Dynamic ultrasound achromatic imaging with a stretchable flexible metalens

Ultrasound imaging is widely used in both engineering and medicine due to its advantages of deep penetration and no ionizing radiation. Focusing techniques can improve image resolution, but conventional methods often suffer from chromatic aberration. We present a novel approach to ultrasound imaging that overcomes this challenge, which utilizes a stretchable flexible metalens to experimentally achieve dynamic achromatic imaging. By carefully stretching and releasing the metalens, we can focus ultrasound of different frequencies at the same depth. This method features remarkable focusing resolutions of 0.6λ in the radial direction and 2.3λ in the axial direction, and a 13% deformation of the metalens enables effective compensation for chromatic aberration of ultrasound from 0.81 MHz to 1 MHz. Furthermore, we demonstrate the dynamic achromatic imaging of microstructures, showcasing its ability to capture high-resolution ultrasound images.超声成像（Ultrasound imaging）因兼具穿透深度深、无电离辐射的优势，在工程与医学领域均得到广泛应用。聚焦技术可提升图像分辨率，但传统方法往往存在色差（chromatic aberration）问题。本文提出一种新型超声成像方案，该方案利用可拉伸柔性超表面透镜（stretchable flexible metalens），通过实验实现了动态消色差成像。通过对超表面透镜进行精准拉伸与释放操作，可将不同频率的超声聚焦于同一深度。该方法的聚焦性能优异：径向分辨率可达0.6λ，轴向分辨率可达2.3λ，且仅需对超表面透镜施加13%的形变量，即可有效补偿0.81 MHz至1 MHz频段内超声的色差。此外，本研究还通过微结构的动态消色差成像验证了该方案的有效性，展示了其获取高分辨率超声图像的能力。