Method and apparatus for enhanced visualization of structural abnormalities

Abstract

The present disclosure relates to a method and apparatus for enhanced visualization of structural abnormalities. The method comprises the steps of acquiring pulse-echo laser ultrasonic propagation imaging video data at a plurality of points in a scanning area on a surface of a structure; post-processing the pulse-echo laser ultrasonic propagation imaging video data using multi-time window amplitude plotting to create a multi-time window amplitude map; and displaying the multi-time window amplitude map on a graphical user interface.

Description

Technical Field

[0001] The present disclosure relates generally to apparatus and methods for processing images, and more particularly to apparatus and methods for processing laser ultrasound propagation images. Background Art

[0002] Pulse-echo laser ultrasonic wave propagation imaging (UWPI) is a non-contact sensing technique that enables three-dimensional (3-D) visualization of anomalies in structures (e.g., fiber-reinforced plastic materials, hereinafter referred to as "composites") for the purpose of non-destructive testing. In some UWPI systems, a Q-switched continuous wave laser is used to linearly scan an area on a structure, with the laser pulses oriented perpendicular to the surface (e.g., in the thickness direction). A laser Doppler vibrometer is then used to detect the laser-generated ultrasonic waves propagating in the thickness direction at each fixed point. The scan data output by the laser Doppler vibrometer is then bandpass filtered to produce raw UWPI video data, which can be further post-processed to enhance the acquired image.

[0003] Previously, single-time window amplitude plotting algorithms were used to post-process individual images using a single time window of ultrasound propagation imaging data. However, this single-time window amplitude plotting algorithm forced the user to select an extended time window to represent each anomaly at different thickness levels, which resulted in the inclusion of unnecessary frames and low-quality anomaly visualization. In addition, using pulse-echo laser UMPI video data to calculate the area of ​​anomalies is limited to simple shapes such as rectangles and circles, and it can be challenging to accurately locate structural anomalies by observing scan results alone. Summary of the invention

[0004] The subject matter disclosed in detail below relates to methods and apparatus for post-processing pulse-echo laser UMPI video data to enhance visualization of structural anomalies. The post-processing enhancements proposed herein are of three types. First, a multi-time window amplitude plotting algorithm is proposed herein that allows the user to select multiple time windows to visualize anomalies at different depths in a single image. Second, a polygonal anomaly area calculation enables automatic calculation of the area of ​​a specified anomaly within the pulse-echo laser UWPI system interface. Third, an anomaly pointing function helps the user to accurately locate anomalies on the structure by interacting with a graphical user interface that is displaying the UWPI video image. These features achieve enhanced visualization quality of anomalies and accurate calculation of the area and location of anomalies.

[0005] Although various embodiments of methods and apparatus for post-processing pulse-echo laser UMPI video data to enhance visualization of structural anomalies will be described in detail below, one or more of these embodiments may be characterized by one or more of the following aspects.

[0006] One aspect of the subject matter disclosed in detail below is a method for enhanced visualization of a structural abnormality, comprising the steps of: (a) acquiring pulse-echo laser ultrasonic propagation imaging video data at a plurality of points in a scan area on a surface of a structure; (b) post-processing the pulse-echo laser ultrasonic propagation imaging video data using multi-time window amplitude plotting to create a multi-time window amplitude map; and (c) displaying the multi-time window amplitude map on a graphical user interface. According to one embodiment, step (b) comprises: specifying the pulse-echo laser ultrasonic propagation imaging video data in a selected time window; summing the amplitude data included in the specified pulse-echo laser ultrasonic propagation imaging video data; and plotting the summed amplitude data.

[0007] Another aspect of the subject matter disclosed in detail below is a method for enhanced visualization of a structural abnormality, comprising the steps of: (a) acquiring pulse-echo laser ultrasound propagation imaging video data at a plurality of points in a scan area on a surface of a structure; (b) post-processing the pulse-echo laser ultrasound propagation imaging video data to create a video freeze frame; (c) displaying the video freeze frame on a graphical user interface; (d) selecting at least three points on the video freeze frame by human interaction with the graphical user interface; (e) calculating the area of ​​a polygon defined by the at least three points; and (f) displaying an alphanumeric symbol representing the area calculated in step (e) on the graphical user interface. The at least three points are located on a boundary of an image of the abnormality displayed on the graphical user interface.

[0008] Yet another aspect of the subject matter disclosed in detail below is a method for enhanced visualization of structural abnormalities, comprising the steps of: (a) acquiring pulse-echo laser ultrasonic propagation imaging video data at a plurality of points in a scanning area on a surface of a structure; (b) post-processing the pulse-echo laser ultrasonic propagation imaging video data to create a video freeze frame; (c) displaying the video freeze frame on a graphical user interface; (d) selecting a point on the video freeze frame by human interaction with the graphical user interface; (e) converting the pixel coordinates of the point selected in step (d) into spatial coordinates in a reference frame of a positioner supporting a laser scanning head; (f) controlling the positioner to move the laser scanning head to a pointing position having the spatial coordinates obtained by step (e); and (g) activating the laser scanning head to emit a laser beam when the laser scanning head is in the pointing position. According to one embodiment, steps (e) to (g) are automatically performed in response to step (d).

[0009] Another aspect of the subject matter disclosed in detail below is a device for enhanced visualization of structural abnormalities, comprising: a pulse echo laser ultrasonic propagation imaging system, the pulse echo laser ultrasonic propagation imaging system including a laser scan head; a graphical user interface; and a computer system, the computer system being configured to perform the following operations: (a) receiving pulse echo laser ultrasonic propagation imaging video data from the pulse echo laser ultrasonic propagation imaging system; (b) post-processing the pulse echo laser ultrasonic propagation imaging video data using multi-time window amplitude plotting to create a multi-time window amplitude map; and (c) controlling the graphical user interface to display the multi-time window amplitude map.

[0010] Other aspects of methods and apparatus for post-processing pulse-echo laser UMPI video data to enhance visualization of structural anomalies are disclosed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The features, functions, and advantages discussed in the foregoing sections may be implemented independently in various embodiments, or may be combined in other embodiments. For the purpose of illustrating the above and other aspects, various embodiments will be described below with reference to the accompanying drawings. The schematic diagrams briefly described in this section are not drawn to scale.

