Comprehensive optimization for full-color holographic stereogram printing system based on single-shot depth estimation and time-controlled exposure

Abstract

A comprehensive optimization method for a full-color holographic stereogram (HS) printing system based on single-shot depth estimation for real-world objects and time-controlled exposure is proposed. Both processing steps, including digital content generation and optical printing, are optimized to ensure possible high-quality three-dimensional (3D) holographic image printing, rapid computation, and proper full-color visualization. In the digital content generation, first a high-resolution two-dimensional (2D) image of the real object is captured, and its depth map is then estimated via a pre-trained convolutional neural network (CNN) model, ensuring an identical resolution with a given 2D image. As a post-processing, the unnecessary scenes and background are removed from the captured color image, without losing the main information of a primary object. Then, a hogel array (HA) is obtained by utilizing the estimated depth map and a post-processed color image through a fast inverse-directed propagation (IDP) method. Each hogel undergoes unique non-iterative phase modulation in a quite short time without the degradation of image quality while the chromatic dispersion errors are minimized. Finally, the hogels are sequentially printed onto holographic material using a time-controlled exposure, to provide the color-balanced full-color reconstruction using a single spatial light modulator (SLM). The overall procedure is seamlessly performed automatically via custom-designed graphical user interface. This study experimentally confirmed a simple and effective optimization for HS printing systems in both digital content generation and optical printing unit.