Digital holography for 3D imaging and display in the IR range: challenges and opportunities

In analog holography, the infrared (IR) range received quite some attention, since it could provide interesting information, not achievable otherwise. Since digital sensors in this band became recently available and affordable, also digital holography (DH) expanded its feasibility beyond the visible wavelengths. In fact, the IR range allows shorter recording distances, unparalleled larger field of view and less stringent requirements on system stability, together with some specific characteristics, like e.g. the possibility to test IR glasses or other materials transparent to IR radiation, which cannot be controlled in visible range. In this paper we review the activities which took place in this field and illustrate the results achieved, referring to the opportunities this technique offers, and the challenges it presents. We show efficient reconstructions of holograms of objects of various materials, recorded with different resolution digital thermal cameras, in various configurations, and moreover we demonstrate optical holographic display through a liquid crystal based Spatial Light Modulator which gives the chance to get direct 3D imaging and display of long IR range. Moreover we believe this opens the route toward holography in THz region.