Resolution in nonlinear laser scanning microscopy

Summary The lateral and depth resolution of nonlinear microscopy was studied systematically. Nonlinear microscopy can be classified into several categories depending on the coherence properties of the process that generates the imaging signal from the illuminating light, on whether a single‐ or a two‐beam geometry is used, and whether the optical setup is Type I or Type II. An evaluation of the imaging equations shows that (i) lateral and depth resolution improve with increasing nonlinearity, (ii) the differences between coherent and incoherent imaging diminish, and (iii) nonlinear imaging allows depth discrimination in Type I microscopy.