In recent years, there have been "double-sided mirror peeping incidents", which has also become the focus of social attention, and then there have been many methods of identifying "double-sided mirror voyeurism" on the Internet, such as the more famous finger identification method, light identification method and so on. But most of these methods do not accurately identify whether the mirror is a double-sided mirror or a single-sided mirror.
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The most widely circulated "finger identification method" says: touch the mirror with the fingertips of the fingers, if the fingers and mirrors directly exist in the gap, then this is an ordinary one-sided mirror; if there is no gap between the fingertips and the mirror, then this is a double-sided mirror.
In fact, this test method seems simple and practical, but in fact, it is not completely accurate, and if you want to crack the double-sided mirror, you still have to start from its principle.
Whether it is a single-sided mirror or a double-sided mirror, it is made of transparent glass plate + mirror coating. The difference is that the single-sided mirror is an opaque mirror mask that can completely reflect light, while the coating of the double-sided mirror is a translucent mirror mask, which can pass through part of the light and reflect another part of the light. So in the industry, we all call it semi-lens.
The structure of the semi-lens is: transparent acrylic sheet + translucent mirror metal film + transparent polymer film
Therefore, the mirror effect on both sides of the semi-lens is the same as the light transmission effect.
In the "finger identification method", the conclusion that "the finger and the mirror image exist directly in the gap, then this is an ordinary single-sided mirror" is obviously wrong. Because the mirror is coated on the back, the finger touches the front of the semi-lens, and the distance between the finger and the mirror is the thickness of the mirror. So even if there is a distance between the finger and the mirror, the mirror may be a semi-lens.
So how do you prevent double-sided/semi-lens peeping?
Method 1: Tap the mirror to listen to the sound
If the sound is found to be relatively hollow and reverberating, then there is a high probability that there is a space behind the mirror, then the mirror may be a double-sided mirror. Because generally single-sided mirrors are attached to a flat wall.
Method two: turn off the room lights, turn on the mobile phone flash close to the glass, see if the glass has light transmission
As mentioned above, a semi-lens can pass through part of the light and reflect another part of the light. If you use a flash to illuminate the mirror in a dark environment, a large part of the light will be transmitted to the room opposite the mirror, and if we look close to the glass, we will faintly see the opposite room.
Method 3: Use a makeup mirror to compare the brightness
Suppose a semi-lens with a light transmittance of 20% can only reflect 80% of the light, and the other 20% of the light will be transmitted to the other side of the half-lens. The reflectivity of ordinary mirrors is about 95%, if the light in the room is turned on, in a bright environment, the imaging brightness of the half-lens will be significantly lower than that of the single-sided mirror, because the reflectivity of the half-lens is lower than that of the single-sided mirror. But the premise of doing so is to have a makeup mirror to carry around.
Try it all three ways, I believe it is possible to correctly judge whether the mirror is a single-sided mirror or a double-sided mirror.
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