[0012] Figure 1 is a block diagram identifying some of the components of a linear scan pulse-echo laser UWPI system according to one embodiment.

[0013] Figure 2 is a schematic diagram showing two windows appearing on a graphical user interface, the left window showing a pulse-echo (PE) laser UWPI video and the right window showing a multi-time window amplitude map (MTWAM) according to one embodiment.

[0014] Figure 3 is a schematic diagram showing steps in a method for generating a multi-time window amplitude map according to one embodiment.

[0015] Figure 4 is a flow chart identifying steps of a method for displaying a multi-time window amplitude graph according to one embodiment.

[0016] FIG. 5A to FIG. 5C Shown are scan results for a 2.75 mm thick composite specimen with artificial inclusion anomalies distributed in the pattern.

[0017] Figure 6 is a flow chart identifying steps of a method for calculating the area of ​​a polygon that approximates the shape of an anomaly in a specimen, according to one embodiment.

[0018] Fig. 7A is a schematic diagram showing a scan area on a structure including a polygonal anomaly.

[0019] Figure 7B It indicates that the graphical user interface is being displayed. Fig. 7A A schematic diagram of a video freeze frame window depicting the scanned area can be selected using the graphical user interface. Fig. 7A The shape of the anomaly depicted in the image is approximated by the vertices of the polygon.

[0020] Fig. 8A is a schematic diagram representing a window on a graphical user interface showing calculation results of the area of ​​an image of one of a plurality of artificial anomalies contained in a 2.75 mm thick composite specimen, the image appearing in a video freeze frame of a UWPI video.

[0021] Figure 8B is a diagram showing a window on a graphical user interface showing the Fig. 8A The calculation result of the area of ​​an abnormal image among the same multiple artificial anomalies appearing in the multi-time window amplitude map derived from the same UWPI, extracted from the same UWPI Fig. 8A Freeze frame of the video depicted in .

[0022] Fig. 9 is a schematic diagram representing a window on a graphical user interface showing the calculation results of the area of ​​an image of one of a plurality of artificial anomalies contained in a 7 mm thick composite test panel having impact damage appearing in a video freeze frame of a UWPI video.

[0023] Fig.10 is a schematic diagram showing the use of the anomaly pointing function to move the laser scanning head to a position where the emitted laser beam is irradiated on an anomaly in a specimen.

[0024] Fig.11 A graphical user interface is shown including a corresponding window containing a video freeze frame, a video image of the test setup acquired by a camera, and a graph showing the amplitude versus time of ultrasonic wave propagation when a laser pulse is directed to an anomaly using an anomaly pointing function.

[0025] Reference will hereinafter be made to the drawings, in which similar elements in different drawings have like reference numerals. DETAILED DESCRIPTION

[0026] Illustrative embodiments of methods and apparatus for post-processing pulse-echo laser UMPI video data to enhance visualization of structural anomalies are described in detail below. However, not all features of actual implementations are described in this specification. It should be understood by those skilled in the art that, in developing any such actual implementation, several implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related limitations, which vary from implementation to implementation. Moreover, it should be understood that such development work may be complex and time-consuming, but is still a routine task for those of ordinary skill in the art who benefit from the present disclosure.

[0027] Figure 1 is a schematic diagram identifying some of the components of a linear scan pulse echo laser UWPI system according to one embodiment. The system includes at least the following components: a source laser controller 12, an ultrasound generating laser 14 (e.g., a Q-switched solid-state diode pumped laser), a first optical mirror 16, a second optical mirror 18, a laser Doppler vibrometer 20 (comprising a sensing laser, a photodetector, and other known optical components), a sensing laser controller 22, an inline signal conditioner 24 (comprising a bandpass filter and amplifier), and a computer system 2 configured with programming to facilitate the acquisition and post-processing of video data acquired by the system. Although in Figure 1 1, but the ultrasound generating laser 14, the first and second optical mirrors 16 and 18 and the laser Doppler vibrometer 20 are fixedly included in the laser scanning head (see Fig.11 The computer system 2 is configured to control the two-axis linear positioner to move the ultrasound generating laser 14 and the laser Doppler vibrometer 20 in space relative to the stationary sample, thereby enabling a region on the surface of the sample to be simultaneously scanned by respective laser beams emitted by the ultrasound generating laser 14 and the laser Doppler vibrometer 20.

[0028] exist Figure 1, a linear scanning pulse echo laser UWPI system is depicted relative to a sample 10, which has been placed in the path of laser pulses generated by an ultrasound generating laser 14 under the control of a source laser controller 12. The laser pulses are generated at a pulse repetition rate by a Q-switching technique. The laser pulses emitted by the ultrasound generating laser 14 are reflected by a first optical mirror 16 toward a second optical mirror 18. The second optical mirror 18 then reflects the laser pulses toward the sample 10 (preferably at an angle perpendicular to the surface of the sample 10). In the case where the sample is a composite laminate comprising a stack of layers having a thickness, the laser pulses are propagating in the thickness direction. The laser pulses emitted by the ultrasound generating laser 14 are irradiated on the surface of the sample, thereby generating thermoelastic waves with a burst thermal expansion. The pulsed thermal expansion of the material of the sample 10 in turn causes ultrasonic waves that propagate in the thickness direction in various modes. These ultrasonic waves in turn move the surface of the sample, which movement is detected by a laser Doppler vibrometer 20.

