Fig. 1
From: Quantum-optimal detection of one-versus-two incoherent optical sources with arbitrary separation
Schematic of the imaging of incoherent point light sources by a spatially-invariant imaging system. The images of two point sources of equal brightness (blue) spaced closer than the width of the point-spread function (PSF) of the imaging system are difficult to distinguish from that of one point source of the same total brightness (red) located midway between them
