Flat-panel see-through three-dimensional display based on integral imaging

Flicker-free dual-volume augmented reality display using a pixelated interwoven integral floating technique with a geometric phase lens

A geometric phase (GP) integral floating display can provide multifocal three-dimensional (3D) augmented reality (AR) images with enhanced depth expression by switching the focal modes of the GP lens via polarization control. However, using temporal multiplexing to switch between the focal modes of GP optics causes flickering as each 3D AR image is fully presented in different frames and their temporal luminance profile becomes easily recognizable, particularly as the number of available focal modes increases. Here, we propose a novel integral floating technique to generate pixelated interwoven 3D AR images; a half of each image is spatially mixed with another and presented in both focal modes simultaneously to resolve the flickering issue. The principle was verified via experimental demonstration and optically measured data.

Adjustable and continuous eyebox replication for a holographic Maxwellian near-eye display

A Maxwellian display presents always-focused images to the viewer, alleviating the vergence-accommodation conflict (VAC) in near-eye displays (NEDs). Recently, many methods of improving its limited eyebox have been proposed, among which viewpoint replication has attracted a lot of attention. However, double-image, blind-area, and image-shift effects always happen in typical eyebox-replication Maxwellian NEDs when the eye moves between the replicated viewpoints, which prevents these NEDs from being applied more widely. In this Letter, we propose a method for designing a holographic Maxwellian NED system with continuous eyebox replication as well as flexible interval adjustment by changing the projection angles of the reconstructed images. Thus, holograms corresponding to the positions of different viewpoints are calculated to match the interval of the replicated viewpoints with the human pupil diameter, making it possible to eliminate or alleviate double-image or blind-area effects. Also, seamless viewpoint conversion in the eyebox is achieved by aligning the images of adjacent viewpoints on the retina via hologram pre-processing independently. These effects are verified successfully in optical experiments and have the potential to be applied in near-eye three-dimensional displays without VAC.

Extending eyebox with tunable viewpoints for see-through near-eye display

The Maxwellian display presents always-focused images to the viewer, alleviating the vergence-accommodation conflict (VAC) in near-eye displays (NEDs). However, the limited eyebox of the typical Maxwellian display prevents it from wider applications. We propose a Maxwellian see-through NED based on a multiplexed holographic optical element (HOE) and polarization gratings (PGs) to extend the eyebox by viewpoint multiplication. The multiplexed HOE functions as multiple convex lenses to form multiple viewpoints, which are copied to different locations by PGs. To mitigate the imaging problem that multiple viewpoints or no viewpoints enter the eye pupil, the viewpoints can be tuned by mechanically moving a PG. We implement our method in a proof-of-concept system. The optical experiments confirm that the proposed display system provides always in-focus images within a 12 mm eyebox in the horizontal direction with a 32.7° diagonal field of view (FOV) and a 16.5 mm eye relief (ERF), and its viewpoints are tunable to match the actual eye pupil size. Compared with other techniques to extend the eyebox of Maxwellian displays, the proposed method shows competitive performances of a large eyebox, adaptability to the eye pupil size, and focus cues within a large depth range.

Compensation of color breaking in bi-focal depth-switchable integral floating augmented reality display with a geometrical phase lens

A bi-focal integral floating system using a geometrical phase (GP) lens can provide switchable integrated spaces with enhanced three-dimensional (3D) augmented reality (AR) depth expression. However, due to the chromatic aberration properties of the GP lens implemented for the switchable depth-floating 3D images, the floated 3D AR images with the red/green/blue (R/G/B) colors are formed at different depth locations with different magnification effects, which causes color breaking. In this paper, we propose a novel technique to resolve the color breaking problem by integrating the R/G/B elemental images with compensated depths and sizes along with experiments to demonstrate the improved results. When we evaluated the color differences of the floated 3D AR images based on CIEDE2000, the experimental results of the depth-switchable integral floating 3D AR images showed that the color accuracies were greatly improved after applying a pre-compensation scheme to the R/G/B sub-images in both concave and convex lens operation modes of the bi-focal switching GP floating lens.

Gigapixel and 1440-perspective extended-angle display by megapixel MEMS-SLM

Orders-of-magnitude increases are desired in the pixel count and density of spatial light modulators (SLMs) for next-gen displays. We present in-plane and simultaneous angular-spatial light modulation by a micro electro mechanical system (MEMS)-based SLM, a digital micromirror device (DMD), to generate gigapixel output by time and angular multiplexing. Pulsed illumination synchronized to the micromirror actuation achieves pixel-implemented and diffraction-based angular modulation, and source multiplexing increases angular selectivity. We demonstrate 1440-perspective image output across a 43.9^∘×1.8^∘ FOV, 8-bit multi-perspective videos at 30 FPS, and multi-focal-plane image generation. We discuss scalability to terapixels and implications for near-to-eye displays.

