Development of a New Underwater Bathymetric Laser Imaging System: L-Bath

The design, construction, and performance of a new high-resolution underwater bathymetric prototype system (L-Bath) with extended imaging capability is presented. The design offers simultaneous reflectance and depth information on a pixel-by-pixel basis so that high-resolution reflectance and bathymetric maps of underwater targets can be provided with exact registration. The design supports operation in shallow coastal waters under daylight conditions where high turbidity and the influence of ambient backscatter are particularly limiting for underwater imaging systems. Its configuration is similar to existing laser line scanning systems but uses a pulsed laser for the source and a fixed field-of-view high-resolution linear charge-coupled device (CCD) as receiver. The pulsed laser allows short camera integration times, thereby reducing the influence of the ambient daylight signal, and the fixed field of view of the detector provides a precision nonmoving multielement receiver with imaging capability. As the laser sweeps across the field of view of the CCD, the position and signal strength of each laser target spot is imaged, permitting a measure of bathymetry and reflectance. Using the CCD, a highresolution slice through the reflected target spot radiance distribution is imaged so that system resolution can exceed the target spot size. The image of the target spot radiance distribution, modified by in-water scattering and target reflectance, provides new opportunities for image manipulation compared to typical underwater laser line scanning based systems. The simultaneous acquisition of reflectance and bathymetric maps permits discrimination capability between real objects of relief from scene reflectance variations.

[1]  Roswell W. Austin,et al.  Underwater laser scanning system , 1991, Optics & Photonics.

[2]  Paul M. Evans,et al.  New technology for subsea laser imaging and ranging system for inspection and mapping , 1998 .

[3]  J. Jaffe,et al.  Monte Carlo modeling of underwater-image formation: validity of the linear and small-angle approximations. , 1995, Applied optics.

[4]  Joel H. Blatt,et al.  Adaptation of video moiré techniques to undersea mapping and surface shape determination , 1992 .

[5]  Joel H. Blatt,et al.  Advanced underwater laser systems for ranging, size estimations, and profiling , 1993 .

[6]  T J Kulp,et al.  Development and testing of a synchronous-scanning underwater imaging system capable of rapid two-dimensional frame imaging. , 1993, Applied optics.

[7]  Donna M. Kocak,et al.  Real-time 3D underwater imaging and mapping using a laser line scan technique , 1997, Optics & Photonics.

[8]  Joel H. Blatt,et al.  Spatially variant and coherent illumination method for undersea object detection and recognition , 1998, IEEE Oceanic Engineering Society. OCEANS'98. Conference Proceedings (Cat. No.98CH36259).

[9]  Michael P. Strand.  Underwater electro-optical system for mine identification , 1995, Defense, Security, and Sensing.

[10]  Kendall L. Carder,et al.  In situ holographic measurements of the sizes and settling rates of oceanic particulates , 1982 .

[11]  C J Funk,et al.  Handbook of Underwater Imaging System Design , 1972 .

[12]  Andrew J. Nevis,et al.  Laser line-scan fluorescence and multispectral imaging of coral reef environments , 1997, Other Conferences.

[13]  V. M. Contarino,et al.  Application of RADAR technology to aerial LIDAR systems for enhancement of shallow underwater target detection , 1995 .

[14]  J. L. Forand,et al.  Range-gated underwater laser imaging system , 1993 .

[15]  Ned H. Witherspoon,et al.  Feasibility testing of a range-gated laser-illuminated underwater imaging system , 1990, Defense, Security, and Sensing.

[16]  Jules S. Jaffe,et al.  Computer modeling and the design of optimal underwater imaging systems , 1990 .

[17]  J. W. Mclean,et al.  Streak-tube lidar allows 3-D ocean surveillance , 1998 .

[18]  J. O. Klepsvik,et al.  A novel laser radar system for subsea inspection and mapping , 1994, Proceedings of OCEANS'94.

[19]  Joseph Katz,et al.  Submersible holocamera for detection of particle characteristics and motions in the ocean , 1999 .

[20]  F. M. Caimi.  A review of recent underwater imaging methods and advancements , 1996, OCEANS 96 MTS/IEEE Conference Proceedings. The Coastal Ocean - Prospects for the 21st Century.