The cat s eye on the anti theft door is not clear, as if there is water vapor in the middle

It is recommended that you buy a smart electronic cat's eye Automatic detection, automatic photography, automatic video recording, and SOS SOS for help are very practical! Now the market is very general.

That's right, I think it should be junior high school physics, using the principle of convex lens imaging.

The "cat's eye" is composed of a concave lens and a convex lens, the objective lens is a concave lens, and the eyepiece is a convex lens, but the focal length of the objective lens is shorter, the focal distance of the eyepiece is longer, and the focal length of the eyepiece should be equal to or greater than the distance between the objective lens and the eyepiece (the length of the cat's eye) and the sum of the focal length of the eyepiece, so that when people look from the inside of the door, they can clearly see the situation outside, and when they look from the outside to the inside, they will not see anything.

The eye can see bai into a special and precise DU optics. >>>More

Concave lenses. The concave lens is a virtual image with upright and shrinking regardless of the distance. It is mounted on the outside of the door. >>>More