Research Article Accommodation-Free Head Mounted Display with Comfortable 3D Perception and an Enlarged Eye-box Pawan K. Shrestha 1 , Matt J. Pryn 1 , Jia Jia 1 , Jhen-Si Chen 1 , Hector Navarro Fructuoso 2 , Atanas Boev 2 , Qing Zhang 2 , and Daping Chu 1 1 Centre for Photonic Devices and Sensors, University of Cambridge, 9 JJ Tomson Avenue, Cambridge CB3 0FA, UK 2 Huawei Technologies Duesseldorf GmbH, European Research Centre, Riesstrasse 25, M¨ unchen 80992, Germany Correspondence should be addressed to Daping Chu; dpc31@cam.ac.uk Received 25 May 2019; Accepted 15 July 2019; Published 25 August 2019 Copyright © 2019 Pawan K. Shrestha et al. Exclusive Licensee Science and Technology Review Publishing House. Distributed under a Creative Commons Attribution License (CC BY 4.0). An accommodation-free displays, also known as Maxwellian displays, keep the displayed image sharp regardless of the viewer’s focal distance. However, they typically sufer from a small eye-box and limited efective feld of view (FOV) which requires careful alignment before a viewer can see the image. Tis paper presents a high-quality accommodation-free head mounted display (aHMD) based on pixel beam scanning for direct image forming on retina. It has an enlarged eye-box and FOV for easy viewing by replicating the viewing points with an array of beam splitters. A prototype aHMD is built using this concept, which shows high defnition, low colour aberration 3D augmented reality (AR) images with an FOV of 36 ∘ . Te advantage of the proposed design over other head mounted display (HMD) architectures is that, due to the narrow, collimated pixel beams, the high image quality is unafected by changes in eye accommodation, and the approach to enlarge the eye-box is scalable. Most importantly, such an aHMD can deliver realistic three-dimensional (3D) viewing perception with no vergence-accommodation confict (VAC). It is found that viewing the accommodation-free 3D images with the aHMD presented in this work is comfortable for viewers and does not cause the nausea or eyestrain side efects commonly associated with conventional stereoscopic 3D or HMD displays, even for all day use. 1. Introduction Wearable displays that seamlessly blend the real and vir- tual world have been topics of research, in both academia and industry for decades. Recent high-profle products launched by large companies such as Google, Magic Leap, and Microsof have sparked further consumer and industry interest. Augmented reality (AR) head mounted displays (HMD) are expected to have a disruptive impact on a diverse range of markets, including education, hospitality, construction, sports, and the military [1, 2]. A stereoscopic 3D efect can be created by the HMD through binocular disparity, where the image displayed to the lef and right eyes is varied slightly. However, this leads to 3D perception problems such as vergence-accommodation confict (VAC) where the ocular focal distance conficts with the intersection distance of the lef and right eyes. VAC causes nausea, dizziness, eyestrain, and inaccurate depth perception. Tis can be avoided by simulating the accommodation cue as well as binocular disparity to eliminate the conficting depth cues. Holographic displays perfectly reconstruct the wavefront of the 3D image [3], but the image quality of these systems is currently poor, with problems such as speckle, system complexity, and a currently unfeasible spatial-temporal band- width required for video rate 3D images. Te viewing angle of holography based 3D displays also is fundamentally limited by the pixel size of the display, with the state of art around 3.7 m for a viewing angle of ±4.9 ∘ [4]. Accommodation correct displays can also be created using a tunable lens [5–8] to temporally adjust the focus of the display to match the image content or by dividing the image onto a discrete set of focal planes [9–12]. However, the spatial temporal information bandwidth required by these systems is still very high, and the optics bulky. Alternatively, the accommodation cue may be completely removed, ensuring that there can be no VAC. Such a display is in focus no matter where the user’s eyes are converging, and thus the accommodation information from the display always matches the user’s vergence cue. A similar concept was frst discussed by Maxwell in 1860 [13], and this type AAAS Research Volume 2019, Article ID 9273723, 9 pages https://doi.org/10.34133/2019/9273723