Fast Ultrasonic Total Focus Imaging Based On FPGA

Ultrasonic detection technology has been widely used in the fields of medical imaging,transportation,nondestructive testing and so on.Among them,the synthetic aperture technology has the characteristics of high resolution,high contrast,and high sensitivity and so on.Total focused synthetic aperture technique is the most complex and high resolution imaging technique in synthetic aperture imaging.However,the influence of high imaging quality is slow imaging rate,and the conventional computer can not meet the needs of real-time imaging.The accelerated computing solution based on total focused synthetic aperture imaging has become a research hotspot.In order to improve the speed of ultrasonic imaging,FPGA is introduced as an accelerated computing device.Realize real time total focus synthetic aperture imaging of 32 elements by FPGA design.By comparing several design models,this paper discusses the advantages and disadvantages of each scheme based on FPGA.Hope that through the design of the FPGA to achieve the most efficient use of resources and ensure the imaging speed and quality.This thesis first analyzes the principle of total focus synthetic aperture imaging algorithm,and designs the software to verify the algorithm,and obtains the ideal result.the total focus imaging algorithm is modeled and analyzed,and the elliptical trajectory characteristics is introduced to discuss the resolution of the total focus imaging algorithm.It is concluded that the imaging area is deeper and the lateral resolution is lower.Based on the elliptical trajectory feature,the imaging algorithm is optimized by weighted overlay.Through the experimental analysis,the imaging API value is reduced by about 26%,which effectively improves the imaging resolution.Then,the parallelism of the full focus algorithm is discussed,and the data processing flow based on parallel A-scanning and parallel processing of the imaging point is analyzed.It is concluded that the parallelism based on A-scanning can be realized more effectively on the FPGA.Based on the above discussion and analysis,two kinds of FPGA processing schemes are designed,one is based on the distance calculation processing scheme.The delay calculation is used to design the recursive distance calculation module on the FPGA,and then the index value is converted and the index is superimposed to obtain the imaging result.The experiments show that FPGA operating frequency up to 166.7MHz.The design based on distance calculation can still be improved in frequency,by increasing the operating frequency,can directly improve the imaging speed.So this paper designed another distance index scheme,the distance value stored in the FPGA on the RAM,the way through the index,can simplify the circuit,and improve the operating frequency.Through the analysis,the distance index needs to take up a lot of memory to store the distance value,and in order to ensure the distance precision,need to improve the storage data bit width.This article has optimized distance index design,by optimizing the design,memory occupancy rate reduced by 80%,and to ensure the operating frequency.In this thesis,the PCI-E interface is connected with the FPGA total focus processing module to realize the data transmission and processing.Then,the experimental results of the fast imaging scheme based on FPGA are analyzed.Full focus imaging of 32 elements.Distance calculation design run frequency is 125MHz,imaging processing time is 17 milliseconds.Distance index design,running frequency up to 250MHz,the experiment shows the actual processing time is about 9 milliseconds,compared to the previous design processing speed increased by 63%.