Coherent artifact-free optical profilometry with improved space bandwidth product using partially spatially coherent light

Optical profilometry, a widely used technique for surface characterization, relies on light to extract surface profiles. The space bandwidth product (SBP) quantifies the imaging capacity of optical profilometry. Our study explores single-shot optical profilometry with high SBP and spatial phase sensitivity (SPS). A trade-off exists between the field of view (FOV) and the system's spatial resolution, i.e., the spatial resolution decreases if we increase FOV. Thus, increasing the FOV with the same or higher resolution results in higher SBP. Optical profilers generally use low-coherence light sources like white light, therefore reducing the interferometric FOV. However, sources such as lasers with high temporal coherence result in larger interferometric FOV but reduce the SPS of the system due to the presence of speckles and spurious fringes. Thus, this study proposes a comparative analysis between the standard white light profiler and a partially spatially coherent light (PSCL) based profiler to get a higher SBP during profiling. The result on industrial samples shows that the PSCL-based optical surface profiler results in high visibility, 8.5 times higher SBP than white light, higher spatial resolution than white light and filtered white light sources, and moderate SPS compared to filtered white light sources. Implementing non-invasive, single-shot optical profilometry utilizing PSCL holds significant promise for facilitating advancements in industrial sectors.