[0029] More specifically, when the laser pulse from the ultrasound generating laser 14 is irradiated on the surface of the sample, an ultrasonic wave is generated at the affected point (e.g., where the laser spot is located), thereby causing the area around the affected point to vibrate. While the ultrasound generating laser 14 is generating laser pulses of a first wavelength, the sensing laser within the laser Doppler vibrometer 20 emits a sensing laser beam having a second wavelength different from the first wavelength of the pulsed laser beam. (In an alternative, a continuous wave laser interferometer may be used to implement the sensing laser.) The laser Doppler vibrometer 20 is positioned so that the emitted sensing laser beam propagates through the second optical mirror 18 and coincides with the pulsed laser beam from the ultrasound generating laser 14. The coincident beam is irradiated on the surface of the sample at the same point. Light is scattered from the target in all directions, but a portion of the light is captured by the laser Doppler vibrometer 20. More specifically, after each laser pulse of the first wavelength is irradiated on the sample 10 , some of the irradiated coincident laser light of the first wavelength and the second wavelength is backscattered to the second optical mirror 18 and transmitted by the second optical mirror 18 to the photodetector of the laser Doppler vibrometer 20 .

[0030] Ultrasonic sensing using the laser Doppler vibrometer 20 is based on detecting the frequency shift of the returning laser light of the second wavelength (e.g., filtering out the frequency shift of the returning laser light of the first wavelength). Specifically, the amplitude and frequency of the ultrasonic wave are extracted from the Doppler frequency shift in the frequency of the reflected laser beam, which is caused by the motion of the surface of the specimen.

[0031] According to one embodiment, the laser Doppler vibrometer 20 is a dual-beam laser interferometer that measures the frequency (or phase) difference between an internal reference beam and a sensing laser beam. The laser sensing beam interferes with the reference beam on a photodetector (usually a photodiode). Most commercial vibrometers operate in a heterodyne regime by adding a known frequency shift (usually 30-40 MHz) to one of the beams. The frequency shift is usually generated by a Bragg cell or an acousto-optic modulator. The output of the photodetector is a standard frequency modulated signal with the Bragg cell frequency as the carrier frequency and the Doppler shift as the modulation frequency. The signal can be demodulated to derive the velocity of the vibrating surface of the sample during a time interval or time window.

[0032] The output of the laser Doppler vibrometer 20 is a continuous analog voltage proportional to the target velocity component along the direction of the laser beam. The electrical signal generated by the photodetector of the laser Doppler vibrometer 20 is amplified and bandpass filtered by the signal conditioner 24 to extract the measured time-domain ultrasonic wave, and then the signal-conditioned electrical signal (representing video data) is stored in a non-transitory tangible computer-readable storage medium, which is contained in the computer system 2 or can be accessed by the computer system 2.

[0033] During post-processing, the computer system 2 executes the signal processing algorithm and then controls the display screen to visualize the wave propagation using the UWPI algorithm. The UWPI algorithm is configured to generate a visualization of the propagation of through-thickness ultrasound waves in the time domain or frequency domain based on 3-D data processing (e.g., a video freeze frame 32 extracted from the UWPI video 30). Figure 1 Some post-processing steps are illustrated in FIG. 2 (these steps are performed by a post-processor included in the computer system 2 ).

[0034] The ultrasonic propagation image generated by the computer system 2 is an image showing an ultrasonic image that has propagated through at least a portion of the thickness of the structure and then returned to the surface over time. The ultrasonic propagation image corresponds to a moving image or a static image, in which the sensing results obtained by scanning are arranged synchronously in time. For example, an ultrasonic wave generated by a laser pulse at the surface of the specimen 10 can propagate toward the back wall of the specimen in the thickness direction, but can be reflected at the interface where the anomaly is located. The penetration thickness position of the anomaly can be calculated based on the propagation time and the propagation speed. In addition, the computer system 2 further processes the signal generated by the sensing in the frequency, wave number or wavelength domain, and presents the sensing results as a moving image or a static image.

[0035] Figure 1At a high level, some aspects of the post-processing operations that the computer system is configured to perform are illustrated. First, the computer system 2 detects the amplitude of the incoming electrical signal from the signal conditioner 24 as a function of time. Optionally, the system operator may input a curve instructing the computer system 2 to plot the amplitude versus time. Figure 4 The display processing may involve an image processor sending data and commands to a separate display processor that controls the display screen, both of which are contained in the computer system 2. The resulting waveform represents the time-varying amplitude of the pulse-echo ultrasound signal.

[0036] Secondly, the image processor is also configured to perform a pulse echo ultrasound propagation imaging technique based on penetrating thickness ultrasound. Figure 1 As shown, based on the penetrating thickness ultrasound acquired from the sample 10, the abnormalities in the sample 10 are visualized (as represented by the image 26 of the abnormalities) by using the pulse echo ultrasound propagation imaging technique as a result of scanning the surface of the sample 10. The one-dimensional electrical signals acquired by scanning the array of points in the area on the surface of the sample are rearranged to form a three-dimensional video data array 6 (hereinafter referred to as "3-D data array 6"). Each time series in the 3-D data array 6 is: a corresponding data subset representing a corresponding pulse echo ultrasound signal at a corresponding point irradiated by the pulsed laser beam during the scanning process. Figure 1 In the example depicted in , the number of data elements in the vertical dimension of the 3-D data array 6 (corresponding to the height of the scan area on the surface of the specimen 10) is V, and the number of data elements in the horizontal dimension of the 3-D data array 6 (corresponding to the width of the scan area on the surface of the specimen 10) is H. Figure 1 The arrow T in represents the time axis. For the purpose of illustration, Figure 1 The exemplary 3-D data array 6 presented in shows black areas of the image 26 representing anomalies.

[0037] The straight dashed line in the 3-D data array 6 represents a cutting plane 28, which can be used to generate a time sequence of N video freeze frames 32 of video data to form a UMPI video 30. Therefore, the total number of data elements in the 3-D data array 6 will be the product of H×V×N. The system operator can input a command instructing the computer system 2 to display any of the multiple video freeze frames 32 on the associated display screen. All video freeze frames 32 can be taken when the maximum ultrasound amplitude at the abnormal location occurs. Therefore, images can be generated along the time axis T to present the UWPI video 30 for viewing. When the moving image is made based on the signal, the system operator can visualize how uniform ultrasound waves propagate through the thickness of the specimen 10 over the entire scan field.

