Neil, M. A. A., Juskaitis, R., and Wilson, T.
Real time 3D fluorescence microscopy by two beam interference illumination.  Optics Communications 153: 1-4 (1998).

We describe a method of obtaining optically sectioned fluorescence images in a widefield conventional microscope by interfering two beams on an object so as to illuminate it with a single spatial frequency fringe pattern. Images taken at three spatial positions of the fringe pattern are processed in real time to produce optically sectioned images which are substantially similar to those obtained with confocal microscopes.