To improve the ability of researchers to "see" through fire, NIST has developed an imaging system using ordinary blue light to dramatically clear the picture. This is a still from the video below, which was shot by J. Gales/York University and edited by D. Sawyer/NIST.
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Seeing through bright flames is normally difficult, as
fire emits its own light. But researchers at the National Institute of Standards and Technology (
NIST; Gaithersburg, MD) and Berkshire Hathaway Specialty Insurance (Boston, MA) have come up with a way to see through flames: use a combination of
narrowband blue (450 nm wavelength) LED illumination and a matched optical filter.
1 The amount of narrowband blue light needed is a factor of 10
4 less than what would be needed if white light were used; for example, a natural-gas fire with a 1 MW power can be seen through using a mere 200 W of blue light. The new technique can help fire researchers when they perform optical metrology. The method provides detailed information to researchers using optical analysis such as digital image correlation (DIC), a technique that compares successive images of an object as it deforms under the influence of applied forces such as strain or heat. By precisely measuring the movement of individual pixels from one image to the next, scientists gain insight about how the material responds over time, including behaviors such as strain, displacement, deformation, and the microscopic beginnings of failure. Because fire is a light source with its power generally spread over a large spectral band, the use of a narrowband illumination source and matched optical filter only has to contend with the relatively small optical power of the fire within the chosen narrow spectral band. In addition, to combat image distortion induced by the flames, the researchers averaged a number of single images together.
