Photodiodes are commonly used in Laser Powder Bed Fusion (LPBF) for process monitoring. However, they spatially average out features within the melt pool. We introduce Spatial Frequency Modulation Imaging (SPIFI), a technique enabling 1D spatially resolved imaging with photodiodes. SPIFI can produce high-resolution images using blackbody radiation or coherent illumination. In LPBF monitoring, we use three photodiodes at different wavelengths (780, 920, and 1070 nm) to obtain 1D SPIFI images of the melt pool temperature and reflected fusing beam. Our experimental results aim to benchmark LPBF physics models for accurate melt process simulations and serve as an in-situ process diagnostic.
New spatial domain (SD) frequency modulation imaging (SPIFI) architectures are developed that enable the use of the full numerical aperture of long working distance excitation optics without sacrificing the field-of-view. When multiplexed with wavelength domain (WD) SPIFI, multiple advantages follow. One, the WD-SPIFI signals can be used to optimize the multiphoton SD-SPIFI signals. Two, these new SD-SPIFI architectures enable video rate SPIFI. Finally, applications of these new architectures to advanced manufacturing will be presented.
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