Technical evaluation of underwater optical imaging
Publish date: 2006-01-01
Report number: FOI-R--2061--SE
Pages: 39
Written in: English
Abstract
A laser triangulation system, to allow an underwater vehicle to scan an area and create 3D images, has been tested and evaluated. The method uses structured light from a thin, divergent, laser fan beam and a conventional video camera to acquire 3D images which makes it a low-cost alternative. The beam intersection with a target will appear at different positions in the camera image depending on the distance to the object and the angle and separation between camera and laser. Different methods to find the center of the laser line and techniques to transfer pixel coordinates into spatial coordinates has been analysed. A 3D image is created by sweeping the laser line over the target. The performance of the system was tested in a number of field and laboratory trials where e.g. the influence from scanning speed and separation between camera and laser was evaluated. In our experimental setup, the range resolution is much higher than the lateral- and longitudinal resolutions. The lateral resolution can be improved either by using a high frame rate camera or simply by using a low scanning speed. Range resolution of less than a millimeter is possible to obtain.