Spectral stray light effect on high-temperature measurements using a near-infrared multi-wavelength pyrometer

• Spectral stray light is corrected for multi-wavelength pyrometer using a laser.
• Corrections for spectral stray light improve the accuracy of optical pyrometer.
• Simplified temperature calibration procedure for optical pyrometer is given.
• Measurement accuracy of calibrated pyrometer is experimentally verified.

The spectral stray light is a major, non-negligible error source affecting spectral intensity measurements for optical instruments. The purpose of this study is to investigate the effects of spectral stray light on high-temperature measurements using a near-infrared (1.0–1.65 μm) multi-wavelength pyrometer. The spectral stray light corrections were measured for the multi-wavelength pyrometer using a pulsed tunable laser for wavelengths from 0.41 μm to 2.63 μm. A matrix correction method was then used for the spectral stray light for the multi-wavelength pyrometer. The spectral response characteristics of the pyrometer were calibrated using a standard high-temperature blackbody source. The experimental results show that the spectral response characteristics are approximately identical for different calibration temperatures when the spectral stray light correction is used. The corrections for the spectral stray light significantly improve the accuracy of the multi-wavelength pyrometer at a blackbody calibration temperature which gives a simplified accurate calibration procedure, unlike the temperature calibrations for general optical pyrometers. Temperature measurement tests using a multi-wavelength pyrometer for standard high-temperature source further verified the measurement accuracy of the calibrated pyrometer which also illustrates the necessity of the spectral stray light corrections for the complex optical pyrometer and the applicability of the multi-wavelength algorithm.