Development of Optical Scatter Filtering for Underwater Optical Proximity Detectors
Abstract
The objective of this project is to perform development and system testing of all-optical filteringmethods that can be used improve the performance of hybrid lidar-radar systems operating in turbidwater.Hybrid lidar-radar (HLR) systems are used to perform high resolution optical proximity detection inturbid water. Light scattering from particles in the water reduces the operating range and rangeaccuracy of these systems. In a recent investigation at Clarkson University, optical coherence filtering(OCF) methods have been identified that have the potential to improve the performance of an HLRsystem operating in turbid water by rejecting scattered light before it can reach the HLR~s opticalphotodetector. These methods use optical wavefront processing as enabled by new spatial lightmodulator (SLM) hardware and beamshaping optics. In proof-of-concept benchtop experiments, OCFhas been shown to readily reject 90% of scattered light, while still allowing 50% or more of theunscattered light to pass through. In this project, these OCF methods will be further developed, andused to make prototype filters for deployment in an operating HLR system. Optical proximity detectortests using the modified HLR with OCF will then be performed in Clarkson University~s water testtank facility.If this project is successful in achieving a scatter suppression gain of 10x or better, preliminary analysisand experiments suggest that the range of HLR systems operating in turbid water could be improvedby 25-50%, and typical HLR range errors could be reduced from centimeter-order to millimeter-order.In this project, the research team will explore multiple kinds of OCF assemblies, based on varioustypes of laser beams. The beams that will be investigated immediately are Bessel beams, Airy beams,and vortex beams. In the first prototype experiments, OCF will be implemented in easily adjustedbenchtop hardware using SLMs and bulk optics, so that various parameters can be tuned to maximizethe separation of the scattered and unscattered light. As appropriate parameter values are chosen, morerobust and transportable versions of the most promising filter(s) will be built, and the filters will beset up in Clarkson~s test tank lab for proximity detector testing. In these tests, the backscatter, targetreflections, and forward scatter will be visible at distinct time positions, so it will be easy to see theeffect of the OCF on the amplitude of each. The reduction in collected scattered light will thus bequantified, along with any changes in collected target-reflected light. Recommendations can then bemade about OCF designs that would allow for maximum improvement in HLR performance inrealistic turbid water conditions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2019
- Source ID
- N000141912427
Entities
People
- William Jemison
Organizations
- Clarkson University
- Office of Naval Research
- United States Navy