A Study On The Compensation Dynamic Focusing Algorithm Of Phased Array Ultrasound Imaging And Its Physical Implementation

Ultrasonic phased array technology, with nearly 20 years of development history, has outstanding performance of its flexible beam deflection and focusing effects. Not only do UPAT can easily locate and distinguish the defects accurately, but also it enhances the detection efficiency and reduces the workload compared with the traditional ultrasonic testing technology.The quality of the reconstructed image(deflection focusing effect) of the phased array ultrasound imaging detection system depends on the transmitting and receiving channels in the system. The delays of the transmitter and receiver affect the focus point of the reconstructed image, thus, they affect the spatial resolution of the system. The delays of phased array transmitter and receiver only form once in the traditional ultrasonic testing technology, that is, only one transmitting focus point and one receiving focus point are formed in the traditional ultrasonic test. Therefore, those defects which are far away from the focus point are biased. For example, the defects of the circular holes often are reconstructed as flat images, that is, the lateral resolution is not good. The reason why the distortion happens is that t he defect point is not the focus point, and the phases of sound waves don’t overlap in the defect point.A new scheme of dynamic depth focusing(DDF) in phased array imaging is proposed in this paper. Based on the traditional process of transmitting and receiving with one focus point, the echo signals of every element received are dynamically compensated in a special position in order to focus in all depths. All the compensation positions can be calculated out and saved in an array. This paper provides the algorithm to calculate the compensation positions. To reduce the huge calculated amount in the compensated algorithm, the traditional method of calculating foca l law is improved, and FPGA is used to implement it.Moreover, this study discusses the focus reconstruction principle and the method of which can achieve the reconstruction. Lastly, it comes up with the method of which can compensate the signal both in the transmitting and receiving process.The computer simulation results show that the proposed scheme significantly improved the lateral resolution in all depths compared with the traditional one.