioned equidistant from the x-ray emitter <NUM> and the inspection filter <NUM>. In some implementations, the position of the zone plate <NUM> is adjustable relative to at least one of the x-ray emitter <NUM> and the inspection filter <NUM>. In some embodiments, the zone plate <NUM> rotates to direct the focused x-ray emission104 to the filter aperture <NUM> as the inspection filter <NUM> is translated or rotated relative to the x-ray emitter <NUM>.

<FIG> is a schematic side view of the x-ray backscatter apparatus <NUM> of <FIG>. The illustrated embodiment includes detectors <NUM> coupled to the base <NUM>. The detectors <NUM> are positioned to receive backscattered x-rays from a part during inspection. Two detectors <NUM> are shown. In some alternative embodiments, the x-ray backscatter apparatus <NUM> includes fewer or more than two detectors <NUM>. For example, the x-ray backscatter apparatus <NUM> may include a single detector <NUM> positioned in front of an outer edge of the inspection filter <NUM> so as to be near an impact point of the x-rays at a part. Alternatively, the x-ray backscatter apparatus <NUM> includes three or more detectors <NUM> to collect additional backscattered x-rays to make a more complete and clear image of the part. In an exemplary embodiment, the detectors <NUM> are shielded from x-rays that are reflected or refracted from the x-ray emitter <NUM>, the zone plate <NUM>, the inspection filter <NUM>, and/or the filter apertures <NUM>. In one embodiment, the detectors <NUM> are fixed while in other embodiments, the detectors <NUM> are adjustable relative to the base <NUM> in order to improve the detection of backscattered x-rays, to reduce image noise from non-backscattered x-rays, or accommodate an inspection constraint. In an additional embodiment, once an optimal position of the detectors <NUM> is determined, the detectors <NUM> may be fixed relative to the base <NUM>.

In the depicted implementation, the zone plate <NUM> is located between the x-ray emitter <NUM> and an inner surface of the inspection filter <NUM>. The zone plate <NUM> remains in place as the inspection filter <NUM> rotates around the x-ray emitter <NUM>. The inspection filter <NUM> position is controlled by a motor <NUM> coupled to the inspection filter <NUM>. As described above, some embodiments include multiple zone plates <NUM> coupled to the inspection filter <NUM> at different points along the inside of the inspection filter <NUM>. The placement of each of the multiple zone plates <NUM> corresponds to the location of one or more of the filter apertures <NUM>.

In the depicted embodiment, the filter apertures <NUM> are placed at consistent intervals along a perimeter of the inspection filter <NUM> with each filter aperture <NUM> at a different distance from the edge of the inspection filter <NUM>. In some embodiments, the filter apertures <NUM> are uniform while in other embodiments, the filter apertures <NUM> vary by location, spatial frequency, size, shape, geometry, material (or lack thereof), or other characteristics. In some implementations, the zone plate <NUM> is positioned based on the characteristics of the filter aperture <NUM> positioned to receive the focused x-ray emission from the zone plate <NUM>. In other implementations, the zone plate <NUM> is fixed but configured to produce a focused x-ray emission sufficient for each of the filter apertures <NUM>.

<FIG> illustrates a schematic view of an x-ray backscatter system <NUM>. In the depicted implementation, the x-ray backscatter system <NUM> is positioned to inspect a part <NUM>. In particular, the x-ray emitter <NUM> generates an incident x-ray emission <NUM> which is received by the zone plate <NUM>. The zone plate <NUM> modifies a beam pattern of the incident x-ray emission <NUM> to generate the focused x-ray emission <NUM>. The focused x-ray emission <NUM> impinges on the inspection filter <NUM> at approximately the filter aperture <NUM>. The filter aperture <NUM> filters the focused x-ray emission <NUM> to pass a portion of the focused x-ray emission <NUM>. In some embodiments, the filtered x-ray emission <NUM> has a particular pattern or characteristic applied by the filter aperture <NUM> at the part <NUM> to facilitate inspection. The filtered x-ray emission <NUM> that passes through the filter aperture <NUM> reaches the part <NUM> and some x-rays are backscattered towards the detector <NUM>. Some of the backscattered x-rays <NUM> are detected by the detector <NUM>. A signal, which corresponds with the detected backscattered x-rays <NUM>, is sent from the detector <NUM> to a control system <NUM>. In some implementations, the inspection filter <NUM> may be rotated so that a different portion of the part <NUM> receives and backscatters the x-rays. Additional signals are generated at the detector <NUM> and sent to the control system <NUM>.

In some embodiments, the control system <NUM> interprets the signals to generate an image or other inspection results. In some embodiments, the control system <NUM> also provides signals to control the generation of x-rays by the x-ray emitter <NUM>, movement of the inspection filter <NUM>, movement of the base <NUM> relative to the part <NUM>, movement of the zone plate <NUM>, control of a cooling system or power source, or monitoring of a system or individual component state via sensors or other devices. The control system <NUM> includes a connection <NUM> to the x-ray backscatter system <NUM>. The connection <NUM> may be a wired or wireless connection. In the depicted implementation, the control system <NUM> is separate from the x-ray backscatter system <NUM>. Alternatively, the control system <NUM> is coupled to the base <NUM> or otherwise integrated into the x-ray backscatter system <NUM>.

