Optical unit for a signalling and / or lighting device

The unit (10) has a reflector for reflecting a part of light emitted by a light source i.e. LED. The reflector forms complementary light beam (Fc1, Fc2) that is provided along an optical axis and associated with a code type oblique cut-off beam (Fw) to provide a total beam (F) adjustable according to the information representing the motor vehicle environment. The light beam produces a lighting area in a plane perpendicular to the axis, where the area includes two rectilinear vertical and horizontal cutting edges creating a right angle, and extends in quarter of a plane defined by the edges. An independent claim is also included for a method for producing a light beam for a motor vehicle.