TS-82
Detection Spilled Oil using a Compact Imaging Lidar System
Kazuo HITOMI*, Susumu YAMAGISHI, Hiroshi YAMANOUCHI, Yoshitaka YAMAGUCHI, and Toshiaki SHIBATA
ABSTBACT;
The fluorescence lidar can positively discriminate oil. Rugged systems mounted in ships and airplanes with real-time display could be significant extension of characterization of pollution detection. This paper describes a compact imaging lidar system which meets the operational requirements for immediate identification of targets. Functions of the proposed of system were basically confirmed by airborne test and ship borne test. Air plane overflights recorded the laser illuminated spots in wide view of images using the proposed compact imaging lidar system. The method of interpreting fluorescence data in terms of substances is explained by using fluorescence characteristics measured with the streak scope in a laboratory. A precise image of light path through the medium provides a convenient procedure to measure the extinction property of the medium.
Key words: fluorescence lidar, oil spill, real-time display, flight test, fluorescence lifetime, extinction
1. INTRODUCTION
Oil and bulk liquid chemicals are regularly transported by tankers with risk of spills. Also intentional oil pollution caused by discharges oil waste when ships clean out their tanks, is far more widespread. Deliberate ship discharges of bilge and ballast waters create oil spills that float on the water. Prevention and control of this kind of pollution is very important. Detection and tracking of the pollution both on the surface and under the surface are required, for providing helpful data to the clean-up operation.
The practical visible techniques are primarily used for oil spills, mainly because of the low cost and the adaptability easily to employ them for various opportunity. Satellite sensors are also useful for synoptic nature, however due to orbit characteristics, a space borne detector can take days or weeks to repeat its coverage of a given area.
Researches in the infrared, ultraviolet visible, and microwave aria have demonstrated for the many cases that surveillance of environment is feasible with remote sensing, but they could not meet requirements of response operation sufficiently. Most of passive techniques is generally used to make documentation because the lack of a positive oil detection mechanism. And also microwave active sensor(SAR; Synthetic Aperture Radar, SLAR;Side Looking Airborne Radar)) suffers from the limitation that several natural phenomena generate area of low back scatter similar in appearance to oil slicks.
A surveillance system is required to achieve following performances;
to function in day and night
to get real time information
to differentiate oil from water and plants
to monitor an extensive area
to survey under the surface
to function under all weather conditions
to measure a quantity of oil
Thus, our interest is focused in the use of an active method.
2. IMAGING LIDAR SYSTEM
The fluorescence lidar is promising because of its high capability of active sensing to positively identify oils from water or biological substances. For detailed description of the method of oil film thickness measurements and oil type evaluation with fluorescence lidar, we refer to articles published1,2,3).
Most of organic chemical compounds have characteristics of fiuorescence emission spectrum in a different wavelength region, hence fluorescence emission is strongly indicative of the presence of oil.
Research and development of fluorescensor have been conducted several countries 4,5,6,7). However, most of systems existed were so large that they could be only installed on a large airplane and were seldom used as an operational tool for the clean up operation.
