声学远场超衍射聚焦技术及声场检测方法

Acoustic super-focusing can significantly improve the resolution of the ultrasound imagining system and accuracy of ultrasound therapy, so it has been a interesting research topic. Some methods, such as three-dimensional surface array structure, a two-dimensional array of perforated plate and F-P resonance array, have breakthrough the traditional focus limit. But all super-focusing are near filed acoustic focus, it can only be used for near field imaging and hinder the promotion for other application field. There are two main difficulties. One is it is difficult to design acoustic element with percise control phase and high transmittance, it also is difficult to accurately map acoustic field due to the interference of acoustic field induced by larger volume of traditional acoustic transducer. The project proposed a subdiffraction acoustic focusing for far field with helical-structured metamaterials and a noninterference acoustic field test technology using fiber laser sensor. The project will theoretically analyze the character of the helical-structured acoustic metamaterial of the high transmittance and arbitrary phase modulation. And then, According to the ligh frequency modulation function under the limited aperture acoustic field, we will fabricate the two-dimension helical-structured acoustic metamaterial array to realize subdiffraction acoustic far-field focusing. A high precise and small volume fiber sensor is used to map acoustic field without interference, as well as accurately evaluate and optimize the effectiveness of subdiffraction acoustic focusing. At last, we will apply this subdiffraction acoustic focusing to the medical imaging of super resolution and the manipulation of ultrasonic scalpel and ultrasonic therapy. We believe that the proposed super-focusing technology will promote the he development of related technologies.

声学超极限聚焦可以提高成像系统的分辨率及超声治疗的准确度，如何超聚焦一直是难点。人们通过三维面阵列结构、二维阵列穿孔板及FP共振阵列等尝试方法突破了传统聚焦的限制。但目前主要都是近场聚焦，只限于近场成像，极大阻碍了超聚焦在其它领域的应用。主要难点在于很难获得高透射率声学相位控制器件，同时较大体积的传统声学探头对待测声场产生干扰。针对这些问题，本项目提出基于螺旋超材料的声学远场超衍射聚焦技术及高空间分辨率和无干扰的光纤激光声场检测方法。利用螺旋结构的声学超材料实现高透射率的任意相位调制器件，将螺旋管组成二维超衍射极限声学阵列，通过有限的孔径下精细的声场高频信息调制函数，实现声学远场超聚焦。利用高灵敏度和小体积的光纤激光声传感器进行非干扰性声信号测量，精确评估远场声学超衍射聚焦效果，最终实现声学远场超衍射极限成像。本研究可以推动声学超聚焦在超分辨率成像、超声手术刀以及超声治疗等相关技术的发展。

本项目研究了基于螺旋超材料的声学远场超衍射聚焦技术及高空间分辨率和无干扰的光纤激光声场检测方法，利用螺旋结构的声学超材料实现高透射率的任意相位调制器件，将螺旋管组成二维超衍射极限声学阵列，通过有限的孔径下精细的声场高频信息调制函数，实现声学远场超聚焦。利用高灵敏度和小体积的光纤激光声传感器进行非干扰性声信号测量，精确评估远场声学超衍射聚焦效果，最终实现声学远场超衍射极限成像。同时，研究了双腔声学共振系统的增强效应，结合FP腔光纤传感器组成新型复合超材料结构，实现在空气中增强局域声场进而提高传感器件的灵敏度。并对超材料表面的低频多频带吸声机理及其应用，利用二维平面上卷曲盘绕的螺旋超构表面通过大大扩展结构中的传播路径，能够实现厚度特定波长的声完全吸收。本研究可以推动声学超聚焦在超分辨率成像、超声手术刀以及超声治疗等相关技术的发展。