The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) has recently been developed to provide the high-accuracy wave-front characterization critical to the development of EUV lithography systems. Here we describe an enhanced implementation of the PS/PDI that significantly extends its measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wave front and flare. PS/PDI-based flare characterization of a recently fabricated EUV 10X-reduction lithographic optical system is presented.