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Air-coupled ultrasonic imaging method based on wavelet analysis and related algorithms

An ultrasonic imaging method and air coupling technology, which is applied in the direction of analyzing solids, analyzing materials, and processing detection response signals by using sound waves/ultrasonic waves/infrasonic waves. Problems such as poor ultrasonic imaging effect and low efficiency of air-coupled ultrasonic transduction can achieve optimal image signal-to-noise ratio, facilitate online data processing, and improve the ability to detect small defects

Active Publication Date: 2016-05-11
GUANGDONG INST OF INTELLIGENT MFG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, the transduction efficiency of air-coupled ultrasound is extremely low, and there are problems of weak signal strength and low signal-to-noise ratio, which make the imaging effect of air-coupled ultrasound poor.
In addition, because the intensity of the air-coupled ultrasonic transmission signal is very sensitive to factors such as the uniformity of the sample thickness, the incident angle of the ultrasonic signal, the diffraction of the signal from around the sample, and even the fluctuation of the surrounding airflow, the intensity of the transmitted wave fluctuates greatly.
The traditional peak imaging method or energy integral imaging method will bring a lot of image noise, and it is difficult to effectively distinguish the existence of packaging defects
On the other hand, because the air-coupled ultrasound is difficult to apply in the frequency band above 5MHz, the point-focused air-coupled ultrasonic probe is far from the position resolution of the traditional high-frequency water immersion probe

Method used

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  • Air-coupled ultrasonic imaging method based on wavelet analysis and related algorithms
  • Air-coupled ultrasonic imaging method based on wavelet analysis and related algorithms
  • Air-coupled ultrasonic imaging method based on wavelet analysis and related algorithms

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Embodiment 1

[0053] In this embodiment, air-coupled ultrasonic testing is performed on the seal of a soft package with a large defect with a width of 1.5 mm (1.5 times the probe focal diameter), and imaging is performed using the method of the present invention. The defect type is leakage channel type, the scanning area size is 30×5mm, the frequency of the point-focused air-coupled probe is 1MHz, the focus diameter is 1mm, the x-axis scanning step is 0.25mm, the y-axis scanning step is 1mm, and the signal sampling rate is 20MHz.

[0054] The specific process of imaging is as follows:

[0055] Air-coupled ultrasonic scanning is performed on each point in the XY plane, and the received transmission signal is denoted as x ij (t); the signal length is 6000 points in total.

[0056] Use db4 wavelet to x ij (t) Carry out 5 layers of wavelet decomposition.

[0057] The frequency band of the wavelet detail coefficient d4 is 0.625-1.25 MHz, so the wavelet coefficients of this sub-frequency band ...

Embodiment 2

[0066] In this embodiment, air-coupled ultrasonic testing is performed on a soft package seal with a small-sized defect (0.5 times the focal diameter of the probe) with a width of 0.5 mm, and imaging is performed using the method of the present invention. The configurations of defect type, scanning sensor probe, data sampling rate, scanning step size, and scanning area size are the same as those in Embodiment 1.

[0067] The imaging processing flow S1-S6 in this embodiment is the same as that in Embodiment 1. The specific steps of S7's adaptive smoothing filter are as follows:

[0068] Step A: The minimum value R in the correlation coefficient R matrix calculated in the previous step min is 0.79, the mean value of the correlation coefficient is 0.97, and the standard deviation σ of the correlation coefficient is 0.03, satisfying Therefore, it is judged that there are small-sized defects in the scanned image, and it is necessary to re-smooth and filter the wavelet coeffi...

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Abstract

The invention discloses an air-coupled ultrasonic imaging method based on wavelet analysis and related algorithms. Imaging is carried out by using wavelet coefficients of a sub-band and related coefficients of a reference signal as characteristic quantities, enabling effective elimination measurement-induced white Gaussian noise and strength fluctuation noise of air-coupled ultrasonic transmitting signals and improving signal to noise ratio of an image. Meanwhile, whether small size defects exist or not is judged through minimum values of related coefficients, thus adaptively adjusting a smooth filter window, the size of the smooth window is enlarged upon a large defect size, thereby reducing background noise, the size of the window is reduced upon a small defect size, highlighting signal details and thereby implementing 'adaptive focusing' and improving the ability to detect small defects. The imaging method has a promising application prospect in the field of air-coupled ultrasonic detection.

Description

technical field [0001] The invention relates to the field of ultrasonic imaging algorithms, in particular to an air-coupled ultrasonic imaging method for soft packaging sealing defects based on wavelet analysis and correlation algorithms. Background technique [0002] At present, flexible packaging occupies a large proportion in the food, pharmaceutical, and daily chemical product industries. Sealing defects such as air bubbles, inclusions, and leakage channels have a serious impact on product quality. The demand for online testing methods for the airtightness of heat-sealed flexible packaging is very extensive and urgent. Ultrasonic testing is one of the non-destructive testing methods for flexible packaging airtightness developed in recent years. Compared with traditional ultrasonic testing technology, air-coupled ultrasonic has the advantages of non-contact, no couplant, non-invasive, and non-polluting, which makes online non-destructive testing of the sealing quality of...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/04G01N29/46
CPCG01N29/04G01N29/46G01N2291/023
Inventor 刘忆森周松斌黄可嘉
Owner GUANGDONG INST OF INTELLIGENT MFG
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