A sensor device is provided for a system for protecting an occupant, in particular a driver, of a vehicle from glare from light sources outside the vehicle. The device includes a projection surface, a shadow-casting object, which is arranged and/or designed such that upon an illumination of an object by a light source located outside the vehicle, at least one shadow of the object is cast onto the projection surface, an image capturing unit that is designed to capture an image of the shadow of the object cast onto the projection surface, and a control unit that is designed to detect at least one property of the at least one light source based on the captured image of the shadow of the object cast onto the projection surface.