Study Of Ultrasonic Sparse Array Image Based On Genetic Algorithm

With the continuous improvement of attention for the non-destructive testing technology and demand for the imaging quality, the total focusing imaging technology has been a great interest in ultrasonic non-destructive testing and evaluation for its high-resolution and high-contrast, and has become one of the great potential imaging techniques in recent years. However, this technique requires acquiring and processing large amounts of data and consuming a lot of time. The low imaging efficiency has limit its wide application in industrial real-time testing and imaging. In order to improve the efficiency of the total focusing imaging technology while ensure the detecting performance and ultrasound image quality, we apply the sparse method to the total focusing imaging technology and study the performance optimization of sparse array by use of genetic algorithm.Firstly, we establish the mathematical model of total focusing imaging algorithm, study the approach of sparse array based on effective aperture theory, and obtain the detection images of arrays with various sparse ratio through simulations on Field II and experiments on the standard ultrasonic test block. The feasibility and effectiveness of this method has been validated from the result of imaging efficiency improvement of 41.7% at the sparse ratio of 0.25.Secondly, according to the characteristics of sparse array optimization, we design the encoding mode, objective function and cross-mutation operator of genetic algorithm. The performance optimization of sparse linear array is processed by successful application of genetic algorithms. The optimized sparse array has well main-lobe and side-lobe feature, and the signal to noise ratio of experiment image has a raise of 5.3dB.Finally, based on the simulation and experiment results, we discuss the influence of optimization parameters for search efficiency and global convergence of genetic algorithm, the imaging contrast of periodic and non-periodic sparse array and the relationship between element in different positions and detection performance of array.The result show that the adoption of sparse method can improve the efficiency of total focusing imaging technology under the premise of guaranteed image quality, and the application of genetic algorithm will improve the detection performance of sparse array.