Accommodation-Free Head Mounted Display with Comfortable 3D Perception and an Enlarged Eye-box.

An accommodation-free displays, also known as Maxwellian displays, keep the displayed image sharp regardless of the viewer's focal distance. However, they typically suffer from a small eye-box and limited effective field of view (FOV) which requires careful alignment before a viewer can see the image. This 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 definition, low colour aberration 3D augmented reality (AR) images with an FOV of 36°. The 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 unaffected 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 conflict (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 effects commonly associated with conventional stereoscopic 3D or HMD displays, even for all day use

Training procedural tasks through the manipulation of multimedia in dynamic visual displays with computer-based technologies

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The use of automated refractors in the military

The use of automated refractors in the militar

The ocular surface and blinking in children

Background: Ocular surface characteristics in children have not been as well investigated as in adults. Children’s digital device usage is rapidly increasing, and smartphones are the most commonly used device. The ocular surface impacts are unknown in children. In adults, use of digital devices induces ocular symptoms, adversely impacts blinking, and disrupts ocular surface homeostasis. Although blinking is integral to a healthy ocular surface, this is yet to be characterised in children, including the effects of digital devices. This thesis aims to characterise the ocular surface of children including blinking and to examine the impact of smartphone use on ocular surface homeostasis in children. Methods: The literature on ocular surface (symptoms, clinical indices, tear film function, blinking) of healthy children was reviewed and a meta-analysis of tear film stability and tear secretion was conducted. Cross-sectional studies of healthy school-aged children were conducted to examine the utility of commonly used adult-validated dry eye symptom questionnaires (SANDE, OSDI, NRS, OCI, DEQ-5, IOSS), and to characterise ocular surface clinical indices. This included blinking which was measured in situ using a novel eye tracking headset (Pupil Labs GmbH, Germany). The impact of one hour smartphone gaming on the ocular surface (including symptoms and blink parameters) of this paediatric population was examined with an intervention study. Blinking was also examined in situ under different conditions and tasks (reading from hard copy and on digital devices, conversation, walking) using the eye tracking headset in healthy adults. Repeatability of blink measurements (blink rate and interblink interval) in adults using the eye tracking headset was determined. Results: Ocular symptoms, tear film function and blinking were sparsely reported in children. The pooled mean by tear stability measurement methods in the meta-analysis were higher than previously reported in healthy adults while the pooled mean for tear secretion by methods were within the expected normal range for adults. Six existing dry eye questionnaires could be successfully used in paediatric eye care, and their repeatability was mostly comparable to that reported previously in adults. More time and assistance were at times required for younger children and specific terms such as ‘gritty’ and ‘foreign body sensation’ were not always well understood by younger children. The DEQ-5 and IOSS are recommended for use in younger age children. Blinking was associated with greater tear volume and worse meibomian gland expressibility but not digital device use, age, sex, or symptoms in children. One hour smartphone gaming led to increased symptoms of dryness, discomfort, and tiredness but did not impact tear film function. Blinking was rapidly reduced by a third within the first minute of gaming and this effect remained unchanged throughout one hour of gaming (p<0.001). Blink rate was consistently slower during all reading tasks compared to conversation (p≤0.002) and walking (p≤0.03), irrespective of task complexity, screen brightness, working distance or device used. Blinking could be reliably measured using a wearable eye tracking headset; the coefficient of repeatability for blink rate was ±12.4 blinks/min. Conclusions: This study established that existing dry eye questionnaires can be reliably used in children to examine the impact of challenges such as digital device use. An eye tracking headset reliably measured blink rate in situ in adults and detected differences in blinking during various real-life tasks. It was successfully used in children to measure blinking in situ showing an immediate and sustained slowing of blinking, evident after up to one hour of smartphone gaming. An hour of smartphone gaming worsened ocular comfort in children but did not appear to disturb the tear film. Given the ubiquitous use of smartphones by children, future work should examine whether effects reported herein persist or get worse over the longer term, potentially causing cumulative damage to the ocular surface. Blink amplitude and relationships with ocular surface clinical indices and digital device use may be explored using the methods established in this study