<FIG> shows a perspective view and a cross-sectional side view of a zone plate <NUM>. In the illustrated embodiment, the zone plate <NUM> has a focal length f. Given a particular focal length f for a system (distance from the zone plate <NUM> to the filter aperture <NUM> or part <NUM> of <FIG>), a radius characteristic of the zone plate <NUM> may be determined. In some embodiments, the zone plate <NUM> includes a surface treatment <NUM>. The surface treatment <NUM> may include plating, doping, hardening, coating, or some other chemical, mechanical, or thermal treatment. In one example, the surface treatment <NUM> includes a gold plating.

Similarly, in the case of a Fresnel zone plate <NUM>, the radii, and corresponding spacing, of the plurality of Fresnel zones <NUM> in the Fresnel zone plate <NUM> may be determined. In some implementations, the focal length f corresponds with the focal point F of each of the plurality of Fresnel zones <NUM>. In other implementations, the Fresnel zones <NUM> may be configured to have different focal lengths f or focal points F to facilitate inspection at a range of depths within a part.

<FIG> is a scanning electron microscope micrograph <NUM> of a zone plate <NUM>. The micrograph <NUM> illustrates the plurality of Fresnel zones <NUM>. The micrograph <NUM> depicts a <NUM> section of the outmost portion of a zone plate <NUM>. In this example, the diameter of the zone plate <NUM> is <NUM> with <NUM> Fresnel zones <NUM> and gold plating over lead. In other examples, the zone plate <NUM> may include fewer or more Fresnel zones, a greater or lesser diameter, and other or no plating materials or surface treatments.

Referring to <FIG>, a method <NUM> of non-destructive inspection of a part by x-ray backscatter is shown. The method <NUM> includes receiving a hard x-ray emission from an x-ray emitter at a zone plate, at <NUM>. Additionally, the method <NUM> includes focusing the hard x-ray emission into a focused hard x-ray emission with the zone plate, at <NUM>. The method <NUM> further includes, directing at least a portion of the focused hard x-ray emission with the zone plate through a first filter aperture of an inspection filter and onto a first portion of the part, at <NUM>.

In the above description, certain terms may be used such as "up," "down," "upper," "lower," "horizontal," "vertical," "left," "right," "over," "under" and the like. These terms are used, where applicable, to provide some clarity of description when dealing with relative relationships. But, these terms are not intended to imply absolute relationships, positions, and/or orientations. For example, with respect to an object, an "upper" surface can become a "lower" surface simply by turning the object over. Nevertheless, it is still the same object. Further, the terms "including," "comprising," "having," and variations thereof mean "including but not limited to" unless expressly specified otherwise. An enumerated listing of items does not imply that any or all of the items are mutually exclusive and/or mutually inclusive, unless expressly specified otherwise. Further, the term "plurality" can be defined as "at least two.

Additionally, instances in this specification where one element is "coupled" to another element can include direct and indirect coupling. Direct coupling can be defined as one element coupled to and in some contact with another element. Indirect coupling can be defined as coupling between two elements not in direct contact with each other, but having one or more additional elements between the coupled elements. Further, as used herein, securing one element to another element can include direct securing and indirect securing. Additionally, as used herein, "adjacent" does not necessarily denote contact. For example, one element can be adjacent another element without being in contact with that element.

As used herein, the phrase "at least one of," when used with a list of items, means different combinations of one or more of the listed items may be used and only one of the items in the list may be needed. The item may be a particular object, thing, or category. In other words, "at least one of" means any combination of items or number of items may be used from the list, but not all of the items in the list may be required. For example, "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" may mean, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

As used herein, "configured to" denotes existing characteristics of a system, apparatus, structure, article, element, component, or hardware which enables the system, apparatus, structure, article, element, component, or hardware to perform the specified function without further modification.

Claim 1:
An x-ray backscatter apparatus (<NUM>/<NUM>/<NUM>) for non-destructive inspection of a part (<NUM>), the apparatus (<NUM>) comprising:
a base (<NUM>);
an x-ray emitter (<NUM>) coupled to the base (<NUM>), comprising:
an x-ray shield (<NUM>), comprising an emission aperture (<NUM>);
a vacuum tube (<NUM>) within the x-ray shield (<NUM>);
a cathode (<NUM>) enclosed within the vacuum tube (<NUM>) and selectively operable to generate an electron emission; and
an anode (<NUM>), enclosed within the vacuum tube (<NUM>) and located relative to the cathode (<NUM>), to receive the electron emission and convert the electron emission from the cathode (<NUM>) to a hard x-ray emission, and located relative to the emission aperture (<NUM>) to direct at least a portion of the hard x-ray emission through the emission aperture (<NUM>);
an inspection filter (<NUM>) movably coupled to the base and selectively operable to receive the hard x-ray emission from the x-ray emitter and pass at least a portion of the hard x-ray emission through a filter aperture (<NUM>) in the inspection filter (<NUM>) to a selectable location on the part (<NUM>); and
a zone plate (<NUM>), external to the x-ray shield (<NUM>) and located relative to the emission aperture (<NUM>), to receive the portion of the hard x-ray emission from the emission aperture (<NUM>) of the x-ray shield (<NUM>) and to focus the portion of the hard x-ray emission received from the emission aperture (<NUM>) into a focused hard x-ray emission, wherein the zone plate (<NUM>) is interposed between the x-ray emitter (<NUM>) and the inspection filter (<NUM>), wherein the zone plate (<NUM>) is configured to direct the focused x-ray emission (<NUM>) toward the filter aperture (<NUM>) of the inspection filter (<NUM>), wherein the zone plate is configured to modify at least portion of the received x-rays emission to a convergent mode from a divergent mode.