[0038] In summary, first, the ultrasound generating laser 14 emits a laser beam pulse that generates various modes of ultrasound waves. In the various modes of ultrasound waves, the laser Doppler vibrometer 20 acquires a pulse-echo ultrasound signal, which is a point in the video freeze frame 32 of the UWPI video 30. Both the laser pulse and the sensing laser beam are emitted as coincident beams at each of a plurality of points covering the scanning area.

[0039] Figure 2 is a schematic diagram showing two windows that can be displayed on a graphical user interface according to an embodiment of the post-processing method proposed herein. The left window displays a freeze frame 32 extracted from a UWPI video 30 that visualizes ultrasonic wave propagation in a specimen 10 having multiple artificial (e.g., manufactured) anomalies distributed in a pattern. The specimen 10 is made of a composite material (e.g., made of carbon fiber / epoxy prepreg) having a thickness of 2.75 mm. The right window uses the method proposed herein to display a multiple-time window amplitude map 34 (MTWAM) derived from the UWPI video 30. The comparison image shows the improvement in anomaly visualization at all depths when using multiple-time window amplitude plotting. A post-processor (e.g., a computer system 2 configured with post-processing software) performs multiple-time window amplitude plotting, polygonal defect area calculation, and defect pointing.

[0040] Figure 3 FIG. 1 is a schematic diagram showing steps in a method for deriving a multi-time window amplitude map 34 from a pulse echo ultrasonic field 36 of a UWPI video 30 according to one embodiment. The complete UWPI video 30 includes a plurality of time window amplitude maps 34 that can be compared to the sample 10 (see FIG. 1 ) based on the velocity of wave propagation. Figure 1 ) in a plurality of video freeze frames 32 (32a, 32b, 32c) corresponding to the depths thereof. Figure 3 In the example depicted in , in the video freeze frame belonging to the first time window 38a, an image 26a of the first anomaly (hereinafter referred to as "first anomaly image 26a") can be seen; in the video freeze frame belonging to the second time window 38b, an image 26b of the second anomaly (hereinafter referred to as "second anomaly image 26b") can be seen; and no abnormal image can be seen in the first video freeze frame of the third time difference 38c. In the next step, a time window containing amplitude information generated by the anomaly (e.g., an amplitude with a maximum amplitude greater than a predetermined threshold) is selected for further processing. Figure 3In the example depicted in , time window 38a and time window 38b are selected. In a final step, the amplitude magnitudes in the selected video freeze frames of time windows 38a and 38b are summed to produce a multi-time window amplitude map 34. The resulting image contains first and second abnormal images 26a and 26b that are easily discernible by an observer.

[0041] The multi-time window amplitude plotting technique described above enables visualization of multiple anomalies at different depths in a specimen in a single image and provides excellent signal-to-noise ratio and visualization quality.

[0042] Figure 4 is a flow chart identifying the steps of a method 50 for displaying a multi-time window amplitude graph 34 according to one embodiment. A first time window is selected in step 52. A determination is then made as to whether processing for deriving a multi-time window amplitude graph 34 should be initiated (step 54). If the additional time window contains an amplitude of interest, then the next time window is added (e.g., selected) in step 56. This iterative process continues until all time windows containing amplitudes of interest have been selected. When there are no more time windows of interest, the amplitude values ​​of the selected time windows are converted to absolute values ​​in step 58, and then these absolute values ​​of the selected time windows are summed in step 60. Finally, as Figure 2 As shown, the summation result is displayed in step 62 in the form of a multi-time window amplitude map (MTWAM).

[0043] FIG. 5A to FIG. 5C Shown are scan results for a 2.75 mm thick composite specimen with artificial inclusion anomalies distributed in the pattern. Figure 5A A PE UWPI video freeze frame at 2.933 μs is shown. Some anomalies are not included because they are placed at different depths. However, Figure 5B A PE UWPI video freeze frame at 5.433 μs is shown, in which it can now be seen Figure 5A By using the 2.933-2.983μs time window and the 5.433-5.850μs time window for multi-time window amplitude plotting, we can obtain the following: Figure 5C A multi-time window amplitude diagram 34 is shown. FIG. 5A to FIG. 5C Comparison of the images depicted in 34 shows that the multi-time window amplitude map encompasses every anomaly and provides a visualization of superior quality.

[0044] According to other aspects of the post-processing techniques presented herein, the computer system 2 is configured to execute an algorithm by which the area of ​​a polygon that approximates the shape of an anomaly in the specimen can be calculated. To the extent that the shape of the anomaly is not an exact polygon, the result of the calculation is an estimated area of ​​the anomaly. To the extent that the shape of the anomaly is derived from a true polygon, this estimate may be different from the actual area of ​​the physical anomaly.

[0045] Figure 6 7 is a flow chart of steps for identifying a method 70 for calculating the area of ​​a polygon that approximates the shape of an anomaly in a specimen according to one embodiment. A user viewing a graphical user interface displaying an image of an anomaly first selects a vertex of a polygon as a starting point by clicking a point on the graphical user interface using a cursor in step 72. As used herein, the term "polygon" refers to a polygon that is either convex or concave and does not intersect itself. It should be remembered at this point in the disclosure that the final polygon will not appear on the graphical user interface when the first vertex is selected, but will only appear completely when all vertices have been selected. In the next step 74, the next vertex (e.g., point) of the polygon is selected by clicking another point on the graphical user interface using the cursor again. Then in step 76, the system receives input from the user as to whether the polygon is complete. If the user responds that the polygon is incomplete, the user repeats step 74, and after step 74, step 76 is repeated. In response to each selection of a vertex, the computer system 2 stores the (x, y) coordinates of the pixel on the display screen where the click was made. Digital data representing a list of pixel coordinates of the vertices selected by the user is stored in a non-transitory tangible computer-readable storage medium.

[0046] Steps 74 and 76 are repeated until the user has indicated that the polygon is complete, meaning that the user has selected all of the vertices of the polygon. Then, in step 78, the user interacts with the graphical user interface to instruct the computer system 2 to run a polygon area calculation algorithm on the list of points. In the process of executing the algorithm, the following operations are performed by the computer system: (1) retrieving digital data representing pixel coordinates of the vertices of the polygon from a non-transitory tangible computer-readable storage medium; (2) converting the retrieved pixel coordinates to spatial coordinates in the reference frame of the specimen based on a conversion ratio determined during a calibration process performed prior to the start of the imaging session; and (3) using the spatial coordinates to calculate an estimate of the area of ​​the polygon. Then, in step 80, the calculated area is displayed on the graphical user interface.

