Nondestructive inspection using acousto-optics

A method and apparatus for inspecting an object. The apparatus comprises a vibration generator and an acousto-optical sensor. The vibration generator is positioned relative to a surface of an object. The vibration generator excites the object at a location on the object such that the portion of the object vibrates. The acousto-optical sensor is coupled to the surface of the portion of the object. The acousto-optical sensor detects a vibratory response generated by the portion of the object in response to excitation of the portion of the object and generates an image of the portion of the object based on the vibratory response.

BACKGROUND INFORMATION

The present disclosure relates generally to inspection systems and, in particular, to nondestructive inspection systems. Still more particularly, the present disclosure relates to a method and apparatus for nondestructively inspecting an object using acousto-optics to determine whether a feature of interest is present in the object.

Nondestructive inspection (NDI) systems are oftentimes used to inspect different types of objects, including composite structures. Nondestructive inspection systems allow an object to be inspected without affecting the object in an undesired manner. In some cases, a nondestructive system may also be referred to as a nondestructive testing (NDT) system or a nondestructive evaluation (NDE) system.

A variety of nondestructive inspection methods are currently available for use with composite structures. However, some of these currently available methods are slower and more expensive than desired. Further, some of these currently available methods may require an expert in nondestructive inspection to perform the nondestructive inspection.

For example, some currently available ultrasonic nondestructive inspection methods, including ultrasonic pulse echo methods, may be more expensive than desired, may be slow to run, may require an expert to perform the inspection, or some combination thereof. A low-frequency bond testing method may be used, but this method may also be slower than desired in some cases. Further, an expert in nondestructive inspection may also be needed to perform low-frequency bond testing.

While faster methods such as laser shearography and infrared thermography able to provide results in substantially real-time are known, these may be prohibitively expensive. Providing results in substantially “real-time” means providing results without significant delay between the performance of the inspection of an object and the generation of the results. These results may take the form of, for example, images, that provide visual indications of whether undesired features of interest are present in an object. The results may then be analyzed or interpreted by, for example, a human operator at the same time at which the results are generated or at some later time. Further, infrared thermography may be unable to detect certain types of features, such as “kissing” bonds. A “kissing” bond may be a bond between two parts that have been positioned and coupled relative to each other with substantially no gap or space present between these parts. This coupling may have been performed using, for example, an adhesive. This type of bond may have reduced strength and, in some cases, substantially zero strength.

Thus, these currently available nondestructive inspection methods may be unable to provide the type of fast, simple, and inexpensive inspection that may be useful in certain situations. Therefore, it would be desirable to have a method and apparatus for performing nondestructive inspection that take into account at least some of the issues discussed above, as well as other possible issues.

SUMMARY

In one illustrative embodiment, an apparatus comprises a vibration generator and an acousto-optical sensor. The vibration generator is positioned relative to a surface of an object. The vibration generator excites the object at a location on the object such that at least a portion of the object vibrates. The acousto-optical sensor is coupled to the surface of the portion of the object. The acousto-optical sensor detects a vibratory response generated by the portion of the object in response to excitation of the portion of the object and generates an image of the portion of the object based on the vibratory response.

In another illustrative embodiment, a nondestructive inspection system comprises a vibration generator, an acousto-coupling sensor, and a coupling element. The vibration generator is positioned relative to a surface of an object. The vibration generator excites the object at an ultrasonic frequency at a location on the object such that at least a portion of the object vibrates. The acousto-optical sensor is coupled to the surface of the portion of the object. The acousto-optical sensor detects a vibratory response generated by the portion of the object in response to excitation of the portion of the object and generates an image of the portion of the object based on the vibratory response. The vibratory response includes a feature response that is produced when a feature is present within the portion of the object such that the image of the portion of the object included a visual representation of the feature. The coupling element couples the acousto-optical sensor to the surface of the portion of the object to facilitate transmission of acoustic energy from the portion of the object to the acousto-optical sensor.

In yet another illustrative embodiment, a method for inspecting an object is provided. The object is excited at a location on the object using a vibration generator positioned relative to a surface of the object such that at least a portion of the object vibrates. A vibratory response generated by the portion of the object is detected in response to excitation of the object using an acousto-optical sensor coupled to the surface of the portion of the object. An image of the portion of the object is generated, by the acousto-optical sensor, based on the vibratory response.

DETAILED DESCRIPTION

The illustrative embodiments recognize and take into account different considerations. For example, the illustrative embodiments recognize and take into account that it may be desirable to have a nondestructive inspection system that does not require an expert to perform the inspection. A nondestructive inspection system that does not require an expert in nondestructive inspection to be present on-site for the inspection may reduce some of the costs associated with the inspection.

For example, it may be desirable for a non-expert to perform an inspection of an object, while an expert located remotely views and analyzes the results of the inspection in substantially real-time. In other cases, it may be desirable to generate the results of the inspection in substantially real-time but have the expert view and analyze the results at a later time.

