This PDF file contains the front matter associated with SPIE Proceedings Volume 12913, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

This study introduces a Maxwellian view system for AR near-eye displays using LBS (Laser Beam Scanning) light engine and TiO² metasurface waveguide. It overcomes accommodation-vergence conflict, offering benefits like depth of field, high definition, compact structure, wide FOV, high brightness, low power consumption, high contrast, and high resolution. The research utilizes a lightweight TiO2 metasurface to address bulkiness while ensuring long-term wear comfort. By combining LBS with the metasurface, collimated light within a 40-degree FOV is efficiently redirected to the pupils, resulting in clear retinal imaging. This study considers the required deflection angles of light rays for nine different screen positions in the LBS system when incident on the metasurface., achieving a maximum correction angle of 60 degrees through metasurface optimization. The overall design successfully demonstrates an FOV size of 40 x 22, encompassing LBS optics and metasurface.

Market penetration of automotive head-up displays (HUD) is increasing and extending from higher-end models to midrange and even compact cars. New HUD use cases will be motivated by autonomous driving as well as improved HUD abilities. Holographic 3D (H3D) HUD will contribute to further improve the usability and attractiveness, specifically by presenting images with a full consistency of all depth cues. Based on results from H3D-HUD implementations, it is explained how H3D images are created and how viewers benefit from the unique 3D solution that eliminates ambiguity of the presented information and improves safety by properly overlaying virtual 3D objects with the real world. The difference between possible SLM options is explained, including references to ongoing development of high-resolution phase-modulating micro-mirror-based SLM (micro mirror arrays, MMA). It is compared how use of MMA vs. LCoS can improve selected features and the user experience. Ongoing development of MMA in a consortium of expert companies and institutions and results of already manufactured MMA are presented.

Offering an ultrathin formfactor and lightweight, diffractive liquid-crystal optics is a promising tool to design a more compact VR display system. However, the severe chromatic aberrations of this diffractive elements need to be solved before further practical applications. Here, we come up with an achromatic system consists of three diffractive liquid-crystal components to address this longstanding color issue. The phase and spectral response of each element are specifically designed to manipulate the polarization states of light and compensate the chromatic aberrations. A significant improvement in color performances has been demonstrated with both our simulations and experiments. Potential applications for metaverse, spatial computing, and digital twins that have found widespread applications in smart tourism, smart education, smart healthcare, smart manufacturing, and smart construction are foreseeable.

Pixelligent’s high-refractive index PixNIL® nanocomposite formulations incorporating ZrO₂, TiO₂, or TiO₂-ZrO₂ coreshell nanoparticles showcase robust nanoimprinting capabilities for surface-relief gratings tailored for extended reality (XR) applications. Thin films exhibit refractive indices ranging from 1.7 to 2.0 @ 589 nm while delivering more than 95% transmission and less than 0.1% haze, attributed to the excellent control over particle size, shape, and surface of the proprietary PixClear® and PixCor™ nanocrystals. While the optical properties of Pixelligent’s nanocrystal dispersions and formulations have been widely reported, less attention has been given to their excellent processability. For XR devices to realize mass market adoption, high yield, robust manufacturing processing, and excellent device reliability must be achieved. In this paper the processability of Pixelligent’s already easy-to-use formulations is reported. PixNIL® ST13A provides a broad soft-bake process window for thin films with a thickness of less than 300nm. Furthermore, PixNIL® formulations extend the usable lifetime of working stamps to over 25 imprints. This paper presents a thorough evaluation of the novel nanoimprint formulation, ST13A, demonstrating significant advancements and introducing a new approach to address key challenges in nanoimprint technologies. The analysis encompasses crucial aspects of the nanoimprinting process, including replication fidelity and soft-bake process window.

