Calibration and operation of an underwater laser triangulation sensor: The varying baseline problem

We describe the calibration and operation of a high-speed underwater scanning depth finder that has been designed for workspace sensing (that is, for ranges of 2 m or less). It 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 mirror system enables fast data capture but introduces alignment problems with standard domed ports. Hence a planar interface is used. This results in the triangulation baseline varying as a function of scan angle. We present a simple but novel solution for the calibration and use of such a device. The effect of the varying baseline is modeled, and a calibration/depth calculation process is presented. Results obtained from using the device in a test tank demonstrate the performance of the system. © 1997 Society of Photo-Optical Instrumentation Engineers.