A light device comprises at least one light source (10) to generate light rays (201, 202, 203), an output lens (5), and lateral walls (7, 8) delimiting a space (27) for passage of the light rays after the lens and exiting out of the light device through a transparent cover (9) covering the space at the front. Between the light source and the output lens, a reflective diaphragm (11) is arranged that comprises fixed reflective lateral walls (11a, 11b), for spatial delimitation of the light rays between the lateral walls before they enter the output lens. The output lens has, in the vertical direction at the side facing the diaphragm, a convex shape and the lateral walls include, at the side facing the output lens, free ends (14) that have a rounded concave shape in the vertical direction, which is substantially complementary to the output lens convex shape.