 Inline coherent imaging (ICI) is a recently developed interferometric technique based on optical coherence tomography that is used for quality assurance of keyhole laser beam welding, a welding method that is gaining popularity in a variety of industries.ICI works by aiming a low-powered broadband light source through the same optical path as the primary welding laser.The beam enters the keyhole of the weld and is reflected back into the head optics by the bottom of the keyhole.