The illustrative embodiments also recognize and take into account that it may be desirable to have a nondestructive inspection system that can produce high-resolution images of features of interest in objects in substantially real-time, while still being lightweight and portable. The illustrative embodiments recognize and take into account that acousto-optical sensors may be lightweight, portable, and capable of producing high-resolution images. Thus, the illustrative embodiments provide a method, apparatus, and system for performing nondestructive inspection using acousto-optics.

In one illustrative example, an object is mechanically excited at a location on the object using a vibration generator positioned relative to a surface of the object such that at least a portion of the object vibrates. An acousto-optical sensor coupled to the surface of the portion of the object is used to detect a vibratory response generated by the portion of the object. The acousto-optical sensor generates an image of the portion of the object based on the vibratory response.

When a feature of interest is present within the portion of the object, the vibratory response may include a feature response corresponding to the feature of interest. The feature response may be a portion of the vibratory response that behaves differently from a rest of the vibratory response generated by the portion of the object. For example, the feature response may be more nonlinear in response to the excitation of the object, whereas the rest of the vibratory response may be more linear. Consequently, the image generated may include a visual representation of the feature of interest that is distinguishable from the visual representation of a rest of the portion of the object in the image.

Referring now to the figures and, in particular, with reference toFIG. 1, an illustration of an inspection environment is depicted in the form of a block diagram in accordance with an illustrative embodiment. In this illustrative example, inspection environment100is any environment in which an object, such as object102, may be inspected.

Object102may take a number of different forms. In one illustrative example, object102may take the form of composite structure103. In other words, composite structure103may be comprised of composite material. Composite structure103may take a number of different structural forms. For example, without limitation, composite structure103may take the form of a laminated, sandwiched, or honeycomb structure, or some other type of composite structure. In other illustrative examples, object102may take the form of a non-composite structure or a partially composite structure. For example, object102may be comprised of any number of metals, metal alloys, plastic materials, composite materials, or combination thereof.

In one illustrative example, object102may take the form of aircraft structure104. Aircraft structure104may be an example of one implementation for composite structure103in some cases. Aircraft structure104may be selected from a group consisting of a fuselage, a wing, a spar, a rib, a skin panel, an aileron, a flap, a stabilizer, or some other type of aircraft part or assembly of aircraft parts. These aircraft parts may be composite parts in some illustrative examples. In other illustrative examples, object102may take the form of a door, a wall, or some other type of structure.

As depicted, nondestructive inspection system106may be used to inspect object102. In particular, nondestructive inspection system106may be used to inspect at least portion118of object102to determine whether one or more features of interest are present within portion118of object102. As used herein, a “portion” of an item, such as portion118of object102, may be an area of the object102such as a section, a piece, or a part of the entire object102. In other illustrative examples, portion118may be the entirety of object102. In some cases, portion118of object102may include an area of object102at which a bond is located. The bond may take a number of different forms, one of which may be a “kissing” bond.

A feature of interest may be, for example, a particular layer in object102, a part that has been bonded to object102, a membrane, or some other type of feature. In some illustrative examples, the feature of interest may be an undesired feature. As used herein, an “undesired feature” may be any inconsistency in object102that is undesired. For example, an undesired feature may be a disbond, a crack, a micro-crack, a delamination, a wrinkle, foreign object debris (FOD), a void, an undesired porosity, or some other type of feature that is not desirable for object102. A disbond may be a bond that has been weakened such that a strength of the bond is below some selected threshold. In some cases, the bond may have been weakened to the extent that the bond has substantially zero strength.

Vibration generator108may be positioned relative to surface114of object102at side116of object102. In one illustrative example, vibration generator108may be positioned such that vibration generator108is in physical contact with object102. In other illustrative examples, vibration generator108may be positioned relative to object102but not in physical contact with object102.

Vibration generator108is configured to excite object102such that object102vibrates. In these illustrative examples, exciting object102may mean exciting some portion of object102or all of object102. For example, vibration generator108may be configured to excite object102at location121on object102such that at least portion118of object102is vibrated. Thus, exciting object102at location121may excite some or all of object102. Location121may be within portion118of object102, around portion118of object102, or within some selected distance from portion118of object102.

Vibration generator108excites object102at ultrasonic frequencies. These ultrasonic frequencies may be between about 1 kilohertz and about 500 kilohertz. In these illustrative examples, vibration generator108mechanically excites object102. Mechanically exciting object102may mean physically exciting object102. For example, vibration generator108may be used to physically contact object102repeatedly at an ultrasonic frequency to excite at least portion118of object102.

In other illustrative examples, vibration generator108may direct ultrasonic waves towards object102that cause surface displacement at surface114of at least portion118of object102when the ultrasonic waves impinge upon, or encounter, surface114. In this manner, the ultrasonic waves impinging upon object102excite object102such that at least portion118of object102vibrates.

