JP2011506927A - Nondestructive inspection using laser ultrasound and infrared thermography - Google Patents

Abstract

  An inspection system for testing the internal structure of the target material is provided. The inspection system includes a generation laser, an ultrasonic detection system, a thermal image processing system, and a processor / control module. The generating laser generates a pulsed laser beam that can be operated to induce ultrasonic displacement and thermal transients in the target material. The ultrasonic detection system detects an ultrasonic surface displacement in the target material. The thermal imaging system detects thermal transients in the target material. The processor analyzes both the detected ultrasonic displacement and the thermal image at the target material to provide information about the internal structure of the target material.

Description

  The present invention relates to nondestructive testing, and more particularly to the use of thermal imaging and ultrasonic testing to inspect the internal structure of materials.

  In recent years, the use of advanced composite structures has grown tremendously in the aerospace industry, automotive industry, and many other private industries. Although composite materials provide significant performance improvements, composite materials require strict quality control procedures both in the manufacturing process and after these materials are used in the finished product. Specifically, the nondestructive evaluation (NDE) method must evaluate the structural integrity of the composite material. Proper evaluation requires the ability to detect inclusions, delamination, and porosity in both areas close to the surface and deep inside.

  Various methods and apparatus have been proposed for assessing the structural integrity of composite structures. In one solution, an ultrasonic source is used to generate ultrasonic surface displacements in the target material. The ultrasonic surface displacement is then measured and analyzed. The ultrasound source may be a pulsed laser beam directed at the target. Laser light from a separate detection laser irradiates the ultrasonic surface displacement and is scattered by the surface of the workpiece. A collection optics then collects the scattered laser energy. The collection optics can be coupled to an interferometer or other device to obtain data about the structural integrity of the composite structure through analysis of the scattered laser energy. Laser ultrasound has been shown to be very effective in inspecting each part during the manufacturing process.

  Typically, the laser light source generates sound waves by thermal expansion at local spots on the surface while the probe laser beam coupled to the interferometer detects the surface displacement or velocity. Thermal expansion by absorbing the generated laser causes displacement that is demodulated by the laser ultrasound detection system, resulting in a pulse at the beginning of the laser ultrasound signal. This echo is usually called a surface echo. A surface echo may mask any echo generated by defects near the surface of the sample. The duration of the surface echo depends on the duration of the generated laser pulse and the frequency bandwidth of the detection system. Typically, using a CO2 generating laser and a confocal Fabry-Perot for detection, the surface echo may last up to a few microseconds. Thus, any defect that will generate an echo during that time may be masked. For these reasons, laser ultrasonic inspection is highly sensitive to defects deep inside and low to defects near the surface.

  Another NDE method, Transient Infrared (IR) thermography, allows for efficient inspection of polymer matrix composites due to its low sensitivity to defects deeper than a few millimeters in polymer matrix parts. Must not.

  Embodiments of the present invention are directed to systems and methods that substantially address the identified needs and other needs described above. Each embodiment of the invention is further described in the following description and claims. The advantages and features of each embodiment of the invention may become apparent from the description, the accompanying drawings, and the claims.

  Each embodiment of the present invention combines laser ultrasound and thermal imaging techniques to substantially address the above identified needs and other needs. Laser ultrasound generation techniques may be used to provide a transient heat source. Thus, transient infrared (IR) thermography may be combined with laser ultrasound to achieve a more complete non-destructive inspection of polymer matrix components (ie, composite materials).

  In one embodiment, an inspection system for inspecting structures near the surface and deep inside the target material is provided. The inspection system includes a generation laser, an ultrasonic detection system, a thermal image processing system, and a processor / control module. The generation laser generates a pulsed laser beam that can operate to induce both ultrasonic displacement and thermal transients in the target material. The ultrasonic detection system detects an ultrasonic surface displacement in the target material. The thermal imaging system detects thermal transients in the target material. The processor / controller analyzes both the detected ultrasonic displacement and thermal images at the target material and correlates them to provide information about the structure near and deep inside the target material.

