This paper presents a consistent and modularized approach to modeling projection optics. Vector nature of light and polarization effect are considered from the very beginning at source, through mask and projection lens down into film stack. High-NA and immersion effect are also included. Of particular interest is the formulation of a modularized framework for computing optical images that allows various mask models (a thin-mask model, an empirical approximate mask model, or a rigorous mask 3D solver) to be used. We demonstrate that under Kirchoff thin-mask assumption our formulation is the same as Smythe formula. A compact film-stack model is formulated. The formulation is first presented in Abbe's source integration approach and then reformulated in Hopkins' TCC approach which allows for a SVD decomposition, which is computationally more efficient for a fixed optical setting.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.