Vibration generator108may take a number of different forms. For example, vibration generator108may take the form of mechanical resonator120. Mechanical resonator120may be selected from one of chirped solenoid122, mechanical impedance probe124, acoustic horn126, speaker system128, or some other type of mechanical resonator.

Mechanical resonator120may cause portion118of object102to vibrate and any features of interest that may be present within portion118of object102to vibrate. For example, a feature of interest, such as feature144, may be present within portion118of object102. When a frequency at which portion118of object102is excited is substantially equal to a natural frequency of feature144that is present within portion118of object102within selected tolerances, feature144may resonate. A frequency within selected tolerances of the natural frequency of feature144may be a frequency within some number of hertz or kilohertz from the natural frequency. This number may be, for example, but is not limited to, 1 hertz, 5 hertz,10hertz, 1 kilohertz, 2 kilohertz, 5 kilohertz, or some other number of hertz or kilohertz.

When the feature resonates, the vibration of feature144may be amplified relative to the vibration of a rest of portion118of object102. Feature144may resonate when excited at or within a certain range of the natural frequency of feature144. The natural frequency of feature144is the frequency at which feature144tends to oscillate in the absence of any driving or damping forces.

Acousto-optical system110may be implemented using acoustography, which is an ultrasound imaging technique that uses a super high-resolution ultrasound detector to produce ultrasound images. Acousto-optical system110may include number of acousto-optical sensors130. As used herein, a “number of” items may include one or more items. In this manner, number of acousto-optical sensors130may include one or more acousto-optical sensors. Acousto-optical sensor132is an example of one of number of acousto-optical sensors130. Acousto-optical sensor132may be implemented using one of the acousto-optical (AO) sensors provided by Santec Systems, Incorporated, headquartered in Wheeling, Ill.

First side134of acousto-optical sensor132may be coupled to surface114of portion118of object102using coupling element138. Coupling element138may take the form of a physical element, a force, a pressure, or some combination thereof used to retain first side134of acousto-optical sensor132in a fixed position relative to portion118of object102. In some illustrative examples, coupling element138may retain acousto-optical sensor132in physical contact with surface114.

Depending on the implementation, coupling element138may comprise at least one element selected from a group consisting of a vacuum seal, an adhesive, mechanical pressure applied to acousto-optical sensor132, an adhesion system, or some other type of element configured for holding acousto-optical sensor132in place relative to portion118of object102. The mechanical pressure may be applied by, for example, without limitation, a human operator holding acousto-optical sensor132against surface114of portion118of object102.

Acousto-optical sensor132detects vibratory response139generated by portion118of object102in response to the excitation of object102by vibration generator108. Vibratory response139may be detected as acoustic energy140. In one illustrative example, acoustic energy140produced by object102in response to the excitation of object102may form a resonance pattern.

In this illustrative example, acousto-optical sensor132receives acoustic energy140generated by vibration of object102at first side134. As depicted, acoustic coupling element141may be associated with first side134of acousto-optical sensor132to facilitate the transmission of acoustic energy140from object102to acousto-optical sensor132. As used herein, when one component is “associated” with another component, the association is a physical association in the depicted examples.

For example, a first component, such as acoustic coupling element141, may be considered to be associated with a second component, such as acousto-optical sensor132, by being at least one of secured to the second component, bonded to the second component, mounted to the second component, welded to the second component, fastened to the second component, or connected to the second component in some other suitable manner. The first component also may be connected to the second component using a third component. Further, the first component may be considered to be associated with the second component by being formed as part of the second component, an extension of the second component, or both.

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, action, process, 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” or “at least one of item A, item B, or 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.

Acoustic coupling element141may include a substance, or material, that allows acoustic energy to be transferred from portion118of object102to acousto-optical sensor132without substantially impeding this transfer of acoustic energy. This substance may have acoustic properties that are similar to portion118of object102and may also have properties that allow a sufficient level of contact and coupling between portion118and acousto-optical sensor132. The substance may provide low reflection of acoustic energy but high transfer of the acoustic energy. In some cases, the substance may be referred to as an acoustically-matched material. The substance may take the form of, for example, but not limited to, water, rubber, glue, gel, some other type of fluid, solid, or semi-solid substance, or some combination thereof.

For example, acoustic coupling element141may take the form of a hollow plate filled with a fluid. The fluid may be comprised of any number of gases, any number of liquids, or some combination thereof. For example, the fluid may be a liquid, such as water. The fluid may be the medium used to facilitate transmission of acoustic energy140to acousto-optical sensor132. In another example, acoustic coupling element141may take the form of a gel, an adhesive material, a rubber material, or some other type of material.

When a feature of interest, such as feature144, is present within portion118of object102, image142may include a visual representation of the feature of interest. In this manner, image142may be used to determine when a feature of interest, such as feature144, is present within portion118of object102.

