A new light microscopic method for the synchronous bidirectional illumination and viewing of living cells in different contrast modes, and/or at different focal levels or magnifications.

A new method of light microscopy for the analysis of the behaviour of living cells in vitro exploits two objects for simultaneous image formation, each serving the other as a condenser. Simultaneous viewing from opposite sides allows the specimen to be examined at: (a) two different magnifications, permitting the locomotion of whole cell (groups) to be studied at a low magnification and details of interaction of colliding surfaces at a high magnification; (b) two different focal levels, permitting, for example, details near the substrate surface to be recorded at the same time as information concerning the behaviour of the free, dorsal surface; and (c) two different contrast modes, such as negative and positive phase contrast, and dark and bright field illuminations. These possibilities can be combined, for example, to contrast a high magnification view in negative phase contrast at one focal level with a low magnification image in ordinary brightfield at another focal level in the same living cells.