Abstract: One subject of the invention is a light guide (13), for an interface module, in particular for a vehicle passenger compartment, for emitting or receiving a light beam in a cone that is elongate in a transverse direction and that is centred on a plane that is inclined by an angle ? with respect to an optical axis (z) of the light guide, taking the form of a prism made of transparent material of index nGL, characterised in that it comprises: •an interior dioptric interface intended to face a printed circuit board (7) bearing a light source (5) or a light detector, forming a convergent lens the focal point of which is located at an expected position of the light source (5) or of the light detector, •a first planar face (15) that is oriented parallel to the optical axis (z) of the light guide, and •a second planar face (17) that is inclined with respect to the first face (15) by an angle ? respecting cos(?+?)=(1??) nGL*cos 3?, with ? a number comprised between ?0.1 and 0.1.

Abstract: One subject of the invention is a light guide (13), for an interface module, in particular for a vehicle passenger compartment, for emitting or receiving a light beam in a cone that is elongate in a transverse direction and that is centred on a plane that is inclined by an angle ? with respect to an optical axis (z) of the light guide, taking the form of a prism made of transparent material of index nGL, characterised in that it comprises: •an interior dioptric interface intended to face a printed circuit board (7) bearing a light source (5) or a light detector, forming a convergent lens the focal point of which is located at an expected position of the light source (5) or of the light detector, •a first planar face (15) that is oriented parallel to the optical axis (z) of the light guide, and •a second planar face (17) that is inclined with respect to the first face (15) by an angle ? respecting cos(?+?)=(1??)nGL*cos 3?, with ? a number comprised between ?0.1 and 0.1.