An ultrasonic phased array sector scan real-time interpolation imaging method

Abstract

The application discloses an ultrasonic phased array fan scanning real-time interpolation imaging method, which comprises the following steps: initializing parameters of an ultrasonic phased array, setting an angle range of the ultrasonic phased array in a tested piece, determining starting sampling positions and delay times of each beam, then controlling a sampling end to sample each beam from the starting sampling position according to the delay times of the beams, calculating pixel values of each pixel point according to sampling values, and finally using multi-thread partition drawing to quickly draw a fan scanning image and realize real-time interpolation imaging.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing technology, and more specifically, relates to a real-time interpolation imaging method for ultrasonic phased array sector scanning. Background Technology

[0002] Ultrasonic phased array testing technology is an advanced defect detection technique in the field of industrial non-destructive testing. Compared with conventional ultrasonic probes, the advantage of phased arrays is that they can obtain multiple beam detection signals through beam deflection and focusing without moving the probe, enabling multi-angle scanning and real-time imaging. This technology can be further subdivided into sector scanning imaging, full-focusing imaging, and linear scanning or electronic scanning imaging.

[0003] The main principle of sector scanning imaging is: using an array probe, the excitation time of each array element is controlled according to the corresponding emission focusing law and reception focusing law to achieve beam deflection and focusing, and the received data of each array element is synthesized to obtain the echo detection signal. After processing the signal, a clear image of the acoustic defect can be obtained.

[0004] The transmit focusing law refers to calculating the arrival time and time difference of the sound waves from each element to the designated focal point when exciting the array elements, and then sequentially exciting each element according to the time difference, so that the sound waves from each element arrive at the focal point simultaneously, achieving beam focusing and deflection. The receive focusing law refers to synthesizing the signals received by each element according to a designated virtual focal point and the sound wave propagation time difference to obtain the echo signal of the beam. There are four commonly used focusing laws: equal depth focusing, equal path focusing, projection focusing, and arbitrary plane focusing. In simple terms, these involve setting the focal points of each beam to have the same vertical depth, the same propagation distance, the same horizontal distance, and any point on the same plane.

[0005] Phased array probes typically require a wedge as an intermediate medium for contact with the workpiece. This serves two purposes: firstly, to protect the probe; and secondly, because sound waves refract at the interface, according to Snell's law, a wedge allows longitudinal waves to exceed the first refraction angle, ensuring only transverse waves enter the workpiece and preventing interference between longitudinal and transverse waves. Furthermore, due to ultrasonic side lobes and other factors, the focusing ability and detection effect decrease as the beam deflection angle increases; the presence of a wedge expands the scanning range at this angle. Currently, ultrasonic phased array sector scanning imaging technology using wedges has become one of the main techniques in ultrasonic non-destructive testing, particularly widely used in the detection of defects in rail welds.

[0006] However, current sector scanning imaging methods, in order to achieve fast and real-time imaging, typically do not perform interpolation processing. Instead, they first perform coordinate transformation and then directly fill the entire quadrilateral region above each sampling point with the gray value of that sampling point. This imaging method firstly exhibits obvious imaging bias, and secondly, the clarity is also low, especially at greater distances, where it appears as distinctly blocky images. To achieve clear and accurate imaging, interpolation imaging methods must be used. However, interpolation inevitably involves a huge amount of computation, posing a challenge to the speed and real-time performance of imaging. In addition, most existing sector scanning interpolation methods use simple linear interpolation, which is not the optimal choice for sector scanning imaging, and its imaging accuracy cannot be guaranteed. Therefore, there is an urgent need for a precise, high-speed, and smooth ultrasonic phased array sector scanning imaging method. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a real-time interpolation imaging method for ultrasonic phased array sector scanning to achieve accurate, high-speed and smooth imaging.

[0008] To achieve the above-mentioned objectives, the present invention provides a real-time interpolation imaging method for ultrasonic phased array sector scanning, characterized by comprising the following steps:

[0009] (1) Initialization of ultrasonic phased array;

[0010] Initialize the parameters of the ultrasonic phased array and set the angular range θ1 to θ2 of the ultrasonic phased array's transmitted beam in the test piece. n ;

[0011] (2) Determine the starting sampling position of each beam;

[0012] (2.1) The point at which each beam passes through the interface between the wedge and the test piece is recorded as the incident point A of each beam. i i = 1, 2, ..., n, where n is the number of beams;

[0013] (2.2) Let H be the center point of the ultrasonic phased array. Then, take the intersection point directly below the center point H and the interface as the center O of the pixel coordinate circle, with the vertical downward direction as the Z axis and the horizontal direction as the X axis, and construct a coordinate system.

