High-speed digital color imaging pyrometry

Abstract

Temperature measurements of high-explosive and combustion processes are difficult to obtain due to the speed and environment of the events. To overcome these challenges, we have characterized and calibrated a digital high-speed color camera that may be used to measure the temperature of such events. A two-color ratio method is used to calculate a temperature using the color filter array raw image data and a graybody assumption. If the raw image data are not available, temperatures may be calculated from the processed images or movies, depending on proper analysis of the digital color imaging pipeline. We analyze three transformations within the pipeline (demosaicing, white balance, and gamma correction) to determine their effect on the calculated temperature. Using this technique with a Phantom color camera, we have measured the temperature of exploded C-4 charges. The surface temperature of the resulting fireball was found to rapidly increase after detonation, and subsequently decayed to a constant value of approximately 1980 K.

Near field optical characterization of explosions

“…These include a three-color integrating pyrometer, a twocolor imaging pyrometer employing cameras filtered at wavelengths of 700 nm and 900 nm, and a full-color single camera pyrometer where wavelength resolution is achieved using the Bayer-type mask covering the sensor chip [4].…”

Imaging Detonations of Explosives

“…In work described here, time-resolved temperature maps of detonations of explosives are made using a full-color single-camera pyrometer where wavelength resolution is achieved using the Bayer-type mask covering the sensor chip 17 and a 2-color imaging pyrometer employing 2 monochrome cameras filtered at wavelengths of 700 and 900 nm, respectively, (wavelength regions adjustable). Each rig operates on the assumption of gray body behavior described previously, but each is specific to the type of explosive being investigated.…”

Chemical Imaging of Explosions – Mapping BO2 Light Emission

“…High-speed framing cameras have been used for decades to produce movies that help to visualize detonationsa nd explosions [1].W hile the detailed movies of these events can be qualitativelyi nformative, retrievingv ariables such as pressures, temperatures, and chemical species concentrations is difficult [2,3].R ecently,s ome success has been realized imaging fireball surface temperatures and peak shock pressures from small-to medium-sized explosions by careful manipulationo fi maging parameters [4].T hese efforts enable peak pressure and temperature "maps" to be produced as the explosion proceeeds [4].I nt his paper, this technique is extended to mapping of chemicals pecies arising from borono xidation during ab allistically initiated explosion.…”

“…The general twocamera methodu sed herein has been describedp reviously [4].T ot he best of our knowledge, the work reported is the first attempt to use the technique to map the evolution of ac hemical species in an explosivee vent.…”