  In another embodiment, a method for inspecting the internal structure of a target is provided. The method includes inducing ultrasonic displacement and thermal transients in the target material. These ultrasonic displacements and thermal transients may be generated using a single pulse generated laser beam. Ultrasonic displacement and thermal transients caused by the generated laser beam directed to the surface of the target may be detected and analyzed. The generating and analyzing step may include synchronizing both ultrasound information and thermal information and correlating them to provide a more complete understanding of the target structure. For example, analysis of ultrasonic displacement may provide information about structures deep inside the composite material. Thermal images may provide information about internal structures near the surface of the composite material. By correlating ultrasonic information and thermal information, the overall internal structure of the target can be better understood.

  In yet another embodiment, a composite material inspection system is provided. The composite inspection system includes a generation laser for generating a pulsed laser beam that induces ultrasonic displacement and thermal transients in the composite. An ultrasonic detection system for detecting ultrasonic surface displacement in a composite material is provided. A thermal imaging system is provided for detecting thermal transients in a composite material. The control module may match the thermal image processing frame acquisition with the pulse rate of the generated laser beam. A processor is provided to analyze and correlate detected ultrasonic displacements and thermal images to provide information about the overall internal structure of the target.

  For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings. In the accompanying drawings, like reference numbers indicate like functions.

FIG. 3 illustrates how laser ultrasonic displacement and thermal transients are generated and detected using a generated laser beam and a detected laser beam in accordance with embodiments of the present invention. 1 is a block diagram showing basic components of a laser ultrasonic / thermal image processing system. 1 is a block diagram or functional diagram of a laser ultrasound and IR image processing system according to each embodiment of the present invention. FIG. 6 illustrates the processing of IR images used to gather information about internal structures near the surface of a target according to embodiments of the present invention. FIG. 4 shows infrared results obtained by scanning a pulsed CO2 laser beam over a polymer plate having a flat hole at the bottom according to each embodiment of the present invention. 3 is a logic flow diagram according to one or more embodiments of the invention. FIG. 3 is a block diagram of a generating laser that can be operated to generate ultrasonic displacements and thermal transients in accordance with embodiments of the present invention.

  Preferred embodiments of the invention are illustrated in the figures, wherein like numerals are used to refer to like and corresponding parts of the various drawings.

  Each embodiment of the present invention combines laser ultrasound and thermal imaging techniques to provide a more complete non-destructive inspection of target materials such as, but not limited to, polymer matrix components (ie, composite materials). . In one embodiment, an inspection system is provided that is operable to inspect the internal structure of the target material. The inspection system includes a generation laser, an ultrasonic detection system, a thermal image processing system, and a processor / control module. The generation laser generates a pulsed laser beam that can operate to induce both ultrasonic displacement and thermal transients in the target material. The ultrasonic detection system detects an ultrasonic surface displacement in the target material. The thermal imaging system detects thermal transients in the target material. The processor analyzes both detected ultrasonic displacements and thermal images at the target material and correlates them to provide information about the overall internal structure of the target material. Each embodiment of the present invention achieves faster inspection speed, improved system reliability, and lower operating costs.

  FIG. 1 illustrates the generation and detection of laser ultrasonic displacements and thermal transients using generated and detected laser beams in accordance with embodiments of the present invention. The laser beam 102 generates ultrasonic and thermal transients while the irradiating (detecting) laser beam 104 detects the ultrasonic waves at a target 106, such as a composite material for testing. As shown, these lasers may be applied coaxially to the target 106. The generated laser beam 102 causes further elastic expansion 112 in the target 106, resulting in the formation of ultrasonic deformation or ultrasonic waves 108. Deformed or ultrasonic wave 108 propagates through target 106 and modulates, scatters, and reflects detection laser beam 104 to produce phase-modulated light 110 directed away from target 106. The light is collected and processed to obtain information representing the internal structure of the target 106.

