Defining phase spatial resolution in quantitative phase imaging

In quantitative phase imaging, spatial resolution and its influencing factors have not been fully explored. Here, we propose to define phase resolution based on the Sparrow limit and investigate the effect of phase inequivalence between adjacent object points. To simulate the measured object phase distribution, the analytical solution to the complex scattered field from a thin phase object is first obtained by solving the inhomogeneous wave equation in the wavevector space. Our theory shows that the phase resolution is not only related to the illumination wavelength and the numerical aperture of the imaging system, but also the object size and the phase detection signal-to-noise ratio. We have validated our findings by simulating phase images of different point arrays and two-point objects under different noise levels.