John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
This device to "see" people trapped behind flames also makes them look supremely creepy.
Finding people inside burning buildings can be like looking for a lost suitcase at the bottom of the Gowanus Canal. Thick smoke often reduces visibility to zero, so the smart (and well-equipped) firefighter might charge in with a handy tool: an infrared sensor that detects human body heat among the sooty gloom.
Firefighters have used thermal sensors to aid in their duties for decades, often to pick up hot spots smoldering behind walls but also to locate trapped or unconscious people and pets. (The first successful rescue with thermal imaging happened as far back as a 1988 fire in New York.) While helpful, these machines still have a major weakness. They can see through smoke, but when in the presence of copious amounts of flame they become overwhelmed by infrared radiation, producing burned-out, nearly useless images.
Recently a team of Italian scientists tested out a new kind of optics device that doesn't have such a limitation. There's a detailed description of their breakthrough in the journal Optics Express, but here's the short version: They ditched the zoom lens found in today's firefighting imagers and went with a lensless model based on digital holography. The result is a working prototype that can peer right through thick sheets of fire and spin out live, three-dimensional views of a moving human.
Oh, and they look terrifying – absolutely, nerve-jangling creepy.
To be honest, both technologies wind up producing images that'd make a lot of people want to throw the camera right into the fire. Here's a comparison furnished by the Optics Society:
The way the flame occludes the top figure makes it appear like a ghost burning in hell. The bust below is little better, looking as it does like that computer-animated villain from The Lawnmower Man. Now check this out:
Perhaps the problem is that the model wore those sunglasses and t-shirt, giving him a demon-in-a-rockabilly-band demeanor. But the freak factor really jumps up when this holographic reconstruction is seen in moving form, like a poltergeist hissing and crackling inside your television:
The next step to get this tech off the ground is to develop a more portable device that could be carried into fires, the researchers say, or mounted in locations where seeing past flames would be crucial, like in a train station tunnel packed with commuter cars or factory with large boiler equipment. Perhaps they can add a "calming" feature, too, where the human's phantom head is replaced with a big, yellow happy face.