[0047] Fig. 7A 1 is a schematic diagram showing a scanning area 40 on a structure including a polygonal anomaly 25 . Figure 7B It indicates that the graphical user interface is being displayed. Fig. 7AA schematic diagram of a window of a video freeze frame 32 of a scanning area 40 is depicted in FIG. 1 , which can be selected using the graphical user interface. Fig. 7A The vertices of a polygon that approximates the shape of the image 26 of the anomaly 25 depicted in FIG. Once the polygonal representation is complete, the area of ​​the polygon can be calculated. According to one proposed embodiment, the polygon area formula disclosed in the CRC standard mathematical tables (CRC Press (1987), Boca Raton, Florida, 28th edition, Beyer, WH (ed.), pp. 123-124; Beyer, WH (Ed.), 28th ed., Boca Raton, Florida, CRC Press (1987), pp. 123-124) can be used.

[0048] like Figure 7B As can be seen in the example depicted in , the user can select n vertices to form an n-sided polygon, where n is an integer greater than 2. The coordinates of the vertices of such an n-sided polygon (in the specimen's reference frame, not pixel coordinates) are (x 1 ,y 1 )、(x 2 ,y 2 )、(x 3 ,y 3 ),…,(x n ,y n ). Then the area A of the polygon can be calculated using the following formula:

[0049]

[0050] In the case of a composite part (such as a wing box of an aircraft) undergoing UWPI and displaying an anomaly, the shape of the anomaly can be approximated by a polygon, the area of ​​which can then be calculated in the coordinate system of the wing box to provide a measure of the size of the anomaly. More precisely, the polygon approximates the shape of the image of the anomaly that appears on the graphical user interface. The polygon is defined by a user selecting at least three points that are located on the boundary of the image of the anomaly.

[0051] Fig. 8A FIG. 1 is a diagram showing a window on a graphical user interface showing the result of calculating the area of ​​an image of one of a plurality of artificial anomalies contained in a 2.75 mm thick composite specimen, the image appearing in a video freeze frame 32 of a UWPI video captured at 5.733 μs. The result of the polygonal anomaly area calculation is 344.04 mm 2 .like Fig. 8A As can be seen in FIG. 3 , the calculation result is displayed on top of the video freeze frame 32 .

[0052] Figure 8Bis a schematic diagram of a window on the same graphical user interface showing the calculation results of the area of ​​an image of one of a plurality of artificial anomalies contained in a 2.75 mm thick composite specimen. The image appears in a plurality of time window amplitude graphs 34, which are generated from Fig. 8A The same UWPI export of video freeze frame 32 depicted in Figure 1 is used for multi-window amplitude plotting using the 2.933-2.983 μs window and the 5.433-5.850 μs window (which is similar to Figure 5C The result of polygonal abnormal area calculation is 129.62mm 2 .like Figure 8B As can be seen in FIG. 3 , the calculation results are displayed on top of the multi-time window amplitude diagram 34 .

[0053] To facilitate another test, a 7 mm thick composite test panel was constructed with different types of anomalies including delamination caused by impact, sanded surface, wrinkles, and patched piezoelectric transducers. This test panel was then subjected to UWPI. Fig. 9 32 depicts a video freeze frame acquired at 8.3 μs, which represents a window on a graphical user interface and also shows the calculation results of the area of ​​the image 26 of the abnormality in the selected area 44 of the video freeze frame 32. In this example, the abnormality is delamination caused by an impact. Other abnormalities include the delamination area 46 (caused by Fig. 9 The other layers and the repaired piezoelectric transducer region 48 (indicated by the dashed circle) in Fig. 9 denoted by the dashed rectangle). Fig. 9 The area of ​​the image 26 indicating the anomaly in the selected region 44 is 814.06 mm 2 , and clearly demonstrates that using the polygonal anomaly area calculation function, accurate area calculation is possible also for impact-induced delamination with very complex shapes.

[0054] Fig.10 1 is a schematic diagram showing the use of the anomaly pointing function to move the laser scanning head 66 to a position where the emitted laser beam is irradiated on an anomaly in the scanning area 40 on the surface of the specimen 10. The laser scanning head 66 houses the ultrasound generating laser 14, the first and second optical mirrors 16 and 18, and the laser Doppler vibrometer 20. As previously mentioned, the scanning laser head 66 is mounted on a two-axis linear positioner 90 (see FIG. 1 ) capable of translating the laser scanning head 66 in the X and Y directions. Fig.11 ).

[0055] Fig.10 The upper left corner rectangle indicates that the scanning area 40 (in Fig.103. The PE UWPI video freeze frame 32 produced by scanning the surface is shown in the upper right corner of FIG. 3. The black dots spaced at regular scanning intervals Δ on the scanning area 40 represent the corresponding laser spots 42 produced during the scanning of the surface. For illustrative purposes, only some of the laser spots 42 are shown, and it should be understood that the entire scanning area 40 is scanned by intermittently activating the laser beam 64 after each incremental movement by a distance equal to the scanning interval Δ.

[0056] Furthermore, while the video freeze frame 32 includes the image 26 that appears as an anomaly having a quadrilateral shape (eg, a polygon having four sides), the scan area 40 includes the physical anomaly 25 that produced the image 26 seen in the freeze frame 32 .

[0057] To further clarify Fig.10 , each pixel of the video freeze frame 32 has pixel coordinates related to the (x,y) coordinate system of the specimen, where the origin (0,0) is at the lower left corner of the freeze frame 32. However, when the scanning laser head 66 is in the initial scanning position 82, the laser beam 64 has coordinates (a,b) in the coordinate system of the two-axis linear positioner 90. Therefore, the command for moving the laser scanning head 66 to another position is given in the form of coordinates in the reference system of the two-axis linear positioner 90. For example, Fig.10 As depicted, if the user selects a point 68 in the video freeze frame 32 having coordinates (x, y) in the reference frame of the specimen, then the computer system 2 (see Figure 1 ) instructs the two-axis linear positioner 90 to move the laser scan head 66 so that the laser beam 64 is irradiated on a point with coordinates (x+a, y+b) in the reference frame of the two-axis linear positioner 90.

