Optical device for an automobile

The invention relates to an optical device (1), in particular for a motor vehicle, such as a lighting or signaling device, this device comprising: - at least two light sources (2; 3) associated with different predetermined photometric functions, - a main light guide (5) comprising an exit face (6) and arranged to guide the light coming from said light sources toward this exit face so that this exit face defines a common illuminating surface for the two photometric functions.