Tu Kefeng, Chen Qiyang, Wang Zi, Lv Guoqiang, Feng Qibin
School of Instrument Science and Opto-Electronics Engineering, Hefei University of Technology, Hefei 230009, China.
National Engineering Laboratory of Special Display Technology, National Key Laboratory of Advanced Display Technology, Academy of Photoelectric Technology, Hefei University of Technology, Hefei 230009, China.
Micromachines (Basel). 2023 May 31;14(6):1167. doi: 10.3390/mi14061167.
The super multi-view (SMV) near-eye display (NED) effectively provides depth cues for three-dimensional (3D) displays by projecting multiple viewpoint images or parallax images onto the retina simultaneously. Previous SMV NED suffers from a limited depth of field (DOF) due to the fixed image plane. Aperture filtering is widely used to enhance the DOF; however, an invariably sized aperture may have opposite effects on objects with different reconstruction depths. In this paper, a holographic SMV display based on the variable filter aperture is proposed to enhance the DOF. In parallax image acquisition, multiple groups of parallax images, each group recording a part of the 3D scene on a fixed depth range, are captured first. In the hologram calculation, each group of wavefronts at the image recording plane (IRP) is calculated by multiplying the parallax images with the corresponding spherical wave phase. Then, they are propagated to the pupil plane and multiplied by the corresponding aperture filter function. The size of the filter aperture is variable which is determined by the depth of the object. Finally, the complex amplitudes at the pupil plane are back-propagated to the holographic plane and added together to form the DOF-enhanced hologram. Simulation and experimental results verify the proposed method could improve the DOF of holographic SMV display, which will contribute to the application of 3D NED.
超级多视图（SMV）近眼显示器（NED）通过同时将多个视点图像或视差图像投影到视网膜上，有效地为三维（3D）显示器提供深度线索。由于图像平面固定，先前的SMV NED存在景深（DOF）有限的问题。孔径滤波被广泛用于增强景深；然而，固定大小的孔径可能会对具有不同重建深度的物体产生相反的影响。本文提出了一种基于可变滤波孔径的全息SMV显示器，以增强景深。在视差图像采集过程中，首先捕获多组视差图像，每组视差图像记录固定深度范围内3D场景的一部分。在全息图计算中，通过将视差图像与相应的球面波相位相乘，计算图像记录平面（IRP）处的每组波前。然后，将它们传播到光瞳平面并与相应的孔径滤波函数相乘。滤波孔径的大小是可变的，由物体的深度决定。最后，将光瞳平面处的复振幅反向传播到全息平面并相加，以形成增强景深的全息图。仿真和实验结果验证了所提方法能够提高全息SMV显示器的景深，这将有助于3D NED的应用。
