Large Eyebox Research Articles

Waveguide holography for 3D augmented reality glasses

Near-eye displays are fundamental technology in the next generation computing platforms for augmented reality and virtual reality. However, there are remaining challenges to deliver immersive and comfortable visual experiences to users, such as compact form factor, solving vergence-accommodation conflict, and achieving a high resolution with a large eyebox. Here we show a compact holographic near-eye display concept that combines the advantages of waveguide displays and holographic displays to overcome the challenges towards true 3D holographic augmented reality glasses. By modeling the coherent light interactions and propagation via the waveguide combiner, we demonstrate controlling the output wavefront using a spatial light modulator located at the input coupler side. The proposed method enables 3D holographic displays via exit-pupil expanding waveguide combiners, providing a large software-steerable eyebox. It also offers additional advantages such as resolution enhancement capability by suppressing phase discontinuities caused by pupil replication process. We build prototypes to verify the concept with experimental results and conclude the paper with discussion.

Inkjet-printed freeform gradient refractive index Alvarez-Lohmann optics for vision correction in respiratory masks

Inkjet-print additive manufactured freeform gradient refractive index representations of an Alvarez-Lohmann lens were developed and optimized for use in vision-correction inserts for respiratory masks. A series of planar 30-mm by 20-mm Alvarez-Lohmann lens pair were printed and characterized. Select lens pairs were mounted with printed mechanical lens mounts and translation guides optimized for vision correction. Metrology showed accurate reproduction of the cubic refractive phase functions. Tests matching simulated performance showed a large diopter adjustment over a large eyebox and a wide gaze angle. The printed optics were environmentally tested and then mounted in a respiratory mask and demonstrated with glove-accessible control electronics. The performance demonstrates the benefits of using printed three-dimensional freeform gradient index optics for implementing complex refractive optical functions for challenging applications including artificial and virtual reality systems.

Eyebox enlargement in holographic AR glasses.

Despite the high output characteristics of holographic optical elements (HOEs), there are still no affordable holographic AR glasses that combine qualities such as a wide field of view (FOV) and a large eyebox (EB). In this study, we propose an architecture for holographic augmented reality glasses that covers both needs. Our solution is based on the combination of an axial HOE with a directional holographic diffuser (DHD) illuminated by a projector. A transparent-type DHD redirects the light from the projector, increasing the angular aperture of the image beams and providing a large EB. A reflection-type axial HOE redirects the light, transforming the spherical beams into parallel ones and providing a wide FOV for the system. The main feature of our system is the coincidence of the DHD position with the planar intermediate image of the axial HOE. This unique condition makes the system free of off-axial aberrations and ensures high output characteristics. The proposed system has a horizontal FOV of 60deg and an EB width of 10mm. We used modeling and a prototype to prove our investigations.

Multiplane holographic augmented reality head-up display with a real-virtual dual mode and large eyebox.

We propose a multiplane augmented reality (AR) head-up display (HUD) with a real-virtual dual mode based on holographic optical elements (HOEs). The picture generation unit (PGU) is only a single free-focus projector, and the optical combiner includes a HOE lens (HOEL) for long-distance virtual image display and a HOE diffuser (HOED) for in-plane real image display. A HOED with directional scattering characteristics in the real image mode can significantly increase the size of the eyebox (EB) without increasing the size of the HOE, and a HOEL with a flexible design for the optical focal length in the virtual image mode can be used to achieve a different depth of the AR display. The proposed AR HUD system, which has a compact structure and offers high light transmittance, high energy usage, a multiplane display, and a large EB, is expected to be widely used in the future.

Neural compression for hologram images and videos.

Holographic near-eye displays can deliver high-quality three-dimensional (3D) imagery with focus cues. However, the content resolution required to simultaneously support a wide field of view and a sufficiently large eyebox is enormous. The consequent data storage and streaming overheads pose a big challenge for practical virtual and augmented reality (VR/AR) applications. We present a deep-learning-based method for efficiently compressing complex-valued hologram images and videos. We demonstrate superior performance over the conventional image and video codecs.

Design and implementation of an optical see-through near-eye display combining Maxwellian-view and light-field methods

We have proposed an optical see-through near-eye display method, which combines Maxwellian-view and light-field displays by a space-division multiplexing method. Recent works have reported that a Maxwellian-view display and a light-field near-eye display are both effective methods to alleviate the vergence–accommodation conflict (VAC). The proposed display method combines the advantages of both the Maxwellian-view and light-field displays; the system can provide an accommodation-free virtual image as a background with a large field of view (FOV, 31.5∘), and a high-resolution full-depth-cue foveal image with a small FOV (10.1°) and a large eye-box. To verify the method, a prototype has been developed to superimpose vivid virtual images onto the real environment.

