Door Viewer

Nov 17, 2014

The door viewer, also known as the cat's eye, belongs to the door hardware. It is a small optical instrument arranged in the residential doors, which is convenient for residents to observe the outdoor situation and has become a necessity for home safe. It consists of a concave lens and a convex lens. The focal length of the lens is very short. It can make the upright and narrowing virtual image of people and things outside, just fell within the eyepiece focus, and finally get an upright and magnified virtual image. And this image properly fell in the situation near the human vision distance, so that the people and things outside will be seen clearly.

Looking out from the room through the door viewer, people can clearly see the scene of outside in the angle of about 120 degrees. But when looking into the room from outside through the door viewer, people can not see anything. Equipped in the door of state-owned house or private apartment, a door viewer will allow you to identify visitors without opening the door or revealing your presence. For family security and safety, it can really play a certain role.