High Resolution Underwater Optical Ranging

OUSD (R&E) MODERNIZATION PRIORITY: Artificial Intelligence (AI)/Machine Learning (ML);General Warfighting Requirements (GWR) TECHNOLOGY AREA(S): Sensors;Weapons OBJECTIVE: Develop techniques to enable high resolution optical ranging in underwater environments that rely on the encoding and decoding of the optical phase and/or the temporal signature of a blue-green laser source while providing accurate range measurements of underwater objects. DESCRIPTION: Laser-based techniques offer the potential of providing range measurements with high speed and accuracy. When such techniques are used in the underwater environment, they must overcome the challenges of optical absorption and scattering in water. Blue-green wavelengths minimize absorption, but scattering distributes the optical signal in both time and space and reduces range accuracy. Techniques which reduce the contribution of scattered light to the range measurement can enhance optical ranging in challenging underwater environments. The challenge is to develop solutions that provide accurate range measurements (less than 5cm error) with processing speeds that are compatible with a moving underwater platform. Current techniques use time-encoded optical waveforms and subsequent time-resolved detection to discriminate between scattered and unscattered light. Such techniques involve hardware that is not compatible with small platforms and/or have insufficient dynamic range to operate in challenging underwater environments. PHASE I: Provide model and/or low fidelity proof of concept results for a proposed optical ranging solution. The results should demonstrate how the proposed approach improves optical ranging in underwater environments. Develop a Phase II plan. PHASE II: Develop a ruggedized hardware prototype that can be operated in relevant laboratory and/or in-situ environments. The prototype should fit within a 10 to 30 inch diameter cylindrical underwater vehicle, and there should be a path to meet the size, weight, and power requirements of a small unmanned underwater platform. Results from the prototype testing should demonstrate improved optical ranging in challenging underwater environments. PHASE III DUAL USE APPLICATIONS: Work with the Government to transition the prototype hardware to a specific platform meeting that platform's size, weight, and power limitations. Dual use opportunities include unmanned underwater vehicle (UUV) surveying (pipeline inspection) and automotive light detection and ranging (LIDAR). REFERENCES: Lee, R.W.; Laux, A. and Mullen, L.J. Hybrid technique for enhanced optical ranging in turbid water environments. Optical Engineering, Vol. 53, No. 5, 2014. https://www.spiedigitallibrary.org/journals/optical-engineering/volume-53/issue-5/051404/Hybrid-technique-for-enhanced-optical-ranging-in-turbid-water-environments/10.1117/1.OE.53.5.051404.short?SSO=1. Jantzi, A.; Jemison, W.; Laux, A.; Mullen, L. and Cochcenour, B. Enhanced underwater ranging using an optical vortex. Optics Express, vol. 26, no. 3, Feb 5, 2018, pp. 2668-2674. https://pubmed.ncbi.nlm.nih.gov/29401804/. KEYWORDS: laser ranging; underwater ranging; scattering; optical vortex; turbid; time of flight; LIDAR; undersea weapon; mine detection, mine countermeasure; underwater sensor