[0014] (2.3) Determine the propagation speed v1 of the beam in the wedge and the propagation speed v2 in the test piece;

[0015] (2.4) Calculate the slope k of each beam in the test piece according to the coordinate system. i Incident point position OA i ;

[0016] According to the coordinate system, mark the backward extension line of each beam, and then record the intersection point B between two adjacent beams;

[0017] (2.5) Determine the starting sampling point C for each beam. i ;

[0018] Based on the angle range θ1~θ n From the maximum angle θ n Initially, the incident point of the nth beam is set to be the same as the starting sampling point. Then, the intersection point B of the backward extensions of the nth and (n-1)th beams is calculated. n,n-1 To C n The distance, denoted as L n ;

[0019] With intersection point B n,n-1 Center, L n Draw an arc with radius C, and denote the intersection of the arc and the (n-1)th beam as the starting sampling point C of the (n-1)th beam. n-1 This process continues until the starting sampling point C1 of the first beam is obtained, ultimately yielding the starting sampling points {C1, C2, ..., C...} for each beam. i ,…,C n};

[0020] (3) Determine the delay time τ of each beam. i ;

[0021] (3.1) For each beam, calculate the distance from the center point H to the incident point A. i distance and the point of incidence A i To the starting sampling point C i distance

[0022] (3.2) Calculate the delay time of each beam in the wedge and the test piece respectively;

[0023]

[0024] in, Let be the delay time of the i-th beam in the wedge. Let be the delay time of the i-th beam in the test piece;

[0025] (3.3) Calculate the delay time τ of each beam. i And send it to the ultrasonic phased array;

[0026]

[0027] (4) Sector scanning imaging of ultrasonic phased array;

[0028] (4.1) The ultrasonic phased array controls the sampling end to sample each beam from the starting sampling point at a fixed sampling distance L according to the delay time of each beam. Then, the sampling points of each beam are combined into a sampling sequence, thus obtaining n sampling sequences.

[0029] (4.2) Select any point in the imaging area of ​​the ultrasonic phased array and denote it as pixel point P. Then calculate the slope of the line connecting pixel point P and the intersection point B of each beam.

[0030] (4.3) Combine the above slopes with the slope k of each beam. i The comparison is performed. If the pixel P is located exactly between the slopes of two adjacent beams, it is determined that the pixel P is located within the angle region between the two beams. Then, the beam numbers and the intersection of the two beams are recorded.

[0031] (4.4) Find the four sampling points closest to pixel P on the two adjacent recorded beams;

[0032] (4.4.1) In the two adjacent beams recorded, the starting sampling point of one beam is denoted as C', and the intersection of the two beams is denoted as B'.

[0033] (4.4.2) Calculate the distance PB' from pixel P to intersection B' and the distance B'C' from intersection B' to the starting sampling point C'. Then, divide the difference between PB' and B'C' by the fixed sampling distance L and round the result to obtain the first sampling point K1 on the beam. Finally, based on the sampling sequence of the beam, find the next adjacent sampling point K2 of the first sampling point K1 and take it as the two sampling points closest to pixel P on the beam.

[0034] (4.4.2) Similarly, using the above method, find the two sampling points closest to pixel P on another beam, denoted as K3 and K4 respectively;

[0035] (4.5) Let B'P be the line connecting the intersection point B' of the two beams and the pixel point P. Then determine the angles between B'P and the two beams respectively.

[0036] (4.6) Calculate the pixel value of pixel point P;

[0037] (4.6.1) Set points K5 and K6, where K5 is located between K1 and K2, and K6 is located between K3 and K4, satisfying the following conditions:

[0038]

[0039]

[0040] Where d represents the normal distance of pixel P from the arc formed by sampling points K1 and K3, and |K| represents the sampling value of sampling point K;

[0041] (4.6.2) Calculate the pixel value of pixel P:

[0042]

[0043] (4.7) Traverse each pixel in the imaging area of ​​the ultrasonic phased array and calculate the pixel value of each pixel according to steps (4.2) to (4.6) to draw the imaging image.

