Backscatter gas absorption imaging (BAGI) has been demonstrated as a useful technique for visualizing gas leaks. BAGI uses active imaging in the infrared to generate a laser- illuminated video image of a scene. A dark cloud in the image is formed when a gas absorbs the illuminating laser radiation in the vicinity of the plume. The sensitivity of the technique is limited by the ability of the operator to distinguish scene contrasts from gas contrasts. To improve its performance, we have developed a differential absorption system to subtract off scene contrasts that can obscure a gas plume. This system is essentially an imaging differential absorption LIDAR (DIAL) that allows one to focus on contrast in a scene due to absorption from a gas plume instead of contrast due to variations in the reflectivity of the target. Practical aspects of this system are presented along with results taken in real-world settings. The noise floor for a differential image is shown to be dominated by uncorrelated speckle fluctuations -- not contrasts in the scene.

Date Published: 13 August 1997
PDF: 4 pages
Proc. SPIE 3061, Infrared Technology and Applications XXIII, (13 August 1997); doi: 10.1117/12.280320

Published in SPIE Proceedings Vol. 3061:
Infrared Technology and Applications XXIII
Bjorn F. Andresen; Marija Strojnik, Editor(s)