Bench-Scale Test Facility for Evaluating the Imaging Performance of Thermal Imagers for Fire Service Applications
Sung C. Kim, Anthony P. Hamins
The present study investigates the characteristics of obscuring media inside an optical smoke cell, which is developed as a bench-scale testing facility for the evaluation of thermal imagers used by fire fighters. The smoke obscuration conditions through the optical smoke cell were characterized by measuring laser transmittance. FTIR measurements examined the gas components in the cell and their effect on energy transmittance within the spectral range of the thermal imager. The laser transmittance along the axial direction of the optical smoke cell was relatively uniform in the upper and lower halves of the cell for various smoke obscuration conditions. In addition to the characterization of smoke media in the optical smoke cell, this study examined the thermal sensitivity of a thermal imager using the Michelson Contrast (CM) as a performance metric for a bar target. The CM was calculated with the thermal imager viewing a target through the smoke-filled cell at different background thermal conditions. The optical smoke cell can be utilized as a well-controlled and effective bench-scale test apparatus to evaluate aspects of the imaging performance of thermal imagers for fire service applications.