A method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement

Abstract

The present invention relates to the field of ultrasonic flaw detection technology, and in particular to a method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement. The following technical scheme is adopted: firstly, a conventional imaging is performed to save the collected full matrix data, the ROI area is delineated and the amplitude of each pixel point in the area is calculated, the point with the maximum amplitude is obtained, the ROI area is simulated displaced, and then the points with the maximum amplitude are obtained respectively, and finally the maximum value and the minimum value are selected from the obtained points to calculate the amplitude fidelity value. The advantages of the present invention are: firstly, a conventional imaging is performed and the full matrix data is collected, and then the ROI area is simulated displaced, which can not only avoid the errors caused by factors such as instruments and detection environment, but also avoid complicated detection processes, and no high-precision encoder and scanning frame are required, which can greatly improve the accuracy and efficiency of amplitude fidelity value calculation.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic flaw detection, and in particular to a TFM imaging amplitude fidelity value calculation method based on ROI simulated displacement. Background Art

[0002] TFM (Total Focusing Method) imaging, that is, ultrasonic full focusing imaging, is a full matrix imaging method based on time-delay superposition. It is necessary to calculate the propagation path of each focus point in the imaging area, and then calculate the propagation time according to the propagation sound speed, and then find the corresponding amplitude value in the collected full matrix data FMC (Full Matrix Capture), and complete the amplitude calculation after superposition. Among them, the acquisition process of FMC data is: assuming that there are N array elements, one array element is transmitted alone, and all array elements receive echoes to form N rows of A-type scan data, and then one array element (the number of array elements can also be adjusted as needed) is stepped alone to transmit, and all array elements receive echoes, and then N rows of A-type scan data are formed. In this way, the transmission and reception are cyclically transmitted and received, and finally N*N A-type scan data matrices are formed, which is the full matrix data FMC. When it is necessary to calculate the amplitude of a point in the ROI (region of interest), it is necessary to calculate the propagation path of the point, calculate the propagation time according to the propagation sound speed, and then find the corresponding amplitude value in the collected FMC, and complete the amplitude calculation of the point after superposition. Therefore, the more points there are in the ROI area, the clearer the final image will be, the better the resolution will be, and the imaging result will be closer to the real image. When the inspector needs to specify the resolution, the inspection procedure should clearly verify the standards and methods for the resolution. According to the standard definition, when the probe moves in all directions with very fine increments, the amplitude range of the maximum peak measured cannot exceed 2dB. The amplitude fluctuation of the maximum peak is the amplitude fidelity AF (Amplitude Fidelity). To ensure that the amplitude fidelity is within the range of 2dB, it is necessary to form a grid with a sufficiently high resolution in the inspection area to provide reliable defect detection and feature description. In actual operation, when the resolution is improved, the number of points that need to be inspected in the inspection area is also greatly increased, which will greatly increase the computing burden and memory burden of the instrument and reduce the frame rate of imaging. Therefore, it is necessary to find a balance between amplitude fidelity and resolution. In this process, it is necessary to determine the amplitude fidelity under a certain resolution condition more quickly to determine the appropriate resolution as soon as possible.

[0003] There are currently two ways to obtain the amplitude fidelity value: one is to use an encoder and a scanning frame to repeatedly move the probe position to calculate the amplitude fidelity value. Since the moving distance of the probe is very short, it often needs to be accurate to the micron level, which requires a high driving accuracy of the scanning frame. In addition, the scanning frame needs to be frequently controlled during operation to drive the probe to move, which is not only prone to errors, but also complicated and inefficient. The other is to use a simple acoustic model for theoretical calculations. This method is a purely theoretical calculation and cannot exclude algorithm errors in the instrument imaging calculation process and errors in the data acquisition and transmission process. It does not take into account other factors that may affect the amplitude fidelity value, such as the physical properties of the workpiece and whether a wedge is added. Therefore, it cannot accurately reflect the resolution of the instrument imaging. Summary of the invention

[0004] The purpose of the present invention is to provide a method for calculating the amplitude fidelity value of TFM imaging, and specifically to provide a method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement, which can quickly and accurately calculate the amplitude fidelity value of TFM imaging.

