Shear-speckle method for non-destructive inspection of sub-micron substrates

Abstract

Shear speckle for non-destructive inspection of sub-micron substrates. Methods and systems for performing dynamic shear speckle inspection are provided. The dynamic shear speckle method allows for non-destructive inspection of layered materials, particularly those including porous materials. The method uses a load profile that increases and decreases the load in a sawtooth fashion, for example, without reducing the load back to the initial loading state, typically zero loading. Using the load profile in this manner constantly refreshes the reference speckle image to minimize background noise and allows defects to be distinguished from noise.

Description

[0001] This application is a divisional application of the original invention patent application No. 201810636373.6 (filed on June 20, 2018, invention title: Shear speckle technique for non-destructive inspection of submicroporous substrates). Technical Field

[0002] This disclosure generally relates to methods and systems for non-destructive inspection. Background Technology

[0003] Shear speckle is a non-destructive inspection method used to detect surface deformation. It works by irradiating the surface of the test object with a laser. An image of the irradiated surface is captured and sheared to generate an interference or "speckle" pattern. Then, while subjecting the surface of the test object to a small load, such as from a vacuum, vibration, or heat, another speckle pattern is captured. Because shear speckle detects out-of-plane deformation, it is particularly useful for inspecting defects beneath the surface of layered materials, such as delamination. Figure 1A A layered material 100 is depicted, consisting of three layers 110, 120, and 130. A delamination 165 exists between layers 110 and 120. Furthermore, another delamination 175 exists between layers 120 and 130. When no load is applied to the top surface 101 of the layered material 100, there is little or no out-of-plane deformation. Conversely, Figure 1B The out-of-plane deformations 185 and 195 corresponding to peeling 165 and 175 are depicted respectively when the top surface 101 of the layered material 100 is subjected to vacuum, heat, or mechanical loading. Figure 1C As shown in the shear speckle image 199, the method detects out-of-plane deformation caused by peeling 165 and 175 by subtracting the speckle pattern of the top surface 101 of the layered material 100 in the unloaded state from the speckle pattern of the top surface 101 in the loaded state.

[0004] Materials used in the interiors of aircraft and other vehicles face stringent performance requirements, including high strength-to-weight ratio, mechanical strength, and dimensional stability. Low heat, smoke, and toxin release in fire conditions are also desirable. To meet these requirements, layered composite materials, such as multilayer laminates, are typically used. Figure 1D The illustration shows composite materials with layered structures (for example, such as...). Figure 1A An exemplary vehicle, aircraft 150, is shown inside (as illustrated). In this case, layer 110 represents a common material used for visible surfaces of aircraft interiors, known as decorative laminates or "declams." Declams typically comprise one or more polymer layers and one or more adhesive layers. Declams typically reside on panel skins, such as... Figure 1A Layer 120 is formed of one or more prepreg adhesive layers. The panel skin then resides on the honeycomb core, for example... Figure 1A On layer 130. Inspecting defects in delaminated composite materials (such as areas covered by declam) during aircraft production and while the aircraft is in service presents challenges, including access only to visible surfaces, extensive surface inspection, and desirable non-destructive methods.

[0005] To date, due to the porous nature of honeycomb cores, the success rate of using shear speckle to inspect areas covered by declamps has been limited. Because defects can be the same size as or smaller than pores, conventional methods for shear speckle inspection suffer from the inability to distinguish defects from noise (e.g., discorrelation noise or "D-noise") caused by the porous material. Therefore, there is an industrial need to address these shortcomings and deficiencies. Summary of the Invention

[0006] According to this teaching, a shear speckle inspection method for detecting defects is provided. The method includes the following steps: illuminating a top surface of a test piece with coherent light and capturing a first shear speckle image including a first speckle pattern while applying a zero vacuum pressure to the top surface; applying a first vacuum pressure to the top surface and capturing a second shear speckle image during the application of the first vacuum pressure to the top surface; the second shear speckle image including a second speckle pattern; then using the first speckle pattern and the second speckle pattern to determine the presence of a defect; then reducing the vacuum pressure at the top surface and applying a second vacuum pressure to the top surface, wherein the second vacuum pressure is less than the first vacuum pressure but greater than the zero vacuum pressure. According to this teaching, a shear speckle inspection method is provided, which may further include a third shear speckle image that can be captured during the application of the second vacuum pressure to the top surface, wherein the third shear speckle image includes a third speckle pattern. The vacuum pressure at the top surface may be increased and a third vacuum pressure may be applied to the top surface, wherein the third vacuum pressure is greater than the first vacuum pressure. A fourth shear speckle image may be captured during the application of the third vacuum pressure. The fourth shear speckle image includes a fourth speckle pattern. The presence of defects in the test specimen can be determined using the third and fourth speckle patterns.

