Near-infrared multi-spectral imaging with Bayer-filter color cameras: a single-exposure approach for soot and temperature diagnostics

The color camera's application in combustion diagnostics is limited by the lack of absolute calibration methods, particularly in the near-infrared range. This study introduces a calibration approach for color cameras with Bayer filter arrays that extracts multi-wavelength spectral radiance from a single raw RGB image. By leveraging a matched multi-bandpass filter and the spectral sensitivity of the channels, the method compensates for spectral overlaps and eliminates the need for multiple exposures. Demonstrated on an ethylene-air flame with spectral emission and light extinction measurements at 550, 660, and 850 nm, the results are in agreement with prior studies, showcasing the potential of color cameras for near-infrared imaging in high-accuracy combustion diagnostics.