基于粒子群算法的超振荡超分辨聚焦声场设计

Super-resolution acoustic focusing based on the particle swarm optimization of super-oscillation

针对传统声束的衍射极限问题,如何构建具有更高分辨率的聚焦声场,是实现超分辨声成像和声操控领域的重大挑战之一.本文在考虑成像分辨率同时兼顾声场可控制性,提出了一种基于粒子群优化算法的多频超振荡超分辨聚焦声场设计方法.基于常规换能器声场的衍射效应,利用半波带法设计中心频率菲涅耳透镜,并以中心频率为基准在换能器带宽范围内设置多频信号来构建超振荡声场,进一步通过粒子群算法对多频声束的振幅和相位进行优化,在远场构建了焦域半径能够小于中心频率半波长的超振荡声场,还发现其尺寸小于最高频率声场的所形成焦域半径,进一步证明其焦域半径随着中心频率和超振荡频率数的增大而减小.研究结果为可控超分辨声聚焦提供了一种简便易行的方法.

The spatial resolution of conventional waves is restricted by the diffraction limit of half wavelength.Hence,how to construct super-resolution acoustic beams with a smaller focal radius is one of the major challenges in recent studies.In the present paper,the super-resolution acoustic focusing method is proposed based on the superposition of multi-frequency super-oscillation beams and the Particle Swarm Optimization(PSO),which can improve the spatial resolution concurrently with good controllability.Based on the diffraction effect of traditional ultrasound fields,the acoustic lens of Fresnel zone plane(FZP)at the center frequency is designed by the half-wave zone method.Multiple acoustic beams at several preset frequencies within the transducer bandwidth are sent out to build the super-oscillation focal area by the pressure superposition.The radius of the super-resolution focal spot constructed by the PSO algorithm with optimized amplitudes and phases is less than the half wavelength at the center frequency,which is even smaller than the focal radius at the highest frequency.Furthermore,the focal radius is also proved to decrease with the increase of the number of multiple frequencies and the center frequency.The favorable results demonstrate the feasibility of super-resolution acoustic focusing based on the PSO of super-oscillation,and provide an applicable strategy for the highresolution acoustic imaging and manipulation.