Infrared cameras can pick up light emitted as plants photosynthesize, as cool stars burn, and as batteries get hot. They can also see through smoke, fog, and plastic. But infrared cameras are much more expensive than visible-light cameras; the energy of infrared light is smaller than visible light, making it harder to capture.
A new method could lead to much more cost-effective infrared cameras, which in turn could enable infrared cameras for common consumer electronics like phones as well as sensors to help autonomous cars see their surroundings more accurately.
Today’s infrared cameras are made by successively laying down multiple layers of semiconductors — a complicated and error-prone process that makes them too expensive to go into most consumer electronics. The new method uses quantum dots — tiny nanoparticles just a few nanometers in size. At that scale, they have odd properties that change depending on their size, which scientists can control by tuning the particle to the right size. In this case, quantum dots can be tuned to pick up wavelengths of infrared light.
This tunability is important for cameras because they need to pick up different parts of the infrared spectrum. Collecting multiple wavelengths within the infrared provides more spectral information — like adding color to black-and-white TV. Short-wave provides textural and chemical composition information; mid-wave provides temperature.
The quantum dots were tweaked to obtain a formula to detect short-wave infrared and one for mid-wave infrared. Both were placed together on top of a silicon wafer. The resulting camera performs extremely well and is much easier to produce. The process involves injecting two solutions into a beaker and waiting 5 to 10 minutes. The resulting solution can be easily fabricated into a functional device.
There are many potential uses for inexpensive infrared cameras including autonomous vehicles that rely on sensors to scan the road and surroundings. Infrared can detect heat signatures from living beings and see through fog or haze, so car engineers would include them if the cost was not prohibitive.