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Actinic patterned mask inspection (APMI) is the last major part of the infrastructure required for EUV lithography to be developed. A coherent imaging approach is proposed as a plausible solution requiring incremental improvements to available components. Diffractive optics direct a mW 13.5nm coherent beam to the mask and to interfere at the imaging detector. A motion system translates the mask between exposures. A non-iterative algorithm generates a complex reflectivity (mask image) estimate from each interferogram, in real time with GPU hardware. Realistic simulation results and requirements for the system components are presented. Except for the FEL that is likely required, many elements of the system are simpler and likely less costly than an incoherent imager. The system can be configured to image the mask through a pellicle. Of note, focus tolerance is loose as the focal distance is a software parameter.