Laser ultrasound array scanning imaging has extremely high flexibility in space arrangement and scanning parameter adjustment. However, a major challenge is how to achieve high-speed inspection and high-resolution real-time defect imaging using a limited number of scanning configurations. In this study, the detection sensitivity of laser ultrasonic synthetic aperture focusing technique (SAFT) is analyzed based on ray theory. According to the theoretical calculation results, a bilateral excitation method is proposed. An optimized delay-multiply-and-sum (DMAS) beamforming method was employed for defect imaging. The optimization efforts encompassed refining the mathematical expression, integrating matrix operations with GPU acceleration to enhance imaging speed, implementing coherent noise suppression, and utilizing image fusion techniques to improve imaging quality. The experiments involve two types of defects: transverse holes at different depth positions, and cracks at different angles of additive manufacturing. The results demonstrate that optimizing the scanning configuration improves image resolution, particularly for additive manufacturing of highly scattering materials. Furthermore, the morphological characteristics of defects are revealed, and better imaging and geometric characteristics can be achieved through image fusion. The proposed method outperforms the time-domain delay-and-sum (DAS) and frequency-domain phase shift migration (PSM) algorithms, achieving a real-time imaging frame rate.

中文翻译：

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基于阵列扫描优化和延迟乘法求和的激光超声实时成像和几何表征


激光超声阵列扫描成像在空间布置和扫描参数调整方面具有极高的灵活性。然而，一个主要挑战是如何利用有限数量的扫描配置实现高速检测和高分辨率实时缺陷成像。本文基于射线理论分析了激光超声合成孔径聚焦技术 （SAFT） 的探测灵敏度。根据理论计算结果，提出了一种双边激励方法。采用优化的延迟乘和（ DMAS ）波束形成方法进行缺陷成像。优化工作包括优化数学表达式、将矩阵运算与 GPU 加速集成以提高成像速度、实施相干噪声抑制以及利用图像融合技术来提高成像质量。实验涉及两种类型的缺陷：增材制造中不同深度位置的横向孔和不同角度的裂纹。结果表明，优化扫描配置可以提高图像分辨率，特别是对于高散射材料的增材制造。此外，揭示了缺陷的形态特征，通过图像融合可以获得更好的成像和几何特征。所提出的方法优于时域延迟和求和（DAS）和频域相移迁移（PSM）算法，实现了实时成像帧速率。