In optical lithography, high-performance exposure tools are necessary to obtain not only fine patterns but also preciseness of the pattern width. Therefore, an accurate theoretical method is necessary to predict these values in practice. Conversely speaking, lithography experiments enables us to evaluate the validity of imaging theory. Thus some pioneer and valuable studies have been argued [1,2,3,4,5,6,7,8,9]. However there might be some ambiguity or no consensus for the treatment of diffraction by object in scalar imaging theory and a paradoxical phenomenon for the inclined entrance plane wave especially in vector imaging theory. Therefore we reconsider the imaging theory and compare the theoretical aerial image intensity with experimental pattern width.