[0005] To achieve the above object, the present invention adopts the following technical solution: a method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement, comprising the following steps:

[0006] S01. First, perform a TFM conventional imaging on any workpiece with defects, determine the defect location in the obtained image and draw an initial ROI area, recorded as ROI1, and save the full matrix data collected during the TFM conventional imaging.

[0007] S02, calculate the amplitude of all the pixels in the initial ROI area drawn in step S01, and obtain the point P1 with the largest amplitude. n ,y m ) of the amplitude I(x n ,y m ) is calculated according to the following formula:

[0008]

[0009] Where N is the number of array elements, r iP is the transmitting element T (x i ,y i ) and pixel point P(x n ,y m ), r jP is the receiving element R (x j ,y j ) and pixel point P(x n ,y m ), c is the speed of sound in the workpiece being tested, u ij (tiPj ) is the full matrix data saved in step S01 in the transmitting array element T (x i ,y i ), the receiving element R (x j ,y j ) at time t iPj The amplitude of the received reflected wave.

[0010] S03, simulate displacement of the initial ROI region ROI1 in step 1, the displacement is (∆x, ∆y), and obtain region ROI2, repeat step S02 in region ROI2, calculate the amplitude of all pixel points in ROI2 respectively, and obtain the point P2 with the largest amplitude;

[0011] S04, repeat step S03, adjust the displacement of ROI1, and obtain ROI3, ROI4, ... ROIn respectively, and obtain the points P3, P4, ... Pn with the largest amplitude respectively, select the maximum amplitude Amax and the minimum amplitude Amin from the amplitudes of the n points from P1 to Pn, and calculate the amplitude fidelity AF=-20log 10 (Amin / Amax).

[0012] Specifically, in steps S03 and S04, when simulating displacement of the initial region ROI1, the displacements ∆x and ∆y in the x-axis and y-axis directions are both integer multiples of a unit step distance, and the unit step distance is 1 / 20 of the wavelength of the sound wave in the workpiece.

[0013] Specifically, when ROI1 performs simulated displacement in steps S03 and S04, the moving direction is one of the moving directions of up, down, left, and right, or a combination of multiple moving directions.

[0014] Specifically, in step S02, iP and r jP The calculation is performed using the following formula:

[0015]

[0016]

[0017] Specifically, in step S03 or S04, after the simulated displacement, the positions of all pixels in ROI1 are shifted according to the displacement amount (∆x, ∆y), and the coordinates of the pixel points after the shift are (x n +∆x,y m +∆y) where r iP and r jP The calculation formula changes to:

[0018]

[0019]

[0020] The advantages of the present invention are: firstly, conventional imaging is performed and full matrix data is collected, then simulated displacement is performed on the ROI area, the maximum amplitude after the simulated displacement is calculated according to the collected full matrix data, and the maximum and minimum values ​​are taken from the maximum amplitudes of multiple simulated displacements to calculate the amplitude fidelity value; not only can the errors caused by factors such as instruments and detection environment be avoided, but also the complicated detection process can be avoided, and no high-precision encoder and scanning frame are required, which can greatly improve the accuracy and efficiency of amplitude fidelity value calculation. DETAILED DESCRIPTION

[0021] Embodiment 1, a method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement, comprises the following steps:

[0022] S01. Perform a TFM conventional imaging on any defective workpiece, determine the defect location in the obtained image and draw an initial ROI area, recorded as ROI1, and save the full matrix data collected during TFM conventional imaging. The full matrix data collected during TFM conventional imaging is an N*N A-type scan data matrix, and the A-type scan data is the echo value received by the receiving array element in real time.

[0023] S02, calculate the amplitude of all the pixels in the initial ROI area drawn in step S01, and obtain the point P1 with the largest amplitude. n ,y m ) of the amplitude I(x n ,y m ) is calculated according to the following formula:

[0024]

[0025] Where N is the number of array elements, r iP is the transmitting element T (x i ,y i ) and pixel point P(x n ,y m ), r jP is the receiving element R (x j ,y j ) and pixel point P(x n ,y m ), c is the speed of sound in the workpiece being tested, u ij (t iPj ) is the full matrix data saved in step S01 in the transmitting array element T (x i ,y i ), the receiving element R (x j,y j ) at time t iPj The amplitude of the received reflected wave.