[0007] According to this teaching, a non-destructive method for detecting defects in multilayer laminates is provided. In this method, the top surface of the multilayer laminate is illuminated with coherent light. Then, a first reference spot image of the top surface of the multilayer laminate is acquired, wherein the top surface is subjected to a first vacuum pressure, and the first vacuum pressure is 0 or greater during the acquisition of the first reference spot image. While capturing a first test spot image of the top surface, a second vacuum pressure is applied to the top surface, wherein the second vacuum pressure is greater than the first vacuum pressure. Next, the vacuum pressure at the top surface is reduced to a third vacuum pressure, wherein the third vacuum pressure is less than the second vacuum pressure but greater than the first vacuum pressure. While applying the third vacuum pressure to the top surface, a second reference spot image of the top surface is acquired. Next, the vacuum pressure at the top surface is increased to a fourth vacuum pressure, wherein the fourth vacuum pressure is greater than the second vacuum pressure. While applying the fourth vacuum pressure to the top surface, a second test spot image of the top surface is acquired. Then, the second reference spot image and the second test spot image are used to determine whether a defect exists in the multilayer laminate.

[0008] According to this teaching, a shear speckle inspection system is provided. The system includes: a coherent light source configured to provide a coherent light beam; one or more optical components for extending the coherent light beam and guiding the extended coherent light beam to illuminate a top surface of a test specimen; a shear speckle camera for capturing a speckle image of the illuminated top surface of the test specimen; and a loading system configured to increase and decrease the load on the top surface of the test specimen. The shear speckle inspection system also includes an image manipulation system for manipulating the speckle image of the illuminated top surface of the test specimen.

[0009] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the scope of this disclosure as claimed. Attached Figure Description

[0010] The accompanying drawings, which are included and form part of this specification, illustrate the present disclosure and, together with the description, serve to explain the principles of the disclosure.

[0011] Figure 1A and Figure 1B Delamination composite materials with defects under loading and unloading conditions are depicted;

[0012] Figure 1C A speckle pattern illustrating out-of-plane deformation produced by shear speckle examination is schematically depicted;

[0013] Figure 1DThe aircraft depicted includes an interior with layered composite materials;

[0014] Figure 2 An exemplary shear speckle examination system according to this disclosure is described;

[0015] Figure 3 An exemplary shear speckle examination method according to this disclosure is described;

[0016] Figure 4 An exemplary shear speckle examination method according to this disclosure, in which vacuum pressure and laser are applied simultaneously, is described. Detailed Implementation

[0017] The exemplary implementations of this disclosure are described in detail below, with embodiments illustrated in the accompanying drawings. Where possible, the same reference numerals are used throughout the drawings to refer to the same or similar components. In the following description, the accompanying drawings, which form a part of this description, are illustrated, and specific exemplary implementations of this disclosure are shown by way of illustration. These implementations are described in sufficient detail to enable those skilled in the art to practice this disclosure, and it is to be understood that other implementations may be utilized, and changes may be made without departing from the scope of this disclosure. Therefore, the following description is merely exemplary.

[0018] The present disclosure addresses the need for methods for non-destructive inspection of layered materials, specifically those including porous material layers. The disclosed dynamic shear speckle method utilizes a load distribution map to continuously refresh a reference image to minimize background noise. In this method, the load can be increased and decreased, for example, in a sawtooth pattern, without reducing the load back to its initial load state, typically zero. This allows defects to be distinguished from decorrelation noise, such as decorrelation noise generated by one or more porous layers of the layered material. Detectable defects include, but are not limited to, disintegration, peeling, cracks, and impact damage. The disclosed dynamic shear speckle method can be used without knowing the approximate location of the defect. Furthermore, the disclosed method can be advantageously automated. Although the examples below provide a method for detecting defects that overcomes decorrelation noise caused by porous layers, those skilled in the art will understand after reading this disclosure that this exemplary method can be used on materials without porous layers and on non-layered materials.

[0019] Figure 2An exemplary shear speckle inspection system 200 is illustrated. The shear speckle inspection system 200 may include a coherent light source 210, such as a laser or any other source providing a coherent beam 211. As used herein, the term coherent light or coherent beam refers to light having the same wavelength and phase, typically originating from a point source such as a laser. The system 200 also includes a beam expander 220 or other optical components that can expand and direct the coherent beam 211 toward the test piece 260 for inspection. A shear speckle camera 230 captures an image of the speckle pattern on the illuminated top surface 261. The term “speckle pattern” is used interchangeably herein with the term “speckle image,” which is embedded in the shear speckle image.

