Waveguide Holography: Towards True 3D Holographic Glasses

We present a novel near-eye display concept which consists of a waveguide combiner, a spatial light modulator, and a laser light source. The proposed system can display true 3D holographic images through see-through pupil-replicating waveguide combiner as well as providing a large eye-box. By modeling the coherent light interaction inside of the waveguide combiner, we demonstrate that the output wavefront from the waveguide can be controlled by modulating the wavefront of input light using a spatial light modulator. This new possibility allows combining a holographic display, which is considered as the ultimate 3D display technology, with the state-of-the-art pupil replicating waveguides, enabling the path towards true 3D holographic augmented reality glasses

Curved holographic optical elements and applications for curved see-through displays

Holographic optical elements (HOEs) have been used as important tools for implementing augmented reality (AR) and see-through displays because they are transparent and thin. Moreover, as HOEs usually come in the shape of a thin film, they can be bent, used for coating, or attached to curved surfaces. While they can be used to implement curved AR displays, however, the applications of the curved HOE have not been sufficiently studied. In this paper, an analysis method for curved/bent HOEs using the coupled-wave theory and the numerical ray tracing method is introduced. Using this method, the influence of the surface curvature on the optical characteristics of HOEs, including the aberration and diffraction efficiency, was analyzed. Also presented herein is a method of designing the optimal curvature that can reduce the aberration. Curved HOEs can be applied to see-through displays such as head-mounted displays (HMDs), head-up displays (HUDs), or transparent screens. They can be used to expand the field of view (FOV) and to reduce the form factor. The proposed analysis method provides a useful guideline for designing practical curved see-through displays

Holographic optical elements for head-up display and near-eye display

As the market interest in augmented reality (AR) displays increases, research on compact and lightweight optical system design using holographic optical elements (HOE) is also actively conducted. HOE plays an essential role in augmented reality optics as an image combiner that provides users with combined real and virtual scenes due to its advantages of transparency and high selectivity of light. However, an optical system using HOE has an issue in which aberrations such as astigmatism occur. Compensating the aberrations and securing wide eye-box and viewing angle to provide users with a convenient and immersive viewing experience remain a challenge for AR optics using HOEs. This paper presents studies conducted to correct aberrations, expand the eye-box and broaden the viewing angle for the AR optical systems using HOEs, such as head-up displays (HUDs) and near-eye displays. In the case of the HUD, we propose a method to correct the aberrations. In the proposed method, two freeform mirror shapes are designed using a commercial raytracing software to minimize the aberrations by the HOE attached to a flat windshield. Combined with the image pre-compensation, the proposed system provides aberration-free consistent images over its entire eye-box. In the case of near-eye displays, the eye-box expansion technique using multiplexed HOE is introduced.N

Key issues and technologies for AR/VR head-mounted displays

We first discuss the key factors of augmented reality (AR) and virtual reality (VR) displays. Various requirements for immersive experiences are categorized as six factors that must be considered when designing the AR/VR head-mounted displays (HMDs). These factors have a strong correlation with other factors and should maintain a moderate balance between them. Based on recent researches we second introduce various technologies for AR/VR. By comparing the pros and cons of each method, we discuss the progression of AR/VR devices that can provide more affordable HMD devices for the public.N

Ultra-high-definition holography for near-eye display

Holographic near-eye displays (NEDs) have large potential for augmented reality (AR) devices as they modulate the wavefront of light. They can provide observers with comfortable three-dimensional (3D) views with focus-cues, and little optical aberrations since the unwanted phase delay added by optical systems can be compensated by wavefront modulation. With the advent of ultra-high-definition (UHD) spatial light modulator (SLM), a degree of freedom in designing holographic NEDs has been further expanded. Here, we introduce several holographic NEDs using UHD SLM. The holographic NED using an HOE is introduced for the optical see-through display. Besides, the holographic NED with enlarged eye-box using point-source array and eye-tracking method will be presented. Finally, the holographic NED of which optical aberration is compensated by Zernike's polynomial adaptation will be introduced.N

Enhancement of Depth Range in LED-based Holographic Near-Eye Display Using Focus Tunable Device

Light emitting diode (LED) has been a prominent component for illumination source of holographic displays. It can replace laser in that it alleviates speckle noise in reconstructed hologram and is regarded as a safer source. However, LED-based holographic displays can reconstruct an image in a limited depth range due to partially coherent characteristic of LED itself. In this paper, we propose a prototype of LED-based holographic near-eye display with focus tunable lens to expand the depth range. The feasibility of the system is supported by several experimental results.N