Inline Temperature Imaging: A Non-contact Temperature Measurement Technique for Laser Processing
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Laser keyhole welding and laser additive manufacturing are high intensity laser based advanced manufacturing techniques that offer numerous advantages over more traditional processes. However, because of the extreme spatial temperature gradients, both have complicated interaction physics that make them hard to control. Moreover, these techniques and their temperatures can prove exceptionally difficult to monitor because of these physics, which can fluctuate the emissivity wildly. This necessitates monitoring techniques that are high-speed and high-resolution to capture these dynamics. Inline coherent imaging (ICI) is a low coherence interferometric ranging technique that has previously been used to characterise the morphology of both processes. In this work, I developed a novel method to collect high-resolution, high-speed absolute temperature measurements during laser processing, inline temperature imaging (ITI), such that ITI can be used in conjunction with ICI. ITI offers spatial resolutions of 30µm at imaging speeds of up to 10kHz, for temperatures ranging from 1600K to 4500K. I have resolved spatial and temporal temperature dynamics in laser processing never before observed. Moreover, I highlight the potential future works of this technique, especially in conjunction with ICI, to better characterise more aspects of laser processing, with a hope for eventual real-time in-situ feedback control.