A method and apparatus for resolving both the angular (nx,ny) and spatial (x,y) dependence of the effective source coherence matrix for lithographic steppers and scanners is described. First an in-situ source metrology instrument is combined with in-situ polarization elements to create an in-situ source imaging polarizer or ISIP. The ISIP is loaded into a photolithographic exposure tool, aligned, and then exposed onto a suitable recording media or recording sensor. The recording sensor comprising either resist coated wafers or electronic sensors capture the image intensity at a multiplicity of different field points. The resulting measurements are entered into a computer program that reconstructs the source coherence matrix as a function of direction cosine at multiple field points. Alternative ISIP configurations are discussed in some detail. Applications of the ISIP include polarization source mapping for deep-UV and EUV lithography, process optimization, process monitoring, and chip manufacturing.