  When a single molecule is detected in a wide-field microscope, the image
approximates the point spread function of the system. However, as the
distribution of molecules becomes denser and their images begin to coincide,
existing solutions to determine the number of molecules present and their
precise three-dimensional locations can tolerate little to no overlap. A
solution to this problem involving matched optical and digital techniques, as
here proposed, is critical to increase the allowable labeling density and to
accelerate single-molecule localization microscopy.