[0020] Those skilled in the art will understand that the shear speckle camera 230 may include a charge-coupled device (“CCD”) image sensor, lenses and / or other optical components, and an image cropping device. The image cropping device may, for example, be a prism and a polarizer to generate a pair of laterally displaced (“sheared”) images. The shear speckle camera provides several functions. It receives an image reflected from a test object and uses a prism to generate a pair of non-parallel images of laterally displaced objects scattered from two nearly collinear, different object points. The polarizer allows the two cropped images to interfere with each other to produce the speckle pattern in the shear speckle image. The shear speckle camera 230 also uses a CCD sensor to capture the shear speckle image, including the embedded speckle pattern. An example of the shear speckle camera 230 includes the digital shear speckle camera model VH-5200VG manufactured by Laser Technology, Inc. (Norristown, PA).

[0021] The shear speckle inspection system 200 may also include a computer 240 with an image manipulation system (e.g., software for manipulating the captured images). Examples of imaging software include NI Vision from National Instruments (Austin, TX) and Imaging Processing Toolbox from Mathworks (Natick, MA). Those skilled in the art will understand that system 200 may include other components. For example, beam splitters, lenses, mirrors, and other optical components may be used to expand, guide, and converge coherent light, and other software / devices may be used to capture, manipulate, and display speckle patterns and shear speckle images.

[0022] The exemplary shear speckle inspection system 200 may also include a loading system for loading a test specimen. This loading system or loading assembly may utilize pressure, heat, and / or mechanical loads to load the test specimen. It should be understood that different loading systems may be used for specific inspection situations. The type of loading and the loading system selected may depend on many factors, including the composition of the test specimen, the size of the defects, and the size of the area to be inspected. For example, in some cases, a vacuum system may be advantageous for inspecting porous composite materials, while thermal or acoustic loads may be used for inspecting non-porous composite materials. Figure 2 An exemplary vacuum system 250 is depicted that encloses a portion of test specimen 260. In an exemplary embodiment, vacuum system 250 may enclose some or all of the other components of a shear speckle inspection system. Vacuum system 250 may apply a vacuum to test specimen 260 to provide loading and unloading conditions. For example, vacuum system 250 may apply a series of vacuum pressures at a fast cycle rate (e.g., 60 Hz or higher).

[0023] Generally, the shear speckle inspection system 200 operates as follows. A coherent light source 210 (e.g., a laser) provides a coherent beam 211 expanded by a beam expander 220. The expanded coherent light 221 exits from the beam expander 220 and is guided to illuminate the top surface 261 of the portion of the test piece 260 enclosed within a vacuum system 250. The test piece 260 is also referred to herein as a workpiece or test object. The test piece 260 can be any material formed of one or more layers. Examples include, but are not limited to, multilayer tires, decorative laminates, foam insulation materials, and thermal protection systems (TPS). The illuminated top surface 261 can be imaged by a shear speckle camera 230. The resulting speckle image can be used as a reference speckle image. Once the reference speckle image is captured, the vacuum system 250 can apply a vacuum to the top surface 261 of the test piece 260. A test speckle image can be captured by the shear speckle camera 230. A computer 240 with imaging software can then compare the reference speckle image with the test speckle image. The presence of a defect can then be determined by comparing the test blob image with a reference blob image. For example, the reference blob image can be subtracted from the test blob image, and the operator / technician can then review the subtracted image to determine if a defect is present. Additionally, these images can be further processed, such as filtered before being reviewed by the operator / technician to make defects more easily distinguishable. In other exemplary embodiments, the operator / technician's judgment can be eliminated by using defect identification software to determine the presence of a defect.

[0024] Figure 3An exemplary dynamic shear speckle method 300 for inspecting composite layered materials according to this disclosure is illustrated, wherein the vacuum pressure can be increased and decreased in a sawtooth pattern (e.g., a linearly increasing sawtooth pattern). As can be seen from the figures, increasing the vacuum pressure refers to a higher vacuum pressure than the vacuum pressure used to capture the previous speckle image. Similarly, decreasing the vacuum pressure refers to a lower vacuum pressure than the vacuum pressure used to capture the previous speckle image. Figure 3 A method 300 is described for applying vacuum pressure at a reference time during inspection. At 310, no vacuum is applied, and therefore no load is applied to the top surface of the test piece. This is also referred to herein as a zero-load state. The zero-load state can be, for example, atmospheric pressure, such as the ambient pressure at sea level or atmospheric pressure. A first reference spot image of the top surface of the test piece is captured in this state. A vacuum is then applied to the test piece, and at 320, a first test spot image is captured under a first vacuum pressure. At this point, a computer can compare the first reference spot image with the first test spot image to determine if a defect is present. Those skilled in the art will understand that a non-automated process can also be applied, in which an operator can review the first reference spot image subtracted from the first test spot image and determine if a defect is present.