This paper introduces a mixed reality near-eye display configuration designed to concurrently achieve a wide field of view (FoV) and dual side display. The proposed system incorporates a dihedral corner reflector array (DCRA), a virtual image display unit, and an eye display unit. The eyepiece within the virtual image display unit is directly imaged onto the eye pupil plane by the DCRA, enabling the simultaneous realization of a wide FoV and a large eyebox. Furthermore, the DCRA projects the eye display unit toward the external environment, accurately presenting the user's eye image at its appropriate depth to the other people facing the user. The system's configuration and principles are validated through optical experiments.

Near-to-eye display (NED) has been widely used for augmented reality (AR) technology. Among them, holographic waveguide employing volume hologram as an input and output coupler is known to have a high diffraction efficiency compared to surface relief grating based image guide to accommodate field of view (FOV) and eyebox. However, in holographic waveguide, the FOV of volume hologram is seriously restricted, around 5 degrees. Here, we demonstrated to expand the FOV of volume hologram based input and output coupler from 5 degrees to 28 degrees and further even to 42 degrees based on polychromatic light source which mostly approaches the FOV limitation of glass-based waveguide, by utilizing multi-layer couplers or waveguides where each pair of them support portion of entire FOV.

We propose an advanced holographic see-through display system with 3D/2D switchable modes based on a liquid-crystalline lens array and a one-shot learning model. The liquid-crystalline lens array switches its role that act like a lens array or glass, according to the state of the electrical polarizer. When the switch of an electrical polarizer is on-state, the camera captures the image of a real-world object, and a one-shot learning model estimates the depth data from the captured image. Then, the 3D model is regenerated based on both color and depth images; and the elemental image array is generated and displayed on the microdisplay while the liquid-crystalline lens array reconstructs as a 3D image. On the other hand, when the switch of the electrical polarizer is off-state, the camera captures the image of a real-world object and is directly displayed by the microdisplay, while the liquid-crystalline lens array simply transmits it to the holographic combiner. The experimental results confirmed that the proposed system can be an advantageous way to implement the 3D/2D switchable holographic see-through system.

Pancake lens has been widely used in mixed reality (MR) due to its compact formfactor. However, using a half mirror to fold the optical path results in a tremendous optical loss. To break this optical efficiency limit while keeping a compact formfactor, we present a new folded optical system incorporating a nonreciprocal polarization rotator. In our proof-of-concept experiment using a commercial Faraday rotator, the theoretically predicted 100% efficiency is validated. Meanwhile, the ghost images can be suppressed to undetectable level if the optics are with anti-reflection coating. Our novel pancake optical system holds great potential for revolutionizing next-generation MR displays.

We present a novel design for a full-color, wide Field-of-View (FoV) Augmented Reality (AR) display, which ingeniously employs a single waveguide along with advanced polarization multiplexing reflective polarization holograms. This innovative approach surmounts the narrow FoV limitation of the present single-waveguide, full-color AR displays. The employed reflective polarization holograms are devised to operate with high efficiency across the entire visible spectrum, accommodating the incident angles required by the expanded FoV. This novel design represents a significant leap forward in AR technology, laying a foundation for immersive and vivid AR experiences.

A novel design of a video see-through super multi-view near-eye display (VST-SMV-NED) with a waveguide-type light source (WLS) and a ferroelectric liquid crystal on silicon (FLCoS) is proposed. The proposed method presents three-dimensional (3D) scenes by projecting the SMV images of deep depth of field into the eye pupil. A temporal multiplexing scheme is adopted to deliver the SMV images within an eye integration time (>30Hz), allowing flicker-free 3D image presentation. Real-world stereo images are captured by a stereo camera and transformed into SMV images. The SMV images of virtual digital images and real-world scenes are merged into augmented reality (AR) SMV scenes, creating VST type 3D AR scene. We experimentally demonstrated the feasibility of the proposed method by displaying VR SMV images on the FLCoS with the WLS illumination.

