Potential Underwater Sensing Using Narrow Beam Lasers

Abstract

This report investigates underwater sensing using images created by reflections of narrow laser beams from surface (laser footprints). These images are captured by a tilted camera to form a picture. Such pictures are affected by ocean bottom features and are subjected to perspective distortions. A methodology is developed and verified by some laboratory experiments for underwater sensing. Multitude Laser beams can be created from a single laser by suitable scanning, refraction grid or laser array. A square laser point grid is formed from single laser beam using a diffraction mask and projected over bottom. The plane of the grid is perpendicular to the gravitational vector. The laser beam or laser array is used to project continuous or discrete (point) images (grid) on the bottom. Laboratory experiment showed this system senses object in the floor successfully with dimension and within error rate below 5%. The characteristics of the laser footprints also studied for flat and tilted bottom.