Collaborative Research: COMPACT SUB-1 Kelvin Resolution Video Rate 94 GHz Passive Imaging Camera Using Optical UP-Conversion

被动毫米波成像的潜在好处早已被认识到。它是在退化的视觉环境中成像和检测的使能技术。该技术的大范围应用包括天文学、空中侦察、对峙威胁检测、门户筛选、持续监视、态势感知和在没有GPS信号的情况下的视频成像导航。毫米波成像可以提供高分辨率，并具有“透视”烟雾、雾、沙尘暴和云的附加功能。因此，它可以在悬停、起飞和着陆操作中为飞行员提供有价值的态势感知。此外，毫米波辐射可以穿透塑料和衣服。考虑到这些优势，无源毫米波成像相机系统可以作为多传感器数据融合新兴领域的补充传感模式，并与可见光谱和红外（IR）相机、LADAR（激光雷达，又名激光雷达）、RFID和其他距离传感器结合使用，以实现单一传感模式无法实现的推断。到目前为止，大多数现场部署的毫米波成像系统都集中在人体扫描上，就像在机场和建筑物入口处遇到的那样。这些系统被认为是有效的，但并非没有缺点。具体来说，它们体积大，速度慢，价格昂贵，显眼，不适合进行对峙成像。因此，需要低成本、紧凑、灵敏和通用的成像系统，以实现更广泛的成像应用领域。医疗和其他科学领域也可以受益于小型高性能毫米波成像相机。本研究提出了一种新的毫米波相机设计，采用集成天线和光子芯片前端，采用光学上转换，所有这些都采用凝视干涉稀疏阵列格式，以实现高对比度和高空间分辨率。在所提出的摄像系统中，入射毫米波辐射在光电调制器内调制光信号。调制信号由光学载波和双边带组成，然后使用集成的片上光学带通滤波器去除载波和其中一个边带，然后投射到标准的近红外相机上。提出了一些创新的方法来实现小相机占地，灵敏度，低成本和更好的分辨率：1)前端天线阵列集成了以94 GHz为中心的黑体辐射的集成光上转换，无需放大；2)将毫米波天线直接集成到电光调制器和光带通滤波器上，从而提高了效率；3)电光调制器结构在有源区域利用聚合物材料的电光效应，实现了低损耗和高调制效率。4)工程溶胶-凝胶特性，提高了高轮询效率、低光传播损耗和高效的单模光纤耦合；5)标准光学透镜和近红外商用相机，用于低成本和简单的高分辨率图像重建；6)干涉稀疏开始阵列探测器前端架构，用于视频速率功能，避免了前端的RF折射透镜。这项研究的影响在许多层面上都是深远的。该摄像机将产生革命性的影响，因为它可以像光学摄像机一样用于高速识别和检测衣服下面或遮挡物后面的隐藏物体。所提出的毫米波相机具有低成本、实时性、高分辨率和高对比度等特点。值得注意的是，为这种相机开发的调制器将有利于其他研究领域和许多应用的众多便携式设备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The potential benefits of passive millimeter-wave imaging have long been recognized. It is an enabling technology for imaging and detection in degraded visual environments. The large range of applications for this technology include astronomy, aerial reconnaissance, stand-off threat detection, portal screening, persistent surveillance, situational awareness, and video imaging navigation in the absence of GPS signals. Millimeter-wave imaging can provide for high resolution and has the added capability to "see through" smoke, fog, sandstorms, and clouds. Therefore, it can provide pilots with valuable situational awareness during hover, takeoff and landing operations. Further, millimeter-wave radiation penetrates through plastic and clothing. With these advantages in mind, a Passive Millimeter-Wave Imaging camera system can be used as a complementary sensing modality in the emerging field of multi-sensor data fusion, and in conjunction with visible spectrum and infra-red (IR) cameras, LADAR (Laser Radar, a.k.a. LIDAR), RFID, and other range sensors to achieve inferences not possible with a single sensing modality. To date, most fielded millimeter-wave imaging systems focus on body scanning, as encountered at airports and building entrances. These systems are considered effective, but not without drawbacks. Specifically, they are bulky, slow, expensive, conspicuous and not suitable for standoff imaging. Therefore, there is a need for low-cost, compact, sensitive, and versatile imaging systems to enable a broader field of imaging applications. Medical and other scientific fields can also benefit from a small and high-performance millimeter-wave imaging camera. The proposed research introduces a new millimeter-wave camera design with integrated antennas and a photonic chip front-end using optical up-conversion, all in a staring interferometric sparse array format for high contrast and high spatial resolution. In the proposed camera system, the incident millimeter-wave radiation modulates an optical signal within an optical electro-modulator. The modulated signal, which consists of the optical carrier and double sidebands, is then stripped of the carrier and one of the sidebands using an integrated on-chip optical bandpass filter before being projected onto a standard near-IR camera. A number of innovative approaches are proposed to achieve small camera footprint, sensitivity, low cost and better resolution: 1) front-end antenna array with integrated optical up-conversion for black-body radiation centered at 94 GHz without a need for amplification, 2) increased efficiency by directly integrating the millimeter-wave antenna onto the electro-optical modulator and the optical bandpass filter on a single chip, 3) electro-optical modulator architecture using the electro-optic effect in polymer material in the active area for low loss and high modulation efficiency, 4) engineered sol-gel properties that promote high polling efficiency, low optical propagation losses, and efficient single mode fiber coupling, 5) standard optical lens and near-IR commercial cameras for low cost and simple reconstruction of high resolution images, and 6) interferometric sparse staring array detector front-end architecture for video rate functionality that avoids RF refractive lens in the front-end. The impact of this research is profound at many levels. The proposed camera will have a transformational impact since it can be used in the same manner as an optical camera to identify and detect hidden objects below clothing or behind obscurants at high speed. The proposed millimeter-wave camera is of low cost, real time, high resolution and high contrast. Notably, the modulator developed for this camera will benefit a multitude of portable devices for other research fields and many applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.