  FIG. 2 shows a block diagram of the basic components for performing ultrasonic laser testing and infrared (TR) thermography. Generation laser 210 generates a generation laser beam 212 and optical assembly 214 directs the beam to target 216. As shown, the optical assembly 214 includes a scanner or other similar mechanism that moves the laser beam 212 along a scanning or testing procedure 218. The optical assembly 214 may include a visual camera, depth camera, IR camera, distance detector, narrowband camera, or other similar optical sensor known to those skilled in the art. Each of these optical sensors may require calibration before performing an inspection. This calibration verifies that the system can integrate the information collected by the various sensors. The generation laser 210 generates ultrasonic waves 108 and thermal transients in the target 216. The thermal image processing system 232 captures a thermal image of the target. These images are processed to provide information about internal structures near the surface of target 216. This process will be described in more detail with reference to FIG.

  The additional elastic expansion 112 that generates the ultrasonic wave 108 and thermal transients is the result of the composite material absorbing the generated laser beam. The composite material 216 easily absorbs the generated laser beam 212 without dissipation or destruction. To overcome signal-to-noise ratio (SNR) problems, higher power generation lasers can result in material dissipation and potentially damage components at the surface of the workpiece. Not necessarily preferred. In other embodiments, depending on the material being tested, some dissipation may be allowed to increase the SNR of the detection signal. The generated laser beam 212 has an appropriate pulse duration, power, and frequency to induce ultrasonic surface deformation and appropriate thermal transients. For example, a transversely excited atmospheric pressure (TEA) CO laser can produce a beam with a pulse width of 100 nanoseconds and a wavelength of 10.6 microns. The laser power must be strong enough to deliver a 0.25 joule pulse to the target, for example, and may require a 100 watt laser operating at a repetition rate of 400 Hz. The generated laser beam 212 is absorbed as heat on the target surface, thereby causing further elastic expansion without dissipating.

  The detection laser 220 operating in the pulse mode or CW mode does not induce ultrasonic displacement. For example, an Nd: YAG laser can be used. The power of this laser must be strong enough to provide, for example, a 100 microsecond pulse at 100 millijoules and may require a 1 kilowatt (KW) laser. The detection laser 220 generates a detection laser beam 222. The detection laser 220 includes or is optically coupled with a filtering mechanism 224 to remove noise from the detection laser beam 224. The optical assembly 214 directs the detection laser beam 224 to the surface of the composite material 216, which scatters and / or reflects the detection laser beam 224. The resulting phase modulated light is collected by the collection optics 226. As shown here, the scattered and / or reflected detection laser light travels backward through the optical assembly 214. Optional optical processor 228 and interferometer 230 process the phase-modulated light to generate a signal that includes information representative of ultrasonic displacement at the surface of composite material 216. Data processing and control system 232 coordinates the operation of the components of the laser ultrasound system and the components of the thermal image to provide information about the internal structure of the target.

  The data processing and control system 232 may be a single processing device or a plurality of processing devices. Such processing units include microprocessors, microcontrollers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, and / or Or any device that processes signals (analog and / or digital) based on operational instructions stored in memory. The memory may be a single storage device or a plurality of storage devices. Such storage devices may be read only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and / or any digital information storage It may be a device. Operational instructions corresponding to at least some of the steps and / or functions to be described will be stored in the memory and executed by the data processing and control system 232.

  FIG. 3 shows a block diagram or functional diagram of a laser ultrasound and IR image processing system 300 according to embodiments of the present invention. The laser ultrasound and IR image processing system 300 includes a generation laser 302, a control module 304, a laser ultrasound detection system 306, a thermal image processing system 308, a processing module 310, and an optical system 312. The generation laser 302 generates a generation laser beam that is directed by the optical system 312 to a target 314 made of a material such as, but not limited to, a composite material, as described above. Is induced. The laser ultrasonic detection system 306 generates a detection laser beam that is directed to the target 314 by the optical system 312 and the detection laser beam is phase modulated by ultrasonic displacement at the surface of the target 314. . The detection laser beam is scattered at the surface of the target. The optical system 312 also collects the scattered phase modulated light. The laser ultrasound detection system 306 processes the collected phase-modulated light to generate a signal that includes information about the ultrasonic displacement. This signal is supplied to the processing module 310.

