Our world is colourful. We see all kinds of colours everywhere. The blue sky, the green trees, and red mud are only some of those colours. All the colours we see make our planet a vibrant one.
But what is colour? Why is the sky blue and not yellow? Why do we see certain colours on certain surfaces and not others?
Colour is our perception of different waves of light. White light comprises seven major colours, the colours of the Rainbow. All these colours are different waves of the same visible light we see. When light hits a surface, it reflects only certain spectrums of this light at us. This certain wavelength of light defines the colour of that surface.
This is the world we see. But there is a hidden world out there. A hidden infrared world. And one team of researchers is bringing this hidden world out into the light.
The Infrared World
We perceive normal color when certain waves of visible light hit our eyes. The visible light spectrum is a narrow band of wavelengths that exists between the ultraviolet and the infrared spectrums. It equips our eyes to perceive only this narrow band of light waves. Ultraviolet light is harmful to our eyes while infrared is invisible. But what is infrared light?
Infrared Radiation (IR) or Infrared Light is a spectrum of light invisible to the human eye but is present as heat. All objects in the universe emit some IR radiation. Technically, IR is electromagnetic radiation, much like light.
It produces IR frequencies when an atom absorbs and then emits energy. IR lies in the mid-lower end of the electromagnetic spectrum. Until now, IR has uses in the thermal imaging industry. Thermal cameras use IR radiation to detect the temperatures of objects. IR lies in the wavelengths above 700 nanometers.
What is interesting is that each of these spectrums contains significant amounts of information on different materials. It encodes this information in the form of color data which we cannot see.
Different materials have different color information with different spectrums of radiation. They have unique signatures that they express as colors. This is prominent in the mid Infrared ranges. For example, cancer cells will have a unique IR signature color because of the concentration of a certain molecule. This makes it easier to identify.
See the World in Infrared
Until now, the currently existing technologies to capture and render images in infrared were expensive and complicated. Most of such IR devices cannot render the colors in IR.
Medical Imaging experiments to convert infrared colors to visible ones required sophisticated equipment. This makes them less available for the general audience.
A team of researchers from Tel Aviv University recently developed a cheaper and efficient technology to render colors in IR. All you need is a camera and a mounting system for the technology.
Dr. Michael Mrejen, Yoni Erlich, Dr. Assaf Levanon, and Prof. Haim Suchowski conducted the research. They are part of TAU’s Department of Physics of Condensed Material. They published the results in Laser & Photonics Reviews October 2020 issue.
This technology will allow us to see different gases and materials like hydrogen and carbon in their unique IR color signatures. Aside from these materials, it will help in imaging biological compounds in nature that is invisible to our eyes.
If we could see in the infrared realm, we would see that elements like hydrogen, carbon, and sodium have a unique color.- Prof. Haim Suchowski, TAU.
Environmental monitoring satellites could pick up images of pollutants from different plants. Spy satellites could find out where enemies are hiding explosives and uranium. It also has the added advantage that we can see it even at night. It also has other applications in fields ranging from computer gaming and photography to security, medicine, and astronomy.
The technology is pending patent under the label of Multi-frequency infrared imaging based on frequency conversion.
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