  Fourier Ptychographic Microscopy (FPM) is a recent technique to overcome the
diffraction limit of a low numerical aperture (NA) objective lens by
algorithmic post-processing of several lower resolved images. It can increase
the space-bandwidth product of an optical system by computationally combining
images captured under different illumination conditions. Vignetting determines
the spatial extent of the bright field and dark field regions in the captured
images that contain information about low and high frequency image content,
respectively. State-of-the-art analyses treat vignetting as a nuisance that
needs to be reduced or excluded from algorithmic consideration by means of
ad-hoc decision rules [1]. In contrast, this work investigates vignetting
effects as a tool to infer a range of properties of the optical system. To
achieve this, we characterize the individual system components of the
experimental setup and compare experimental data to both, geometrical and wave
optical simulations. We demonstrate that using vignetting as an analytical tool
enables the modeling of the geometric and coherence properties of the optical
system as evidenced by the good agreement between our simulation and
experiment. Moreover, our work investigates pupil aberrations in the FPM setup
and enables their partial characterization, despite not yet encompassing all
aspects.
