Can the cat's eye at the door see inside from the outside?

The cat's eye at the door can't see from the outside.

Cat's eye is a small optical instrument installed on the door of a house. Because the light it refracts looks like the light emitted by Persian cat's eyes in the distance at night, it is nicknamed cat's eye. Looking out from the room through the door mirror, you can see all the scenes in the range of about 120 degrees outside the door, but you can't see anything in the room through the door mirror from the outside. If this kind of mirror is installed on the door of public house or private house, it can play a certain role in family safety and theft prevention.

The objective lens of the door cat's eye is concave and the eyepiece is convex, but the focal length of the objective lens is short and the focal length of the eyepiece is long. The focal length of the eyepiece is equal to or greater than the sum of the distance between the objective lens and the eyepiece (the length of the cat's eye) and the focal length of the objective lens, and the length of the door mirror is about 3cm.

Safety hidden trouble of traditional optical cat's eye

1, the observation angle is narrow, the visual range is not wide, and the safety hazard is invisible.

2, the material is not good, it is easy to be pried open. Even a few adults can pry open the cat's eye with their bare hands.

3. You must be close to the door to see the situation outside the door with an optical cat's eye.

Night is the most dangerous and critical moment, but it is impossible to see the situation outside the door because of the dim corridor.

5. The eyes of the elderly at home are not good, and the children are not tall enough to use cat's eyes normally.

6. Both sides of the traditional cat's eye are transparent mirrors, and criminals can peek at the indoor situation from the outside through the cat's eye peeper.

After peeping, the criminals found that there was no one in the room. They can pry open the cat's eye, use tools to pass through the cat's eye hole, and turn the indoor door handle with a lever to break into houses.