Distributed Laser Line Scan (DLLS) system concepts have been proven capable of acquiring high-quality imagery over large numbers of beam attenuation lengths and exhibiting greater immunity to highly variable optical conditions when compared with the LLS imagers used primarily aboard solitary underwater platforms.
Further advantages relate to relatively low laser power, low cost, and simplicity of operational hardware. However, in very turbid conditions, to stay within the optimal operating envelope (i.e., to maintain operational target-to-receiver distances of tens of meters), distances between illuminator and target need to be no more than a couple of meters. Therefore, the target region from which imagery is obtainable from single imagers is quite small, and long operational times are necessary to cover typical survey areas.
For multiple-contact optical identification missions, it is therefore preferred to obtain simultaneous images from multiple small patches of seabed using multiple platforms.
Our findings can be summarized as follows:
- Method is useful through a much greater range of turbidities and more than five times the distance of LLS sensors on single platforms
Results confirm that laser-to-target distance is a key factor in image quality; desirable system design goals include:
- maximize radiant intensity at target element
- minimize target element dimensions for high-resolution imagery
- maximize receiver collection aperture
- develop robust multiplexing schemes for multi-contact missions
- Method is very well suited to imaging in complex and confined areas (e.g., ship hull inspection) and multi-perspective visualization to enhance identification
- Imagery may be possible directly from seabed through water-air interface
- To fully realize potential, requires groups of co-operative unmanned underwater vehicles, which presents significant additional challenges
- It is necessary to test the system over longer distances in a variety of coastal and oceanic waters -- this is the next step
For more information, please contact Fraser Dalgleish
Dalgleish F. R., Ramos, B., Britton, W. B., and Caimi F. M., 2010, “Multistatic distributed laser line scan underwater imaging architecture.” Proc. ONR/NASA Ocean Optics XX. Sept 27th-Oct 1st 2010. Anchorage, AK.
Dalgleish, F. R. Caimi, F. M., Vuorenkoski, A. K., Britton, W. B. and Ramos. B., 2009 "Experiments in bistatic Laser Line Scan (LLS) underwater imaging". Proc. MTS/IEEE Oceans 2009, October 26-30 2009, Biloxi. MI.