Low-Cost Two-Color Pyrometry for Laser-Powder Bed Fusion

Laser-Powder Bed Fusion (L-PBF) additive manufacturing relies on precise control of melting and solidification, making accurate thermal measurement essential for maintaining build quality and detecting process instabilities. This work presents a novel method for real-time, pixel-wise temperature measurement in L-PBF using a low-cost two-color pyrometry system built from synchronized Near-Infrared (NIR) cameras. The system uses two high-resolution USB 3.0 Basler acA5472 cameras—one monochrome and one color—outfitted with narrowband filters centered at 900 nm and 750 nm, respectively, along with neutral density filtering to prevent sensor saturation. Spatial and temporal alignment is achieved through a custom calibration routine using a 9×11 circular grid pattern, enabling precise perspective correction between the two camera images. Temperature mapping is performed using a ratio-of-radiance approach based on Wien’s approximation, with calibration constants derived from a tungsten filament reference source. The resulting output yields high-resolution, repeatable thermal maps of the melt pool that correlate well with expected trends and reference data from a FLIR A50 radiometric camera. The system demonstrates a scalable, cost-effective solution for in-situ thermal monitoring in metal additive manufacturing and offers a strong foundation for future investigations into melt pool dynamics, process stability and closed-loop control.