A masking device disposed over a display has a first viewing region, a second viewing region, a first operating mode, and a second operating mode, wherein in the first operating mode the masking device allows a first observer located in the first viewing region to observe information displayed on the display, and also allows a second observer located in the second viewing region to observe the displayed information, wherein in the second operating mode the masking device projects light to the second viewing region so as to prevent the second observer from observing the displayed information.