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针对传统的工业无损检测超声图像散斑噪声降噪方法,不能很好的保持图像边缘和细节,提出了一种新的基于粗集与小波的工业超声图像降噪方法.该方法通过考察散斑噪声的统计特征,利用粗集中的等价关系将工业超声图像划分为若干子图,对子图进行对数变换后完成小波变换,采用自适应阈值函数处理小波系数,应用小波逆变换和指数变换得到降噪后的子图,将降噪后的子图进行叠加得到最终的降噪图像.通过新算法在实际工业超声图像中的应用,实现了在保证降噪效果的同时能够较好地保持图像边缘及细节特征,验证了算法的有效性. 相似文献
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焊接视觉图像检测是实现焊接过程自动控制的重要步骤.针对焊接图像噪声大、稳定性差的特点,提出了一种基于小波降噪和形态学模糊检测的算法.首先分别用小波变换和灰度形态学算法对焊接熔池图像进行降噪处理,然后将两者结果融合进行模糊处理,最后完成灰度形态学边缘检测.实验结果表明,此方法能够从含有较强噪声的弧焊视觉图像中获取清晰、准... 相似文献
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针对射线检测图像的高噪声、低对比度、图像模糊等特点,提出了一种射线图像的自适应多尺度积阈值降噪算法,解决了常用射线检测图像降噪算法存在的降噪效果差、图像模糊、缺陷边缘和细节丢失等问题。该算法利用噪声估计、多尺度、积阈值、小波等方法对射线检测图像进行降噪处理,获得了高质量的降噪图像。以实际的工业焊缝射线检测图像为例,将所提算法与常用的小波降噪、中值滤波、维纳滤波、小波中值等算法进行降噪对比研究。试验结果表明,所提算法不仅具有优异的降噪性能,而且能够较好地保留缺陷图像边缘、细节等重要特征。 相似文献
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超声TOFD检测信号中混入的无关噪声常导致从检测图像中难以分辨缺陷特征。本研究通过小波包分解技术分析缺陷衍射波特征信号的时、频域分布特征,采用小波包统一阈值对超声TOFD检测信号进行降噪处理,对比软、硬阈值函数对检测信号的降噪结果。研究结果表明:采用软、硬阈值对长度10 mm、深度5 mm的裂纹缺陷信号降噪,其信噪比由原始的22.88 dB分别提高至186.66、176.65 dB,对长度28 mm、深度8 mm的夹杂缺陷信号降噪,其信噪比由原始的16.62 dB分别提高至33.74、28.16 dB;基于小波包软、硬阈值去噪后信号进行图像重构可有效抑制干扰条纹并提高缺陷特征图像的分辨力,而采用软阈值法几乎完全去除了原始超声TOFD检测图像中的噪声条纹。 相似文献
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《组合机床与自动化加工技术》2017,(11)
针对传统Bayes阈值不能随小波分解尺度变换以及提高传统算法图像降噪效果的问题,文章提出一种改进的基于小波维纳滤波与Bayes自适应阈值估计图像降噪算法,该算法在多层小波变换的基础上,对小波分解后的第一层细节系数进行维纳滤波处理,对其他层细节系数进行改进Bayes软阈值估计算法处理,最后对处理后的小波系数进行重构,得到降噪图像。实验结果表明,该方法在图像峰值信噪比(PSNR)定量指标上优于传统的小波Bayes软阈值估计图像降噪方法,并将该方法成功的应用于轴承缺陷图像的降噪预处理以及轴承缺陷图像边缘检测中,达到了图像降噪的优化效果。 相似文献
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非线性滤波在射线图像降噪增强中的应用 总被引:1,自引:2,他引:1
射线数字成像是当前射线检测与诊断技术发展的方向,图像降噪增强是提高射线成像检测灵敏度和分辨力的关键。重点探讨以排序滤波为代表的非线性滤波图像降噪增强方法,对射线图像的处理表明,线性滤波在降噪的同时会引起较大的边级模糊,而排序滤波不仅降低噪声且能保持图像细节,提高图像质量效果明显。 相似文献
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GPR signal de-noising by discrete wavelet transform 总被引:2,自引:0,他引:2
Jamel Baili Samer Lahouar Mounir Hergli Imad L. Al-Qadi Kamel Besbes 《NDT & E International》2009,42(8):696-703
Ground penetrating radar (GPR) is a non-destructive investigation tool used for several applications related to civil infrastructures; including buried objects detection and structural condition evaluation. Although GPR can be effectively used to survey structures, signal analysis can be sometimes challenging. The GPR signals can be easily corrupted by noise because the GPR receiver has usually an ultra-wide bandwidth (UWB). The noise collected by the system can easily mask relatively weak reflections resulting from the inhomogeneities within the surveyed structure; especially when they are at a relatively deep location. This paper presents the use of discrete wavelet transform (DWT) to de-noise the GPR signals. Various mother wavelets were used in this study to de-noise experimental GPR signals collected from flexible pavements. The performance of wavelet de-noising was evaluated by computing the signal-to-noise ratio (SNR) and the normalized root-mean-square error (NRMSE) after de-noising. The study found that wavelet de-noising approach outperforms traditional frequency filters such as the elliptic filter. At the same level of decomposition, the Daubechies order 6 and Symlet order 6 outperform the Haar and Biorthogonal mother wavelets when de-noising GPR signals by soft thresholding. 相似文献