[0025] As shown at 330, the vacuum pressure can be reduced to a second vacuum pressure. This second vacuum pressure can be a fraction of the first vacuum pressure, such as half (1 / 2), one-third (1 / 3), one-quarter (1 / 4), etc., but should be a higher vacuum pressure than the initial state (e.g., zero vacuum pressure) and lower than the first vacuum pressure. This fraction should be less than 1. A second reference spot image can then be captured under the second vacuum pressure.

[0026] At 340, the vacuum pressure can then be increased to a third vacuum pressure greater than the first. A second test spot image of the top surface of the test piece can be captured under this third vacuum pressure. A computer or operator can then use the second reference spot image and the second test spot image to determine if a defect is present. If a defect is detected, the test can be stopped and the inspection completed.

[0027] If no defect is detected and inspection is not completed, the vacuum pressure can be reduced to a fourth vacuum pressure, as shown at 350. The fourth vacuum pressure at 350 can be a fraction of the third vacuum pressure at 340, such as half, one-third, one-quarter, etc., but greater than zero vacuum pressure. In some exemplary methods, it can be the same fraction as the second vacuum pressure being a fraction of the first vacuum pressure. In other words, if the second vacuum pressure is half of the first vacuum pressure, then the fourth vacuum pressure can be half of the third vacuum pressure. In other embodiments, the second vacuum pressure can be an increment between the initial state (no load) and the first vacuum pressure. The fourth vacuum pressure can be the same increment between the second and third vacuum pressures. For example, if the second vacuum pressure is the midpoint between the initial no-load state and the first vacuum pressure, then the fourth vacuum pressure can be the midpoint between the second and third vacuum pressures. A third reference spot image can then be captured at the fourth vacuum pressure.

[0028] The vacuum pressure can then be increased to a fifth vacuum pressure at 360°. This fifth vacuum pressure at 360° is greater than the third vacuum pressure. A third test spot image can be captured on the top surface of the test piece. A computer or operator can then use the third reference spot image and the third test spot image to determine if a defect is present. If a defect is detected, the test can be stopped.

[0029] If no defects are detected, the vacuum pressure can be repeatedly increased and decreased in the manner described herein, and reference and test spot images can be captured. For example, this exemplary method 300 can continue until the highest vacuum pressure reaches approximately 5 psi. This exemplary method 300 can continue until defects in the captured spot images can be distinguished from D noise. It is to be understood that... Figure 3 Time is described in a relative way, not in absolute terms. Although in Figure 3 The vacuum pressure is depicted as a point, but the vacuum pressure at 330 and 350 can remain stable for a period of time, thus allowing for the acquisition of reference images. Similarly, the vacuum pressure at 320, 330, and 360 can remain stable for a period of time, thus allowing for the acquisition of test images and the identification of defects before the end or continuation of inspection. In other words, the vacuum pressure can be increased and decreased without reducing it back to its initial state (e.g., atmospheric pressure or ambient pressure); however, the vacuum pressure can remain stable for a period of time, thus allowing for the acquisition of reference images, for example, at... Figure 3 The peak values ​​at 320, 340, and 360 and the valley values ​​at 330 and 350 were used to obtain the blob image.

[0030] Alternatively, the dynamic shear speckle test can begin at 310°, with an initial load applied to the top surface of the test piece. In this case, the initial load represents a vacuum pressure that will not fall below a certain threshold. For example, as... Figure 3 As shown, during the inspection, the vacuum pressure at 320, 330, 340, 350, and 360 will never be equal to or lower than the initial vacuum pressure at 310. Because the vacuum pressure never drops back to zero or below the vacuum pressure when the first reference image was captured at 310, the reference spot image is constantly refreshed to minimize D-noise.

[0031] The disclosed dynamic shear speckle imaging method allows for the detection of defects, particularly in layered composite materials including microporous foam layers. As disclosed herein, the applied load (e.g., vacuum pressure) is increased and decreased without returning to zero or the initial loading state. Under a first increase in load, for example at 320°, the pores in the microporous layer expand as much as the defects. If the signal from the expanding pores (e.g., D noise) masks the signal from the expanding defects, then the defects may not be detected. When the load is decreased to obtain another reference image, for example at 330° and 350°, the expansion of pores and defects decreases, but never returns to their initial unexpanded state. As the load is further increased, for example at 340° and 360°, eventually the pores will no longer expand further, while the defects continue to expand. At this point, the signal from the defects overcomes the noise from the pores, and thus the comparison between the test image and the reference image reveals the defects.

[0032] Figure 4 The diagram depicts the simultaneous application of vacuum pressure and laser irradiation of a test specimen in a dynamic shear speckle method 300. By synchronizing one or both of the vacuum pressure and the laser, noise can be reduced or even eliminated, allowing for more accurate defect detection. At 410, the test specimen is placed in the vacuum system such that a portion of its top surface is within the vacuum system, and inspection begins. At 420, the laser is switched on and irradiates said portion of the top surface of the test specimen. At 422, a first reference image is captured.