[0058] The process for enabling a user to initiate the automatic anomaly pointing function will now be described. First, the user selects a point 68 on the image 26 of an anomaly visible in the video freeze frame 32. The selected point has a position (x, y) in the coordinate system of the specimen 10. This position is then converted to a corresponding position (x+a, y+b) in the coordinate system of the two-axis linear positioner 90. Finally, the scanning laser head 66 is moved from the Fig.10 The position indicated by the dotted line in the figure is moved to the selected position (x+a,y+b) (by Figure 14 (indicated by the solid line in FIG. 4 ) to direct the laser beam 64 toward the anomaly 25. Thus, the laser beam 64 can be moved so that it is directed toward any location within the scanning area 40 that the user has selected. During nondestructive testing of a composite component, the ability to direct the laser beam 64 toward a point on the composite component by clicking on a corresponding point on the video freeze frame 32 allows the inspector to subsequently perform additional inspections of the anomaly, including additional UWPI. In the alternative, the inspector can mark the location of the pointing on the composite component, thereby designating the area for testing or repair at a later time.

[0059] While the method of employing the anomaly pointing function disclosed above involves a user selecting a point 68 in a video freeze frame 32 , in the alternative, a user may achieve the same automatic pointing by selecting a corresponding point on a multi-time window amplitude graph 34 .

[0060] Fig.11 A graphical user interface 100 is shown including a first window containing a video freeze frame 32, a second window including a video image 92 of the test setup acquired by a camera (not shown), and a graph showing amplitude versus time. Figure 4 The window of FIG. 30 is a graph showing the propagation of ultrasonic waves generated when the laser pulse is directed to an anomaly using the anomaly pointing function. Optionally, the coordinates of the laser spot can be displayed on the video freeze frame 32. Fig.11 In the example depicted in , the coordinates of the selected position in the reference frame of the two-axis linear positioner 90 are (124.75, 121.5).

[0061] like Fig.11 As can be seen in the figure, the two-axis linear positioner 90 includes: a fixed mounting table 84, an X-axis linear table 86, and a Y-axis linear table 88, wherein the X-axis linear table 86 is translationally coupled to the mounting table 84 for translation in either direction along the X-axis, and the Y-axis linear table 88 is translationally coupled to the X-axis linear table 86 for translation in either direction along the Y-axis. The laser scanning head 66 is fixedly coupled to the Y-axis linear table 88. The structure and operation of multi-axis linear positioners are well known in the field of robotics.

[0062] Additionally, this disclosure includes examples according to the following clauses:

[0063] Item 1: A method for enhanced visualization of structural anomalies, comprising the steps of: (a) acquiring pulse echo laser ultrasonic propagation imaging video data at multiple points in a scanning area on a structural surface; (b) post-processing the pulse echo laser ultrasonic propagation imaging video data using multi-time window amplitude plotting to create a multi-time window amplitude map; and (c) displaying the multi-time window amplitude map on a graphical user interface.

[0064] Item 2: A method according to Item 1, wherein step (b) includes: specifying pulse echo laser ultrasonic propagation imaging video data in a selected time window; summing the amplitude data included in the specified pulse echo laser ultrasonic propagation imaging video data; and plotting the summed amplitude data.

[0065] Item 3: According to the method described in Item 1, the method also includes the following steps: (d) selecting at least three points on the multi-time window amplitude graph through human interaction with a graphical user interface; (e) calculating the area of ​​a polygon defined by the at least three points; and (f) displaying an alphanumeric symbol representing the area calculated in step (e) on the graphical user interface.

[0066] Clause 4: The method of clause 3, wherein the at least three points are located on a boundary of an image of the anomaly displayed on a graphical user interface.

[0067] Item 5: According to the method described in Item 3, the method also includes the following steps: (g) selecting a point on the multi-time window amplitude diagram through human interaction with a graphical user interface; (h) converting the pixel coordinates of the point selected in step (g) into spatial coordinates in a reference system of a locator supporting a laser scanning head; (i) controlling the locator to move the laser scanning head to a pointing position having the spatial coordinates obtained by step (h); and (j) when the laser scanning head is in the pointing position, starting the laser scanning head to emit a laser beam.

[0068] Clause 6: The method of clause 5, wherein steps (h) to (j) are automatically performed in response to step (g).

[0069] Item 7: According to the method described in Item 1, the method also includes the following steps: (d) selecting a point on a multi-time window amplitude graph through human interaction with a graphical user interface; (e) converting the pixel coordinates of the point selected in step (d) into spatial coordinates in a reference system of a locator supporting a laser scanning head; (f) controlling the locator to move the laser scanning head to a pointing position having the spatial coordinates obtained by step (e); and (g) when the laser scanning head is in the pointing position, starting the laser scanning head to emit a laser beam.

[0070] Clause 8: The method of clause 7, wherein steps (e) to (g) are automatically performed in response to step (d).

[0071] Item 9: A method for enhanced visualization of structural anomalies, comprising the following steps: (a) acquiring pulse echo laser ultrasonic propagation imaging video data at multiple points in a scanning area on a structural surface; (b) post-processing the pulse echo laser ultrasonic propagation imaging video data to create a video freeze frame; (c) displaying the video freeze frame on a graphical user interface; (d) selecting at least three points on the video freeze frame through human interaction with the graphical user interface; (e) calculating the area of ​​a polygon defined by the at least three points; and (f) displaying an alphanumeric symbol representing the area calculated in step (e) on the graphical user interface.

[0072] Clause 10: The method of clause 9, wherein the at least three points are located on a boundary of an image of the anomaly displayed on a graphical user interface.