[0026] Among them, r iP and r jP The calculation is performed using the following formula:

[0027]

[0028]

[0029] S03, simulate the displacement of the initial ROI region ROI1 in step 1, the displacement is (∆x, ∆y), and obtain the region ROI2. Repeat step S02 in the region ROI2, calculate the amplitudes of all pixel points in ROI2 respectively, and obtain the point P2 with the largest amplitude.

[0030] After the simulated displacement, the positions of all pixels in ROI1 are shifted according to the displacement (∆x, ∆y). The coordinates of the pixels after the shift are (x n +∆x,y m +∆y) where r iP and r jP The calculation formula changes to:

[0031]

[0032]

[0033] S04, repeat step S03, adjust the displacement of ROI1, and obtain ROI3, ROI4, ... ROIn respectively, and obtain the points P3, P4, ... Pn with the largest amplitude respectively, select the maximum amplitude Amax and the minimum amplitude Amin from the amplitudes of the n points from P1 to Pn, and calculate the amplitude fidelity AF=-20log 10 (Amin / Amax).

[0034] Specifically, in steps S03 and S04, when simulating displacement of the initial region ROI1, the displacements ∆x and ∆y in the x-axis and y-axis directions are both integer multiples of a unit step distance, and the unit step distance is 1 / 20 of the wavelength of the sound wave in the workpiece.

[0035] Specifically, when ROI1 performs simulated displacement in steps S03 and S04, the moving direction is one of the moving directions of up, down, left, and right, or a combination of multiple moving directions.

[0036] Of course, the above are only preferred embodiments of the present invention, and are not intended to limit the scope of use of the present invention. Therefore, any equivalent changes made to the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement, characterized in that: The following steps are involved: S01, first perform a TFM conventional imaging on any workpiece with defects, determine the defect location in the obtained image and draw an initial ROI area, recorded as ROI1, and save the full matrix data collected during the TFM conventional imaging; S02, calculate the amplitude of all the pixels in the initial ROI area drawn in step S01, and obtain the point P1 with the largest amplitude. n ,y m ) of the amplitude I(x n ,y m ) is calculated according to the following formula: Where N is the number of array elements, r iP is the transmitting element T (x i ,y i ) and pixel point P(x n ,y m ), r jP is the receiving element R (x j ,y j ) and pixel point P(x n ,y m ), c is the speed of sound in the workpiece being tested, u ij (t iPj ) is the full matrix data saved in step S01 in the transmitting array element T (x i ,y i ), the receiving element R (x j ,y j ) at time t iPj The amplitude of the received reflected wave; S03, simulate displacement of the initial ROI region ROI1 in step 1, the displacement is (∆x, ∆y), and obtain region ROI2, repeat step S02 in region ROI2, calculate the amplitude of all pixel points in ROI2 respectively, and obtain the point P2 with the largest amplitude; S04, repeat step S03, adjust the displacement of ROI1, and obtain ROI3, ROI4, ... ROIn respectively, and obtain the points P3, P4, ... Pn with the largest amplitude respectively, select the maximum amplitude Amax and the minimum amplitude Amin from the amplitudes of the n points from P1 to Pn, and calculate the amplitude fidelity AF=-20log 10 (Amin / Amax).

2. The method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement according to claim 1, characterized in that: In the steps S03 and S04, when simulating displacement of the initial region ROI1, the displacements ∆x and ∆y in the x-axis and y-axis directions are both integer multiples of a unit step distance, and the unit step distance is 1 / 20 of the wavelength of the sound wave in the workpiece.

3. The method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement according to claim 2, characterized in that: When ROI1 performs simulated displacement in steps S03 and S04, the moving direction is one of the moving directions of up, down, left and right, or a combination of multiple moving directions.

4. The method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement according to claim 1, characterized in that: In step S02, iP and r jP The calculation is performed using the following formula: 。 5. The method for calculating the amplitude fidelity value of TFM imaging based on ROI simulated displacement according to claim 4, characterized in that: In step S03 or S04, after the simulated displacement, the positions of all pixels in ROI1 are shifted according to the displacement amount (∆x, ∆y), and the coordinates of the pixel points after the shift are (x n +∆x,y m +∆y) where r iP and r jP The calculation formula changes to: 。

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