Speckle induced by reflections in pipe propagation of a structured laser beams

This study explores how reflections affect the transverse intensity profile of a structured laser beam (SLB) in alignment systems. The research evaluates the impact of pipe material and geometry on noise affecting the inner core (IC) of the SLB's transverse intensity profile. The results show that using a vacuum pipe setup with a black, undulated pipe of high surface roughness and a low-coherence laser source significantly reduces noise, enhancing the detection accuracy of the IC. A 140 m long-distance measurement demonstrates that discrepancies between various position detection algorithms are reduced to sub-pixel levels with such a setup. These findings facilitate the development of highly accurate and reliable optical alignment systems based on a reference line defined by an SLB.