Measurement of modulation transfer function of desert atmospheres

摘要

Abstract: A unique research program is being conducted for passive, remote sensing of horizontal contrast transmittance and the modulation transfer function (MTF$-A$/) of desert atmospheres, including the DC, low, and high spatial frequency MTF$-A$/ components that are attributed to contrast, aerosols, and turbulence, respectively. The research makes it possible, for the first time, to measure the overall low spatial frequency response of the aerosol MTF$-A$/ components of actual desert atmospheres. The required measurements are based on utilizing digital image processing of remote video scenes which include two optically-identical castellated targets, contrasted against the horizon sky background. Ratios of apparent contrast and MTF measurements of these two targets are used to determine the contrast transmittance and MTF$-A$/ in the atmospheric region between the two targets, independent of the imaging system and the actual optical properties of the targets. The experimental technique is described along with current MTF$-A$/ measurements.!