Master thesis and internship[BR]- Master's thesis : Holography based on incoherent thermal infrared light in view of metrology applications[BR]- Internship

Abstract

The main objective of this work was to perform holography using self-emitted infrared light. To do so, holography was first studied by exploring a variety of scientific articles. These articles revealed that two main types of interferometers were used in that field, i.e., the Michelson and the Mach-Zehnder. Following this, it was possible to perform a preliminary study involving optical components assessment and ray tracing simulations. Then, it was possible to determine that the Mach-Zehnder setup was the most practical one, given the ZnSe components' availability in the laboratory. At this point, the practical implementation of the Mach-Zehnder could begin, involving the alignment in the visible domain using a coherent source, i.e., a Helium-Neon laser. Following that, a visible incoherent source, the SuperK Compact, was chosen. It was then possible by using filters to start from a low coherence and progressively decrease it up until reaching a totally incoherent source, i.e., without filters. Thus, the interferometer was aligned to enable interferometry with a white incoherent source. Finally, it was possible to use a self-emitting source, in this case, a welding iron at 450°C, to perform holography. For that purpose, images were recorded using a thermal camera, however, due to the beamsplitters' reflectance, the signal of interest was mixed with noise. Since no other beamsplitters were available at the laboratory, it was not possible to overcome this. However, it was supposed that increasing the reflection of the first beam splitter would yield a better signal-to-noise ratio, therefore effectively increasing the signal of interest compared to the thermal background noise.