IR holography helps firefighters blinded by the light
ROME – Firefighters may have a new tool when it comes to finding a person hidden in a thick veil of smoke and intense flames: lensless infrared digital holography. The new imaging method can “see” through flames, capturing potentially lifesaving details.
Although current infrared (IR) cameras can image through smoke, these devices are blinded by the intense IR radiation emitted by flames. Such conditions overwhelm the sensitive detectors, limiting their usefulness.
To see through smoke, scientists employ lenses to collect and focus light, but using the same technique with flames results in saturation in some areas of the resulting image (top). The new CNR system
does not employ a lens, so collected light is distributed over the whole array of camera pixels, avoiding
this saturation and the blind spots it produces (bottom).
By employing a specialized lens-free technique, researchers at the Consiglio Nazionale delle Ricerche (CNR) have devised a system that copes with the flood of radiation from an environment filled with smoke and flames.
“IR cameras cannot ‘see’ objects or humans behind flames because of the need for a zoom lens that concentrates the rays on the sensor to form the image,” Pietro Ferraro of CNR’s Istituto Nazionale di Ottica said in a university release. By eliminating the need for the zoom lens, the new technique avoids this drawback.
“The numerical reconstructions of digital holograms allow [the user] to visualize the image,” Ferraro told Photonics Spectra. This means that the reconstruction algorithm acts as a “virtual lens” of sorts that decodes the images to reveal objects beyond the smoke and flames, resulting in a live 3-D movie of the room and its contents.
Lab demonstrations revealed that a holographic recording of a live person can be achieved even while the body is moving, Ferraro said.
Two images of a human subject as seen through flames. When viewed in infrared or white light, the man is almost completely occluded (left). The new system uses holography to reproduce the image behind
the flames, revealing a man wearing a T-shirt and glasses (right).
The scientists aim to develop a tripod-based system that houses both the laser source and the IR camera.
“The development of a compact laser system would help a lot in pushing the technology toward a realized portable system,” Ferraro said. The device could also serve as a fixed unit inside buildings or tunnels to observe and understand behaviors in real fire scenarios.
Next, “we will test our technology in realistic fire scenes outside of the lab,”
Biomedical applications of the technology include breath monitoring, cardiac beat detection and analysis, and body deformation measurement.
Findings were reported in Optics Express (doi: 10.1364/OE.21.005379).
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