Ocean Visibility and Optics Lab
Description
Over the last several decades, developments in underwater laser line scan (LLS) serial imaging sensors have resulted in significant improvements in turbid-water imaging performance. In the last few years, there has been renewed interest in distributed, truly bi-static LLS sensor configurations in which the laser transmitter and optical receiver are distributed amongst multiple platforms. In addition to high-quality image acquisition capability through tens of beam attenuation lengths, whilst simultaneously establishing a non-line-of-sight free-space communications link, these system architectures also have the potential to provide more synoptic imaging of larger regions of seabed and the flexibility to simultaneously examine a target from different perspectives. A related issue worth investigation is how to utilize these capabilities to improve rendering of the underwater scenes. In this regard, light field rendering (LFR), a type of image-based rendering (IBR) technique, offers several advantages. LFR enables multi-perspective target visualization without measuring the geometrical dimensions of the target. Compared to other IBR techniques, LFR can provide signal-to-noise ratio improvements and the ability to image through obscuring objects in front of the target. On the other hand, multi-static LLS can be readily configured to acquired images to generate LFR. This research investigates the application of LFR to images taken from a distributed bi-static LLS imager using both line-of-sight and non-line-of-sight imaging geometries to create multi-perspective rendering of an unknown underwater scene. An experiment conducted in the HBOI-FAU optical imaging test tank demonstrated the viability of a bi-static/multi-static LLS system to generate LFR and verified the proposed image processing flow. A texture feature and mutual information-based image quality metrics were used in the analysis of the experimental results.
(a) HBOI Optical Imaging Test Tank (b) Target configuration (c) Raw image
One advantage of LFR is that it enables synthetic aperture imaging, allowing users to “see through” an obscure object in front of the target, as demonstrated in the mesh experiment below.
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f=0.1 |
f=0.25 |
f=0.7 |
f=1 |
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Mesh screen synthetic aperture images at different virtual focal lengths (f=0.25 is provided optimal result)
For more information, please contact Bing Ouyang .
B. Ouyang, F. R. Dalgleish, A. Vuorenkoski, W. Britton, B. Ramos and B. Metzger, “Visualization for Multi-static Underwater LLS System using Image Based Rendering”, submitted to IEEE Journal of Oceanic Engineering (2011).
