Angle-Sensitive Metasurfaces for Lens-Free Compound-Eye Cameras

标题：无镜头复眼相机的准表面非技术描述：该项目旨在开发一种新的相机技术，其特点是极大尺寸的微型化，灵感来自于自然界中常见的复眼视觉模式，这种模式在昆虫和甲壳类等小型无脊椎动物中常见。复眼通常由许多成像元件(包括透镜和感光器)组成的曲线阵列组成，每个成像元件的方向都是为了探测沿不同方向入射的光。然后，从所有这些元素的组合输入重建被可视化的对象的完整图像。由于标准的光电子器件是基于平面衬底的，因此这种视觉形式的光电实现通常因其曲面结构而变得复杂。复眼视觉模式代表了最适合的解决方案，在尽可能小的封装内提供具有可忽略失真的广角视场。此外，复眼可以在任意距离产生物体的聚焦图像，而不需要任何焦距调整，从而提供几乎无限的景深和极高的运动敏锐度。因此，建议的相机可以为小尺寸、大视场和高时间分辨率特别重要的广泛成像应用提供一种使能技术。具体的例子包括机器视觉(例如，用于避障和自主导航)、监视和内窥镜医学成像。拟议的活动还将通过培训研究生和本科生在纳米光子学、光电子学和图像处理领域的广泛主题来促进教育。相关的课程开发工作将影响其他学科的学生。技术描述：拟议的研究将利用纳米光子学和超材料方面的最新进展，开发一种由成像像素的平面阵列组成的平面无透镜复眼相机。每个像素的角度选择性由在每个光电探测器表面构图的特殊设计的金属纳米颗粒(光学准表面)阵列提供。这项研究的关键创新是开发了亚表面，它可以选择性地将仅沿单一几何可调方向(在小范围内)入射的光传输到基片上。沿任何其他方向入射的光都会被反射。有了这种安排，就可以使用现有的cmos或ccd图像传感器阵列来实现无镜头复眼相机。每个像素都将覆盖不同的变形表面，以允许检测来自不同方向的光。所提出的角度敏感光电探测器将通过全波数值模拟设计，在硅衬底上制造，并通过角度分辨光电流测量来表征。然后将开发这些设备的阵列，以对其成像能力进行概念验证演示。先进的计算成像算法将被用来优化从单个传感器的组合信号中重建图像。除了相机潜在的技术影响外，这项研究还将通过探索新颖的设计和应用来推动光学超曲面的科学和技术，并将在新兴的计算成像领域创造新的研究机会。

Title: Metasurfaces for Lens-Free Compound-Eye Cameras Non-Technical Description:This project aims at developing a new camera technology featuring extreme size miniaturization, inspired by the compound-eye vision modality that is commonly found in nature in small invertebrates such as insects and crustaceans. Compound eyes typically consist of a curved array of many imaging elements (including lenses and photoreceptors), each oriented so as to detect light incident along a different direction. The full image of the object being visualized is then reconstructed from the combined inputs of all such elements. The optoelectronic implementation of this vision modality is generally complicated by its curved architecture, since standard optoelectronic devices are based on planar substrates. The compound-eye vision modality represents the optimally adapted solution to provide wide-angle field of view with negligible distortion within the smallest possible package. Furthermore, compound eyes can create focused images of objects at arbitrary distances without the need for any focal-length adjustment, and thus offer nearly infinite depth of field and extremely high acuity to motion. The proposed cameras could therefore provide an enabling technology for a wide range of imaging applications where small size, large field of view, and high temporal resolution are of particular importance. Specific examples include machine vision (e.g., for obstacle avoidance and autonomous navigation), surveillance, and endoscopic medical imaging. The proposed activities will also promote education through the training of graduate and undergraduate students in a wide range of topics within nanophotonics, optoelectronics, and image processing. Related curriculum development efforts will impact students in other disciplines.Technical Description:The proposed research will leverage recent advances in nanophotonics and metamaterials to develop a planar lens-free compound-eye camera consisting of a planar array of imaging pixels. The angle selectivity of each pixel is provided by specially designed arrays of metallic nanoparticles (optical metasurfaces) patterned on the surface of each photodetector. The key innovation of the proposed research is the development of metasurfaces that can selectively transmit into their substrate only light incident along a single geometrically tunable direction (within a small range). Light incident along any other direction will be reflected. With this arrangement, lens-free compound-eye cameras can be implemented using existing CMOS or CCD image-sensor arrays. Each pixel will be coated with a different metasurface designed to allow for the detection of light from a different direction. The proposed angle-sensitive photodetectors will be designed via full-wave numerical simulations, fabricated on silicon substrates, and characterized through angle-resolved photocurrent measurements. Arrays of these devices will then be developed for a proof-of-concept demonstration of their imaging capabilities. Advanced computational imaging algorithms will be employed to optimize the image reconstruction from the combined signals of the individual sensors. In addition to the potential technological impact of the proposed cameras, this research will also advance the science and technology of optical metasurfaces through the exploration of novel designs and applications, and will create new research opportunities in the emerging field of computational imaging.