A lensless full-color holographic Maxwellian near-eye display using a single amplitude-type spatial light modulator is proposed in this Letter. The color holographic image is directly projected onto the retina without any eyepiece. The color crosstalk is clearly separated from the signal in the space owing to the encoded spherical wave and carrier wave. An aperture numerical filter and a real polarized filter are used at the pupil plane to accurately stop the crosstalk light. A high-quality dynamic speckless color holographic image was produced in the mid-air within a specific depth range. The horizontal eyebox expansion is achieved simply through multiple spherical wave encoding and verified through an optical experiment. The proposed display is compact and promising as the augmented reality near-eye display.

The holographic Maxwellian display is a promising technique for augmented reality (AR) display because it solves the vergence-accommodation conflict while presenting a high-resolution display. However, conventional holographic Maxwellian display has the inherent trade-off between depth of field (DOF) and image quality. In this paper, two types of holographic Maxwellian displays, the spherical wave type and the plane wave type, are proposed and analyzed. The spherical wavefront and the plane wavefront are produced by a spatial light modulator (SLM) for Maxwellian display. Due to the focusing properties of different wavefronts, the two types of display have complementary DOF ranges. A hybrid approach combining the spherical wavefront and plane wavefront is proposed for a large DOF with high image quality. An optical experiment with AR display is demonstrated to verify the proposed method.

A holographic super multi-view (SMV) Maxwellian display based on flexible wavefront modulation is proposed for the first time, to the best of our knowledge. It solves the issue that the previous holographic Maxwellian displays could not provide depth cues for monocular vision. Different from the previous methods, two or more parallax images are multiplied by quadric phase distributions and converged to the viewpoints existing in the pupil to provide 3-D vision. A time division method is proposed to eliminate the cross talk caused by the coherence of different spherical waves. Experiments demonstrate that the proposed method can accurately reconstruct images at different depth without cross talk. The proposed method inherits the previous holographic Maxwellian display's advantages of flexible viewpoint position adjustment and large depth of field (DOF). Superior to geometric optics based SMV displays, the proposed system is compact without lens aberration since only a single spatial light modulator (SLM) is needed without any additional optical elements.

We proposed a simple and fast algorithm for computer-generated hologram (CGH) based on pinhole-type II using a look-up table. The method consists of two steps: in the first step, the unity amplitude diffraction pattern of the center pinhole on hologram plane is pre-calculated and stored as many sub-regions. Secondly, diffraction patterns for other pinholes are obtained by simply shifting and tiling the pre-calculated sub-regions, and the final CGH is obtained by adding them all together. The calculation time is short because only addition and multiplication of the stored diffraction pattern are required. In addition, the required memory space is small since only one diffraction pattern is stored. Numerical simulation and reconstruction are performed on both plane object and object with continuous depth profile to verify the proposed method. Result shows that the proposed method can easily achieve real-time hologram generation with several CPU threads running simultaneously.

Compressive light field (CLF) display using multi-layer spatial light modulators (SLMs) is a promising technique for three-dimensional (3D) display. However, conventional CLF display usually uses the reference plane with fixed depth, which does not consider the relationship between the depth distribution of the object and the image quality. To improve the quality of the reconstructed image, we further analyze the relationship between them in the paper. The theoretical analysis reveals that the object with a closer distance to the physical layer has a better reconstruction quality when the SLM layers have the same pixel density. To minimize the deviation between the reconstructed light field and the original light field, we propose a method based on the depth distribution feature to automatically guide the light field optimization without increasing the layered number or the refresh rate. When applied to a different scene, it could detect the dense region of depth information and map them as close to the physical layers as possible by offsetting the depth of the reference plane. Simulation and optical experiments with the CLF display are demonstrated to verify the proposed method. We implement a CLF display that consists of four-layer stacked display panels and the distance between two adjacent layers is 5cm. When the proposed method is applied, the peak signal-to-noise ratio (PSNR) is improved by 2.4dB in simulations and 1.8dB in experiments.