Measuring resolution degradation of long-wavelength infrared imagery in fog

The scattering of light in fog is a complex problem that affects imaging in many ways. Typically, imaging device performance in fog is attributed solely to reduced visibility measured as light extinction from scattering events. We present a quantitative analysis of resolution degradation in the long-wave infrared regime. Our analysis is based on the calculation of the modulation transfer function from the edge response of a slant edge blackbody target in known fog conditions. We show higher spatial frequencies attenuate more than low spatial frequencies with increasing fog thickness. These results demonstrate that image blurring, in addition to extinction, contributes to degraded performance of imaging devices in fog environments.