A device including at least one optical module for emission of a light beam which is mounted on a support arranged on a frame orthogonal to the axis of emission and is mounted in adjustable manner on the frame by means of a sighting mechanism which includes at least two parallel threaded rods carried by the support. Each module extends an associated hole in the frame and carries a spherical nut having an active clamping spherical face which cooperates with a complementary bearing surface formed of the frame. The two threaded rods include one reference threaded rod carrying a nut whose active face cooperates with a complementary spherical reference bearing surface of truncated spherical profile, and at least one adjustment threaded rod which carries a nut whose active face cooperates with a complementary cylindrical adjustment bearing surface of truncated cylindrical profile.