Movable opaque element preventing the focussing of the sun rays in a headlamp

The device has an optical focusing device (12) receiving light generated by a primary light source (7) i.e. LED, for forming a main light beam. An opaque element (14) is moved between two positions (A, A') and arranged in one of the positions such that the opaque element is interposed between the main light source and the optical focusing device to prevent the optical focusing by the focusing device along a line or a light point (2) from an outer side of the device. An optical module includes a switchgear of a main beam (11). An independent claim is also included for a method for controlling a lighting and/or signaling device of a car.