Polarization imaging is key for various applications ranging from biology to machine vision because it can capture valuable optical information about imaged environments, which is usually absent in intensity and spectral content. Conventional polarization cameras rely on a traditional single-eye imaging system with rotating polarizers, cascaded optics, or micropolarizer-patterned image sensors. These cameras, however, have two common issues. The first is low sensitivity resulting from the limited light utilization efficiency of absorptive polarizers or cascaded optics. The other is the difficulty in device miniaturization due to the fact that these devices require at least an optical-path length equivalent to the lens’s focal length. Here, we propose a polarization imaging system based on compound-eye metasurface optics and show how it enables the creation of a high-sensitivity, ultra-thin polarization camera. Our imaging system is composed of a typical image sensor and single metasurface layer for forming a vast number of images while sorting the polarization bases. Since this system is based on a filter-free, computational imaging scheme while dramatically reducing the optical-path length required for imaging, it overcomes both efficiency and size limitations of conventional polarization cameras. As a proof of concept, we demonstrated that our system improves the amount of detected light by a factor of ∼2, while reducing device thickness to ∼1/10 that of the most prevalent polarization cameras. Such a sensitive, compact, and passive device could pave the way toward the widespread adoption of polarization imaging in applications in which available light is limited and strict size constraints exist.

中文翻译：

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复合眼超表面光学元件可实现高灵敏度，超薄偏振相机

偏振成像是从生物学到机器视觉的各种应用的关键，因为它可以捕获有关成像环境的有价值的光学信息，而这些信息通常在强度和光谱含量上是不存在的。常规的偏振相机依赖于传统的单眼成像系统，该系统具有旋转偏振器，级联光学器件或微偏振器模式的图像传感器。但是，这些相机有两个常见问题。首先是由于吸收型偏振器或级联光学器件有限的光利用效率而导致的低灵敏度。另一个是由于这些设备需要至少等于透镜焦距的光路长度这一事实而导致设备小型化的困难。这里，我们提出了一种基于复眼超表面光学的偏振成像系统，并展示了它如何实现高灵敏度，超薄偏振相机的创建。我们的成像系统由典型的图像传感器和单个超表面层组成，用于在分类偏振基时形成大量图像。由于该系统基于无滤波器的计算成像方案，同时大大减少了成像所需的光路长度，因此它克服了传统偏振相机的效率和尺寸限制。作为概念证明，我们证明了我们的系统将检测到的光量提高了约2倍，同时将设备的厚度减小到最普遍的偏振摄像机的约1/10。如此灵敏，紧凑，