For example, when feature144is present within portion118of object102, vibratory response139of portion118of object102includes feature response146. Feature response146may be any portion of vibratory response139that is different, and thus distinguishable, from a rest of vibratory response139. For example, feature144may respond differently to the excitation of portion118of object102as compared to a rest of portion118. Thus, the vibratory response of feature144, herein referred to as feature response146, may be different from the vibratory response of the rest of portion118. In one illustrative example, feature response146may be a portion of vibratory response139that is more nonlinear than the rest of vibratory response139, which may be more linear.

For example, when vibration generator108excites object102such that portion118of object102resonates, a resonance pattern may be created. The resonance pattern created by portion118of object102having feature144may be different from the resonance pattern created when feature144is not present. The difference between these two resonance patterns may be feature response146.

Consequently, image142produced when feature144is present may be different from image142produced when feature144is not present. When feature144is present, image142may include a visual representation of feature144that is distinguishable from the rest of portion118of object102in image142. For example, image142may include indication148that feature144is present.

Indication148, and thereby image142, may change in response to a change in the frequency at which object102is excited using vibration generator108. These changes to image142may be produced in substantially real-time or near real-time with respect to the changes in the frequency. In some cases, indication148may only be present or readily distinguishable in image142at certain frequencies.

In these illustrative examples, indication148of feature144may be easily and readily distinguishable such that even a non-expert may be able to identify indication148of feature144in image142. The location of indication148within image142may correspond to a location of feature144within portion118of object102. In this manner, a human operator, including a non-expert, may easily and quickly be able to at least determine when a feature of interest, such as feature144, is present and locate that feature of interest in object102.

Further, image142may be generated in substantially real-time such that a feature of interest may be detected and evaluated without significant delay. In particular, acousto-optical sensor132may be configured to detect vibratory response139and generate image142immediately or almost immediately after object102is excited using vibration generator108.

The feature of interest may be detected in a number of different ways. For example, without limitation, a comparison of image142to a collection of images associated with specific features of interest may be made. In particular, this comparison may determine whether image142substantially matches or is similar to any images in the collection of images that are known to visually represent the feature of interest. The comparison may be performed by a human operator or a computer system, depending on the implementation.

Number of acousto-optical sensors130may include one or more acousto-optical sensors having any number of shapes and sizes. When multiple acousto-optical sensors are included, these acousto-optical sensors may be coupled to different portions of object102at the same time. In this manner, different portions of object102may be quickly and easily inspected at substantially the same time. This type of inspection may provide the ability to compare different features of interest within the different portions of object102relative to each other.

As described above, nondestructive inspection system106may include imaging system112. Imaging system112may take the form of a camera, a video camera, or some other type of imaging system. Imaging system112may be positioned away from acousto-optical sensor132such that second side136of acousto-optical sensor132is within a field of view of imaging system112.

Imaging system112may be used to generate number of images150that captures image142visually presented at second side136of acousto-optical sensor132. In one illustrative example, number of images150may be sent to computer system152over one or more communications links. Computer system152may be comprised of one or more computers in communication with each other. Computer system152may be located entirely within inspection environment100, entirely outside of inspection environment100, or partially within inspection environment100.

When computer system152is located outside of inspection environment100in a remote location, remote expert154may use computer system152to view and analyze number of images150. Remote expert154may be an expert having a desired level of knowledge and skill with respect to nondestructive inspection who is not located proximal to object102. In other words, remote expert154may be an expert who is located remotely with respect to object102.

In some cases, number of images150may be sent to computer system152as number of images150are generated such that remote expert154may view number of images150in substantially real time. In other illustrative examples, number of images150may be stored on computer system152for later viewing and evaluation by remote expert154, some other human operator, or a program.

For example, in some cases, imaging system112may not be included in nondestructive inspection system106. In some illustrative examples, number of images150may be sent to a number of remote servers in addition to or in place of computer system152. In other illustrative examples, acousto-optical system110may take the form of a plurality of acousto-optical sensors having a grid-type arrangement or some type of other arrangement or configuration. Using multiple acousto-optical sensors may allow portions of an object having different shapes and sizes to be inspected substantially simultaneously. Further, when using multiple acousto-optical sensors, the configuration of the acousto-optical sensors relative to each other may be changed during inspection of object102.

As one illustrative example, ten acousto-optical sensors may be used to inspect portion118of object102rather than a single acousto-optical sensor. These acousto-optical sensors may be arranged in a grid pattern or some other pattern over portion118of object102. At a later time, a different portion of object102may need to be inspected. This portion may be smaller than portion118of object102. All ten acousto-optical sensors may be unable to properly fit over this portion. Rather, only five acousto-optical sensors may be needed to cover this portion.

In this manner, using multiple smaller-sized acousto-optical sensors instead of a single larger-sized acousto-optical sensor may allow portions of different shapes and sizes to be easily inspected. In some cases, this type of implementation may reduce the overall cost of acousto-optical sensors needed.

