CAREER: 4D mm-Wave Compressive Sensing and Imaging at One Thousand Volumetric Frames per Second

毫米波传感和成像系统被广泛用于广泛的应用，例如用于预报天气的地球大气探测，用于检测机场检查站潜在威胁的安全监测，以及用于伤口诊断和愈合的表层组织的生物成像。当场景动态变化不是很快时，这些系统通常运行良好。不幸的是，在新兴的社会重要应用中并非如此，比如救援任务中的无人机集群，道路上的智能自动驾驶汽车，或者在自杀式炸弹袭击者移动时搜索他们的网络物理系统。随着首个四维(4D)毫米波成像系统的开发，该项目将造福于我们的社会，该系统运行在快速变化的场景中，在这种场景中，必须迅速做出关键的安全决策。该系统的新应用之一将是在购物中心、体育场馆和办公楼等开放区域发现隐藏在衣服或背包内的安全威胁。具体地说，该系统将能够扫描在26立方米的体积区域内移动的多人，每秒产生1000个三维图像帧，从而超过目前在机场检查站使用的现有毫米波传感和成像系统。除了社会影响，首席调查员(PI)还将建立一个强大的教育项目，通过该项目，不同的受众可以了解基于波的成像系统的原理和局限性。研究和教育的整合将通过为学生开发新的课程和研究培训方法，以及通过与东北大学(NEU)合作教育计划合作制定学生向行业过渡的路线图来实现。外展计划包括与东北大学科学、技术、工程和数学(STEM)中心合作，为K-12、本科生和代表性不足的学生提供研究经验，以及通过在线材料和公共场所进行教育。该职业计划的研究目标是了解使用4D(时间和空间)编码的自适应压缩传感和成像系统的理论原理和基本限制，并通过新型4D毫米波自适应压缩成像雷达系统开发和实验验证这些原理。该系统将产生每秒1000帧以上的4D体积帧速率，每帧具有超过100万像素。实现4D自适应成像系统的主要挑战如下：1)系统必须能够处理变化的动力学，即以不同的速度移动和位于不同焦距的对象；2)系统必须在有限的时间内以足够的信噪比采样数据；以及3)系统必须以极快的速度采样数据，以执行具有高体积帧速率的快速4D视频重建。该项目将解决这些挑战如下：(I)它将开发一种新的理论，将功能分析、信息论、压缩传感和自适应超材料结合在一起，以提高传感系统的信息传输效率；(Ii)它将开发一个新的数学框架，以根据压缩成像系统所需的信息率和能量效率来优化4D码；以及(Iii)该系统将利用空间光调制器、涡旋元透镜和压缩反射器来执行编码并动态适应成像区域的状态。这项研究的结果将为所提出的新型传感和成像系统奠定科学基础，通过提高成像性能、可靠性和效率，同时降低系统的硬件复杂性、总体成本和能耗。

Millimeter-wave sensing and imaging systems are used ubiquitously for a wide range of applications, such as atmospheric sounding of the earth to forecast the weather, security monitoring to detect potential threats at airport checkpoints, and biological imaging of superficial tissues for wound diagnosis and healing. These systems typically operate well when the scene dynamics do not change rapidly. Unfortunately this is not the case in emerging societally-important applications like swarms of drones in rescue missions, smart self-driving cars on roadways, or cyber-physical systems searching for suicide bombers when they are on the move. This project will benefit our society with the development of the first four-dimensional (4D) millimeter-wave imaging system operating in fast changing scenarios, in which safety-critical decisions must be made quickly. One of the new applications of this system will be finding security threats, concealed under clothing or inside backpacks, in open areas like shopping malls, sport venues, and office buildings. Specifically, the system will have the capability to scan multiple people moving within a volumetric region of 26 cubic meters, producing 1000 image frames per second in three dimensions, thus outperforming existing millimeter-wave sensing and imaging systems that are currently used at airport checkpoints. In addition to the societal impact, the Principal Investigator (PI) will build a strong educational program through which diverse audiences can understand the principles and limitations of wave-based imaging systems. The integration of research and education will be accomplished through the development of new curricula and research training methods for students, as well as through the elaboration of a roadmap for transitioning students into industry, in collaboration with Northeastern University (NEU) Cooperative Education Program. The outreach plan includes enabling research experiences for K-12, undergraduate, and underrepresented students in collaboration with the Science, Technology, Engineering, and Mathematics (STEM) centers at NEU, as well as education through online materials and public venues.The research goal of this CAREER program is to understand the theoretical principles and fundamental limitations of adaptable compressive sensing and imaging systems using 4D (temporal and spatial) coding and to develop and experimentally validate these principles through a novel 4D millimeter-wave adaptive compressive imaging radar system. This system will produce 4D volumetric frame rates beyond 1000 frames per second, each frame having over one million pixels. The primary challenges of implementing 4D adaptable imaging systems are the following: 1) the system must be capable of handling variable dynamics, i.e., objects moving with different velocities and located at different focal ranges; 2) the system must sample data with sufficient signal to noise ratio during the limited period of time; and 3) the system must sample data extremely fast to perform fast 4D video reconstruction with high volumetric frame rates. This project will address these challenges as follows: (i) it will develop a new theory that brings together functional analysis, information theory, compressive sensing, and adaptable metamaterials to enhance the information transfer efficiency of sensing systems; (ii) it will develop a new mathematical framework to optimize 4D codes based on the desired information rate and energy efficiency of the compressive imaging system; and (iii) the system will utilize spatial light modulators, vortex-meta-lenses, and compressive reflectors to perform the coding and to dynamically adapt to the state of the imaging region. The result of this research will establish the scientific basis for the proposed new sensing and imaging systems, by enhancing the imaging performance, reliability, and efficiency while reducing the hardware complexity, overall cost, and energy consumption of the system.