  Generation laser 302 also generates a thermal transient for thermographic measurement of target 314. A thermal image processing system 308, such as an IR camera, acquires thermal images or frames of thermal transients within the target 314. An image is acquired for each generated laser pulse. Additional images may be acquired a predetermined number of times after each generated pulse. These various images are processed to realize a thermographic inspection of the entire area to be inspected by laser ultrasound.

  The results from thermography complement the results of laser ultrasound, thus achieving a more complete and more reliable inspection. Transient IR thermography alone does not provide efficient inspection of composite parts such as polymer matrix composites. Transient IR thermography is sensitive only to the top surface of the composite part because of the low thermal conductivity of the top surface on the polymer matrix. Thus, IR thermography cannot be used to detect and identify deep defects in polymer matrix parts or composite parts.

  Laser ultrasound and IR image processing system 300 incorporates both laser ultrasound to provide a deep interior inspection system and thermal imaging to inspect near the surface of target 314. This addresses the problems associated with the fact that laser ultrasonic inspection may be less sensitive to defects near the surface. The combination of these two techniques allows for a more complete non-destructive inspection of the composite part or material than when using only laser ultrasound or IR thermography.

  FIG. 4 shows the processing of the IR image to collect information about the internal structure of the target 314. Thermal images may be collected every time or after a predetermined time after the generated laser beam is fired. When the generated laser beam is fired or pulsed toward the target 314A, the generated laser beam will be scanned along the scan path 316. Each point 318 where the generated laser beam is directed will have a thermal transient 320. Target 314N shows a scan of path 316 by repeatedly irradiating target 314 with the generated laser beam and collecting numerous thermal images. These thermal transients may be used to determine the thermal properties associated with the target material. For example, the quantitative thermal wall thickness may be determined by analyzing a thermal image at the target over time. This may be presented in the form of a composite visual image, as shown in FIG. This processing technique analyzes infrared images (more specifically, temperature changes as a function of time in different images). The relative temperature change curve is composed of all OR images at each point of the IR camera.

  In other examples, a scanning IR thermography technique may be provided to inspect the material for backside defects. This can limit the target peak heat load in that only a small portion of the target is heated at any point in time. Such a system uses a scanning laser to induce a thermal transient.

  FIG. 5 shows the infrared results obtained by scanning a pulsed CO2 laser beam over a polymer plate with a flat bottom hole. Defects in the target 502 are clearly visible in the gray scale image SOV. Image 500 includes various points 504 in material 502. This image may be generated using an image processing method, such as the method described in US Pat. No. 6,367,969, entitled “Synthetic reference thermal imaging method,” which is incorporated by reference for all purposes. . IR transient thermography analysis techniques may be used to accurately measure the thickness of the target and provide a visually encoded display that represents the thickness of its cross section over the desired area of the target.

  Basically, the use of IR transient thermography at the inflection point in the temperature-time (Tt) response analysis of the surface of a rapidly heated target can be obtained from observation of a “front” IR camera. preferable. This inflection point occurs relatively early in the Tt response and is essentially independent of the lateral heat loss mechanism. (Such considerations can be particularly important when dealing with metals, for example. Due to the high thermal conductivity of metals, the thermal response of metal targets is rather rapid and can therefore be used to obtain measurements of thermal data. Because time is usually short). Inflection points are extracted from thermal data acquired over a predetermined period from successive IR camera image frames. This period is preferably at least somewhat longer than the expected characteristic time based on an estimate of the target thickness being evaluated.

