Automatic microscope systems in the CHORUS experiment

CHORUS searches for τ neutrino appearance in interactions of an originally pure νμ beam with an active target built with nuclear emulsions. The sample of events located and studied up to now (about 170 000)(Phys. Lett. B, to be published) could not have been collected without automatic microscope systems. The principles and the features of the technique are outlined; further details are then given about various implementations. The status and future developments of the various systems are described.