In this paper, we introduce a novel holographic foveated near-eye display, leveraging the capabilities of two reflective-type phase-modulating spatial light modulators (SLMs). Reconstructed holographic three-dimensional images are imaged with different magnifications by polarization optics, creating a peripheral and foveal holographic three-dimensional image. The core element of the proposed system is a geometric phase (GP) lens, having different optical power based on the circular polarization state of the incident light. The proposed optical system has a compact form factor because the GP lens has only a millimeter thickness and two SLMs can be placed very close to the polarizing beam splitter.

In this work we demonstrate the potential of Vertical-Aligned Spatial Light Modulators in the simulation and correction of High Order Aberrations by testing visual acuity and contrast sensitivity function in a set of healthy subjects.

Optical systems for AR/VR headsets are designed for those who do not require vision correction. The reality, however, is that around 60% of the population have an ophthalmic prescription, and users generally prefer not to wear eyeglasses under a headset. This results in the user experience being compromised optically when compared to the design intent, even when the device has been designed with additional space to allow for glasses to be worn underneath. AR/VR devices are being engineered with high resolution displays and the optics optimised to for MTF, however with very little refractive error, the user will not be able to resolve such detail. Therefore, prescription correction is required for most users to be able to experience most new VR & AR devices as per their design. Market research suggests the limitations of current VR devices suggest that the very few understand their vision or know their prescription and fewer are aware of existing prescription correction solutions. This presentation discusses the advantages and disadvantages of prescription correction solutions for dedicated and shared use cases.

Exit pupil expansion is one the main functionalities of diffractive augmented reality (AR) waveguide combiners. Generation of interference is an inherent problem in diffractive exit pupil expansion gratings. It can significantly reduce the image quality of AR waveguide displays. In this paper, we explain qualitatively how these interference effects are generated and how they appear in the output image uniformity. We also present simulation results for two solutions preserving image sharpness. The simulation results were obtained via numerical multi-variable optimization in the Dispelix Waveguide Studio.

Diffractive optical devices are essential in developing compact and thin augmented reality (AR) devices. Surface-reliefgratings (SRG) and volume-holographic gratings (VHG) are typical gratings with periodic material changes. VHG is relatively easy to manufacture, making it a popular choice for R&D teams developing AR exit pupil expander (EPE) applications. In the past, the Kogelnik algorithm was combined with the Ansys Zemax OpticStudio ray tracing engine to simulate VHG for AR applications. However, due to its more approximate calculations, the accuracy of this method is lower than that of the rigorous coupled wave analysis (RCWA) method. This study aims to investigate the theoretical differences between the Kogelnik and RCWA methods, implement their algorithms in practice, and compare the accuracy of the two methods for AR EPE applications using the Zemax OpticStudio ray tracing engine.

Most near-eye displays with one fixed focal plane suffer from the vergence-accommodation conflict (VAC) and cause visual discomfort to users. In contrast, a light field display with continuous focal planes offers the most natural and comfortable AR/VR visual experiences without VAC and holds the promise to be the ultimate near-eye 3-D display. It projects light rays onto human retina as if the light rays were emanated from a real object. This paper considers a near-eye light field display comprising a light field generator, a collimator, and a geometric waveguide as the three main components. It takes 4-D light field data in the form of an array of 2-D subview images as input and generates a light field as output. The light field generator is the device responsible for converting the light emitted from the display panel to the light representing the light field of a virtual scene. The geometric waveguide along with a collimator ensures that the light rays propagating in the waveguide are collimated. The partially reflective mirrors of the waveguide replicate the optical path to achieve exit pupil expansion (EPE) and a large eyebox. However, existing waveguide eyepieces for near-eye AR/VR displays are not designed for, and hence may not fit light field displays. In this work, we look into a geometric waveguide for light field display and find that the light fields replicated by the partially reflective mirrors cannot perfectly overlap on the user’s retina, resulting in the appearance of multiple repetitive images—a phenomenon we call “ghost artifact”. This paper delves into the cause of this artifact and develops a solution for applications that require short-range interaction with virtual objects, such as surgical procedures. We define a working range devoid of noticeable ghost artifact based on the angular resolution characteristics of human eye and optimize the orientation of an array of partially reflective mirrors of the waveguide to meet the image quality requirement for short-range interaction. With the optimized waveguide, the ghost artifact is significantly reduced. More results of the optimized waveguide will be shown at the conference.