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In the ultrasonic detection of defects in friction welded joints, it is difficult to exactly detect some weak bonding defects because of the noise pollution. This paper proposed an improved threshold function based on the multi-resolution analysis wavelet threshold de-noising method which was put forward by Donoho and Johnstone, and applied this method in the de-noising of the defective signals. This threshold function overcomes the discontinuous shortcoming of the hard-threshold function and the disadvantage of soft threshold function which causes an invariable deviation between the estimated wavelet coefficients and the decomposed wavelet coefficients. The improved threshold function is of simple expression and convenient for calculation. The actual test results of defect noise signal show that this improved method can get less mean square error (MSE) and higher signal-to-noise ratio of reconstructed signals than those calculated from hard threshold and soft threshold methods. The improved threshold function has excellent de-noising effect. 相似文献
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微型电机振动信号信噪比低,环境噪声复杂,对噪声信号进行有效去除是对其进行质量检测的关键步骤。针对传统小波降噪阈值函数连续性差、降噪效果不理想等问题,提出一种基于样本熵的改进小波阈值函数,能够根据信号混乱程度自动对阈值函数进行调节。仿真结果表明:在低信噪比环境下,基于样本熵的改进阈值函数降噪效果明显优于传统阈值函数和普通改进阈值函数,信号信噪比得到显著提升。对微型电机异音信号进行降噪处理和特征提取,结合SVM分类器进行训练测试,试验结果表明:改进的小波降噪算法能够有效去除电机信号环境噪声,提取有效的信号特征,对出厂电机性能优劣进行准确判断。该方法将为微型电机厂家大规模质量检测提供理论依据和支持。 相似文献
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Feature extraction of machine sound using wavelet and its application in fault diagnosis 总被引:3,自引:0,他引:3
Machine sound always carries information about the working of the machine. But in many cases, the sound has a very low SNR. To obtain correct information, the background noise has to be removed or the sound must be purified. A de-noising method is given in this paper and is successfully used in feature sound extraction. We can easily diagnose a machine using the purified sound. This de-noising method is based on the wavelet technique and uses the Morlet wavelet as the mother wavelet, because its time–frequency resolution can be adjusted to adapt to the signal to be analyzed. The method is used for extracting the sound of some vehicle engines with different types of failure. The feature sound is extracted successfully. 相似文献
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目的有效滤除带钢表面缺陷图像高斯噪声。方法高斯噪声是影响带钢图像质量的主要噪声类型之一,针对带钢表面缺陷图像高斯噪声去噪,首先对传统K-SVD(K-means and singular value decomposition)算法中的字典进行升级改造,然后采用正交匹配追踪(OMP,Orthogonal Matching Pursuit)算法对图像进行重构,滤除噪声,最后运用此算法对缺陷图像进行高斯滤波处理。为验证该算法去噪效果,选取几种常见的典型缺陷图像(划伤、气泡、氧化色、粘结纹)进行测试仿真,并选用中值滤波、均值滤波、小波变换、维纳滤波、3维块匹配(BM3D)等多种传统滤波方法进行比较。结果该算法对四种典型缺陷去噪的PSNR(Peak Signal to Noise Ratio)值平均可达33.976 d B,MSE(Mean Square Error)平均值为27.607,SSIM(Structural Similarity)平均值为0.912。结论该算法对带钢表面缺陷重构图像的边缘细节清晰,PSNR、MSE、SSIM三个性能指标明显优于其他传统滤波算法,去噪效果良好。 相似文献
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由于MAG焊外部干扰大,用CCD采集的MAG焊熔池区图像不够清晰.因此,在进行进一步处理比如边缘检测之前,需要进行必要的图像增强和去噪等预处理操作,这样才能获得更加清晰的图像边缘信息.针对以上问题,采用超分辨率技术对MAG焊熔池图像进行处理和分析.在此基础上,提出了基于小波分形插值的超分辨率图像重建方法.结果表明,该方法相对于基于传统的小波双线性插值的超分辨率方法,能有效提高MAG焊图像的分辨率,获得更加清晰的焊缝位置和图像的边缘信息,为后续的焊接质量控制和焊缝跟踪工作提供了很好的基础. 相似文献