An assembly for projecting a light beam includes a first sub-assembly for generating light rays, and a second sub-assembly comprising a converging lens. The first sub-assembly is arranged upstream of the second sub-assembly such that the light rays coming from the first sub-assembly are sent to the converging lens and such that the light rays emerging from the converging lens form the light beam. According to the invention, the projection assembly includes at least one connection system connecting the first sub-assembly to the second sub-assembly and allowing at least one translational movement of the first sub-assembly and the second sub-assembly relative to each other in a first longitudinal direction (X). Moreover, the connection system comprises a locking member that is movable between a first position in which the first sub-assembly and the second sub-assembly are motionless with respect to each other and a second position enabling the translational movement.