Optical module for a motor vehicle comprising: - at least one light source capable of emitting an initial light beam, - a primary optical means formed in a block by a solid part produced in a translucent or transparent material, comprising an input surface arranged to receive the initial light beam which is propagated in the primary optical means and comprising a cutoff member (28, 30) arranged to transform said initial light beam into a secondary light beam that is propagated in a longitudinal direction and that has a predetermined bottom cutoff extending overall transversely, - a projection means arranged to project a final light beam having a top cutoff formed by an inverted image of the secondary light beam with cutoff, the primary optical means comprising a light deflection member arranged to deflect a part of the light rays of the initial light beam below the cutoff of the secondary beam towards the projection means, the primary optical means being a solid part produced in a translucent or transparent material, the cutoff member being formed by a notch produced in a bottom face of the primary optical means which has a top transverse cutoff edge whose profile corresponds to the form of the predetermined cutoff, characterized in that the deflection member is formed by an exit face produced in the primary optical means in an interception face arranged to reflect all of the light rays above the edge, the exit face forming an angle with the interception face such that the light rays strike the exit face with an angle of incidence less than the angle of refraction and pass through the face, thus transmitting a portion of the initial beam out of the primary optical means below the cutoff edge. - at least one light source capable of emitting an initial light beam, - a primary optical means formed in a block by a solid part produced in a translucent or transparent material, comprising an input surface arranged to receive the initial light beam which is propagated in the primary optical means and comprising a cutoff member (28, 30) arranged to transform said initial light beam into a secondary light beam that is propagated in a longitudinal direction and that has a predetermined bottom cutoff extending overall transversely, - a projection means arranged to project a final light beam having a top cutoff formed by an inverted image of the secondary light beam with cutoff, the primary optical means comprising a light deflection member arranged to deflect a part of the light rays of the initial light beam below the cutoff of the secondary beam towards the projection means, the primary optical means being a solid part produced in a translucent or transparent material, the cutoff member being formed by a notch produced in a bottom face of the primary optical means which has a top transverse cutoff edge whose profile corresponds to the form of the predetermined cutoff, characterized in that the deflection member is formed by an exit face produced in the primary optical means in an interception face arranged to reflect all of the light rays above the edge, the exit face forming an angle with the interception face such that the light rays strike the exit face with an angle of incidence less than the angle of refraction and pass through the face, thus transmitting a portion of the initial beam out of the primary optical means below the cutoff edge.