Autostereoscopic transparent display using a wedge light guide and a holographic optical element: implementation and results

We present a transparent autostereoscopic display consisting of laser picoprojectors, a wedge light guide, and a holographic optical element. The holographic optical element is optically recorded, and we present the recording setup, our prototype, as well as the results. Such a display can superimpose 3D data on the real world without any wearable.

3D view image reconstruction in computational integral imaging using scale invariant feature transform and patch matching

This paper realizes a computational integral imaging reconstruction method via scale invariant feature transform (SIFT) and patch matching to improve the visual quality of reconstructed 3D view images. To our knowledge, the 3D view images reconstructed from the elemental images suffer from artifacts, which leads to degradations in the visual quality. To prevent image degradation, in this paper, we use the correct regions obtained from the view images taken directly from the original object or use patch matching to replace the distorted regions. However, the initial matching regions could not meet our requirements owing to the limitations of the equipment and the inevitable shortcomings of the experimental operation. To solve these problems, we adopt SIFT descriptors and perspective transform to get the satisfying correct regions. We present the simulation and experimental results of the 3D view images and the evaluation of the quality of the corresponding images to test the performance of the proposed method. The simulation and experimental results indicate that the proposed method can significantly improve the visual quality of the 3D view images and verify the feasibility and effectiveness of the proposed method.

Design of a light-field near-eye display using random pinholes

Light-field near-eye displays can solve the accommodation/convergence conflict problem that can cause severe discomfort to the user. However, in actual systems, convergence depth and accommodation depth may not match each other due to the repeated zones or flipped images produced by traditional light-field methods. Also, Moiré fringes are another problem which is caused by interaction between two periodic structures. We present a method of constructing a light-field near-eye display based on random pinholes, where the random structure is employed as a spatial light modulator to break the periodicity of elemental images. Light-field images for a unique view zone in space without Moiré fringes can be provided. A proof-of-concept prototype has been developed to verify the proposed method.

Design of an optical see-through light-field near-eye display using a discrete lenslet array

In this paper, we propose a novel method to construct an optical see-through light-field near-eye display (OST LF-NED) by using a discrete lenslet array (DLA). The DLA is used as a spatial light modulator (SLM) to generate dense light field of three-dimensional (3-D) scenes inside the user's eyebox of the system and provide correct focus cues to the user. A corresponding light-field image rendering method is also proposed and demonstrated. The light emitted from the real objects passes through the transparent region of the display panel and the planar area of the DLA successively without redirection, so the user can have a clear view of the real scene as well as the virtual information. The stray light that may degrade the image quality has been analyzed in detail. The experimental result shows that the proposed method is capable of obtaining a corrected depth perception of the virtual information in augmented reality (AR) applications.

Twin imaging phenomenon of integral imaging

The imaging principles and phenomena of integral imaging technique have been studied in detail using geometrical optics, wave optics, or light filed theory. However, most of the conclusions are only suit for the integral imaging systems using diffused illumination. In this work, a kind of twin imaging phenomenon and mechanism has been observed in a non-diffused illumination reflective integral imaging system. Interactive twin images including a real and a virtual 3D image of one object can be activated in the system. The imaging phenomenon is similar to the conjugate imaging effect of hologram, but it base on the refraction and reflection instead of diffraction. The imaging characteristics and mechanisms different from traditional integral imaging are deduced analytically. Thin film integral imaging systems with 80μm thickness have also been made to verify the imaging phenomenon. Vivid lighting interactive twin 3D images have been realized using a light-emitting diode (LED) light source. When the LED is moving, the twin 3D images are moving synchronously. This interesting phenomenon shows a good application prospect in interactive 3D display, argument reality, and security authentication.

Optical see-through Maxwellian near-to-eye display with an enlarged eyebox

We propose a Maxwellian near-to-eye display implemented using a multiplexed holographic optical element. Maxwellian configuration removes the focal cue of the displayed virtual image completely, presenting an always-focused image to the observer regardless of the focal length of the eye. The transparent property of the holographic optical element enables the optical see-through feature, making the proposed near-to-eye display suitable for augmented reality applications. The multiplexing of multiple concave mirrors into a single holographic optical element enlarges the effective eyebox, relaxing the limitation of the conventional Maxwellian displays. Optical experiment confirms that the proposed display can present always-focused images on top of the real environment with 9.2°(H)×5.2°(V) field of view, and 9  mm (H)×3  mm (V) eyebox.