SMART WEARABLES: ADVANCING MYOPIA RESEARCH THROUGH QUANTIFICATION OF THE VISUAL ENVIRONMENT

Myopia development has been attributed to eyeball elongation, but its driving force is not fully understood. Previous research suggests lack of time spent outdoors with exposure to high light levels or time spent on near-work as potential environmental risk factors. Although light levels are quantifiable with wearables, near-work relies solely on questionnaires for data collection and there remains a risk of subjective bias. Studies spanning decades identified that eye growth is optically guided. This proposal received further support from recent findings of larger changes in the thickness of the eye’s choroidal layer after short-term optical interventions compared with daily eye-length changes attributed to myopia. Most of these studies used a monocular optical appliance to manipulate potential myogenic factors, which may introduce confounders by disrupting the natural functionality of the visual system. This thesis reports on improvements in systems for characterising the visual dioptric space and its application to myopia studies. Understanding the driving forces of myopia will prevent related vision loss. Study I: An eye-tracker was developed and validated that incorporated time-of-flight (ToF) technology to obtain spatial information of the wearer’s field of view. By matching gaze data with point cloud data, the distance to the point of regard (DtPoR) is determined. Result: DtPoR can be measured continuously with clinically relevant accuracy to estimate near-work objectively. Study II: Near-work was measured with diary entries and compared with DtPoR estimations. Diversity of the dioptric landscape presented to the retina was assessed during near-work. Results: Objective and subjective measures of near-work were not found to highly correlate. Ecologically valid dioptric landscape during near-work decreases by up to -1.5 D towards the periphery of a 50˚ visual field. Study III: Choroid thickness changes were evaluated after exposure (approximately 30min) to a controlled, dioptrically diverse landscape with a global, sensitivity enhanced model. Result: No choroid thickness changes were found within the measuring field of approximately 45˚. Discussion The developed device could support future research to resolve disagreement between objective and subjective data of near-work and contribute to a better understanding of the ecological valid dioptric landscape. Proposed choroid layer thickness model might support short-term myopia-control research

IMI – Clinical Management Guidelines Report

Best practice clinical guidelines for myopia control involve an understanding of the epidemiology of myopia, risk factors, visual environment interventions, and optical and pharmacologic treatments, as well as skills to translate the risks and benefits of a given myopia control treatment into lay language for both the patient and their parent or caregiver. This report details evidence-based best practice management of the pre-, stable, and the progressing myope, including risk factor identification, examination, selection of treatment strategies, and guidelines for ongoing management. Practitioner considerations such as informed consent, prescribing off-label treatment, and guides for patient and parent communication are detailed. The future research directions of myopia interventions and treatments are discussed, along with the provision of clinical references, resources, and recommendations for continuing professional education in this growing area of clinical practice

The adaptive elements of disparity vergence: Dynamics and directional asymmetries.

