Navy

Optical vortex for improved object detection and light transmission in turbid media

Photonics Sensors

Scientists at the Naval Air Warfare Center’s Aircraft Division have developed a novel method and device for improving light transmission and object detection in light-scattering (turbid) media like hazy water and fog.

Detection of objects in turbid air and water is impeded by light attenuation and the adverse effect of incoherently scattered light (clutter) on the coherent non-scattered light returned from an object. The Navy’s optical vortex improves underwater visibility by increasing discrimination between object and clutter. Combined with LiDAR, it potentially improves remote sensing and ranging of objects in turbid media by increasing the detection range and reliability. It can also increase the accuracy of transmissometer (light attenuation) measurements. (Navy photo)

The Navy’s inventions address both of these issues and it has applied for U.S. patents on the technology.

In this innovation, Navy scientists use the spatial structure of the beam itself to aid in object and clutter discrimination by exploiting the optical properties of Orbital Angular Momentum (OAM).

Deploying a spiral phase plate in front of a CCD camera, simple diffractive optics can impart OAM onto a beam of light.

Optical beams with such a helical phase result in an intensity vortex that serves as a coherence (object) filter, to spatially separate object returns from clutter.

The results of this work show high agreement with theoretical models of attenuation, the ability to detect object returns 100-1000x below clutter levels, and a simple method of detecting coherent light without complicated optical heterodyning.

Brandon Cochenour, an electrical engineer at Naval Air Warfare Center Aircraft Division and one of the technology’s inventors, demonstrates how twisted light travels through ocean water. Cochenour’s research on optical vortices enhances naval capability in remote laser sensing and communications. (Navy photo)

Potential commercial applications of the technology include improved devices and techniques for optical communications, transmissometry, and LiDAR in air, water, and space.

There are a wide range of commercial and military applications including runway safety, chemical and biosensing, and tissue imaging.

Military applications may include helicopter guidance in a brownout, non-acoustic mine and explosive ordinance detection, non-acoustic anti-submarine warfare, and covert broadband communications.

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