With reference now toFIG. 2, an illustration of an inspection environment is depicted in accordance with an illustrative embodiment. In this illustrative example, inspection environment200may be an example of one implementation for inspection environment100inFIG. 1.

In inspection environment200, nondestructive inspection system202is used to inspect aircraft structure204. Aircraft structure204is an example of one implementation for aircraft structure104inFIG. 1. In this illustrative example, aircraft structure204is fuselage206.

Nondestructive inspection system202is an example of one implementation for nondestructive inspection system106inFIG. 1. Nondestructive inspection system202includes vibration generator208, acousto-optical sensor210, and imaging system212, which may be examples of implementations for vibration generator108, acousto-optical sensor132, and imaging system112, respectively, inFIG. 1.

Vibration generator208mechanically excites aircraft structure204at location213on aircraft structure204such that at least portion223of aircraft structure204vibrates. In this illustrative example, vibration generator208takes the form of mechanical resonator214. Mechanical resonator214has end216that contacts surface218of aircraft structure204to excite at least portion223of object aircraft structure204. End216may contact surface218repeatedly at a frequency selected to cause a feature of interest within portion223to vibrate in a particular manner. In this illustrative example, the frequency may be selected to cause amplified vibration of the feature of interest. In some cases, the frequency may be selected to cause the feature of interest to resonate.

In other illustrative examples, the frequency with which end216contacts surface218may be changed to perform a frequency sweep across a range of frequencies. For example, a plurality of preselected frequencies that are selected to perform a frequency sweep of portion223of aircraft structure204may be used to excite portion223of aircraft structure204.

In another example, the frequency may be swept through a continuous range of frequencies, such as from about 10 kilohertz to about 200 kilohertz. In yet another example, the range of frequencies may be a discontinuous range that includes the frequencies at some selected interval from about 10 kilohertz to about 200 kilohertz. For example, the frequency at every 1 kilohertz, 5 kilohertz, 10 kilohertz, 20 kilohertz, 50 kilohertz, or some other selected interval within a particular range may be included. The range of frequencies may be selected such that excitation of portion223of aircraft structure204will produce amplified vibration or in particular, resonance, of the feature of interest.

The particular frequency or range of frequencies selected for use in exciting portion223of aircraft structure204with vibration generator208may be based on, for example, test results performed using a reference object or standard for aircraft structure204. As one illustrative example, the standard may be excited at different frequencies until the particular frequency at which the standard resonates is identified. This particular frequency or some range of frequencies around this particular frequency may then be used to inspect aircraft structure204.

Frequency control220may be used to control the frequency at which vibration generator208excites aircraft structure204at location213of aircraft structure204. In this illustrative example, frequency control220may be controlled by a human operator, a computer, a processor unit in vibration generator208, a microprocessor, or some other type of controller.

As depicted, vibration generator208is portably mounted on wheeled stand222. Wheeled stand222may be used to move and position vibration generator208relative to aircraft structure204. In this illustrative example, wheeled stand222may also be used to adjust a height of vibration generator208relative to aircraft structure204.

In other illustrative examples, other means of moving vibration generator208may be used. For example, some other type of device, including, but not limited to, a robotic device, a positioning system, a movement system, an automated movement system, or some other type of device may be used to move vibration generator208relative to aircraft structure204.

Acousto-optical sensor210is coupled to surface218of aircraft structure204. In particular, acousto-optical sensor210is coupled to surface218of portion223of aircraft structure204using vacuum seal224. Vacuum seal224is an example of one implementation for coupling element138inFIG. 1. Vacuum seal224retains a first side (not shown in this view) of acousto-optical sensor210in physical contact against surface218. This type of coupling of acousto-optical sensor210to surface218of aircraft structure204is simple, may be performed quickly, and may not require an expert to be performed.

In this illustrative example, acousto-optical sensor210visually presents image225of portion223on second side226of acousto-optical sensor210. Image225may be generated by acousto-optical sensor210based on the vibratory response of aircraft structure204to excitation by vibration generator208as detected by acousto-optical sensor210.

Image225includes indication228of a feature of interest. Indication228is a visual representation of a feature of interest within portion223of aircraft structure204. Indication228may be, for example, without limitation, one or more colors that indicate an amplified vibratory response of the feature of interest as compared to the vibratory response of the rest of portion223of aircraft structure204.

The feature of interest may be hidden under surface218of aircraft structure204but detectable based on the vibratory response of aircraft structure204to excitation by vibration generator208. Indication228may reflect that portion223of aircraft structure204has a different resonance pattern than the resonance pattern that portion223would have if the feature of interest were not present. This determination may be made by reference to standard vibrations for aircraft structure204being evaluated. In this manner, indication228provides a simple way to determine in substantially real-time whether or not the feature of interest is present.

Changing the frequency at which vibration generator208excites aircraft structure204may change image225. Examples of different images that may be generated for the feature of interest in portion223of aircraft structure204at different excitation frequencies is depicted inFIG. 7, described below.

