An optical distributor for deflecting a light beam in different directions comprises a single semi-reflecting mirror 30 carried by a motor-driven turntable 31. The mirror is capable of pivoting about an axis 33 when a stop 46 is withdrawn (position Z of the notch and of the stud 38) and of taking up a position 52 in which it does not intercept the light beam 14. in the other positions (X and Y), the mirror intercepts the beam 14 and deflects it in the desired directions.