Light consists of individual particles that propagate in the waves. The wavelength determines the color and energy of light.
The human eye can only perceive a small section of this spectrum, approximately between 400 and 700 nanometers.
For this reason, we, humans, cannot see the infrared range, with its 750 nanometers longer wavelengths at a millimeter.
So, to see infrared light, we needed relatively bulky night vision glasses or night vision devices with their own energy source – so far.
China infrared contact lenses
Researchers from the University of Science and Technology of Hefei, Eastern Chinahave now developed a contact lens which converts infrared light into visible light, allowing humans to see in darkness.
Yuqian MA and his team combined conventional soft contact lenses with 45 nanometric particles composed of gold, sodium gadolinium fluoride, yterbium ions and erbium.
Ascending conversion contact lenses (UCL) convert infrared light with wavelengths between 800 and 1,600 nanometers in visible light, wrote the team in the scientific newspaper Cell.
Nanoparticles enrich the long waves of infrared light with energy. In doing so, they convert the infrared light into three primary colors, making them visible to the human eye.
A drawback is that the resulting images are very vague because the nanoparticles of the lenses disperse the light, which the team was able to partially compensate by adding additional lenses.
However, infrared contact lenses are still far from being as powerful as night vision glasses, which amplify weak infrared signals, making them visible.
An even better vision with closed eyes
The team first injected nanoparticles into mouse retinas and their behavior has shown that they could see in darkness.
The newly developed contact lenses are much more practical because they are not invasive – which means no injection into our retinas.
In tests, humans were able to recognize the reasons, letters and infrared indicative signals in the dark. And infrared lenses work even better with closed eyes, because infrared light can easily penetrate the eyelids and the generation of images is not disturbed by normal visible light.
Animal infrared capacities
Several animal species are able to perceive infrared light, which is extremely useful during hunting in darkness. They do not consider infrared light as a “light” in the sense of human vision. Instead, they perceive the thermal radiation emitted by objects.
This helps certain cold blood reptiles such as snakes (bell snakes and pit vipers), certain fish (piranhas and the cichlids), certain amphibians (ouaouarons) and certain blood insects (mosquitoes and insects) with an orientation or a hunt in the dark.
Animals with hot blood – like humans, other mammals and birds – cannot see infrared light because their eyes do not have the appropriate receptors and thermal radiation of their body would also interfere with the perception of infrared light.
Big question about the advantages
As fascinating as Chinese innovation is, it remains to be seen how it could be used in daily life.
According to the promoters, lenses could be used in surgical procedures, in the area of encryption or cryptographyor for counterfeit protection.
Indeed, infrared light is what makes characteristics or invisible inks visible on documents, for example.
Lentils could also be used to save people in poor visibility conditions, as they make objects to the heat visible. However, many criticisms doubt it, as night vision devices are much easier to use and are also much more powerful.
This article was initially written in German.
Source:
Vision of almost infrared spatio-temporal colors in humans activated by contact lenses of upward conversion
https://www.cell.com/cell/FullText/s0092-8674(25)00454-4