In this illustrative example, imaging system212is used to generate images that capture second side226of acousto-optical sensor210. Imaging system212is positioned away from acousto-optical sensor210such that second side226of acousto-optical sensor210is within the field of view of imaging system212. Imaging system212may be a video camera configured to generate video comprising a sequence of images. In another illustrative example, imaging system212may be a camera configured to generate still images.

The images generated by imaging system212are sent to computer230over wired communications link232in this illustrative example. In other examples, the images may be sent over a wireless communications link, an optical communications link, or some other type of communications link to computer230or some other computer system located remotely. For example, the images generated by imaging system212may be sent wirelessly to a remote computer system such that an expert located remotely may be able to view and analyze the images in substantially real-time or at a later time.

With reference now toFIG. 3, an illustration of a cross-sectional side view of acousto-optical sensor210and aircraft structure204fromFIG. 2is depicted in accordance with an illustrative embodiment. In this illustrative example, first side300of acousto-optical sensor210is shown.

Acoustic coupling element302is associated with acousto-optical sensor210at first side300of acousto-optical sensor210. Acoustic coupling element302facilitates the transmission of acoustic energy generated by portion223of aircraft structure204in response to excitation by vibration generator208inFIG. 2to acousto-optical sensor210. Acoustic coupling element302ensures that the vibratory response of aircraft structure204is detected by acousto-optical sensor210with a desired level of accuracy.

Feature304within portion223of aircraft structure204is seen inFIG. 3. Feature304is an example of a feature of interest. In some cases, feature304may be an undesired feature. Indication228in image225inFIG. 2is a visual representation of feature304.

With reference now toFIG. 4, an illustration of a different type of coupling element used to retain acousto-optical sensor210against surface218of aircraft structure204fromFIG. 2is depicted in accordance with an illustrative embodiment. In this illustrative example, adhesive400is used to couple acousto-optical sensor210to surface218of portion223of aircraft structure204.

Adhesive400is an example of one implementation for coupling element138inFIG. 1. Adhesive400is implemented using temporary adhesive strip402, temporary adhesive strip404, temporary adhesive strip406, and temporary adhesive strip408. This type of coupling of acousto-optical sensor210to surface218of aircraft structure204is simple, may be performed quickly, and does not require an expert to be performed.

With reference now toFIG. 5, an illustration of a different type of coupling element used to retain acousto-optical sensor210against surface218of aircraft structure204fromFIG. 2is depicted in accordance with an illustrative embodiment. In this illustrative example, mechanical pressure is used to couple acousto-optical sensor210to surface218of portion223of aircraft structure204.

In particular, human operator500may use hand502to apply mechanical pressure to acousto-optical sensor210to hold acousto-optical sensor210in a fixed position relative to aircraft structure204. This type of coupling of acousto-optical sensor210to surface218of aircraft structure204is simple, may be performed quickly, and does not require an expert to be performed.

With reference now toFIG. 6, an illustration of an integrated ultrasonic imaging system is depicted in accordance with an illustrative embodiment. In this illustrative example, vibration generator208and acousto-optical sensor210fromFIGS. 2-5have been integrated to form integrated ultrasonic imaging system600.

In particular, vibration generator208and acousto-optical sensor210have been associated with each other using retaining member602. As depicted, vibration generator208is associated with retaining member602by being mounted to retaining member602. Further, acousto-optical sensor210is also associated with retaining member602. In particular, an outer edge of acousto-optical sensor210may be associated with retaining member602. Retaining member602holds vibration generator208in place relative to acousto-optical sensor210.

Integrated ultrasonic imaging system600also includes adhesion system604. Adhesion system604may be a vacuum adhesion system comprised of plurality of adhesion members606. Adhesion system604may be an example of one implementation for coupling element138inFIG. 1.

In one illustrative example, each of plurality of adhesion members606may be implemented as a structure having a seal associated with the structure and in communication with a channel within the structure. The seal may be configured to adhere to surface218of aircraft structure204when air is drawn into the channel of the structure through the seal. In some cases, the seal may be configured to rotate relative to the structure to at least partially conform to a shape of surface218. A gap, or “air cushion,” may be created between the seal and surface218. The gap may function as an air bearing such that the seal “floats” over surface218.

In this manner, plurality of adhesion members606may be used to form non-contact vacuum adhesion to surface218such that plurality of adhesion members606may “float” above surface218. This non-contact vacuum adhesion may hold vibration generator208and acousto-optical sensor210in place relative to each other and to surface218of aircraft structure204. Although plurality of adhesion members606may float over surface218, the vacuum adhesion of acousto-optical sensor210to surface218resulting from the air being drawn through plurality of adhesion members606may be sufficiently strong to hold acousto-optical sensor210in place.

