Diffraction-engineered holography: Beyond the coherent limits of holographic displays

Abstract Holography is considered as one of the most prominent approaches to realize true-to-life reconstructions of objects. However, owing to the limited resolution compared to static holograms, state-of-the-art computer generated holograms with dynamic display capabilities reconstruct objects exhibiting various coherent properties, such as interference-induced noise and content-dependent defocus blur. Since real world scenes are composed of incoherent light, the coherent properties of reconstructed scenes severely distort the depth perception. Here, we propose a diffraction-engineered hologram, which imitates real world incoherent light by adopting a multi-plane hologram, thereby offering a real world-like defocus blur and a photorealistic reconstruction. Our hologram is synthesized by optimizing a wave field to reconstruct numerous varifocal images after propagating the corresponding focal distances where the varifocal images are rendered using a physically-based renderer. By explicitly adopting out-of-focus images as the optimum intensities, the hologram can be synthesized to reconstruct the scene with the correct defocus blur. Moreover, to reduce the computational costs associated with rendering and optimizing, we also demonstrate a network-based synthetic method that requires only an RGB-D image. We experimentally confirm the incoherent-like depth expression of the hologram, while successfully suppressing unnecessary interference in the reconstructed hologram. Our diffraction-engineered hologram offers comparable synthetic time to previously reported methods while presenting significantly more accurate depth cues, moving one step further to reconstructing naturalistic scenes of a virtual world.