[0044] The objective of this invention is achieved as follows:

[0045] This invention discloses a real-time interpolation imaging method for ultrasonic phased array sector scanning. First, the parameters of the ultrasonic phased array are initialized, and the angular range of the ultrasonic phased array's transmitted beam in the test piece is set. Then, the starting sampling position and delay time of each beam are determined. Next, the ultrasonic phased array controls the sampling end to sample each beam from the starting sampling point according to the delay time of each beam. The pixel value of each pixel is calculated based on the sampled values. Finally, multi-threaded partitioning drawing is used to quickly draw the sector scan image, thereby realizing real-time interpolation imaging.

[0046] Meanwhile, the ultrasonic phased array sector scanning real-time interpolation imaging method of the present invention also has the following beneficial effects:

[0047] (1) By setting the starting sampling position, the present invention realizes interpolation according to the angle ratio and distance ratio, resulting in more accurate and smoother imaging, and the imaging detail can be arbitrarily set according to the computing power of the computer.

[0048] (2) This invention does not require coordinate transformation like ordinary sector scanning imaging.

[0049] (3) Since it is pixel-by-pixel drawing, the time cost is relatively large. By drawing bitmaps in a multi-threaded partition, the advantages of the computer's multi-core processor can be fully utilized to achieve fast imaging. Attached Figure Description

[0050] Figure 1 This is a flowchart of a real-time interpolation imaging method for ultrasonic phased array sector scanning according to the present invention;

[0051] Figure 2 This is a diagram of a coordinate system;

[0052] Figure 3 This is a schematic diagram of the initial sampling position;

[0053] Figure 4 This is a schematic diagram of the traditional sector sweep interpolation method;

[0054] Figure 5 This is a schematic diagram of the sector sweep interpolation method of the present invention. Detailed Implementation

[0055] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0056] Example

[0057] Figure 1 This is a flowchart of a real-time interpolation imaging method for ultrasonic phased array sector scanning according to the present invention.

[0058] In this embodiment, as Figure 1 As shown, the present invention provides a real-time interpolation imaging method for ultrasonic phased array sector scanning, comprising the following steps:

[0059] S1. Initialization of ultrasonic phased array;

[0060] Initialize the parameters of the ultrasonic phased array and set the angular range θ1 to θ2 of the ultrasonic phased array's transmitted beam in the test piece. n ;

[0061] S2. Determine the starting sampling position for each beam;

[0062] S2.1. The point where each beam passes through the interface between the wedge and the test piece is recorded as the incident point A of each beam. i i = 1, 2, ..., n, where n is the number of beams;

[0063] S2.2. Let H be the center point of the ultrasonic phased array. Then, take the intersection point directly below the center point H and the interface as the center O of the pixel coordinate circle, with the vertical downward direction as the Z-axis and the horizontal direction as the X-axis, and construct... Figure 2 The coordinate system shown;

[0064] S2.3 Determine the beam propagation speed v1 in the wedge and the beam propagation speed v2 in the test piece;

[0065] S2.4. Calculate the slope k of each beam in the test piece according to the coordinate system. i Incident point position OA i ;

[0066] According to the coordinate system, mark the backward extension line of each beam, and then record the intersection point B between two adjacent beams;

[0067] S2.5 Determine the starting sampling point C for each beam. i ;

[0068] Based on the angle range θ1~θ n From the maximum angle θ n Initially, the incident point of the nth beam is set to be the same as the starting sampling point. Then, the intersection point B of the backward extensions of the nth and (n-1)th beams is calculated. n,n-1 To C n The distance, denoted as L n ;

[0069] With intersection point B n,n-1 Center, L n Draw an arc with radius C, and denote the intersection of the arc and the (n-1)th beam as the starting sampling point C of the (n-1)th beam. n-1 This process continues until the starting sampling point C1 of the first beam is obtained, ultimately yielding the starting sampling points {C1, C2, ..., C...} for each beam. i ,…,C n};

[0070] In this embodiment, as Figure 3 As shown, there are 4 beams in total. The incident points of each beam are {A1, A2, A3, A4}, the initial sampling points are {C1, C2, C3, C4}, and the intersection points between adjacent beams are {B1, B2, B3}.

[0071] S3. Determine the delay time τ of each beam. i ;

[0072] S3.1 For each beam, calculate the distance from the center point H to the incident point A. i distance and the point of incidence A i To the starting sampling point C i distance

[0073] S3.2 Calculate the delay time of each beam in the wedge and the test piece respectively;

[0074]

[0075] in, Let be the delay time of the i-th beam in the wedge. Let be the delay time of the i-th beam in the test piece;

[0076] S3.3 Calculate the delay time τ of each beam. i And send it to the ultrasonic phased array;

[0077]

[0078] S4, Sector scanning imaging of ultrasonic phased array;

[0079] S4.1 The ultrasonic phased array controls the sampling end to sample each beam from the starting sampling point at a fixed sampling distance L according to the delay time of each beam. Then, the sampling points of each beam are combined into a sampling sequence, thus obtaining n sampling sequences.

