Blackbody fitting for temperature determination

A method for making precise non-contact temperature measurements of a sample based on its thermally-emitted radiation, said method comprising the steps of:

• A. providing a spectrometer;
• B. providing a sample to be measured;
• C. acquiring wavelength-dependent spectra from the heated sample in the infrared (IR) portion of the spectrum with the spectrometer;
• D. providing a mathematical equation defining ideal blackbody spectral radiance (I) as a non-linear function of wavelength (λ) and temperature (T), whereby the mathematical equation expresses a unique ideal blackbody spectral radiance curve I(λ,T) for any given temperature;
• E. selecting one ideal blackbody spectral radiance curve I(λ,T) closely corresponding to the spectra data, the corresponding ideal blackbody spectral radiance curve I(λ,T) being associated with an absolute temperature;
• F. adopting the absolute temperature of the corresponding ideal blackbody spectral radiance curve I(λ,T) for the unknown temperature of the sample;
• and
• G. prior to said selecting step, correcting the spectra by a predetermined correction factor to correct for any variations in the spectrometer response with wavelength.

A method for making precise non-contact temperature measurements of a sample based on its thermally-emitted radiation, comprising the steps of:

• A. providing a solid state spectrometer;
• B. establishing a correction factor for the spectrometer by flat field adjusting;
• C. providing a sample to be measured;
• D. heating the sample to an unknown temperature;
• E. acquiring raw, wavelength-dependent, spectra from the heated sample in the IR portion of the spectrum with the spectrometer;
• F. correcting the raw spectra by the correction factor to produce corrected spectra data;
• G. providing a mathematical equation defining ideal blackbody spectral radiance (I) as a non-linear function of wavelength (λ) and temperature (T), the mathematical equation including an amplitude variable (A), whereby the mathematical equation expresses a unique ideal blackbody spectral radiance curve I(λ,T) for any given temperature;
• H. comparing the corrected spectra data to the mathematical equation to find the best fit to one specific ideal blackbody spectral radiance curve I(λ,T) associated with an absolute temperature and a specific amplitude value (A);
• I. adopting the absolute temperature of the best fit ideal blackbody spectral radiance curve I(λ,T) for the unknown temperature of the sample without knowing the value of A;
• J. storing the amplitude value (A);
• K. locking the stored amplitude value (A) into the mathematical equation;
• L. making at least one new sample temperature measurement by the steps of:
• 1) acquiring new wavelength-dependent spectra from a heated sample in the infrared (IR) portion of the spectrum with the spectrometer;
• 2) correcting the new spectra by the correction factor;
• and
• M. calculating a new sample temperature by best fitting to the mathematical equation using the newly acquired spectra and the stored amplitude value (A) as a known factor.