MONTE-CARLO CALCULATIONS OF THE MODULATION TRANSFER-FUNCTION OF AN OPTICAL-SYSTEM OPERATING IN A TURBID MEDIUM

Using a Monte Carlo method, we investigate the effect of a turbid medi um on image transmission by means of the modulation transfer function approach. We present results that refer to a medium that consists of a random distribution of water spherical particles in air. We analyze t he effect of geometric conditions (medium width and position) and sour ce characteristics (Lambertian, beam emission). We present results for small spheres (Rayleigh scattering) and spheres (1.0-mum diameter) th at are not small in comparison with the wavelength lambda = 0.6328 mum . Numerical data show a large modulation transfer function dependence on the source emission aperture and a substantial independence of the medium width for a fixed value of the optical depth. In accordance wit h reciprocity principles, we test an inverse scheme of Monte Carlo cal culation, the advantage of this scheme being a substantial reduction i n calculation time.