Multi-color holograms rely on simultaneous illumination from multiple light sources. These multi-color holograms could utilize light sources better than conventional single-color holograms and can improve the dynamic range of holographic displays. In this letter, we introduce AutoColor, the first learned method for estimating the optimal light source powers required for illuminating multi-color holograms. For this purpose, we establish the first multi-color hologram dataset using synthetic images and their depth information. We generate these synthetic images using a trending pipeline combining generative, large language, and monocular depth estimation models. Finally, we train our learned model using our dataset and experimentally demonstrate that AutoColor significantly decreases the number of steps required to optimize multi-color holograms from > 1000 to 70 iteration steps without compromising image quality.

The optical architecture of VR/AR devices usually puts the image plane of the display 1.5 – 2.0 meters from the eyes, whilst stereoscopy is used to give an impression of depth. The resulting mismatch in where the crystalline lens of the eye focuses (accommodation) and the vergence of the eye, is unnatural to the visual system and causes an imbalance that can lead to nausea. Developer guidelines from manufacturers advise against placing content closer than the image plane to avoid VAC induced discomfort. A similar problem is more apparent with AR headsets, where content shown on the display is not in focus if the eyes are focused on a real-world target closer than about 1.5 meters. This focal rivalry presents challenges for the many new applications utilising hand tracking to stimulate interaction with virtual objects. Focus tuneable lenses can be used to move the focal plane of the display to match the plane of accommodation. This presentation will compare the approaches to mitigate VAC and assess focus tuneable lenses in more detail, along with some details of a study using voice-coil actuated Alvarez lenses.

High-speed eye tracking is a key requirement for upcoming AR and VR devices, as it enables novel applications such as display enhancement through gaze-contingent rendering, saccadic endpoint prediction to minimize system latency, and gaze-based biometric user identification. The update rate of state-of-the-art mobile video oculography sensors is limited by system-level power consumption, which is mainly caused by the exponentially increasing computational power requirements for pupil detection in camera images with respect to the update rate. To overcome this limitation and enable unconstrained high-speed eye tracking with low power consumption, we propose to fuse eye movement velocity data acquired by laser feedback interferometry sensors with camera images acquired at a low sampling rate. We propose a model-based sensor fusion approach that involves a combination of a glint-free, model-based video-oculography approach and high-speed interpolation between successive camera images using velocity information derived from the laser feedback interferometry sensors to achieve an outstanding eye tracking sensor system update rate of 1 kHz. We evaluated the proposed hybrid sensor system in an experimental setup and achieved a gaze accuracy of 1.63°.

Hand tracking algorithms relying on a single camera as the sensing device can only provide relative depth information, resulting in limited practicality. This limitation underscores the necessity for effective and accurate estimation of the absolute distances between hand joints and the camera in the real world. We respond to this pressing need by introducing a methodology that exploits the autofocus functionality of a camera for hand tracking. It takes advantage of the unutilized potential of a camera and removes the need for additional power-demanding and costly depth sensors to accurately estimate the absolute distances of hand joints. Our methodology undergoes rigorous experimental validation and consistently outperforms traditional methods across different lens positions.

Estimating camera pose is one of the main obstacles to implement Simultaneous Localization and Mapping (SLAM) technology. In this paper, we suggest a new phase-based SLAM technique for a single-camera single-projector Digital Fringe Projection (DFP) System. This method incorporates a second fixed global projector that projects fringe images and gray codes across a larger field of view. Utilizing conventional algorithms, the camera’s position relative to the global projector is accurately calculated, compensating for error accumulation issues in traditional Visual Odometry (VO) methods. This eliminates the need for additional hardware or computationally expensive self-correction algorithms. The proposed technique has the potential to replace VO as the primary method for camera pose estimation, allowing for seamless stitching of multiple images to create a precise 3D map.

