Multi-wavelength pyrometric systems for emissivity-independent non-contact temperature sensing
Department of Electrical and Computer Engineering
Doctor of Philosophy
Manikopoulos, Constantine N.
Ravindra, N. M.
Shi, Yun Q.
A Multi-Wavelength Imaging Pyrometer (M-WIP) for real-time remote sensing of temperature profiles of targets with unknown emissivity was developed and demonstrated. To measure the spectral radiance of a target at several distinct wavelengths an M-WIP system was implemented based on an 320x122-element PtSi IR-CCD imager with an assembly of 7 narrow-band 1k filters in the range from 1790nm to 4536nm. A real-time algorithm for simultaneous estimation of the temperature and model parameters of the target emissivity from the least-squares fit of the theoretical model of 1k camera output signal to the experimental spectral measurements was developed and implemented. This rea1-time least-squares minimization was accomplished by combination of Levenberg-Marquardt and simulated annealing algorithms. The least-squares-based calibration algorithm was developed for evaluation of effective values of peak transmissions and center wavelengths of M-WIP channels based on the detection of radiation from pre-calibrated blackbody source. To achieve high radiometric accuracy, compensation for the dark current charge as function of the detected signal level was implemented. The effect of the response non-linearity of IR imager was minimized by developing an algorithm for imager operation at fixed pre-selected signal level for each M-WIP spectral channel based on adaptive control of the duration of the optical integration time of the imager. Initial testing demonstrated an accuracy of ±l.0°C for real-time temperature measurements of the center of the blackbody aperture in the range from 500°C to 1000°C. Temperature resolution of ±3°C was demonstrated for the blackbody source viewed through a double side polished silicon wafer with unknown spectral transmissivity in the temperature range from 500°C to 900°C.
njit-etd1997-033 (147 pages ~ 7,534 KB pdf)
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Created October 27, 2008