Investigation of the influence of inhomogenous scattering media on image quality: the shower curtain effect

Abstract

Imaging quality of optical systems in a turbid environment is influenced not only by the contents of the turbid layer between the object and the optical receiver but also by the inhomogeneity of that medium. This is important particularly when imaging is performed through clouds, non homogeneous layers of dust, or over vertical or slant paths through the atmosphere. Forward small angle scattering influences more severely image quality and blur when the scattering layer is closer to the receiver. In this study the influence of the position of the scattering layer along the optical axis on the image quality and modulation transfer function (MTF) is investigated. The scattering layer was in controlled laboratory experiments consisted of calibrated polystyrene particles of known size and quantity. A point source was imaged by a computerized imaging system through a layer containing polystyrene particles and the point spread function (PSF) was recorded. The scattering MTF was calculated using the measured PSF. The MTF was measured as a function of the relative distance of the layer from the receiver. The experimental results were compared to theoretical models based on the solution of the radiative transfer theory under the small angle approximation.