A door eye viewer, also known as a peephole, is a small security device that's typically mounted on the front door of a building. It has a small lens that allows people inside to see who's outside without opening the door. Door viewers are often used on apartment, motel, and hotel entrance doors. Door viewers use one or more concave lenses to create a panoramic view of the area outside the door. The lenses minimize the size of specific objects, giving a wide view of the entire area.
