Application of multi-spectral camera for biomedical use to two-color temperature measurement in welding phenomena

This study tested a two-color temperature measurement method using a multi-spectral camera designed for biomedical use. We selected the images of 735 nm and 930 nm as wavelengths. Two calibrations were performed before using them for temperature conversion. One was sensitivity calibration between wavelengths, which was conducted by heating the steel surface coated with blackbody spray from the opposite surface and comparing it with the temperature measured by thermography. Another calibration was a pixel shift that took into account the array of elements. This is a correction peculiar to a multi-spectral camera, and it was possible to eliminate a steep temperature error at the end of the temperature discontinuity. In this report, the electrode temperature of the gas tungsten arc was reported as an application example.