Standoff real-time detection of floating and submerged objects in ocean water

Abstract

Detecting and identifying floating or submerged objects in the ocean is very challenging with the current state of the art maritime-LIDAR technology. A LIDAR sensor has limitations in detecting objects that are near the surface of water due to strong glint produced by the reflection of the laser from the surface of water. In addition, whitecaps, foam, and air bubbles give strong scattering signals which make it difficult for a LIDAR sensor to detect and identify an object which is floating or is just below the ocean surface. We have developed a fluorescence sensor for standoff detection of objects that are either floating or submerged in shallow ocean waters. The fluorescence sensor is an active sensor that utilizes a nano-second Nd:YAG laser simultaneously emitting 355 and 532 nm laser pulses for illuminating a wide area for fluorescence excitation. The sensor provides live color images of floating and submerged objects in the ocean with each laser pulse excitation. The fluorescence sensor works in both daytime and nighttime operations and the presence/absence of direct sunlight; and surface reflections, air bubbles, and foam are not limiting factors for detection of objects in ocean water. The sensor is also immune to reflection or scattering of incident laser light from the ocean surface, overcoming challenges associated with LIDAR technology. The sensor can be integrated into a surface boat platform or an aerial platform e.g. drone, allowing it to provide real-time images of plastics and manmade objects (plastic bottles, clothes, fishing lines, ropes, oil spills, etc.) along with human bodies.