Apart from mirror door handles, glass door fittings like door mirror which consists of a concave lens (objective lens) and a convex lens is also important. The focal length of the objective lens is extremely short, which makes the outdoor person or object a virtual image that is upright and narrow. This image falls within the focus of the eyepiece, and finally an enlarged erect virtual image is obtained. This image is within the distance of distinct vision of human so that you can see things outside the door clearly.
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. If you install this mirror on glass shower door of a public house or private apartment imported by shower room importer, it can play a certain role in anti-theft and safety.
The door mirror is a combination of two lenses. The focal length of the objective lens L1 is extremely short, and the outdoor person or object AB is formed into a small erect virtual image A’B’, which falls within the first focus of the eyepiece L2, and L2 functions as a magnifying glass. Finally, a more enlarged erect virtual image A’B’ is obtained, which is just in the vicinity of the bright distance of the human eye. The situation outside the door can be seen clearly.
Then, why do you see nothing from the outside of the door?
When looking reversely, L1 becomes the eyepiece, and L2 becomes the objective lens. Because the aperture of the door mirror is very small, the outdoor person has to look close to the eyepiece L1 so that the distance between the human eye and the image A’B’ is only 2 to 3 cm, which is much smaller than the near point of the normal human eye. So door mirror is one of an important glass door fittings among all other shower enclosure products.