Think a mirror cannot lie? Researchers have proven otherwise
A mirror is supposed to do a simple thing: show us what is in front of it. However, a new study recently published in the scientific journal Nature Communications presents a possibility that sounds almost like science fiction — a mirror capable of intentionally showing something completely different.
A mirror is supposed to do a simple thing: show us what is in front of it. However, a new study recently published in the scientific journal Nature Communications presents a possibility that sounds almost like science fiction — a mirror capable of intentionally showing something completely different.
Researchers from the University of California, Los Angeles (UCLA) have developed a prototype of what they call a "lying mirror." The mirror does not just distort our shape like a funhouse mirror, but changes the information reaching it using light, creating a different, pre-defined image. Simply put: if you place something in front of a regular mirror, you will see it. In front of the "lying mirror," you could, in principle, see something else.
How can a mirror "lie"?
The secret lies in its surface. Instead of a regular, smooth surface, the mirror is built from tiny structures designed to change the way light is reflected. When we look at an object, the light coming from it carries the information that allows our eyes to identify it. The researchers found a way to change this light so that instead of reconstructing the original object, it creates a different image.
For illustration, let's assume the researchers want the mirror to always display a duck. They can design the mirror's surface so that a variety of different images reaching it undergo a change, and the resulting outcome is that same duck image. This is not a screen displaying an image, nor a projector hiding the reflection. The surface itself changes the light that hits it.
Aydogan Ozcan, an engineer and inventor from UCLA, explained that unlike a projector or a screen, which usually require electricity and processing systems to display an image, the "lying mirror" is a passive optical component. Once manufactured, it uses the light reaching it to create the result.
The role of deep learning
To make the mirror "know" how to change the light, the researchers used deep learning. The computer determines how those tiny structures on the surface should look so that when light hits them, the desired image is obtained. Once the surface is manufactured, it does not decide anew each time which image to show. The "lie" is already built into it. If it is designed to display a certain image, that is the image it will try to create from the variety of things placed in front of it.
In the first stage, the researchers conducted computer simulations. They designed different versions of the mirror to turn images of clothing items into an image of a bag, various handwritten digits into the digit 8, and simple drawings into a panda face. They even tested what happens when the system is shown images that were not used in its design process, and even then, an image was obtained that could be identified as the target.
From laboratory to reality
After the simulations, the researchers decided to build a real version of the system. They chose a version designed to create the digit 8 and used an array of tiny mirrors. When they showed the system various handwritten digits, the light passing through it created the pre-determined image of the 8. The experiment worked with red, green, and blue light separately and also when all three colors were turned on together. The researchers also developed another version designed to work in a wider range of visible light.
Despite the results, the researchers emphasize that there is still a long way to go from the experiment to a product that can be used in the real world. The experiment was conducted under highly controlled laboratory conditions. The real world is much more complicated; sunlight or room lighting come from different directions and behave differently than the light used in some of the experiments. Ozcan explained that the system still relies heavily on a "highly controlled optical array in laboratory conditions," and it is not yet a device that can simply be hung on a living room wall. To work in normal lighting, it may be necessary to build more complex, multi-layered structures.
Potential applications
One of the uses the researchers suggest for the mirror is camouflage. The idea is not to make an object invisible, but to make someone looking in its direction think they are seeing something normal and uninteresting. Ozcan gives the example of sensitive equipment that one wants to hide. A "lying mirror" could be placed in front of that equipment and return to the observer an innocent and routine image instead of the visual information coming from the real object. Alongside camouflage, the researchers point to potential uses in the fields of security, defense, and entertainment.