Vergence eye movements alter the angle between the two visual axes, creating changes in binocular fixation distance. They are primarily stimulated by retinal image disparities, but can also be driven by inputs from ocular accommodation (accommodative-vergence) and perceived proximity (size) changes. Because of these diverse and complex sensory inputs, the neuro-motor substrates that sub-serve vergence control possess robust adaptive capabilities to manage the interactions with other oculomotor systems (accommodation). This adaptive plasticity in vergence allows for a high degree of precision in binocular alignment to be maintained throughout life in the face of constantly changing environmental demands. The precise alignment of each eyes’ fovea is a fundamental requirement for stereopsis and the perception of depth in 3 dimensions. In a significant portion of the ophthalmic clinical population, the adaptive capacities of vergence are reduced or dysfunctional, leading to difficulties focusing clearly and comfortably at near distances such as books, computer screens and other hand-held devices. Furthermore, new wearable technologies such as virtual and augmented reality increase the demand on the adaptive capacities of vergence by drastically altering the congruency of the sensory inputs to vergence. Currently, our understanding of the mechanisms that underlie this adaptive control and their behavioral limits are limited. This knowledge gap has led to conjecture in the literature regarding proper rehabilitative therapies for clinical dysfunctions of vergence control and in the optimal environmental design parameters that should provide comfortable and compelling user experiences in wearable technologies like VR and AR. The inward (convergence) and the outward (divergence) turning of the eyes in response to retinal disparities are controlled by two separate systems and demonstrate significant directional asymmetries in their reflexive response properties. In general, reflexive divergence responses tend to be slower and longer than their convergence counter-parts. It is unclear whether the adaptive mechanisms are influence by these reflexive asymmetries. It is also unknown whether similar directional differences exist in the different adaptive capacities possessed by vergence. The purpose of the following dissertation was to characterize the effects of stimulus direction on the adaptive behavior of disparity-driven vergence eye movements with an end goal aimed at improving rehabilitation therapies for clinical populations with vergence dysfunction and providing valuable insight for the design and future development of wearable technologies like virtual and augmented reality environments. A series of 4 experiments were conducted in order to characterize the effect of stimulus direction and the physiological limits of the adaptive behavior within the two-main disparity vergence motor controllers, fast-phasic and slow-tonic. In each study, binocular viewing conditions were dichoptic, which allowed retinal disparity to be altered while the accommodative and proximity cues were clamped. Such designs create incongruencies between the sensory stimuli to vergence and thus elicits a much stronger adaptive response for observation than would normally occur when viewing real-world objects. Eye movements were monitored binocularly with a video-based infrared eye-tracking system at 250Hz using the head-mounted EyeLink2 system. A total of 14 adult binocularly normal controls and 10 adult participants with dysfunctional convergence control (convergence insufficiency) were recruited for the main studies. 4 controls completed the first two studies, 10 additional controls completed the third and fourth studies while the 10 participants with convergence insufficiency completed the fourth study. The results of this dissertation make four significant contributions to the current scientific literature pertaining to vergence oculomotor control and plasticity. 1) Both fast-phasic and slow-tonic vergence controllers display directional asymmetries in their general behavior and adaptive responses. 2) Reflexive fast-phasic divergence responses in controls tend to saturate at lower disparity-stimulus amplitudes than convergence under specific viewing conditions. This saturation limit is defined when the primary vergence response amplitude and peak velocity are unable to increase when the stimulus amplitude increases, suggesting saturation in neural recruitment and firing rates. Saturated reflexive vergence responses instead recruit an increased response duration (neural firing time) in order to produce larger amplitude responses. 3) Saturation in the fast-phasic divergence mechanism leads to saturation in the speed slow-tonic vergence adaptation. The function of the underlying reflexive fast-phasic response was found to be associated with the adaptive behavior of the slow-tonic mechanism, suggesting one drives the other, which is consistent with model predictions. 4) Convergence responses from individuals with convergence insufficiency are generally indistinguishable from that of the slower divergence responses of controls. These impaired convergence responses lead to impairment of the adaptive mechanisms underlying each fast-phasic and slow-tonic controller. Clinically, these results suggest that rehabilitative therapies for vergence control dysfunctions should primarily target the performance of the fast-phasic reflexive vergence mechanism. This work also suggests that improvements in adaptive capacities of vergence, known to be the mechanism under-pinning symptom reduction in these patient populations, should follow when reflexive fast-phasic responses are normalized. In terms of wearable technology, the generally limited adaptive plasticity demonstrated within divergence responses when compared to convergence in controls, provides a behavioral explanation for the increase in symptoms of discomfort when viewing distant objects in virtual reality environments. Future investigations should seek to determine the effects of other disparity stimulus parameters, such as contrast and spatial frequency on the adaptive behaviors of both fast-phasic and slow-tonic mechanism. Finally, the cerebellum is known to be central to the adaptation of almost every motor system and yet its role in the different adaptive capacities of disparity-vergence control remain unclear. Future studies should aim to characterize these neural structures role in the different vergence oculomotor adaptive mechanisms described here

