Formulation of off-axis single reference beam and two angle views for digital holography

摘要

Photo-plates used in classical holography have several advantages, mainly a high resolution and the ability to overlap several holograms. Conversely, they suffer from chemical processing and delays in getting the useful signal. In contrast to film holography, digital holography offers quick and easy access to the desired information but suffers from the low resolution of the CCD sensors and their small detecting areas. This is why many holographers were limited to the in-line scheme, because of its simplicity and ability to overcome this resolution problem. But it still suffers from several problems when recording particles such as depth of focus,superposition of twin images and others. This is why, in spite of a more complex optical arrangement, we propose an appropriate off-axis scheme and a theoretical formulation that enables us to record simultaneously two holograms on the same CCD sensor from two angle views using a single reference beam. Furthermore, such a scheme, simpler than other off-axis proposals, provides spatially separate reconstruction of the two views and overcomes the above cited problems. As the aim of our development is to measure the influence of concentration of solid particles on their velocity for mixing flows, we show here examples without extended analysis.