Forward multiple scattering corrections as a function of detector field of view

Theoretical formulations are given for an approximate method based on the solution of the radiative transfer equation in the small angle approximation. The method is approximate in the sense that an approximation is made in addition to the small angle approximation. Numerical results were obtained for multiple scattering effects as functions of the detector field of view as well as the size of the detector's aperture for three different values of the optical depth τ (= 1.0, 4.0, and 10.0). Three cases of aperture size were considered, namely, equal to, smaller, or larger than the laser beam diameter. The contrast between the on-axis intensity and the received power for the last three cases is clearly evident.