Monochrome AR-3D display based on pixelated volumetric holographic grating

Visual perception has driven the evolution of display technologies from static and dynamic to 3D. Traditional 2D displays, lacking depth information, can hardly meet the demand for immersion; whereas 3D displays with binocular and motion parallax are capable of creating a visual experience with depth and realism.This study carries out systematic research on monochromatic pixelated volume grating diffraction elements and their virtual-real fusion 3D display technology. In this paper, the Gerchberg-Saxton (GS) algorithm is adopted to construct pixelated grayscale diffraction elements containing 4 horizontally distributed rectangular viewpoints. By optimizing the viewpoint interval to 3° and introducing a specific pixel arrangement mechanism, structural space reuse and improvement of light energy utilization rate are achieved. Combined with parallel laser direct writing technology and Microlab micro-nano processing equipment, the preparation of micron-level high-precision elements is completed, and a reflective volume grating recording optical path is built to realize the fabrication of high-quality diffraction elements. Finally, through the illumination of a projection light source with precisely matched reference light incident angles and wavelengths, 4 horizontally uniformly distributed rectangular viewpoints are successfully presented (with a field of view of 9°), which verifies that the system has horizontal continuous motion parallax effect and excellent optical transmission characteristics. Furthermore, by accurately mapping multi-view mixed parallax images with projector pixels and then projecting them onto the volume grating elements, the seamless fusion display of virtual images and real objects is realized, which confirms the practicality and effectiveness of the system.