[0080] S4.2 Select any point within the imaging area of ​​the ultrasonic phased array, and denote it as pixel point P. Then calculate the slope of the line connecting pixel point P and the intersection points B of each beam.

[0081] S4.3, Combine the above slopes with the slope k of each beam. i The comparison is performed. If the pixel P is located exactly between the slopes of two adjacent beams, it is determined that the pixel P is located within the angle region between the two beams. Then, the beam numbers and the intersection of the two beams are recorded.

[0082] In this embodiment, as Figure 5 As shown, the second and third adjacent beams were found to satisfy the condition, and the intersection of these two beams is denoted as B2;

[0083] S4.4 Find the four sampling points closest to pixel P on the two adjacent recorded beams;

[0084] In this embodiment, a relatively simple and direct imaging method is to first calculate the two neighboring points of the next beam corresponding to each pixel, then combine this with the next sampling point of the beam, and use the gray value of the sampling point to draw a rectangle around these four points, such as... Figure 4 As shown in Figure ABCD. A major advantage of this imaging method is its low computational load and fast drawing speed, but its disadvantages are also obvious. Its imaging has significant deviations and low clarity, especially at far distances, where it will appear as obvious rectangular blocks.

[0085] To achieve accurate and smooth imaging, interpolation is necessary. However, most current interpolation methods are not very reasonable. For example, the interpolation method disclosed in the invention patent application number "201510219036.3", entitled "Scanning Detection Method and Device for Sector Scan Imaging of Ultrasonic Phased Array", is... Figure 4 As shown, because sampling starts from the interface and the sampling intervals are equal, the interpolation region is always an irregular quadrilateral, making bilinear interpolation unsuitable. The interpolation method first gives two conditions: AE / EB equals CF / FD, and the line connecting EF passes through the interpolation point. Then, the coordinates of points E and F are calculated by solving a system of equations, and interpolation is performed based on the positional proportion of the interpolation point on line segment EF. This interpolation method considers each quadrilateral region individually, without considering the overall picture; theoretically, the interpolation between adjacent quadrilateral regions will inevitably be uneven.

[0086] For sector scanning, interpolation using angle and distance ratios is theoretically and logically the most accurate and smoothest method. However, the challenge lies in the fact that the extensions of each beam do not intersect at the same center, and the intersection points of any two beams are not the same. Figure 2 As shown. In addition, to achieve interpolation by angle and distance, it is necessary to ensure that the sampling points of two adjacent beams are at the same distance from the center of the circle. Therefore, in addition to setting the wedge delay for the phased array, the starting sampling position must also be set.

[0087] Based on this, the pixel interpolation of the present invention is as follows: Figure 5 As shown, we first obtain the sampled values ​​of four points A, B, C, and D. Then, we calculate the values ​​of points E and F based on the distance ratio. Finally, we use E and F to calculate the pixel value of that pixel based on the angle ratio. The specific process is described in detail below:

[0088] S4.4.1 In the two adjacent beams recorded, the starting sampling point of one beam is denoted as C', and the intersection of the two beams is denoted as B'.

[0089] S4.4.2 Calculate the distance PB' from pixel P to intersection B' and the distance B'C' from intersection B' to the starting sampling point C'. Then, subtract B'C' from PB' and divide the difference by the fixed sampling distance L, and round the result to obtain the first sampling point K1 on the beam. Finally, based on the sampling sequence of the beam, find the next adjacent sampling point K2 of the first sampling point K1, and take it as the two sampling points on the beam that are closest to pixel P.

[0090] S4.4.2 Similarly, using the method described above, find the two sampling points closest to pixel P on another beam, denoted as K3 and K4 respectively;

[0091] S4.5. Denote the line connecting the intersection point B' of the two beams and the pixel point P as B'P. Then determine the angles between B'P and the two beams respectively.