[0033] At 424, a first vacuum pressure is applied, and at 426, a first test image is captured. Then, at 428, the laser is disconnected. A computer with imaging software uses the first test image and the first reference image to determine whether a defect has been detected, as shown at 430. If a defect is detected, the inspection may optionally be stopped at 435.

[0034] If no defect is detected, at 440, inspection can continue by turning on the laser. Then at 442, the vacuum pressure can be reduced to a fraction of the first vacuum pressure, but still greater than zero vacuum pressure. In other examples, the vacuum pressure can be reduced to the incremental pressure between the initial state and the first vacuum pressure, for example, the midpoint between the two pressures. At 444, a second reference image is captured.

[0035] At 446, the vacuum pressure is increased to a second vacuum pressure higher than the first vacuum pressure. At 448, a second test image is captured, and then at 450, the laser is disconnected. A computer with imaging software then uses the second test image and the second reference image to determine if a defect has been detected, as shown at 450. If a defect is detected, the inspection can optionally be stopped at 455.

[0036] If no defect is detected, at 460, inspection can continue by turning on the laser. Then at 462, the vacuum pressure can be reduced to a fraction of the second vacuum pressure, but still greater than zero vacuum pressure. In other examples, the pressure can be reduced by the same amount as at 442; for example, the vacuum pressure can be reduced to the midpoint between the second vacuum pressure and the reduced vacuum pressure at 442. At 464, a third reference image is captured.

[0037] At 466, the vacuum pressure is increased to a third vacuum pressure, higher than the second vacuum pressure. At 468, a third test image is captured, and then at 470, the laser is disconnected. A computer with imaging software uses the third test image and a third reference image to determine if a defect is present, as shown at 472. If a defect is detected, the inspection may optionally stop at 475. If no defect is detected, the inspection may continue at 480 by repeating the steps described above: increasing the vacuum pressure and capturing a reference spot image, then reducing the vacuum pressure to a fraction of the previously increased vacuum pressure and capturing a test spot image. These steps may be repeated as needed. For example, the inspection may continue until a defect is detected or until a predetermined endpoint is reached. For inspecting composite materials including microporous foam, the predetermined endpoint may be 5 psi, as vacuum pressures greater than 5 psi can damage the microporous foam.

[0038] Having read this disclosure, those skilled in the art will understand that the inspection can also be stopped after comparing the reference blob image with the test blob image (e.g., at 455, 475) for a variety of reasons. For example, the inspection can be stopped when the applied vacuum pressure reaches a threshold. In the declam example, the inspection can be stopped when the applied vacuum pressure reaches approximately 5 psi. Alternatively, the inspection can be stopped shortly after the D noise plateaus.

[0039] Some or all of the disclosed methods can be advantageously automated. For example, increasing and decreasing vacuum pressure can be accomplished without an operator by utilizing computer-controlled changes in vacuum pressure. This allows inspections to be performed at a faster rate, thus enabling the inspection of larger areas compared to operator-dependent methods. Automation can also include determining the presence of defects by utilizing image processing and pattern recognition software. This avoids the need for trained technicians to perform inspections and increases the consistency of results.

[0040] Furthermore, this disclosure includes examples pursuant to the following provisions:

[0041] 1. A shear speckle inspection method for detecting defects, the method comprising the steps of: irradiating a top surface of a test piece with a coherent light beam; capturing a first shear speckle image including a first speckle pattern, wherein a zero vacuum pressure is applied to the top surface; applying a first vacuum pressure to the top surface; capturing a second shear speckle image including a second speckle pattern while the first vacuum pressure is applied to the top surface; determining the presence of a defect using the first speckle pattern and the second speckle pattern; and reducing the vacuum pressure at the top surface and applying a second vacuum pressure to the top surface, wherein the second vacuum pressure is less than the first vacuum pressure but greater than the zero vacuum pressure.

[0042] 2. The method according to Clause 1, further comprising the steps of: capturing a third shear speckle image including a third speckle pattern while applying the second vacuum pressure to the top surface; increasing the vacuum pressure at the top surface and applying a third vacuum pressure to the top surface, wherein the third vacuum pressure is greater than the first vacuum pressure; capturing a fourth shear speckle image including a fourth speckle pattern while applying the third vacuum pressure; and using the third speckle pattern and the fourth speckle pattern to determine whether a defect exists in the test specimen.

[0043] 3. The method according to Clause 1, wherein, after capturing the first shear speckle image, the vacuum pressure at the top surface of the test piece is maintained greater than zero until the shear speckle examination is completed.