[0073] Item 11: The method according to Item 9 further includes the following steps: (g) selecting a point on the freeze frame through human interaction with a graphical user interface; (h) converting the pixel coordinates of the point selected in step (g) into spatial coordinates in a reference system of a locator supporting a laser scanning head; (i) controlling the locator to move the laser scanning head to a pointing position having the spatial coordinates obtained by step (h); and (j) starting the laser scanning head to emit a laser beam when the laser scanning head is in the pointing position.

[0074] Clause 12: The method of clause 11, wherein steps (h) to (j) are automatically performed in response to step (g).

[0075] Item 13: A method for enhanced visualization of structural abnormalities, comprising the following steps: (a) acquiring pulse echo laser ultrasonic propagation imaging video data at multiple points in a scanning area on a structural surface; (b) post-processing the pulse echo laser ultrasonic propagation imaging video data to create a video freeze frame; (c) displaying the video freeze frame on a graphical user interface; (d) selecting a point on the video freeze frame through human interaction with the graphical user interface; (e) converting the pixel coordinates of the point selected in step (d) into spatial coordinates in a reference frame of a locator supporting a laser scanning head; (f) controlling the locator to move the laser scanning head to a pointing position having the spatial coordinates obtained by step (e); and (g) when the laser scanning head is in the pointing position, starting the laser scanning head to emit a laser beam.

[0076] Clause 14: The method of clause 13, wherein steps (e) to (g) are automatically performed in response to step (d).

[0077] Item 15: A device for enhanced visualization of structural abnormalities, comprising: a pulse echo laser ultrasonic propagation imaging system, the pulse echo laser ultrasonic propagation imaging system including a laser scan head; a graphical user interface; and a computer system, the computer system being configured to perform the following operations: (a) receiving pulse echo laser ultrasonic propagation imaging video data from the pulse echo laser ultrasonic propagation imaging system; (b) post-processing the pulse echo laser ultrasonic propagation imaging video data using multi-time window amplitude plotting to create a multi-time window amplitude map; and (c) controlling the graphical user interface to display the multi-time window amplitude map.

[0078] Item 16: An apparatus according to Item 15, wherein step (b) includes: receiving data representing pulse-echo laser ultrasonic propagation imaging video data specified in a selected time window; summing the amplitude data included in the received specified pulse-echo laser ultrasonic propagation imaging video data; and plotting the summed amplitude data.

[0079] Clause 17: An apparatus according to clause 15, wherein the computer system is further configured to perform the following operations: (d) receiving data representing at least three points selected from a multi-time window amplitude graph; (e) calculating the area of ​​a polygon defined by the at least three points; and (f) controlling a graphical user interface to display an alphanumeric symbol representing the area calculated in operation (e).

[0080] Clause 18: The apparatus of clause 17, wherein the at least three points are located on a boundary of an image of the anomaly displayed on a graphical user interface.

[0081] Item 19: An apparatus according to Item 17, wherein the pulse echo laser ultrasonic propagation imaging system further includes a locator on which the laser scanning head is mounted, and the computer system is further configured to perform the following operations: (g) receiving data representing a point selected from a multi-time window amplitude diagram; (h) converting the pixel coordinates of the selected point into spatial coordinates in a reference frame of the locator; (i) controlling the locator to move the laser scanning head to a pointing position having the spatial coordinates obtained by operation (h); and (j) starting the laser scanning head to emit a laser beam when the laser scanning head is in the pointing position.

[0082] Clause 20: The apparatus of clause 19, wherein the positioner is a two-axis linear positioner.

[0083] More specifically, some of the above features may be combined to provide a method for enhanced visualization of structural abnormalities, the method comprising the following steps: (a) acquiring pulse-echo laser ultrasonic propagation imaging video data at a plurality of points in a scan area on a surface of a structure; (b) post-processing the pulse-echo laser ultrasonic propagation imaging video data using a multi-time window amplitude plot to create a multi-time window amplitude map; (c) displaying the multi-time window amplitude map on a graphical user interface; (d) selecting at least three points on the multi-time window amplitude map through human interaction with the graphical user interface; (e) calculating a plurality of time window amplitude maps obtained by the multi-time window amplitude plot; and (f) performing a post-processing operation on the pulse-echo laser ultrasonic propagation imaging video data. (f) displaying on a graphical user interface an alphanumeric symbol representing the area calculated in step (e); (g) selecting points on the multi-time window amplitude map by human interaction with the graphical user interface; (h) converting the pixel coordinates of the points selected in step (g) to spatial coordinates in a reference frame of a positioner supporting a laser scanning head; (i) controlling the positioner to move the laser scanning head to a pointing position having the spatial coordinates obtained in step (h); and (j) activating the laser scanning head to emit a laser beam when the laser scanning head is in the pointing position. In an alternative, the polygonal anomaly area calculation and anomaly pointing functions can be implemented by a user interacting with a portion of the graphical user interface that is displaying a freeze frame.

[0084] Although the method and apparatus for post-processing pulse-echo laser UMPI video data to enhance visualization of structural abnormalities have been described with reference to various embodiments, it will be appreciated by those skilled in the art that various changes may be made and that equivalents may be substituted for elements thereof without departing from the scope of the teachings herein. In addition, many modifications may be made to adapt the teachings herein to specific circumstances without departing from the scope of the invention. Therefore, the claims are not intended to be limited to the specific embodiments disclosed herein.

[0085] As used herein, the term "computer system" should be broadly interpreted to encompass a system having at least one computer or processor, and a system may have multiple computers or processors communicating through a network or bus.

[0086] Some steps of the methods described herein may be encoded as executable instructions contained in a non-transitory tangible computer-readable storage medium (including but not limited to a storage device and / or a memory device). When these instructions are executed by a processing system or a computing system, the system device performs at least a portion of the methods described herein.

[0087] Unless the claim language explicitly specifies or states a particular order for performing some or all of the steps, the method claim as set forth should not be interpreted as requiring the steps recited in the invention to be performed in alphabetical order (any alphabetical order in the claim is used only to reference the steps previously described) or in the order in which they are recited. Nor should the process claim be interpreted to exclude any portion of two or more steps from being performed simultaneously or alternately, unless the claim language explicitly states a situation excluding such an interpretation.

