Image-processing method of modeling underwater imagery from gated and gain-modulated scannerless range imagers

John William Edwards; Jimmy Touma; Michael R. Wellfare; Monte A. Owens; Joseph Foster; Donna Foster; Bradley T. Blume; Robert O. Nellums; Steve Leiben; Jeff W. Rish III; Jody L. Wood-Putnam

doi:10.1117/12.391884

12 July 2000 Image-processing method of modeling underwater imagery from gated and gain-modulated scannerless range imagers

John William Edwards, Jimmy Touma, Michael R. Wellfare, Monte A. Owens, Joseph Foster, Donna Foster, Bradley T. Blume, Robert O. Nellums, Steve Leiben, Jeff W. Rish III, Jody L. Wood-Putnam

Author Affiliations +

Proceedings Volume 4039, Information Systems for Divers and Autonomous Underwater Vehicles Operating in Very Shallow Water and Surf Zone Regions II; (2000) https://doi.org/10.1117/12.391884
Event: AeroSense 2000, 2000, Orlando, FL, United States

Abstract

An Underwater Scannerless Range Imager illuminates a wide field-of-view with a broadbeam laser pulse and captures the entire scene with an image intensified solid state camera. By imaging the received light onto a microchannel plate (MCP) receiver whose gain is modulated, and focusing the CCD camera on the phosphor screen that fluoresces upon excitation by the MCP output pulse, a sequence of images differing in the phase of the modulation waveform can be formed, and high precision target ranges can be inferred for each pixel of the viewed scene. When the medium between transmitter and target is obscured, as by turbid water, the return signal is temporally extended so that the inferred range picks up a bias owing to backscatter. The intimate relationship between the spatial and temporal behavior of the signals (near targets produce different temporal profiles than distant ones) adds complexity that cannot be handled by point spread functions, as is common for CW illumination and range-gated systems with constant gain. The method described here breaks the propagation problem into four channels depending on whether the light is scattered by the medium on the way to or from the target (or both, or neither), and calculates arrays to represent mean pathlengths and their variances. A fairly rigorous sensor model based on the various layers in a particular implementation (photocathode, MCP, phosphor, CCD array, A/D converter) and on receiver modulation transfer characteristics completes the prescription for generating realistic synthetic USRI images in moderate turbidity.

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John William Edwards, Jimmy Touma, Michael R. Wellfare, Monte A. Owens, Joseph Foster, Donna Foster, Bradley T. Blume, Robert O. Nellums, Steve Leiben, Jeff W. Rish III, and Jody L. Wood-Putnam "Image-processing method of modeling underwater imagery from gated and gain-modulated scannerless range imagers", Proc. SPIE 4039, Information Systems for Divers and Autonomous Underwater Vehicles Operating in Very Shallow Water and Surf Zone Regions II, (12 July 2000); https://doi.org/10.1117/12.391884

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