[0044] 4. The method according to Clause 2, further comprising the steps of: synchronizing the source of the coherent beam to disconnect after capturing the second shear speckle image and the fourth shear speckle image, and to reconnect before reducing the vacuum pressure to the second vacuum pressure.

[0045] 5. A non-destructive method for detecting defects in a multilayer laminate, the method comprising the steps of: irradiating a top surface of the multilayer laminate with a coherent light beam; acquiring a first reference spot image of the top surface of the multilayer laminate, wherein the top surface is subjected to a first vacuum pressure, and the first vacuum pressure is zero (0) or greater during the acquisition of the first reference spot image; simultaneously capturing a first test spot image of the top surface and applying a second vacuum pressure to the top surface, wherein the second vacuum pressure is greater than the first vacuum pressure; reducing the vacuum pressure at the top surface to a third vacuum pressure, wherein the third vacuum pressure is less than the second vacuum pressure but greater than the first vacuum pressure; simultaneously applying the third vacuum pressure to the top surface and acquiring a second reference spot image of the top surface; increasing the vacuum pressure at the top surface to a fourth vacuum pressure, wherein the fourth vacuum pressure is greater than the second vacuum pressure; simultaneously applying the fourth vacuum pressure to the top surface and acquiring a second test spot image of the top surface; and using the second reference spot image and the second test spot image to determine whether a defect exists in the multilayer laminate.

[0046] 6. The method according to Clause 5, further comprising the steps of: reducing the vacuum pressure at the top surface to a fifth vacuum pressure, wherein the fifth vacuum pressure is less than the fourth vacuum pressure but greater than the third vacuum pressure; acquiring a third reference spot image of the top surface while applying the fifth vacuum pressure to the top surface; increasing the vacuum pressure at the top surface to a sixth vacuum pressure, wherein the sixth vacuum pressure is greater than the fourth vacuum pressure; acquiring a third test spot image of the top surface while applying the sixth vacuum pressure to the top surface; and using the third reference spot image and the third test spot image to determine whether defects exist between the multilayer laminates.

[0047] 7. The method according to Clause 6, the method further comprising the steps of: synchronizing a coherent light source to disconnect the coherent beam after acquiring the first test spot image and the second test spot image, and to reconnect it after reducing the vacuum pressure to the third vacuum pressure and the fifth vacuum pressure.

[0048] 8. The method according to Clause 5, wherein the multilayer laminate comprises: a decorative laminate; a panel skin bonded to the decorative laminate; and a core bonded to the panel skin, wherein the core comprises honeycomb or microporous foam.

[0049] 9. The method according to Clause 6, wherein the third vacuum pressure and the fifth vacuum pressure are one of 1 / 2, 1 / 3, or 1 / 4 of the second vacuum pressure and the fourth vacuum pressure.

[0050] 10. The method according to Clause 6, wherein the third vacuum pressure is the increment between the first vacuum pressure and the second vacuum pressure, and the fifth vacuum pressure is the increment between the third vacuum pressure and the fourth vacuum pressure.

[0051] 11. The method according to Clause 7, wherein the third vacuum pressure is a fraction of the second vacuum pressure, and the fifth vacuum pressure is a fraction of the fourth vacuum pressure, wherein the fraction is less than 1.

[0052] 12. The method according to any one of clauses 5 to 11, wherein the step of determining the presence of a defect using the second reference spot image and the second test spot image includes the step of subtracting the second reference spot image from the second test spot image.

[0053] 13. The method according to Clause 8, wherein the step of determining the presence of a defect using the second reference spot image and the second test spot image includes the step of determining whether there is a peel between the decorative laminate and the panel skin.

[0054] 14. The method according to Clause 8, wherein the step of determining the presence of a defect using the second reference spot image and the second test spot image includes the step of determining whether there is a peel between the panel skin and the core.

[0055] 15. The method according to any one of clauses 5 to 14, the method further comprising the step of: using the first reference spot image and the first test spot image to determine whether a defect exists in the multilayer laminate.

[0056] 16. The method according to Clause 6, wherein the sixth vacuum pressure is approximately 5 psi.

[0057] 17. A shear speckle inspection system comprising: a coherent light source 210 configured to provide a coherent beam; one or more optical components for amplifying and guiding the amplified coherent beam to illuminate a top surface of a test specimen; a shear speckle camera for capturing speckle images of the illuminated top surface of the test specimen; a loading system 250 configured to increase and decrease the load on the top surface of the test specimen in a linearly increasing sawtooth pattern without returning to a zero-load state; and an image manipulation system for manipulating the speckle images of the illuminated top surface of the test specimen.

[0058] 18. The shear speckle examination system according to Clause 17, wherein the loading system 250 is configured to apply one of a vacuum, heat, or mechanical load.

