| Popis: |
Fog is a commonly occurring degraded visual environment which disrupts air traffic, ground traffic, and security imaging systems. For many application of interest, spatial resolution is required to identify elements of the scene. However, studying the effects of fog on resolution degradation is difficult because the composition of naturally occurring fogs is variable, and data collection is reliant on changing weather conditions. For our study, we used the Sandia National Laboratories fog facility to generate repeatable characterized fog conditions. Sandia’s well characterized fog generation allowed us to relate the resolution degradation of active and passive long-wave infrared (LWIR) imagers to the properties of fog. Additionally, the fogs we generated were denser than naturally occurring fogs. This allowed for testing of long range imaging in the shorter optical pathlengths obtainable in a laboratory environment. In this presentation, we experimentally investigate the resolution degradation of LWIR wavelengths in realistic fog droplet sizes. Transmission of LWIR wavelengths has been studied extensively in literature. To date however, there are few experimental results quantifying the resolution degradation for LWIR imagery in fog. We present experimental results on resolution degradation for both passive and active LWIR systems. The degradation of passive imaging was measured using 37˚C blackbody with a slant edge resolution targets. The active imaging resolution degradation was measured using a polarized CO2 laser reflecting off a set of bar targets. We found that the relationship between meteorological optical range and resolution degradation was more complicated than described purely by attenuation. |
