Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
Nat Commun. 2019 Jan 14;10(1):204. doi: 10.1038/s41467-018-08221-7.
The resolution of acoustic imaging suffers from diffraction limit due to the loss of evanescent field that carries subwavelength information. Most of the current methods for overcoming the diffraction limit in acoustics still operate in the near-field of the object. Here we demonstrate the design and experimental realization of an acoustic far-field subwavelength imaging system. Our system is based on wave vector filtering and conversion with a transmitter at the near-field and a spatially symmetrical receiver at the far-field. By tuning geometric parameters of the transmitting/receiving pair, different spatial frequency bands can be separated and projected to the far-field. Furthermore, far-field imaging and edge detection of subwavelength objects are experimentally demonstrated. The proposed system brings new possibilities for far-field subwavelength wave manipulation, which can be further applied to medical imaging, nondestructive testing, and acoustic communication.
由于携带亚波长信息的消逝场的损失，声成像的分辨率受到衍射极限的限制。目前大多数克服声学衍射极限的方法仍然在物体的近场中工作。在这里，我们展示了一种声远场亚波长成像系统的设计和实验实现。我们的系统基于波矢量滤波和转换，在近场使用发射器，在远场使用空间对称接收器。通过调整发射/接收对的几何参数，可以分离不同的空间频带并投射到远场。此外，还实验演示了亚波长物体的远场成像和边缘检测。所提出的系统为远场亚波长波的控制带来了新的可能性，可进一步应用于医学成像、无损检测和声学通信。
