1. A photomultiplier tube segmented into a plurality of elementary photomultipliers comprising a photocathode and a multiplier of the type using sheets partitioned into a plurality of elementary multipliers associated with the said elementary photomultipliers, characterized in that the input space of the said photomultiplier tube located between the photocathode and the multiplier is partitioned into a plurality of elementary input spaces associated with the elementary photomultipliers and defining a plurality of elementary photocathodes, each elementary input space having a focussing electrode which causes the photo electrons emitted by the associated elementary photocathode to converge on the corresponding elementary multiplier.