Asymmetric integral imaging system for a see-through three-dimensional display with background imaging function

A see-through three-dimensional display with variable background imaging function is proposed. The proposed display system is based on integral imaging and consists of three lens arrays and a transparent flat-panel display. An asymmetric alignment of the three lens arrays enables variable background imaging. The background scene situated at any distance from the display system can be imaged at an intended distance from the display system. The possible imaging regions are shown. The proposed technique was experimentally verified using two optical systems that consisted of lens arrays with large and small lens pitches.

Compact see-through 3D head-mounted display based on wavefront modulation with holographic grating filter

A compact see-through three-dimensional head-mounted display (3D-HMD) is proposed and investigated in this paper. Two phase holograms are analytically extracted from the object wavefront and uploaded on different zones of the spatial light modulator (SLM). A holographic grating is further used as the frequency filter to couple the separated holograms together for wavefront modulation. The developed preliminary prototype has a simple optical facility and a compact structure (133.8mm × 40.4mm × 35.4mm with a 47.7mm length viewing accessory). Optical experiments demonstrated that the proposed system can present 3D images to the human eye with full depth cues. Therefore, it is free of the accommodation-vergence conflict and visual fatigue problem. The dynamic display ability is also tested in the experiments, which provides a promising potential for the true 3D interactive display.

See-through multi-projection three-dimensional display using transparent anisotropic diffuser

We propose a see-through multi-projection three-dimensional (3D) display using a transparent anisotropic diffuser. By immersing a metal-coated anisotropic diffuser into index matching oil which has the same refractive index of anisotropic diffuser, a transparent anisotropic diffuser is implemented. The reflectance of the transparent anisotropic diffuser is analyzed with the transfer matrix. Two multi-projection methods are proposed based on reflection type integral imaging and multi-view method. Especially, the reflection type multi-view-based system is realized with a curved anisotropic diffuser. High resolution see-through 3D display can be realized with the proposed methods. They can be used in various applications with the two multi-projection methods. In order to show the augmented reality features, real objects and virtual 3D images are presented at the same time in the experimental setup.

Holographic display for see-through augmented reality using mirror-lens holographic optical element

A holographic display system for realizing a three-dimensional optical see-through augmented reality (AR) is proposed. A multi-functional holographic optical element (HOE), which simultaneously performs the optical functions of a mirror and a lens, is adopted in the system. In the proposed method, a mirror that is used to guide the light source into a reflection type spatial light modulator (SLM) and a lens that functions as Fourier transforming optics are recorded on a single holographic recording material by utilizing an angular multiplexing technique of volume hologram. The HOE is transparent and performs the optical functions just for Bragg matched condition. Therefore, the real-world scenes that are usually distorted by a Fourier lens or an SLM in the conventional holographic display can be observed without visual disturbance by using the proposed mirror-lens HOE (MLHOE). Furthermore, to achieve an optimized optical recording condition of the MLHOE, the optical characteristics of the holographic material are measured. The proposed holographic AR display system is verified experimentally.

See-through integral imaging display with background occlusion capability

Background occlusion capability is provided to a flat-panel-type integral imaging display that has a transparent screen and can superimpose three-dimensional (3D) images on real scenes. A symmetric integral imaging system that comprises two integral imaging systems connected by an additional lens array, is proposed. Elementary images are displayed on a flat-panel display on one integral imaging system to generate 3D images, and the occlusion mask patterns are displayed on a flat-panel display on the other integral imaging system to selectively block rays from background scenes. The proposed system was constructed and experimentally verified.

Dual-view integral imaging 3D display by using orthogonal polarizer array and polarization switcher

In this paper, a dual-view integral imaging three-dimensional (3D) display consisting of a display panel, two orthogonal polarizer arrays, a polarization switcher, and a micro-lens array is proposed. Two elemental image arrays for two different 3D images are presented by the display panel alternately, and the polarization switcher controls the polarization direction of the light rays synchronously. The two elemental image arrays are modulated by their corresponding and neighboring micro-lenses of the micro-lens array, and reconstruct two different 3D images in viewing zones 1 and 2, respectively. A prototype of the dual-view II 3D display is developed, and it has good performances.