  Thermal reference data is calculated for each (x, y) pixel location of the imaged target and then used to determine the contrast as a function of time for each pixel. The computer system controls the image processing system, records and analyzes the surface temperature data acquired using the IR camera, and produces an image with a unified color or gray pattern that accurately corresponds to the target thickness. Generate. This information may be combined with laser ultrasound data to generate a more detailed internal image of the target.

  Acquisition of surface temperature data is initiated by firing a generated laser to irradiate and heat a portion of the target surface. A thermal image frame is then recorded over a period of time after each generated laser pulse and using the recorded image, temperature-time (T-t), such as the history associated with thermal transient 320 in FIG. Create a history of.

  A T-t history heat flow analysis is then performed on each pixel in the acquired image frame to determine the thickness of the target at each resolving element location. Typically, the analysis of transient heat flow through the solid portion of a target is the property required for a “pulse” of thermal energy to penetrate the target at the first surface, reflect off the opposite surface, and return to the first surface. It is necessary to determine the time. Since this characteristic time is related to the distance between the two surfaces, it can be used to determine the thickness of the target between the two surfaces at the desired point. A contrast versus time curve is determined for each (x, y) pixel location corresponding to each decomposition element on the target surface.

  FIG. 6 shows a logic flow diagram illustrating a method for inspecting materials, such as but not limited to composite materials, according to embodiments of the present invention. Process 600 applies both laser ultrasound techniques and thermal imaging techniques or infrared thermography techniques to inspect and test the internal structure of the material being tested. Process 600 begins at step 602, where ultrasonic displacement and thermal transients are induced in the target material. Both of these may be done using a generated laser beam in conjunction with a laser ultrasound system. As previously described with reference to FIGS. 1-4, this generated laser beam generates both ultrasonic displacement and thermal transients when directed to the surface of the target material. At step 604, ultrasonic displacement and thermal transients are detected. The ultrasonic displacement may be detected using an ultrasonic system such as, but not limited to, a laser ultrasonic system. Thermal transients may be detected by acquiring a thermal image of the target material. As described above, thermal transients and ultrasound generation may be synchronized or correlated. This information may be used to match the results of each analysis performed in step 606. At step 606, the detected ultrasonic displacement and thermal image are analyzed. The detected ultrasonic displacement will provide information about structures deep inside the target material, but thermal transient thermal images may be processed to determine structures near the surface in the target material. Since ultrasonic displacement and thermal transients are initiated by the same generated laser beam, this information may be used to facilitate correlation of detected ultrasonic displacement and thermal images. This allows a detailed and complex understanding at step 608 of both near-surface and deep-in-structure structures of the target material.

  Partial correlation may be obtained by adding a time stamp to the acquired thermal image. Similarly, the thermal image processing acquisition frame rate may be matched to the pulse rate of the generated laser beam. Thermography makes it possible to determine a composite image for other representations of the target material. This may require determining the quantitative thermal thickness obtained by analyzing the thermal image. A quantitative thermal wall thickness change may indicate defects near the surface in the target material at the point where an unexpected change in the quantitative thermal wall thickness occurs. This information may be visualized with a contrast display where a sharp change in contrast indicates a quantitative thermal wall thickness discontinuity or change.

  The generated laser beam may be a Mid-IR ultrasound generated laser. Such a generated laser realizes a compact, high average power Mid-IR laser for generating ultrasonic and thermal transients. As shown in FIG. 7, the generation laser 700 includes a pump laser head 702 having a fiber laser therein, and the fiber is coupled to the generation laser head 704. By using a fiber laser, the laser pump can be located remotely from the production laser head 704. The pump laser head may be coupled to the production laser head 704 via an optical fiber 702.

  By placing the pump laser head 702 a few meters away from the production laser beam delivery head 704, the overall payload and the robot used to deliver the production laser beam and acquire thermal images. A compact Mid-IR generated laser head is possible that reduces the stability requirements on the system. Only the compact and lightweight module, including the production laser beam delivery head and the IR camera, needs to be installed in the inspection head of the robot system. This makes it possible to introduce a Mid-IR laser light source using a smaller robot. Thus, a new combined inspection opportunity is created for in-field combined NDA using portable laser ultrasound systems and IR thermography systems. These approaches are discussed in US Patent Application No. 1 entitled “FIBER LASER TO GENERATE ULTRASOUND” and are incorporated herein by reference for all purposes.

