Measurements and lidar calculations have been made for 1574 nm laser light pulsed through hydrocarbon smoke generated by wood. A pulsed laser signal is directed to the end of wood smoke filled chamber. The signal is reflected back through the smoke by a mirror and the end of the chamber and the total returned energy is measured as a function of the smoke density. The results are compared with a lidar calculation using Rayleigh-Debye-Ganz scattering theory for fractal aggregates. Measurements and calculations are also made of the total backscattered signal for a smoke chamber with a non-reflecting surface. Relatively good agreement between the theory and experimental results are achieved in both cases. These results are used in the feasibility studies of a FireLidar active imaging system being developed for use in search and rescue in smoke and flame environments.
FireLidar, an active optical imaging system, is being developed for use as an aid to search and rescue in smoke and flame environments. The system is intended to augment currently available passive thermal imaging technology by imaging in the presence of a thermal bloom, heavy smoke conditions, or species which strongly absorb thermal radiation, such as water. We present experimental verification of a theoretical model for FireLidar. Lidar range equations for compartment fire scenarios are derived and compared to measurements taken in a controlled smoke chamber. Extinction measurements of near-infrared light through soot particulate provide information about optical properties of fire environments necessary to predict Lidar returns. Measured extinction values are compared to a single-scattering approximation, based on the Rayleigh-Debye-Gans scattering theory for fractal aggregates. Component specifications for a FireLidar prototype system are discussed, including laser power, filter bandwidth, and camera integration times. A man-portable prototype system using specified components is scheduled for completion by the end of 2005, with a handheld device following soon thereafter.