The invention concerns a miniaturized optical head provided to equip the distalend of a beam of flexible optical fibres scanned by a laser beam, said optical headbeing designed to come in contact with a sample and to excite said sample confocally；this optical head consisting of means for correcting spherical aberrationsand focusing means. According to the invention, the focusing means comprise:at least a first lens (L4) of high convergence associated with a spherical or hemisphericallens (L5) arranged at the distal end of the optical head, and means for correctionof the axial and lateral chromatic aberration provided with a single divergentlens (3b) the curvature of which is substantially centred on the pupil of the opticalfibre beam and arranged at the exact distance for this pupil for which the conditionsof lateral achromatization coincide with the conditions of axial achromatization；this divergent lens being associated with a second convergent lens (L3a) in theform of a doublet (L3).
