Polarization-enhanced, Long-range, Wide-area, High-resolution Imaging System

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Directed Energy (DE); Integrated Sensing and Cyber; Trusted AI and Autonomy OBJECTIVE: Develop polarization-based techniques to improve target detection and identification and scene clutter characterization at long-range and over a wide field-of-view. DESCRIPTION: Detection and identification of small targets at long range on the ocean surface is challenging due to wave clutter, reduced observation time from shadowing, and often poor target contrast. To enhance target detection and identification, the USN seeks to exploit the additional information content provided by polarization. Specifically, 3D polarization imaging has improved significantly in recent years as multiple strategies have been developed to resolve the polar and azimuthal angular ambiguities [Ref 1]. Measurement of polarization often provides increased discrimination of man-made objects from nature backgrounds, while the 3D variant could increase the likelihood of positive identification. Moreover, many new polarization-based techniques have been developed in recent years that could significantly increase performance over the conventional Stokes vector analysis, which alone often yields favorable results, but only for specific applications. Within the scope of this STTR topic, the USN seeks to develop a 3D polarization imaging system to significantly improve long-range detection and identification of targets in maritime clutter from surface-ship platforms. In principle, all wavelength bands from the UV to mm-wave will be considered, although transmission and depolarization with passage through the atmosphere in the maritime environment should be considered. Novel polarization techniques, such as point-spread-function engineering [Ref 2] or speckle correlation [Ref 3], which could potentially improve depth resolution or sampling rate, are also of interest. The use of multi-point correlation functions, such as the complex degree of mutual polarization [Ref 4] or other polarization correlation functions, would be of interest if these techniques can be used to enhance target identification or discrimination in clutter. In addition to the development of imager hardware, a processing component can be anticipated, which could exploit local measurements of the environment, such as ocean wave power spectra or the air-sea temperature jump, to enable optimization of data acquisition and interpretation [Ref 5]. PHASE I: Develop a preliminary design of hardware and algorithms for a novel polarization-based imaging and sensing system that significantly exceeds the current state-of-the-art and enables improved detection and ID of small targets in a maritime environment at ranges beyond 1 km. Targets of shorter range are not of interest under this topic. Additionally, proposed solutions can explore polarization techniques combined with other techniques to further augment 3D image formation. The design should be supported by ample modelling and simulation results to justify construction in Phase II and by risk mitigation experiments as needed. PHASE II: Develop a hardware/software realization of the design proposed under Phase I. Laboratory based testing should be completed under the Phase II effort to demonstrate the performance of the system. PHASE III DUAL USE APPLICATIONS: Refine the design of improved ruggedness, size, weight, and power needs to broadly enable use of the system. Produce a sufficiently rugged system to enable field testing under relevant maritime conditions. REFERENCES: Li, X et al. Polarization 3D imaging technology: a review. Frontiers in Physics, 9 May 2023. Ghaneka, B. et al. PS2F: Polarized Spiral Point Spread Function for Single-Shot 3D Sensing. IEEE Transactions on Pattern Analysis and Machine Intelligence, 1 12, 29 August 2022. Du, Y. et al. Accurate dynamic 3D deformation measurement based on the synchronous multiplexing of polarization and speckle. Optics Letters 48 (9) ,2329 (2023). Eshaghi, M. and Dogariu, A. Discriminating randomly polarized fields. Optics Letters 45 (7), 1970, (2020). Shaw, J.A. and Churnside, J.H. Scanning-laser glint measurements of sea-surface slope statistics. APPLIED OPTICS 36 (18), 4202, (1997). KEYWORDS: infrared imaging; polarization; polarimetric imaging; infrared; IR; electro-optical/infrared; EO/IR; maritime sensing