Long wavelength video detection of fire in ship compartments

This paper describes progress using filtered, long wavelength video image-based detection (LWVD) of events in laboratory tests and full scale fire testing within the Volume Sensor Program at the U.S. Naval Research Laboratory (NRL). This effort toward developing a real-time, remote sensing detection system utilizes video image detection (VID) systems based on cameras that operate in the visible region, which were developed for detecting smoke and have recently been adapted to detecting fire. However, VID systems are not effective at detecting fire outside the direct line of sight of the camera. Our studies demonstrate that long wavelength imaging achieves effective detection of reflected flame emission compared to visible video images. A system that combines visible and long wavelength image capabilities may be more accurate and sensitive than either alone. Our LWVD approach exploits the long wavelength response of standard CCD arrays used in many cameras. A long pass filter (typically in the range 700-900 nm) increases the contrast for flaming and hot objects and suppresses the normal video image of the space, thereby effectively providing a degree of thermal imaging. There is more emission from hot objects in this spectral region than in the visible region (<600 nm). Testing has demonstrated the detection of objects heated to 400 degrees C or higher. A simple luminosity-based algorithm was developed and used to evaluate camera/filter combinations for fire, smoke and nuisance (false) event detection and response times. (C) 2006 Elsevier Ltd. All rights reserved.