However, the vacuum adhesion may not be so strong as to prevent plurality of adhesion members606from being pulled away from surface218with sufficient force or from plurality of adhesion members606being moved along surface218with sufficient force. For example, plurality of adhesion members606may be used to adhere acousto-optical sensor210to one location on surface218for inspection. After inspection of this location, plurality of adhesion members606may be pulled away from surface218. Then, plurality of adhesion members606may be moved to a new location on surface218and used to adhere acousto-optical sensor210to surface218at this new location for inspection of this new location. This process may be repeated any number of times such that any number of locations on surface218may be inspected.

As depicted, robotic device608may be associated with integrated ultrasonic imaging system600by being associated with retaining member602. Robotic device608may be used to move and position retaining member602, and thus the entirety of integrated ultrasonic imaging system600, relative to surface218of aircraft structure204. In some cases, the movement of retaining member602and integrated ultrasonic imaging system600by robotic device608may be automated such that integrated ultrasonic imaging system600is moved to a plurality of predefined locations on aircraft structure204or along some predefined pathway along surface218.

In other illustrative examples, integrated ultrasonic imaging system600may be moved relative to aircraft structure204manually by a human operator. For example, the human operator may use handles (not shown in this view) on retaining member602to move integrated ultrasonic imaging system600.

With reference now toFIG. 7, an illustration of images generated using an acousto-optical sensor is depicted in accordance with an illustrative embodiment. In this illustrative example, image700, image702, image704, image706, image708, and image710may be generated by acousto-optical sensor210fromFIG. 2. These images may all be images of portion223of aircraft structure204inFIG. 2.

Each of image700, image702, image704, image706, image708, and image710is generated based on the vibratory response of portion223of aircraft structure204to excitation at a different frequency. In this illustrative example, image700, image702, image704, image706, image708, and image710may correspond to excitation frequencies at about 11 kilohertz, about 22.500 kilohertz, about 28 kilohertz, about 36 kilohertz, about 43 kilohertz, and about 49 kilohertz, respectively.

The illustrations of inspection environment200inFIGS. 2 and 4-6, acousto-optical sensor210inFIG. 3, and the images shown inFIG. 7are not meant to imply physical or architectural limitations to the manner in which an illustrative embodiment may be implemented. Other components in addition to or in place of the ones illustrated may be used. Some components may be optional.

The different components shown inFIGS. 2-6may be illustrative examples of how components shown in block form inFIG. 1can be implemented as physical structures. Additionally, some of the components inFIGS. 2-6may be combined with components inFIG. 1, used with components inFIG. 1, or a combination of the two. Further, the images shown inFIG. 7may only be examples of the types of images and types of indications that may be generated for a feature of interest at different frequencies.

For example, in some cases, vibration generator208and acousto-optical sensor210may be associated with each other in some manner other than retaining member602shown inFIG. 6. In some illustrative examples, a human operator may be used to move and position vibration generator208relative to surface218of aircraft structure204. For example, a human operator may hold vibration generator208in one hand relative to surface218of aircraft structure204, while holding acousto-optical sensor210against surface218of aircraft structure204in the other hand.

With reference now toFIG. 8, an illustration of a process for inspecting an object is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated inFIG. 8may be implemented using nondestructive inspection system106inFIG. 1.

The process begins by exciting an object at a location on the object using a vibration generator positioned relative to a surface of the object such that at least a portion of the object vibrates (operation800). In operation800, the portion of the object may be excited at a particular frequency selected to cause a feature of interest to produce a feature response. In other illustrative examples, the object may be excited over a range of frequencies to perform a frequency sweep to inspect for one or more features of interest.

A vibratory response generated by the object in response to excitation of the object is detected using an acousto-optical sensor coupled to the surface of the portion of the object (operation802). An image of the portion of the object is generated based on the vibratory response by the acousto-optical sensor (operation804), with the process terminating thereafter.

When a feature of interest is present within the portion of the object, the image generated in operation804may include a visual representation of the feature. In particular, the image may include an indication that the feature is present. This indication may be easily distinguishable. Thus, a human operator may be able to quickly determine whether a feature of interest is present based on the image.

The overall process described inFIG. 8may be repeated any number of times such that any number of portions of the object may be inspected. For example, the vibration generator may be repositioned relative to the object and coupled to another portion of the object. The repositioning of the vibration generator may include translating the vibration generator, rotating the vibration generator, or both. In this manner, different portions of the object may be quickly and easily inspected.

With reference now toFIG. 9, an illustration of a process for inspecting an object is depicted in the form of a flowchart in accordance with an illustrative embodiment. The process illustrated inFIG. 9may be implemented using nondestructive inspection system106inFIG. 1.

The process begins by positioning a mechanical resonator relative to a surface of an object (operation900). In some cases, in operation900, the mechanical resonator may be coupled to the surface of the object.