Claims

1. A method for enhanced visualization of an abnormality (25) of a structure (10), the method comprising the following steps: (a) acquiring pulse-echo laser ultrasonic propagation imaging video data (6) at a plurality of points in a scanning area (40) on the surface of the structure (10); (b) post-processing the pulse-echo laser ultrasound propagation imaging video data using a multi-time window amplitude plot to create a multi-time window amplitude map (34), wherein: The post-processing includes: specifying a plurality of time windows (38a-38c) comprising a plurality of video freeze frames (32a-32c), wherein each of the video freeze frames (32a-32c) is associated with a corresponding depth in the structure (10) based on a speed of wave propagation; Selecting a time window (38a-38c) in which the amplitude value of the wave with the largest amplitude is greater than a predetermined threshold value among a plurality of waves with different amplitudes; creating a multiple time-window amplitude map (34) defined as a single image based on summed amplitude values ​​in selected video freeze frames (32a-32c) of selected time windows (38a-38c); and (c) displaying (62) the multi-time window amplitude graph on a graphical user interface (100).

2. The method according to claim 1, wherein: The selection of the time windows (38a-38c) of step (b) is repeated until all time windows (38a-38c) having amplitude values ​​of the waves with the largest amplitudes among the plurality of amplitudes are selected.

3. The method according to claim 1, further comprising the steps of: (d) selecting at least three points on the multi-time window amplitude graph (34) through human interaction with the graphical user interface; (e) calculating the area (A) of a polygon defined by the at least three points; and (f) displaying (80) on the graphical user interface an alphanumeric symbol representing the area calculated in step (e) (SELECTED AREA=).

4. The method according to claim 3, wherein: The at least three points are located on a boundary of an image (26) of the anomaly displayed on the graphical user interface.

5. The method according to claim 3, further comprising the steps of: (g) selecting a point on the multi-time window amplitude graph (34) through human interaction with the graphical user interface; (h) converting the pixel coordinates of the point selected in step (g) into spatial coordinates ((x1, y1), (x2, y2), (x3, y3)) in the reference frame of a positioner (90) supporting the laser scanning head (66); (i) controlling the positioner to move the laser scanning head to a pointing position having the spatial coordinates obtained in step (h); and (j) When the laser scanning head is in the pointing position, the laser scanning head is activated to emit a laser beam (64).

6. The method according to claim 5, wherein: Steps (h) to (j) are automatically performed in response to step (g).

7. The method according to claim 1, further comprising the steps of: (d) selecting (52) a point on the multi-time window amplitude graph (34) through human interaction with the graphical user interface; (e) converting the pixel coordinates of the point selected in step (d) into spatial coordinates ((x1, y1), (x2, y2), (x3, y3)) in the reference frame of a positioner (90) supporting the laser scanning head (66); (f) controlling the positioner to move the laser scanning head to a pointing position having the spatial coordinates obtained in step (e); and (g) When the laser scanning head is in the pointing position, the laser scanning head is activated to emit a laser beam (64).

8. The method according to claim 7, wherein: Steps (e) to (g) are automatically performed in response to step (d).

9. A device for enhanced visualization of an abnormality (25) of a structure (10), the device comprising: A pulse echo laser ultrasonic propagation imaging system, the pulse echo laser ultrasonic propagation imaging system comprising a laser scanning head (66); A graphical user interface (100); and A computer system (2), wherein the computer system (2) is configured to perform the following operations: (a) receiving pulse echo laser ultrasonic propagation imaging video data (6) from a pulse echo laser ultrasonic propagation imaging system; (b) post-processing the pulse-echo laser ultrasound propagation imaging video data using a multi-time window amplitude plot (58, 60) to create a multi-time window amplitude map (34), wherein the post-processing includes: specifying a plurality of time windows (38a-38c) comprising a plurality of video freeze frames (32a-32c), wherein each of the video freeze frames (32a-32c) is associated with a corresponding depth in the structure (10) based on a speed of wave propagation; Selecting a time window (38a-38c) in which the amplitude value of the wave with the largest amplitude is greater than a predetermined threshold value among a plurality of waves with different amplitudes; creating a multiple time-window amplitude map (34) defined as a single image based on summed amplitude values ​​in selected video freeze frames (32a-32c) of selected time windows (38a-38c); and (c) controlling the graphical user interface to display (62) the multi-time window amplitude graph.

10. The device according to claim 9, wherein: The computer system (2) performing step (b) is further configured to repeat the selection of the time windows (38a-38c) until all time windows (38a-38c) having amplitude values ​​of waves with the largest amplitudes among a plurality of amplitudes are selected.

11. The device according to claim 9, wherein: The computer system is further configured to perform the following steps: (d) receiving data representing a selection of at least three points from the multi-time window amplitude map; (e) calculating the area (A) of a polygon defined by the at least three points; and (f) controlling the graphical user interface to display an alphanumeric symbol representing the area calculated in step (e) (SELECTED AREA=).

12. The device according to claim 11, wherein The at least three points are positioned, by the computer system (2), on the border of an image (26) of the anomaly displayed on the graphical user interface to approximate the shape of the anomaly.

13. The device according to claim 11, wherein: The pulse echo laser ultrasonic propagation imaging system further comprises a positioner (90), the laser scanning head is mounted on the positioner (90), and the computer system is further configured to perform the following steps: (g) receiving data representing selected points from the multi-time window amplitude map (34); (h) converting the pixel coordinates of the selected point into spatial coordinates ((x1, y1), (x2, y2), (x3, y3)) in the reference system of the locator; (i) controlling the positioner to move the laser scanning head to a pointing position having the spatial coordinates obtained in step (h); as well as (j) When the laser scanning head is in the pointing position, the laser scanning head is activated to emit a laser beam (64).

14. The device according to claim 13, wherein: The positioner is a two-axis linear positioner (86, 88).

15. The apparatus according to any one of claims 9 to 14, wherein: The laser scanning head (66) includes an ultrasound generating laser (14), a first optical mirror (16), a second optical mirror (18), and a laser Doppler vibrometer (20).

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