中国激光, 2020, 47 (1): 0114001, 网络出版: 2020-01-09   

小波去噪在太赫兹无损检测中的应用 下载: 1495次

Application of Wavelet Denoising in Terahertz Nondestructive Detection
作者单位
1 长春理工大学光电工程学院光电测控与光信息传输技术教育部重点实验室, 吉林 长春 130022
2 长春理工大学光电工程学院光电工程国家级实验教学示范中心, 吉林 长春 130022
3 中国人民解放军93367部队, 吉林 四平 136000
摘要
提出了层析短时积分成像法,并通过实验验证了该方法的数据质量更高,成像效果优于传统的层析成像法;在小波去噪理论方面,结合太赫兹信号的特点提出δ-σ评价规则,利用该评价规则遴选出最优的小波去噪组合(即sym7小波,分解尺度为5),并以此为基础设计酚醛塑料样件进行无损检测层析短时积分成像实验,对比不同的小波去噪组合,从识别缺陷数量、缺陷识别率这两个主观评价指标和韦伯对比度这一客观评价指标上对比小波去噪的效果,结果表明:sym7小波(分解尺度为5,软阈值处理)对酚醛楔形缺陷无损检测信号小波去噪具有良好的效果,信号预处理后的样件无损检测图像背景噪声带得到了有效抑制,预制缺陷与背景区域的对比效果更加明显,能够清晰准确地获取样件的内部结构变化。
Abstract
This paper proposes a tomographic short-time integral imaging method. In terms of terahertz tomography, the experimental results show that the data quality and imaging effect of the proposed short-time integral imaging method are better than those of the traditional method. In the wavelet denoising theory, a δ-σ evaluation rule is proposed based on the characteristics of the terahertz signal, and the optimal wavelet denoising combination (e.g., the sym7 wavelet with a decomposition scale of 5) is selected using the evaluation rule. Based on this, the short-time integral imaging experiment of nondestructive detection tomography of phenolic plastic samples is set up, and different wavelet denoising combinations are compared. The effect of wavelet denoising is compared from two subjective evaluation indexes of defect number and defect recognition rate and the objective evaluation index of Weber contrast. Results prove that the sym7 wavelet (with the decomposition scale of 5, soft-threshold processing) is effective in wavelet denoising of nondestructive detection signals of phenolic wedge defects. The background noise in the nondestructive detection image of the sample after signal preprocessing is effectively suppressed. The contrast effect between prefabricated defects and the background area is more obvious, and the internal structural changes in the sample can be detected easily and accurately.

张霁旸, 任姣姣, 陈思宏, 李丽娟, 赵常双. 小波去噪在太赫兹无损检测中的应用[J]. 中国激光, 2020, 47(1): 0114001. Jiyang Zhang, Jiaojiao Ren, Sihong Chen, Lijuan Li, Changshuang Zhao. Application of Wavelet Denoising in Terahertz Nondestructive Detection[J]. Chinese Journal of Lasers, 2020, 47(1): 0114001.

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