超声相控阵全聚焦成像算法具有精度高、全范围动态聚焦的优点，但存在的成像耗时长问题限制了其实际工业应用。为提高实际检测中相控阵全聚焦成像效率，以常用的楔块耦合检测为例，基于Fermat原理计算两层介质下各阵元的延迟时间，建立两层介质相控阵全聚焦成像算法。通过减少发射/接收阵元数，以与全矩阵下具有一致的有效孔径为条件，研究发射/接收阵元分布的权重函数，建立两层介质修正稀疏全聚焦算法。以弧形分布的侧边孔为例，进行了两层介质的全聚焦成像及稀疏全聚焦成像试验，并讨论了稀疏发射阵列对缺陷定量精度及全聚焦算法计算效率的影响。结果表明：修正稀疏全聚焦算法可在保证成像精度前提下显著提高成像效率。对于32阵元换能器，当稀疏发射阵元数达到8时，稀疏矩阵相对于全矩阵的误差值在5.2%以内，但计算效率提高了近4倍。
Ultrasonic phased array total focusing method has the advantages of high accuracy and dynamic focusing in all regions, but the problem of long imaging time limits of the actual industrial application. In order to improve the imaging efficiency of phased array total focusing method, taking commonly used wedge coupling detection for example, the delay time of all array elements are calculated in two-layer medium based on Fermat principle, a two-layer medium phased array total focusing method is built. By reducing the number of transmitting/receiving elements, with the same effective aperture as the whole array, the weighting function of transmitting/receiving elements distribution is studied, and a two-layer medium corrected sparse total focusing method is proposed. Taking the side-drilled holes with arc distribution for example, two images of total focusing method and sparse total focusing method in the two-layer medium are formed, and the effects on defect quantitative precision and calculation efficiency are discussed when the transmitter array is sparse. The results show that the corrected sparse total focusing method can improve the imaging efficiency obviously in the meanwhile the imaging accuracy is kept. For a 32-element transducer, when the number of the sparse transmitting elements reaches 8, the error between sparse matrix and full matrix is less than 5.2%, while the computational efficiency is nearly fourfold improved.
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