  In summary, each embodiment of the present invention provides an inspection system that can be operated to inspect the internal structure of a target material. The inspection system includes a generation laser, an ultrasonic detection system, a thermal image processing system, and a processor / control module. The generating laser generates a pulsed laser beam that can be operated to induce ultrasonic displacement and thermal transients in the target material. The ultrasonic detection system detects an ultrasonic surface displacement in the target material. The thermal imaging system detects thermal transients in the target material. The processor analyzes both the detected ultrasonic displacement and the thermal image at the target material to provide information about the internal structure of the target material.

  As will be appreciated by those skilled in the art, the terms “substantially” or “approximately” are accepted by the industry for their corresponding terms as may be used herein. Degrees. As such, industry-accepted tolerances range from less than 1 percent to 20 percent, including component numbers, integrated circuit process variations, temperature variations, rise and fall times, and / or heat. Corresponds to noise, but is not limited to it. As will be further understood by one of ordinary skill in the art, the term “operably coupled” as used herein may be a direct coupling and other components, elements, circuits, or Includes indirect coupling through modules, where an intervening component, element, circuit, or module does not change signal information and adjusts its current level, voltage level, and / or power level There are things to do. As will also be appreciated by those skilled in the art, inferred coupling (ie, one element is inferred by another element) is equivalent to 2 being “operably coupled”. Includes direct and indirect coupling between two elements. As will be further understood by one skilled in the art, the term “advantageously compared” is used by comparing between two or more elements, items, signals, etc., as may be used herein. To provide the desired relationship. For example, when the desired relationship is that the amplitude of signal 1 is greater than that of signal 2, the amplitude of signal 1 is greater than the amplitude of signal 2, or the amplitude of signal 2 is less than the amplitude of signal 1. An advantageous comparison may be performed.

  Having described the invention in detail, it should be understood that various changes, substitutions, and modifications can be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims. I want you to understand.

Claims (25)

