On the optical performance of incoherent digital holography for extended 3D objects

Digital Holography (DH) technology has grown fast over the years, offering the possibility to encode complex information from three-dimensional real-world objects onto two-dimensional digital supports. Accessing the object as an entire numerical complex wavefront raised large expectations in the fields of imaging and display. Holographic vision through fog, smoke, and flames in the far infrared (IR) range would be, in principle, applicable to the fields of automotive, video surveillance, and homeland security. However, the need for bulky, high-coherence laser sources has dampened the enthusiasm around the development of holographic cameras for use in such a context. Here, we investigate self-interference digital holography (SIDH) as a method for obtaining refocusable wavefronts by using low-coherence light sources, a category including light bulbs, arc lamps, light-emitting diodes, low-coherence IR lasers, heat sources, and sunlight. We develop and analyze a model to study the optical performance of SIDH in terms of reconstruction distance range, lateral magnification, resolution, and limiting factors. Then, we propose a configuration for reshaping the system Point Spread Function (PSF) and enhancing resolution by tuning the visibility of high-frequency fringes. The model is experimentally verified by imaging various scenes under incoherent illumination in the visible range. As a last testbed, we provide a first proof of concept SIDH imaging in the far IR range by retrieving and refocusing the complex wavefront back-scattered by point sources illuminated by low-coherence IR light.