Researchers from National Institute of Standards and Technology (NIST) suggested that ordinary blue light could enable imaging of objects on fire.
The researchers from NIST devised a blue-light imaging method that is capable of obtaining visual data from large test fires, where conventional electrical and mechanical sensors could disable or destroy due to high temperatures. The new method utilizes optical analytical method 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. It was possible to gain valuable insight of the mechanism of the material’s response over time through precise measurements of the movement of individual pixels from one image to the next. The researchers were able to measure the strain, displacement, deformation and even the microscopic beginnings of failure of the object. The researchers opted to use blue light lasers used in glass and steel industry to contend with the red light given off by glowing hot materials that blind the sensors. Blue light-emitting diode (LED) lights with a narrow-spectrum wavelength around 450 nanometers were used for the experiment.
A target object was placed behind the gas-fueled test fire and illuminated it in three different ways. First method involved using only white light, second method used blue light directed through the flames, and the third involved blue light with an optical filter placed in front of the camera. It was observed that the third method was most efficient in reducing the observed intensity of the flame by 10,000-fold and yielded highly detailed images of the object. The researchers tested the imaging method on two instances where in one instance, fire bends steel beams and in other, partial combustion progressively chars a wooden panel. The results in both cases provided highly detailed images. The research was published in the journal Fire Technology on July 23, 2018.