비등방성 광학 소자를 이용한 광 시야각 근안 디스플레이

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2019. 2. 이병호.Near-eye display is considered as a promising display technique to realize augmented reality by virtue of its high sense of immersion and user-friendly interface. Among the important performances of near-eye display, a field of view is the most crucial factor for providing a seamless and immersive experience for augmented reality. In this dissertation, a transmissive eyepiece is devised instead of a conventional reflective eyepiece and it is discussed how to widen the field of view without loss of additional system performance. In order to realize the transmissive eyepiece, the eyepiece should operate lens to virtual information and glass to real-world scene. Polarization multiplexing technique is used to implement the multi-functional optical element, and anisotropic optical elements are used as material for multi-functional optical element. To demonstrate the proposed idea, an index-matched anisotropic crystal lens has been presented that reacts differently depending on polarization. With the combination of isotropic material and anisotropic crystal, the index-matched anisotropic crystal lens can be the transmissive eyepiece and achieve the large field of view. Despite the large field of view by the index-matched anisotropic crystal lens, many problems including form factor still remain to be solved. In order to overcome the limitations of conventional optics, a metasurface is adopted to the augmented reality application. With a stunning optical performance of the metasurface, a see-through metasurface lens is proposed and designed for implementing wide field of view near-eye display. The proposed novel eyepieces are expected to be an initiative study not only improving the specification of the existing near-eye display but opening the way for a next generation near-eye display.근안 디스플레이는 높은 몰입감과 사용자 친화적인 인터페이스로 인해 증강 현실을 구현하는 가장 효과적인 기술로 최근 활발한 연구가 계속되고 있다. 이러한 근안 디스플레이의 중요한 성능 중 시야각은 매끄럽고 몰입감 있는 경험을 사용자에게 전해줌으로써 가장 중요한 광학적 평가지표 중에 하나이다. 본 논문에서는 기존의 반사형 아이피스 (eyepiece) 를 대신하는 투과형 아이피스를 제안한다. 이러한 투과형 아이피스를 구현하기 위해서는 외부 정보에 대해서는 투명한 유리와 같이 투과시키며, 동시에 가상 정보는 렌즈로 작동하여 먼 거리에 띄울 수 있는 광학소자를 개발하여야 한다. 이러한 투과형 아이피스를 구현하기 위해서 편광에 따라 다르게 반응하는 굴절률 정합 이방성 결정 렌즈 (index-matched anisotropic crystal lens) 를 제안하였다. 이방성 결정 구조 (anisotropic crystal)로 이루어진 렌즈와 이를 둘러싼 등방성 물질 (isotropic crytal) 로 이루어진 굴절률 정합 이방성 결정 렌즈는 편광에 따라 다르게 작동한다. 이러한 투과형 아이피스는 기존의 근안 디스플레이에 비해 넓은 시야각을 제공할 수 있지만 이방성 결정 구조의 낮은 굴절률 차이로 인해 시스템의 크기가 커지는 단점을 가지고 있다. 본 논문에서는 이러한 단점을 개선하기 위해 메타 표면을 증강 현실 디스플레이 분야에 적용하였다. 메타 표면의 기존 광학 소자를 능가하는 놀라운 광학 성능을 이용하여 넓은 시야각을 가지는 근안 디스플레이를 구현하기 위해 투명 메타 렌즈를 제안하였다. 편광에 따라 다르게 반응하는 투명 메타렌즈는 넓은 시야각과 경량화 시스템 구현이 가능하며 이를 입증하기 위해 투명 메타렌즈의 설계 방법 뿐 아니라 실제 구현을 통한 가능성을 입증하였다. 이러한 새로운 아이피스에 대한 개념은 기존의 근안 디스플레이의 사양 개선에 유용하게 사용될 뿐 아니라 차세대 근안 디스플레이를 위한 선도적인 역할을 할 것으로 기대된다.Abstract Contents List of Tables List of Figures Near-eye displays with wide field of view using anisotropic optical elements Chapter 1 Introduction 1.1 Near-eye displays for augmented reality 1.2 Optical performances of near-eye display 1.3 State-of-the-arts of near-eye display 1.4 Motivation and contribution of this dissertation Chapter 2 Transmissive eyepiece for wide field of view near-eye display 2.1 Transmissive eyepiece for near-eye display Chapter 3 Near-eye display using index-matched anisotropic crystal lens 3.1 Introduction 3.2 Index-matched anisotropic crystal lens 3.2.1 Principle of the index-matched anisotropic crystal lens 3.2.2 Aberration analysis of index-matched anisotropic crystal lens 3.2.3 Implementation 3.3 Near-eye displays using index-matched anisotropic crystal lens 3.3.1 Near-eye display using index-matched anisotropic crystal lens 3.3.2 Flat panel type near-eye display using IMACL 3.3.3 Polarization property of transparent screen 3.4 Conclusion Chapter 4 Near-eye display using metasurface lens 4.1 Introduction 4.2 See-through metasurface lens 4.2.1 Metasurface lens 4.3 Full-color near-eye display using metasurface lens 4.3.1 Full-color near-eye display using metasurface lens 4.3.2 Holographic near-eye display using metasurface lens for aberration compensation 4.4 Conclusion Chapter 5 Conclusion Bibliography AppendixDocto