Speckle-Free 3D Holography in the Wigner Domain

Abstract

Computer-generated hologram (CGH) provides an approach to modulate the 3D coherent wavefront and has been widely used in many optical applications. Over the past few decades, extensive efforts have been made to design optimization models for high-quality reconstruction. However, the reconstruction quality is still limited due to the mismatch of the bandwidth between the reconstructed field of interest and the reconstructed complex amplitude field in 3D space. Here, an ideal numerical light field mapping physical model from the hologram plane to the 3D image plane for speckle-free 3D holography in the Wigner domain is established. With the aid of the Wigner distribution function (WDF), which allows the analysis of a light field from not only the space domain but also the spatial frequency domain, the bandwidth properties of the reconstructed field in 3D space are analyzed, which provides a guideline for the sampling of the reconstructed field to efficiently describe the speckles and artifacts. Accordingly, a comprehensive CGH optimization method in the Wigner domain is proposed to constrain the reconstructed intensity fluctuations without errors and omissions for high-quality reconstruction. As such, this method enables speckle-free and artifact-free reconstruction with a twice improvement in peak signal-to-noise ratio (PSNR) and a five times improvement in structural similarity index measure (SSIM) compared to conventional phase-only holograms. The optical experimental results show that this method paves the road for the future implementation of speckle-free color 3D holography harnessing the advanced integrated photonic devices, and also offers an efficient and practical route for various optical applications, such as 3D display, optical encryption, beam shaping, optical computing and so on.