CALIBRATION AND OPERATION OF AN UNDERWATER LASER TRIANGULATION SENSOR- THE VARYING BASE-LINE PROBLEM

We describe the calibration and operation of a high-speed underwater s canning depth finder that has been designed for workspace sensing (tha t is, for ranges of 2 m or less), II uses standard components mounted in an underwater housing fitted with a planar viewing port. The use of a laser line forming element coupled with a single galvanometer mirro r system enables fast data capture but introduces alignment probIems w ith standard domed ports. Hence a planar interface is used. This resul ts in the triangulation baseline varying as a function of scan angle, We present a simple but never solution for the calibration and use of such a device, The effect of the varying baseline is modeled, and a ca libration/depth calculation process is presented, Results obtained fro m using the device in a test tank demonstrate the performance of the s ystem. (C) 1997 Society of Photo-Optical Instrumentation Engineers.