If you hold up a sign 0.85 miles away, someone might still be able to read it. A new laser-based imaging system provides this capability for civilians and maybe spies.
How far is 0.85 miles exactly? About 1.36 kilometers or 14 football fields away. If somebody is this far away from an open book, they could read its text. Scientists in China have built a system that can make out letters that are just a few millimeters tall.
To create this laser device, scientists borrowed a technique from astronomy called interferometry, which is normally used to study stars. It allows combining light from different telescopes to get sharper images. But in the case of producing the laser, instead of looking at starlight, scientists were firing infrared lasers at a target here on Earth and then studied how the light bounced back.
They used a specific version of the technique called intensity interferometry, which doesn’t rely on wave patterns or phase – it compares brightness fluctuations picked up by two detectors. These fluctuations hold hidden spatial information about what the laser hit.
At first, the lasers were too “coherent,” meaning all their light waves were moving in sync and thus caused too much noise. Therefore, researchers split their laser into eight beams, each taking a slightly different path through the air. This gave the system enough random variation to make meaningful interference patterns, like turning a blurry image into a sharp one.
This allowed scientists to recreate letters just 3mm tall. The setup gave them a 14 times bigger improvement in resolution over a standard telescope.
What’s the main use case of the device?
As reported by the Physical Review Journal this laser can be used in a variety of ways: to track space debris, monitor wildlife or insect activity across large areas, or scan distant industrial sites without physically being there.
But there’s also surveillance. Being able to read text from more than a kilometer away with lasers could raise eyebrows depending on how the tech is used. The researchers admit it could be used for remote spying.
They’re now looking to improve the system even further by adding AI and deep learning to sharpen the images and help identify what’s being viewed more accurately.
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