Dean Sarah E, Munro Josephine, Li Neuton, Sharp Robert, Neshev Dragomir N, Sukhorukov Andrey A
ARC Centre of Excellence for Transformative Meta-Optical Systems (TMOS), Department of Electronic Materials Engineering, Research School of Physics, Australian National University Canberra ACT 2600 Australia
Research School of Astronomy and Astrophysics, Australian National University Weston Creek ACT 2611 Australia.
Nanoscale Adv. 2025 Apr 30;7(11):3579-3587. doi: 10.1039/d5na00298b. eCollection 2025 May 27.
Polarisation imaging is used to distinguish objects and surface characteristics that are otherwise not visible with black-and-white or colour imaging. Full-Stokes polarisation imaging allows complex image processing like water glint filtering, which is particularly useful for remote Earth observations. The relatively low cost of small-satellites makes their use in remote sensing more accessible. However, their size and weight limitations cannot accommodate the bulky conventional optics needed for full-Stokes polarisation imaging. We present the modelling of an ultra-thin topology-optimised diffractive metasurface that encodes polarisation states in five different diffraction orders. Positioning the metasurface in a telescope's pupil plane allows the diffraction orders to be imaged onto a single detector, resulting in the capability to perform single-shot full-Stokes polarisation imaging of the Earth's surface. The five rectangular image swaths are designed to use the full width of the camera, and then each successive frame can be stitched together as the satellite moves over the Earth's surface, restoring the full field of view achievable with any chosen camera without comprising the on-ground resolution. Each set of four out of the five orders enables the reconstruction of the full polarisation state, and their simultaneous reconstructions allow for error monitoring. The lightweight design and compact footprint of the polarisation imaging optical system achievable with a metasurface is a novel approach to increase the functionality of small satellites while working within their weight and volume constraints.
偏振成像用于区分在黑白或彩色成像中无法看到的物体和表面特征。全斯托克斯偏振成像允许进行复杂的图像处理，如水闪滤除，这对于地球遥感观测特别有用。小卫星成本相对较低，使得它们在遥感中的应用更加可行。然而，它们的尺寸和重量限制无法容纳全斯托克斯偏振成像所需的笨重传统光学元件。我们展示了一种超薄拓扑优化衍射超表面的建模，该超表面在五个不同的衍射级中编码偏振态。将超表面放置在望远镜的光瞳平面中，可使衍射级成像到单个探测器上，从而能够对地球表面进行单次全斯托克斯偏振成像。五个矩形图像条带的设计使用了相机的整个宽度，然后随着卫星在地球表面移动，每个连续的帧可以拼接在一起，恢复使用任何选定相机可实现的全视场，而不影响地面分辨率。五个级中的每四个级的组合都能够重建完整的偏振态，并且它们的同时重建允许进行误差监测。利用超表面实现的偏振成像光学系统的轻量化设计和紧凑占地面积，是在小卫星的重量和体积限制内增加其功能的一种新颖方法。
