Modulation transfer function and image transmission through randomly distributed spherical particles

Abstract

Image transmission through a random medium is important in many areas. Transmitted images are often affected by the presence of particulate matter and turbulence between the object and the detector. This paper presents the results of controlled experiments for the modulation transfer function (MTF) through a random distribution of polystyrene microspheres suspended in water. Experimental results show that the MTF has two distinct regions separated by a cutoff frequency. When the spatial frequency is higher than the cutoff frequency, the MTF becomes almost constant. On the other hand when the spatial frequency is less than the cutoff frequency, the MTF increases exponentially with decreasing spatial frequency and the slope depends on the optical distance of the medium. The cutoff frequency increases as the particle size increases. Results are obtained for particle sizes of 0.109, 0.46, 1.101, 2.02, 5.7, and 11.9 μm, densities ≪1%, and optical distances between 0 and 15. The experimental results are compared with the results of the small-angle approximation for the equation of transfer.