[0059] 19. The shear speckle examination system according to Clause 17, wherein the loading system 250 is configured to increase and decrease the load at a frequency of 60 Hz or higher.

[0060] 20. A speckle pattern inspection system according to any one of clauses 17 to 19, wherein the image manipulation system is configured to automatically subtract speckle images, visually display the subtracted speckle images, and terminate the inspection based on the determination of a defect.

[0061] While this teaching has been illustrated with reference to one or more implementations, changes and / or modifications may be made to the illustrated embodiments without departing from the spirit and scope of the appended claims. For example, it should be understood that although the process is described as a series of actions or events, this teaching is not limited to the order of these actions or events. Some actions may occur in different order and / or simultaneously with other actions or events besides those described herein. For example, the steps of the method have been described as first, second, third, etc. As used herein, these terms merely refer to a relative order with respect to each other; for example, the first occurs before the second. Moreover, according to one or more aspects or implementations of this teaching, it may not be necessary to implement a methodology with all processing stages. It should be understood that structural components and / or processing stages may be added, or existing structural components and / or processing stages may be removed or modified. Moreover, one or more of the actions described herein may be performed in one or more separate actions and / or stages. Furthermore, with regard to the use of the terms "comprising," "having," "with," or variations thereof in any detailed description and / or claims, such terms are intended to be included in a manner similar to the term "comprising." The term "at least one of" is used to indicate that one or more of the listed items can be selected. As used herein, the term "one or more of" with respect to listed items (e.g., A and B) means A alone, B alone, or A and B. The term "at least one of" is used to indicate that one or more of the listed items can be selected. Moreover, in the discussion and claims herein, the term "on" with respect to the use of two materials, one "above" the other, means that there is at least some contact between the materials, while "above" means that the materials are close together but may have one or more additional intermediary materials, making contact possible but not required. Neither "on" nor "above" implies any directionality as used herein. The term "conformal" describes a coating material in which the angle of the underlying material is preserved by conformal design. The term "approximately" indicates that the listed values ​​may vary slightly, as long as such variation does not cause the treatment or structure to deviate from the illustrated implementation. Finally, "exemplary" indicates that this description is used as an embodiment and not implying that it is ideal. Other implementations of this teaching will be apparent to those skilled in the art based on consideration of the specification and practice of this disclosure herein. This specification and the embodiments are to be regarded as exemplary only, and the true scope and spirit of this teaching are indicated by the appended claims.

[0062] The terms for relative position used in this application are defined based on a plane parallel to the workpiece's conventional plane or working surface, regardless of the workpiece's orientation. The terms "horizontal" or "lateral" as used in this application are based on a plane defined as parallel to the workpiece's conventional plane or working surface, regardless of the workpiece's orientation. The term "vertical" refers to a direction perpendicular to the horizontal. Terms such as "above," "side" (e.g., "sidewall"), "higher," "lower," "above," "top," and "below" are defined relative to a conventional plane or working surface on the top surface of the workpiece, regardless of the workpiece's orientation.

Claims

1. A shear speckle inspection method for detecting defects, the method comprising the following steps: The top surface (261) of the test piece (260) is illuminated by a coherent beam (211). Capture a first shear speckle image including a first speckle pattern, wherein zero vacuum pressure is applied to the top surface; A first vacuum pressure is applied to the top surface; During the application of the first vacuum pressure to the top surface, a second shear speckle image including a second speckle pattern is captured; The presence of defects is determined using the first and second spot patterns. The vacuum pressure at the top surface is reduced and a second vacuum pressure is applied to the top surface, wherein the second vacuum pressure is less than the first vacuum pressure and greater than the zero vacuum pressure; During the application of the second vacuum pressure to the top surface, a third shear speckle image including a third speckle pattern is captured; Increase the vacuum pressure at the top surface and apply a third vacuum pressure to the top surface, wherein the third vacuum pressure is greater than the first vacuum pressure; During the application of the third vacuum pressure, a fourth shear speckle image, including a fourth speckle pattern, is captured; and The presence of defects in the test specimen is determined using the third and fourth spot patterns.

2. The method according to claim 1, wherein, After the first shear speckle image is captured, the vacuum pressure at the top surface (261) of the test piece (260) is maintained at a level greater than zero until the shear speckle examination is completed.

3. The method according to claim 1, further comprising the following steps: The source of the coherent beam (211) is synchronized to be disconnected after capturing the second shear speckle image and the fourth shear speckle image, and turned on before the vacuum pressure is reduced to the second vacuum pressure.

