Analysis of Small Deflections by Double-Exposure Digital Holographic Interferometry

We analyzed small deflections (similar to 1 mu m) of an opaque object by means of the double-exposure digital holographic interferometry technique, using an off-axis lensless Fourier holographic arrangement. The deflections were caused by heating the object with a flowing dc current. In our holographic arrangement, out-of-plane displacements of around 300 nm can be precisely detected by using a He-Ne laser as the coherent illumination source. However, this resolution could be improved by modifying the experimental setup or even choosing an appropriate object reference state. We briefly show the theoretical description of the technique and conduct experiments and simulations to test the results. Since the object we have studied in this work is a bimetallic strip, the obtained results point towards further research concerning precise temperature sensing devices.