Holographic pancake optics for thin and lightweight optical see-through augmented reality.

Holographic pancake optics have been designed and fabricated in eyewear display optics literature dating back to 1985, however, a see-through pancake optic solution has not been demonstrated to date. The key contribution here is the first full-color volume holographic pancake optic in an optical see-through configuration for applications in mobile augmented reality. Specifically, the full-color volume holographic pancake is combined with a flat lightguide in order to achieve the optical see-through property. The fabricated hardware optics has a measured field of view of 29 degrees (horizontal) by 12 degrees (vertical) and a measured large eyebox that allows a ±10 mm horizontal motion and ∼±3 mm vertical motion for a 4 mm diameter pupil. The measured modulation transfer function (average orientation) is 10% contrast at 10 lp/deg. Three holograms were characterized with respect to their diffraction efficiency, angular bandwidth, focal length, haze, and thickness parameters. The phase function in the reflection mode hologram implements a spherical mirror that has a relatively simple recording geometry.

42.1: Invited Paper: Design Considerations for Near‐eye Displays using a Holographic Display Method

Introducing holographic display methods into near‐eye displays is currently a hot topic to solve vergence accommodation conflict. Due to the etendue conservation, it is hard to achieve a near‐eye display with both a large field of view and a large eye box. Design considerations have been discussed, and these information provide give inspiration to the following researches on both near‐eye displays and holographic devices.

P‐23: Image Adaptation to Human Vision (Eyeglasses Free): Full Visual‐Corrected Function in Light‐Field Near‐to‐Eye Displays

Many design factors are highly demanded in developing optimum near‐to‐eye display, such as higher resolution and wider FOV for vivid image quality, embedded vision correction for visual comfort, and light, compact and large eye box size for wearing comfort and stylish. Several optical approaches could achieve the visual correction, such as time‐multiplexed light field, space‐multiplexed light field, holographic display, multi‐focal planes, etc. In this study, based on the space‐multiplexed light field, the authors propose a special method that can adapt the variable pupil distance and deliver several virtual image planes at the same time by an algorithm of image processing. LFNEDs utilize this method which can adapt to the diversified facial shape and avoid wearing prescription glasses in using AR/VR glasses, no matter users have myopia, hyperopia, and astigmatism.

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.

Breaking the field-of-view limit in augmented reality with a scanning waveguide display

The ultimate augmented reality (AR) should be a glass-type see-through display with uncompromised optical performances. The major technical challenge of present AR display systems is to fulfill wide field-of-view (FOV) and large eye box simultaneously for a comfortable visual experience. Here, we propose a novel scanning waveguide display to break the theoretical limit of present waveguide displays while maintaining a large eye box. The core component is an off-axis reflective lens array, which is fabricated by an innovative chiral liquid crystal polarization holography method. The lens array consists of 8 × 15 lenslets whose pitch length is 2 mm and f-number is 0.41 at 639 nm. Such a scanning waveguide display dramatically extends the diagonal FOV from the state-of-the-art 52° (HoloLens 2) to 100°. These approaches not only significantly advance the optical design of present AR display systems but also open new applications to a broad range of optical systems, including high-precision imaging, sensing, and advanced photonic devices.

Near-eye varifocal augmented reality display using see-through screens

We present a new optical design for see-through near-eye displays that is simple, compact, varifocal, and provides a wide field of view with clear peripheral vision and large eyebox. Key to this effort is a novel see-through rear-projection screen. We project an image to the see-through screen using an off-axis path, which is then relayed to the user's eyes through an on-axis partially-reflective magnifying surface. Converting the off-axis path to a compact on-axis imaging path simplifies the optical design. We establish fundamental trade-offs between the quantitative parameters of resolution, field of view, and the form-factor of our design. We demonstrate a wearable binocular near-eye display using off-the-shelf projection displays, custom-designed see-through spherical concave mirrors, and see-through screen designs using either custom holographic optical elements or polarization-selective diffusers.

50-3: A Full Windshield Head-Up Display using Simulated Collimation

A 3D Stereoscopic Head-Up Display (HUD) using direct projection on a transparent screen is presented. Symbol incrustation on the real world (Augmented Reality) is performed by using simulated collimation offering a large eye-box, in excess of conventional HUD. Experimentation performed on this system shows that Accommodation-Vergence issues, occurring when looking outside while reading on a foreground screen can be acceptable for a screen distance greater than 60 cm, and comfortable from 1.7 m.