相关算法软包装热封缺陷空气耦合超声检测

摘要

In order to realize online nondestructive testing of flexible package seal defects, air-coupled ultrasonic testing was applied to detect seal defects of flexible package. A spot focused air-coupled ultrasonic probe whose center frequency is 1 MHz and focus diameter is about 1mm was applied and envelop integration method and correlation method were applied to scan defects of 0.5 mm to 1.5 mm leakage paths in sealing areas. Results show that this method can realize the non-contact imaging of seal leak defects of flexible package. Taking the ultrasonic signal envelope and standard signal envelope correlation coefficients after band-pass filtering as imaging characteristic quantity can effectively eliminate transmission energy fluctuating noise of the air-coupled ultrasound. Compared with the envelop integration method,the correlation method can significantly improve the signal-to-noise ratio of images and the small defects detection ability.%为实现软包装热封缺陷的在线无损检测，将空气耦合超声检测技术应用于软包装热封缺陷检测。采用中心频率为1 MHz、焦点直径约1 mm的点聚焦空气耦合超声探头，并分别采用包络积分算法和相关算法对带有0.5~1.5 mm泄漏通道型缺陷的热封封口进行面扫描成像。实验结果表明该方法可实现软包装热封泄漏缺陷的非接触成像。将带通滤波后的超声信号包络与标准信号包络相关性系数作为成像特征量，可有效消除空气耦合超声的透射能量波动噪声。相对于包络积分算法，相关算法可显著提升图像信噪比以及小尺寸缺陷检出能力。