Rescue workers may soon have a new tool to locate victims amid the blinding smoke and chaotic flames of a house fire.
By Emily Elert Posted 02.27.2013 at 5:55 pm 6 Comments

Digital Infrared Holography Optics Express

When firefighters go looking for victims trapped inside a burning building, they often encounter rooms and hallways filled with thick, blinding smoke. If no flames are present, a rescuer can use an infrared camera to spot the heat signatures of warm, living bodies. But in the midst of a raging inferno, heat from the flames will overwhelm the camera's sensors and obscure nearby objects.

Researchers in Italy may have found a solution: a digital imaging system that captures infrared signals in 3-D and converts them to holographic video in real-time, thus allowing firefighters to distinguish flames from heat-emitting objects behind them.

Here's a demonstration video the researchers made to show the system in action (right), compared with a standard infrared camera (left):

The imaging system generates video using the basic principles of holography, which are explained nicely in a press release accompanying the study:

To create a hologram, such as those typically seen on credit cards, a laser beam is split into two (an object beam and a reference beam). The object beam is shone onto the object being imaged. When the reflected object beam and the reference beam are recombined, they create an interference pattern that encodes the 3-D image.

How Holography Works

The researcher used an infrared laser, which sends out longer wavelengths of light than a laser operating in the visible spectrum, for two reasons: first, visible light can't penetrate a smoke-filled room, while infrared light gets through with little scattering; second, laser beams of longer wavelength recombine to form a larger interference pattern, allowing the system to generate large, human-size holograms.

In order to turn a single static into a video, the infrared laser sends out repeated, pulsed beams. Each pulsed beam recombines to form a new 3-D image.

The imaging system would be a major improvement to regular infrared cameras, but before it's ready for action, the researchers need to figure out a way to combine the laser source and camera into a single set-up.

6 Comments

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notagain
02/27/13 at 6:39 pm

Seeing through flames with thermal imaging isn't that new. FLIR does this already with flame filters for specific IR wavelengths, which was invented for furnace inspections (see http://www.flir.com/cs/emea/en/view/?id=41800 ). I think I read about this half a year ago.

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p_ferraro
02/27/13 at 8:03 pm

Please download the paper :

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-5-5379

Imaging live humans through smoke and flames using far-infrared digital holography
M. Locatelli, E. Pugliese, M. Paturzo, V. Bianco, A. Finizio, A. Pelagotti, P. Poggi, L. Miccio, R. Meucci, and P. Ferraro »View Author Affiliations

Optics Express, Vol. 21, Issue 5, pp. 5379-5390 (2013)
http://dx.doi.org/10.1364/OE.21.005379

read it and you will understand the difference between FLIR and Holography
and fault of your comment.
yesagain -

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GregN913
02/27/13 at 10:31 pm

I must ask where the reference beam is coming from? The person's IR profile is the object beam, so does the camera emit the IR reference beam, or does it use a coherence filter to attenuate the fire's IR signature?
Also the hologram graphic used for this story is a "White Light" or Reflection hologram design, where as I can only imagine the device works using a Transmission holographic design. The author of this piece should research their subject before picking the first image available off of Wikipedia.

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GregN913
02/27/13 at 10:43 pm

Ah ha, silly me skipping over the bottom paragraph. Indeed is is a Reflection holographic design, and as stated the IR laser source differs from the camera itself... I stand corrected.

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notagain
02/28/13 at 5:25 pm

@p_ferraro: I know there is a difference between FLIR and holography. My point was that there are already ways to see through flames. My phrasing was a bit wrong.

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p_ferraro
02/28/13 at 6:43 pm

..if your read the paper you will find there explanations why FLIR for furnaces is strictly limited for special types of flames..



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