Mitchell Steven, Thayer Jeffrey P, Hayman Matthew
University of Colorado, Department of Aerospace Engineering Sciences, Boulder, Colorado 80309, USA.
Appl Opt. 2010 Dec 20;49(36):6995-7000. doi: 10.1364/AO.49.006995.
A bathymetric, polarization lidar system transmitting at 532 nm and using a single photomultiplier tube is employed for applications of shallow water depth measurement. The technique exploits polarization attributes of the probed water body to isolate surface and floor returns, enabling constant fraction detection schemes to determine depth. The minimum resolvable water depth is no longer dictated by the system's laser or detector pulse width and can achieve better than 1 order of magnitude improvement over current water depth determination techniques. In laboratory tests, an Nd:YAG microchip laser coupled with polarization optics, a photomultiplier tube, a constant fraction discriminator, and a time-to-digital converter are used to target various water depths with an ice floor to simulate a glacial meltpond. Measurement of 1 cm water depths with an uncertainty of ±3 mm are demonstrated using the technique. This novel approach enables new approaches to designing laser bathymetry systems for shallow depth determination from remote platforms while not compromising deep water depth measurement.
