Imaging pyrometry for most color cameras using a triple pass filter

A simple combination of the Planck blackbody emission law, optical filters, and digital image processing is demonstrated to enable most commercial color cameras (still and video) to be used as an imaging pyrometer for flames and explosions. The hardware and data processing described take advantage o...

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Bibliographic Details
Published in:Review of scientific instruments 2021-06, Vol.92 (6), p.063102-063102
Main Authors: McNesby, Kevin, Dean, Steven, Benjamin, Richard, Grant, Jesse, Anderson, James, Densmore, John
Format: Article
Language:English
Subjects:
Algorithms
Algorithms and data structure
Bandpass filters
Blackbody
Cameras
Color
Corrections
Data processing
Digital imaging
Emission
Emission spectroscopy
Emitters
Explosions
Image filters
Image processing
Optical filters
Optical spectroscopy
OTHER INSTRUMENTATION
Pyrometry
Sensor arrays
Temperature
Temperature metrology
Thermal instruments
Thermodynamic states and processes
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Summary:A simple combination of the Planck blackbody emission law, optical filters, and digital image processing is demonstrated to enable most commercial color cameras (still and video) to be used as an imaging pyrometer for flames and explosions. The hardware and data processing described take advantage of the color filter array (CFA) that is deposited on the surface of the light sensor array present in most digital color cameras. In this work, a triple-pass optical filter incorporated into the camera lens allows light in three 10-nm wide bandpass regions to reach the CFA/light sensor array. These bandpass regions are centered over the maxima in the blue, green, and red transmission regions of the CFA, minimizing the spectral overlap of these regions normally present. A computer algorithm is used to retrieve the blue, green, and red image matrices from camera memory and correct for remaining spectral overlap. A second algorithm calibrates the corrected intensities to a gray body emitter of known temperature, producing a color intensity correction factor for the camera/filter system. The Wien approximation to the Planck blackbody emission law is used to construct temperature images from the three color (blue, green, red) matrices. A short pass filter set eliminates light of wavelengths longer than 750 nm, providing reasonable accuracy (±10%) for temperatures between 1200 and 6000 K. The effectiveness of this system is demonstrated by measuring the temperature of several systems for which the temperature is known.
ISSN:0034-6748
1089-7623
DOI:10.1063/5.0037230