Darrel G. Garvis

Development and testing of a synchronous-scanning underwater imaging system capable of rapid two-dimensional frame imaging

The design and construction of a synchronous-scanning underwater imaging system capable of rapid two-dimensional scanning are described. The imager employs a 7-W, all-lines, argon-ion laser in onjunction with a galvanometrically driven raster scanner and an image-dissector tube receiver. The imager is capable of directly generating real-time RS-170 video imagery. The results of an in-water test of the imaging system, in which a high-contrast imaging test pattern was imaged, demonstrate operating anges of up to 4 attenuation lengths (AL) when the test was run at real-time frame rates, ranges of 5.1-5.5 AL when the system operated with an eight-frame running average, and ranges of 6.3 AL when a 128-frame running average was used. The system performance was compared with that of several floodlight/silicon-intensified-target TV camera configurations, which produced a maximum imaging range of ∼2.6 AL. Also, an imaging configuration that used the raster-scanned beam of the laser as an illumination source for the sil n-intensified-target camera was tested. That system had an ultimate range of ∼ 4 AL.

Results of the final tank test of the LLNL/NAVSEA synchronous-scanning underwater laser imaging system

The design and construction of a synchronous-scanning underwater imaging system capable of rapid two-dimensional scanning is described. The imager employs a 7 W all-lines argon ion laser in conjunction with a galvanometrically driven raster scanner and an image-dissector tube receiver. The imager is capable of directly generating real-time RS-170 video imagery. The results of in-water test of the imaging system demonstrate operating ranges of up to 4 attenuation lengths (AL) when running at real-time frame rates, ranges of 5.1 - 5.5 AL when operating with an 8-frame running average, and ranges of 6.3 AL when using a 128-frame running average. Future frame averaging requirements are expected to be relaxed, due to improvements in the detector preamplifier. The system performance was compared with that of several floodlight/silicon intensified target (SIT) television camera configurations, which produced a maximum imaging range of about 2.6 AL. Also, an imaging configuration that used the raster-scanned beam of the laser as an illumination source for the SIT camera was tested. That system had an ultimate range of about 4 AL.

Fluorescence microstructure using a laser/fiber optic profiler

Field tests were conducted during Aug/Sept 1989 of the second generation of a laser/fiber optic fluororneter attached to a microstructure proffling instrurnent (Rapid Sampling Vertical Profiler - RSVP). This instrumentation is designed to provide centirneter-scale biological measurements coincident with and at the same sampling frequency as those for temperature, conductivity, and horizontal velocity microstructure. The instrument used during the summer of 1989 employed a 200m dual fiber system, SMA optical fiber connectors used underwater, and an optrode (12mm diameter) containing two fibers, GRIN lenses, and filters. Shipboard laser excitation (488nrn or 514nm) was transmitted down a 2OOtm core excitation fiber, and the fluorescence emission spectrum returned via a 400pm core detection fiber to a shipboard multichannel array detector. Fluorescence emission spectra were acquired 30 times per second at an instrument drop rate of approximately 60 cm per second.

A well-head instrument package for multi-parameter measurement during well water sampling

Abstract A portable well-head instrument package was designed to provide more reliable measurements of pH and redox potential and to continuously monitor these parameters along with conductivity and temperature to insure proper well water sampling in the field. The values of these parameters are conveniently displayed on four digital displays and water sampling is begun after they stabilize.

Current Status Of The NAVSEA Synchronous Scanning Laser Imaging System

This paper constitutes an update on our efforts to develop an underwater laser-based imaging system (UWLIS). The work is being performed under contract from the Naval Sea Systems Command Office of Salvage and Diving (NAUSEA/00C) in order to provide instrumentation that will improve the visibility range available to deep-ocean (1500-6000 m) submersible vehicles during ocean-floor search-and-salvage operations. In general, these submersibles are remotely operated vehicles (ROV) that currently employ high-intensity floodlights and low-light-level TV cameras to produce video images of the seafloor, which are relayed to the mother ship to allow target identification. Often, these floodlight-based systems require that the ROV come within 6 to 10 m of the target in order to positively identify it. This poses both a risk of damaging the vehicle on outcropping seafloor terrain features and an increase in mission cost due to the time lost on maneuvering to identify false targets. Given that salvage-operation costs typically range from

Desian And Preliminary Evaluation Of An Underwater Laser-Based Imaging System

1000 to

Field Applications of Fiber-Optic Sensors. Part I: Temperature Measurements in a Geothermal Well

3000 per hour, a system that would improve the visibility range from 10 to 100 m would save thousands of dollars and greatly increase the probability of success of these missions.

Results of the second tank trial of the LLNL/NAVSEA underwater laser-imaging system

The design and preliminary evaluation of an underwater laser-based imaging system (UWLIS) being developed by the Lawrence Livermore National Laboratory for the Naval Sea Systems Command is described. The system is composed of a synchronously scanning argon-ion laser beam and a very narrow (4 milliradian) field-of-view detector. The laser beam and detector field of view are separated at the imaging system, but converge at the target to reduce the common optical scattering volume. The system produces a standard real-time TV image and has a predicted range of 100 m for 5 watts of laser power. The results of evaluations conducted in a 15-m deep tank at the Naval Coastal Systems Center are presented and discussed. The performance of the UWLIS in various turbid water conditions is compared to typical low-light-level underwater TV systems.

Development and testing of a backscatter absorption gas imaging (BAGI) system capable of imaging at a range of 300 m

We have initiated a program for developing and field testing fiber-optics-based sensors to monitor in situ physical and chemical parameters in highly corrosive environments, such as geothermal wells, oil wells, and hot-water boiler reactors. Inability to sample hot geothermal wells or to measure the chemical composition of hot brines limits our understanding of in situ conditions in geothermal fields. In this communication, we report preliminary results obtained with a temperature optrode to profile the temperature in a geothermal steam well. To our best knowledge, this is the first time in situ geothermal well measurements have been made with the use of a fiber-optic sensor.

Application of backscatter absorption gas imaging to the detection of chemicals related to drug production

This report provides a summary of the second in-water test of the LLNL/NAVSEA Underwater Laser Imaging System (UWLIS). The UWLIS is a laser-based, synchronous-scanning, underwater imaging device that is designed to operate at greater ranges than is possible with conventional underwater TV cameras. It differs from earlier prototype synchronousscanning systems in that it is capable of high scan rates that allow the generation of real-time, RS-170 video images. The UWLIS is being developed for eventual use on Remotely Operated Vehicles (ROVs) during deep-ocean Naval salvage missions. The floodlight-illuminated television cameras presently used on NAVSEA vessels can produce images at ranges up to about 2 attenuation lengths (AL) (2). Beyond that point, common volume backscatter from particulates in the intervening seawater between the imager and the target overwhelms the return signal, and the image is lost. The special optical geometry of the synchronous-scanning imager is designed to minimize common-volume effects. Previous theoretical studies (1) indicate that a system of this type should be capable of operation at distances as great as 6 to 7 attenuation lengths. An improvement of this magnitude would greatly increase the efficiency of salvage operations, thus decreasing their cost.