ABSTRACT
Image quality in long range surveillance is generally limited by atmospheric effects rather than by equipment limitations. In locations whose ground or sand particles are not adhesed to the ground, such as desert and beach areas, significantly wavelength dependent multiple forward scattering by relatively large particulates noticeably limit image resolution. Imaging through desert and non-desert atmospheres is compared from the standpoint of interactions of optics and meteorology. In non-desert atmospheres image quality is governed primarily by atmospheric background illuminance and by atmospheric turbulence. The former serves to decrease contrast in much the same way as background illuminance from ceiling lights decreases image contrast on the movie screen in a movie theater. Atmospheric turbulence describes the common situation where atmospheric refractive index fluctuates randomly, thus causing random refractions of light. Light propagating from a point source should be ideally imaged into a point image.