[0092] S4.6 Calculate the pixel value of pixel P;

[0093] S4.6.1 Set points K5 and K6, where K5 is located between K1 and K2, and K6 is located between K3 and K4, satisfying the following conditions:

[0094]

[0095]

[0096] Where d represents the normal distance of pixel P from the arc formed by sampling points K1 and K3, and |K| represents the sampling value of sampling point K;

[0097] In this embodiment, K1 to K6 respectively correspond to Figure 5 Points A through F in the diagram;

[0098] S4.6.2 Calculate the pixel value of pixel P:

[0099]

[0100] S4.7. Traverse every pixel in the imaging area of ​​the ultrasonic phased array and calculate the pixel value of each pixel in multi-threaded calculation according to steps S4.2 to S4.6 to draw the imaging image.

[0101] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A real-time interpolation imaging method for ultrasonic phased array sector scanning, characterized in that, Includes the following steps: (1) Initialization of ultrasonic phased array; Initialize the parameters of the ultrasonic phased array and set the angular range of the ultrasonic phased array's transmitted beam in the test piece. ; (2) Determine the starting sampling position for each beam; (2.1) The point at which each beam passes through the interface between the wedge and the test piece is recorded as the incident point of each beam. , , Number of beams; (2.2) Let the center point of the ultrasonic phased array be denoted as . Then, with the center point The point where the pixel coordinates intersect with the interface directly below is taken as the center of the circle. A coordinate system is constructed with the vertical direction downward as the Z-axis and the horizontal direction as the X-axis; (2.3) Determine the beam propagation speed in the wedge. Propagation speed in the test piece ; (2.4) Calculate the slope of each beam in the test piece according to the coordinate system. Incident point position ; Mark the backward extension lines of each beam according to the coordinate system, and then record the intersection points between adjacent beams. ; (2.5) Determine the starting sampling point for each beam. ; According to the angle range From the largest angle Begin, set the first The incident point of the beam is at the same position as the initial sampling point, and then the 1st beam is calculated. Bundle and the first The intersection of the backward extensions of the beam arrive The distance is denoted as ; Intersection Center of the circle Draw an arc with radius , the arc and the first The intersection of the beams is denoted as the first. Beam beam starting sampling point And so on, until the starting sampling point of the first beam is obtained. Finally, the starting sampling points of each beam are obtained. ; (3) Determine the delay time of each beam. ; (3.1) For each beam, calculate the center point. to the point of incidence distance and the point of incidence To the starting sampling point distance ; (3.2) Calculate the delay time of each beam in the wedge and the test piece respectively; ； in, For the first The delay time of the beam in the wedge, For the first The delay time of the beam in the test piece; (3.3) Calculate the delay time of each beam. And send it to the ultrasonic phased array; ； (4) Sector scanning imaging of ultrasonic phased array; (4.1) The ultrasonic phased array controls the sampling end to sample each beam at a fixed distance from the starting sampling point, based on the delay time of each beam. Sampling is performed, and then the sampling points of each beam are combined into a sampling sequence to obtain... Sampled sequences; (4.2) Select any point within the imaging area of ​​the ultrasonic phased array and denote it as a pixel. Then calculate the pixel points Intersection with each beam The slope of the line connecting them; (4.3) Combine the above slopes with the slopes of each beam. The comparison is performed, and if the pixel is exactly between the slopes of two adjacent beams, then the pixel is determined. Located within the area between these two beams, then record the beam numbers and the intersection of the two beams; (4.4) Find the distance pixel on the two adjacent recorded beams. The four most recent sampling points; (4.4.1) Among the two adjacent beams recorded, denote the starting sampling point of one of the beams as... The intersection of the two beams is ; (4.4.2) Calculate pixel points to the intersection distance and intersection To the starting sampling point distance Then use minus Difference divided by fixed sampling distance The calculation result is then rounded to obtain the first sampling point on the beam. Finally, based on the sampling sequence of the beam, the first sampling point is found. The next adjacent sampling point And as the distance to the pixel on that beam. The two most recent sampling points; (4.4.3) Similarly, the distance to the pixel is found on another beam using the method described above. The two most recent sampling points are denoted as follows: , ; (4.5) The intersection point of the two beams is With pixels The connection is denoted as Then determine The angles between the two beams respectively , ; (4.6) Based on the included angle , Calculate pixels Pixel values; (4.6.1) Setting point , ,in lie in and between, lie in and Between, and satisfying: ； ； in, Represents pixels Distance from sampling point , The normal distance of the arc formed. Indicates sampling point The sampled values; (4.6.2) Calculate pixel points Pixel values: ； (4.7) Traverse each pixel in the imaging area of ​​the ultrasonic phased array and calculate the pixel value of each pixel in multi-threaded manner according to steps (4.2) to (4.6) to draw the imaging image.

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