A method for inspecting a target,
Generating a generated laser beam that is operable to induce ultrasonic displacement and thermal transients at the target;
Directing the generated laser beam to a surface of the target, the generated laser beam generating ultrasonic displacement and the thermal transient at the target;
Detecting the ultrasonic displacement and the thermal transient at the target;
Analyzing both the ultrasonic displacement detected at the target and a thermal image of the target to provide information about the target. The target comprises a composite material;
By analyzing the detected ultrasonic displacement, it provides information about the structure deep inside the composite material,
The method of claim 1, wherein analyzing a thermal image at the target provides information about internal structures near a surface of the composite material.   The method of claim 2, further comprising correlating information about the interior deep structure of the composite material and an internal structure near the surface of the composite material.   The method of claim 1, further comprising correlating the detected ultrasonic displacement with the thermal image.   The method of claim 1, wherein detecting the ultrasonic displacement and the thermal transient at the target further comprises matching thermal imaging with a pulse rate of the generated laser beam.   The method of claim 1, wherein detecting the ultrasonic displacement and the thermal transient at the target further comprises matching a thermal imaging frame rate with a pulse rate of the generated laser beam.   The method of claim 1, wherein the field of view of the thermal image includes a scan plane of the generated laser beam.   The method of claim 1, wherein the quantitative thermal wall thickness is determined by analyzing a thermal image at the target.   9. The method of claim 8, wherein an unexpected change in the quantitative thermal wall thickness indicates a defect in the unexpected change in the target.   The method of claim 1, wherein analyzing a thermal image at the target comprises infrared (IR) transient thermography. Generating a detection laser beam;
Directing the detection laser beam to the surface of the target;
Scattering the detection laser beam at the surface of the target to generate light phase modulated by ultrasonic surface displacement;
Condensing the phase modulated light;
Processing the phase modulated light to obtain data representing the ultrasonic surface displacement at the surface;
Collecting the data with the information and analyzing the structure in the target. An inspection system operable to inspect the internal structure of the target,
A generating laser operable to generate a pulsed laser beam operable to induce ultrasonic displacement and thermal transients in the target;
An ultrasonic detection system operable to detect the ultrasonic surface displacement at the target;
A thermal imaging system operable to detect the thermal transient at the target;
An inspection system comprising: a processor operable to analyze both the ultrasonic displacement detected at the target and a thermal image of the target to provide information about the internal structure of the target. The ultrasonic detection system includes:
A detection laser operable to generate a detection laser beam operable to irradiate the ultrasonic surface displacement at the target;
A condensing optical device for condensing the phase-modulated light by ultrasonic surface displacement from the detection laser beam scattered on the target surface;
An interferometer that processes the phase-modulated light and generates at least one output signal;
The inspection system according to claim 12, further comprising: a processing unit that processes the at least one output signal to obtain data representing the ultrasonic surface displacement at the target.   The inspection system of claim 12, wherein the thermal image processing system comprises an infrared (IR) transient thermography system.   The inspection system of claim 14, wherein the IR transient thermography system comprises an IR sensitive camera operable to acquire an image frame of the target illuminated by the generated laser beam.   The target image frame includes an array of pixels and is assigned a frame number corresponding to an elapsed time, and the quantitative thermal wall thickness is determined by analyzing sequential frames of the thermal image. Item 16. The inspection system according to Item 15.   The inspection system according to claim 15, wherein the processing unit correlates the detected ultrasonic displacement and the thermal image.   16. The inspection system of claim 15, further comprising a control module operable to match a thermal imaging frame acquisition with a pulse rate of the generated laser beam. The target comprises a composite material;
The processing unit is
Analyzing the detected ultrasonic displacement to provide information about the structure deep inside the composite material;
Analyzing thermal images at the target to provide information about internal structures near the surface of the composite material;
16. The inspection system of claim 15, wherein the inspection system correlates information about the deep interior structure of the composite material and the internal structure near the surface of the composite material. A generating laser capable of operating to generate a pulsed laser beam capable of operating to induce ultrasonic displacement and thermal transients in the composite material;
An ultrasonic detection system operable to detect the ultrasonic surface displacement in the composite material;
A thermal imaging system operable to detect the thermal transient in the composite material;
A control module operable to match a thermal imaging frame acquisition with a pulse rate of the generated laser beam;
A large area composite inspection comprising a processor operable to analyze both the ultrasonic displacement detected in the composite material and a thermal image of the target to provide information about the internal structure of the target. system. The processing unit is
Analyzing the detected ultrasonic displacement to provide information about the structure deep inside the composite material;
Analyzing thermal images at the target to provide information about internal structures near the surface of the composite material;
21. The inspection system of claim 20, wherein information about the deep structure inside the composite material and information about the internal structure near the surface of the composite material is correlated. The ultrasonic detection system includes:
A detection laser operable to generate a detection laser beam operable to irradiate the ultrasonic surface displacement at the target;
A condensing optical device for condensing the phase-modulated light by ultrasonic surface displacement from the detection laser beam scattered on the target surface;
An interferometer that processes the phase-modulated light and generates at least one output signal;
21. The inspection system of claim 20, comprising a processing unit that processes the at least one output signal to obtain data representative of the ultrasonic surface displacement at the target.   21. The inspection system of claim 20, wherein the thermal image processing system comprises an infrared (IR) transient thermography system.   24. The inspection system of claim 23, wherein the IR transient thermography system comprises an IR sensitive camera operable to acquire an image frame of the target illuminated by the generated laser beam.   21. The image frame includes an array of pixels, assigned a frame number corresponding to an elapsed time, and the quantitative thermal wall thickness is determined by analyzing sequential frames of the thermal image. The inspection system described.

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