Next, an acousto-optical sensor is positioned relative to the object and coupled to the surface of a portion of the object (operation902). This portion may be an area, a section, or a part of the object designated for inspection. The object is then excited using the mechanical resonator such that at least the portion of the object vibrates (operation904). Depending on the frequency or frequencies at which the portion of the object is excited, a feature of interest, when present within the portion of the object, may resonate.

A vibratory response of the portion of the object is detected as acoustic energy having a resonance pattern using the acousto-optical sensor (operation906). When a feature of interest is present within the portion of the object and resonates in response to excitation of the portion of the object, the vibratory response detected in operation906may include a feature response.

Amplitude of the acoustic energy is converted into optical intensity to generate an image of the portion of the object (operation908). When the vibratory response detected in operation906includes the feature response, the image generated in operation908includes an indication that visually represents the feature of interest.

A number of images of the image generated by the acousto-optical sensor are generated and sent to a computer system (operation910). In one illustrative example, operation910may be performed using an imaging system positioned relative to the acousto-optical sensor such that the acousto-optical sensor is within the field of view of the imaging system.

Thereafter, a determination is made as to whether inspection of the object has been completed (operation912). If the inspection of the object has been completed, the process terminates. Otherwise, the process repositions the acousto-optical sensor relative to the object and couples the acousto-optical sensor to the surface of a next portion of the object (operation914), with the process then returning to operation904as described above.

The flowcharts and block diagrams in the different depicted embodiments illustrate the architecture, functionality, and operation of some possible implementations of apparatuses and methods in an illustrative embodiment. In this regard, each block in the flowcharts or block diagrams may represent a module, a segment, a function, a portion of an operation or step, some combination thereof.

The illustrative embodiments of the disclosure may be described in the context of aircraft manufacturing and service method1000as shown inFIG. 10and aircraft1100as shown inFIG. 11. Turning first toFIG. 10, an illustration of an aircraft manufacturing and service method is depicted in the form of a block diagram in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method1000may include specification and design1002of aircraft1100inFIG. 11and material procurement1004.

During production, component and subassembly manufacturing1006and system integration1008of aircraft1100inFIG. 11takes place. Thereafter, aircraft1100inFIG. 11may go through certification and delivery1010in order to be placed in service1012. While in service1012by a customer, aircraft1100inFIG. 11is scheduled for routine maintenance and service1014, which may include modification, reconfiguration, refurbishment, and other maintenance or service.

With reference now toFIG. 11, an illustration of an aircraft is depicted in the form of a block diagram in which an illustrative embodiment may be implemented. In this example, aircraft1100is produced by aircraft manufacturing and service method1000inFIG. 10and may include airframe1102with plurality of systems1104and interior1106. Examples of systems1104include one or more of propulsion system1108, electrical system1110, hydraulic system1112, and environmental system1114. Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry.

The apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method1000inFIG. 10. In particular, nondestructive inspection system106fromFIG. 1may be used to inspect a structure of aircraft1100during any one of the stages of aircraft manufacturing and service method1000. For example, without limitation, nondestructive inspection system106fromFIG. 1may be used to inspect one or more aircraft structures during at least one of component and subassembly manufacturing1006, system integration1008, certification and delivery1010, in service1012, routine maintenance and service1014, or some other stage of aircraft manufacturing and service method1000. Still further, nondestructive inspection system106fromFIG. 1may be used to inspect airframe1102, interior1106, or any one of plurality of systems1104of aircraft1100.

In one illustrative example, components or subassemblies produced in component and subassembly manufacturing1006inFIG. 10may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft1100is in service1012inFIG. 10. As yet another example, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production stages, such as component and subassembly manufacturing1006and system integration1008inFIG. 10. One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft1100is in service1012, during maintenance and service1014inFIG. 10, or both. The use of a number of the different illustrative embodiments may substantially expedite the assembly of and reduce the cost of aircraft1100.

Thus, the illustrative embodiments provide a method and apparatus for quickly and easily inspecting objects. The inspection method provided using nondestructive inspection system106inFIG. 1may allow inspections to be performed without requiring an expert in nondestructive inspection to operate the various components of nondestructive inspection system106. A non-expert may be able to easily operate acousto-optical sensor132inFIG. 1. Further, a non-expert may be able to easily and quickly determine whether a feature of interest is present in an object, such as object102inFIG. 1, just by looking at image142generated by acousto-optical sensor132.

The non-expert may be able to mark the location on object102at which the feature of interest is detected without needing to understand how image142is generated or how to analyze image142. Further, imaging system112inFIG. 1may be used to send “still” images or video capturing image142generated by acousto-optical sensor132to an expert located remotely for analysis in substantially real-time or at a later time.

As one illustrative example, the expert may compare the “still images” or video capturing image142to a database of reference images in which each reference image includes a visual representation of a specific, known feature of interest. A substantial match between image142and one of these reference images may be a detection of the specific, known feature of interest visually represented in the reference image. Thus, nondestructive inspection system106may be well-suited for remote nondestructive inspection methodologies.