4. A non-destructive method for detecting defects in multilayer laminates, the method comprising the following steps: The top surface (261) (420) of the multilayer laminate is irradiated with a coherent beam (211). Acquire a first reference spot image (422) of the top surface of the multilayer laminate, wherein the top surface is subjected to a first vacuum pressure, and the first vacuum pressure is 0 or greater during the acquisition of the first reference spot image; While capturing a first test spot image (426) of the top surface, a second vacuum pressure is applied to the top surface, wherein the second vacuum pressure is greater than the first vacuum pressure; The vacuum pressure at the top surface is reduced to a third vacuum pressure, wherein the third vacuum pressure is less than the second vacuum pressure and greater than the first vacuum pressure; While applying the third vacuum pressure to the top surface, a second reference spot image (444) of the top surface is acquired. The vacuum pressure at the top surface is increased to a fourth vacuum pressure (446), wherein the fourth vacuum pressure is greater than the second vacuum pressure; While applying the fourth vacuum pressure to the top surface, a second test spot image (448) of the top surface is acquired. The presence of defects in the multilayer laminate is determined using the second reference spot image and the second test spot image (452). The vacuum pressure at the top surface (261) is reduced to a fifth vacuum pressure, wherein the fifth vacuum pressure is less than the fourth vacuum pressure and greater than the third vacuum pressure; While applying the fifth vacuum pressure to the top surface, a third reference spot image (464) of the top surface is acquired. The vacuum pressure at the top surface is increased to a sixth vacuum pressure (466), wherein the sixth vacuum pressure is greater than the fourth vacuum pressure; While applying the sixth vacuum pressure to the top surface, a third test spot image (468) of the top surface is acquired; and The presence of defects between the multilayer laminates is determined using the third reference spot image and the third test spot image (472).

5. The method according to claim 4, further comprising the following step: A synchronous coherent light source (210) is used to disconnect the coherent beam (211) after acquiring the first test spot image and the second test spot image, and to reconnect it after reducing the vacuum pressure to the third vacuum pressure and the fifth vacuum pressure.

6. The method according to claim 4, wherein, The multi-layer laminate includes: Decorative laminate (110); The panel skin (120) is bonded to the decorative laminate; and A core (130) is bonded to the panel skin, wherein the core comprises honeycomb or microporous foam.

7. The method according to claim 4, wherein, The third vacuum pressure and the fifth vacuum pressure are one of 1 / 2, 1 / 3, or 1 / 4 of the second vacuum pressure and the fourth vacuum pressure.

8. The method according to claim 4, wherein, The third vacuum pressure is the increment between the first vacuum pressure and the second vacuum pressure, while the fifth vacuum pressure is the increment between the third vacuum pressure and the fourth vacuum pressure.

9. The method according to claim 5, wherein, The third vacuum pressure is a fraction of the second vacuum pressure, and the fifth vacuum pressure is a fraction of the fourth vacuum pressure, wherein the fraction is less than 1.

10. The method according to any one of claims 4 to 9, wherein, The step of determining the presence of a defect using the second reference spot image and the second test spot image includes the following steps: subtracting the second reference spot image from the second test spot image.

11. The method according to claim 6, wherein, The step of determining the presence of defects using the second reference spot image and the second test spot image includes the following steps: determining whether there is a peel (165) between the decorative laminate (110) and the panel skin (120).

12. The method according to claim 6, wherein, The step of determining whether a defect exists using the second reference spot image and the second test spot image includes the following steps: determining whether there is a peel (175) between the panel skin (120) and the core (130).

13. The method according to any one of claims 4 to 9, the method further comprising the step of: The presence of defects in the multilayer laminate is determined using the first reference spot image and the first test spot image.

14. The method according to claim 4, wherein, The sixth vacuum pressure is approximately 5 psi.

15. A shear speckle examination system (200), the shear speckle examination system comprising: A coherent light source (210) is configured to provide a coherent beam (211). One or more optical components (220) are used to extend the coherent beam and guide the extended coherent beam to illuminate the top surface (261) of the test piece (260). A shear speckle camera (230) is used to capture speckle images of the irradiated top surface of the test specimen; A loading system (250) configured to increase and decrease the load on the top surface of the test piece in a linearly increasing sawtooth pattern without returning to a zero-load state; and An image manipulation system (240) for manipulating a speckle image of the illuminated top surface of the test specimen. The loading system (250) is a vacuum system, and a portion of the test piece (260) is enclosed within the vacuum system. The shear speckle examination system (200) is configured to perform the method according to any one of claims 1 to 3.

16. The shear speckle examination system according to claim 15, wherein, The loading system (250) is configured to apply one of a vacuum, heat, or mechanical load.

17. The shear speckle examination system according to claim 15, wherein, The loading system (250) is configured to increase and decrease the load at a frequency of 60 Hz or higher.

18. The shear speckle examination system according to any one of claims 15 to 17, wherein, The image manipulation system is configured to automatically subtract speckle from the image, visually display the subtracted speckle image, and terminate the inspection based on the determination of defects.

Images