Study On Real-Time Ultrasonic Phased Array Imaging Using Total Focus Method

Ultrasonic Phased Array flaw detection is an important method in industrial nondestructive testing field,applying Total Focusing Method in ultrasonic phased array systems can significantly improve the detection rate and accuracy.However,Total Focusing Method is usually used in post-processing imaging according to its large time consumption.In this paper,based on fully investigating the current research status and theory,A real-time Total Focusing Method based on Sparse Matrix Capture and FPGA acceleration is proposed and the method is verified based on 16×64 ultrasonic phased array platform.Sparse Matrix Capture technology is introduced to reduce data volume and improve imaging efficiency,the maximum effective aperture is used for sparse emission array to reduce the loss of imaging quality caused by the Sparse Matrix Capture.The change trend of the Sparse Matrix Capture-Total Focusing Method image with the decrease of the emission element number is studied by the Field II ultrasonic simulation platform.The simulation results show that the image resolution of Sparse Matrix Capture-Total Focusing Method is close to the 64-element Full Matrix Capture-Total Focusing Method when the number of emission elements is up to 8,and also the affects of noise and artifact are small.Total Focus Method hardware design scheme based on FPGA parallel acceleration is proposed.The unit is divided into index calculation module,A-scan storage module and image synthesis module according to modular design idea.The index calculation module adopts the parallel processing method of 16 receiving channels,and the sound path calculation is implemented by the SQRT IP core embedded in FPGA;The A-scan storage module adopts ping-pong control of RAM,which can save the time requirement for data acquisition;The image synthesis module uses a single RAM to buffer sub images,and realizes the superposition of sub images by controlling the time-division multiplexing of RAM.Total Focus Method unit adopts pipeline architecture to improve the processing speed.After Tested and verificated based on 16 × 64 ultrasonic phased array platform,the frame rate of 64-array Full Matrix Capture-Total Focus Method can reach 6.4Hz when focus points number is 62500,and the SNR is about 46.5d B.When the number of transmitting elements is12,the image resolution and SNR of the Sparse Matrix Capture-Total Focus Method is similar to that of the Full Matrix Capture-Total Focus Method,the SNR is slightly lost,about 41.7d B,but the frame rate is 34.5Hz,greatly improving the efficiency of detection.The results show that the acceleration of Total Focusing Method meet the requirement of real-time detection,which provides a reference for the practical application of Total Focusing Method in the ultrasonic phased array flaw detection system.