[en] Single ion bombardment of biological cells using an ion microprobe is a promising technique. However, for microprobe investigations of biological processes at a cellular level the precise recognition of a single cell and particularly of its nucleus is required. Moreover, cells must be examined in their natural state and environment (i.e. without previously being killed, preferentially not fixed nor stained) and, also, the use of ultraviolet light for cells observation should be avoided. Additionally, in order to obtain statistically significant results of irradiation, the possibility of fast automatic recognition of thousands of objects must be provided. Because computer recognition strongly depends on the quality of an image, the optical imaging system is of crucial importance. For this purpose one of the best solutions could be the Quantitative Phase microscopy (QPm) technique. QPm is the recent digital technique of phase contrast microscopy, providing quantitative phase and intensity data obtained from a series of defocused images. The following phase contrast modalities may be generated digitally from the computed QPm phase data with a greater degree of flexibility: Pure phase images (intensity-free), standard phase contrast (e.g. Zernike phase contrast), differential interference contrast (DIC), Hoffman modulation contrast, and simulated darkfield. (c) 2005 Elsevier B.V. All rights reserved.