3D Step Profiler with LED Source and 2D Continuous Wavelet Transform

Fringe Projection Profilometry (FPP) is a widely used and reliable technique for non-contact three-dimensional (3D) surface measurements. However, when applied at micrometric and millimetric scales, its measurement accuracy may be degraded due to the limited depth of field and the speckle noise that arises in laser-based fringe patterns. In this study, a novel optical setup based on a light-emitting diode (LED) light source and a Gate’s interferometer configuration is presented. The proposed system aims to reduce speckle effects by exploiting the low coherence of the LED light source. In addition, the fringe pattern is diversified by employing two beam splitters together with an additional beam-splitting element that generates a horizontal fringe structure, with the objective of enhancing the spatial resolution of the system. To the best of our knowledge, the combined use of an LED light source and two-dimensional Continuous Wavelet Transform (2D CWT) analysis within this interferometric fringe projection framework is reported for the first time in this study. The experimentally obtained phase maps are analyzed using a two-dimensional Continuous Wavelet Transform (2D CWT) method, enabling three-dimensional surface reconstruction. To evaluate the performance of the LED light source, images of the same measurement regions are also acquired using a laser light source, and a comparative analysis is performed. The comparison results indicate that, based on cross-sectional evaluations, the LED-based configuration provides, albeit limited, a reduction in noise level and an improvement in surface profile stability compared to laser-based systems