It is commonly known for digital logic integrated circuitries that they heavily scale with down-scaling of the process node enabling the integration of more functionality. However, this was not true so far for OLED microdisplays which were basically stuck at 90nm…250nm process nodes for several reasons. This paper will present a new approach to realize a microdisplay architecture with extended functionality as well as a first implementation in 28nm utilizing very small pixels of 2.5um, a flexible interface architecture, framerates up to 10kHz along with integration of totally new driving schemes to serve the power and form factor requirements of upcoming near-to-eye systems in AR/VR/MR applications.

Display requirements for AR glasses are driving micro displays to be smaller, lower power, and higher performance. With these improvements, AR display systems can enable longer battery life, small and lightweight products and compelling user experience. Technologies such as micro-LED (Light Emitting Diode), micro-OLED (Organic-LED), LCoS (Liquid Crystal on Silicon), Texas Instruments DLP^® technology, and LBS (LASER Beam Scanning) are available today to be used in AR applications.

The next generation of DLP Pico chipsets (digital micromirror devices and DLP controllers) are optimized for low power and small size while building upon DLP technology’s industry leading performance and optical efficiency standards.

The new digital micromirror device (DMD) will enable improved contrast while reducing optical engine volume. The new DLP controller will include features that improve performance (display resolutions of up to 4K UHD, input video frame rates of up to 1kHz, faster DMD refresh rates, reduced display latency and support for variable refresh rates) and reduce power consumption (panel self-refresh, intermittent display standby and compressed video input modes).

The chipsets will also include AR-centric features such as dynamic color adjustment & display dimming (based on ambient conditions), dynamic input image resizing and smart motion interpolation (reducing input bandwidth) and content adaptive illumination control (reducing illumination power).

This paper intends to introduce the next generation of Texas Instruments DLP Pico technology, elaborate on the new capabilities included in these chipsets, and showcase how DLP technology, combined with the high efficiency optical design presented at Photonics West Opto 2023, is well positioned to enable low power AR displays.

We introduce an enhanced version of a full-color, RGB hybrid LD-SLED light source module for near-to-eye display systems, predominantly tailored for laser beam scanning (LBS) architectures. This light source module integrates blue and green semiconductor laser diodes (LD) emitting at wavelengths of 455 nm and 520 nm, respectively, along with a red superluminescent diode (SLED) operating at 638 nm. Besides the RGB emitter devices, this micro-RGB module includes collimation optics, wavelength-combining filters, and a prism pair to achieve circular output beams, all packaged with an innovative micro-optical, free-space bench architecture. With a compact footprint of 5.5 mm x 8.6 mm, this module produces collimated, circular, and collinearly aligned RGB beams with minimal divergence and large diameters of 1.0-1.3 mm at the module output. This third generation of an micro-RGB light source module delivers up to 50 mW of optical power per color at a total power dissipation of 1.2 W.

Augmented Reality (AR) see-through applications challenge the display design to be bright enough for outdoor use on one hand and with minimal power consumption for prolonged usage on the other hand. Laser-Beam-Scanning (LBS) displays are perfectly suited for this task, utilizing laser brightness. However, lasers are known to be “power-hungry” components of such displays. Maradin presents a novel laser modulation scheme that enables the reduction of laser power consumption for see-through LBS displays, saves up to 70% of laser power, and enables high-resolution use of AR displays for an outdoor all-day application.

A laser engine is demonstrated based on a silicon-nitride PIC. It uses a flip-chip assembly process for hybrid integration of the red, green and blue laser diodes, into etched recesses in the silicon nitride PIC and is based on passive alignment, meaning the laser is not tuned on during assembly. The TriPleX^® waveguide technology optimizes the ellipticity of the modes at the laser side from 1:3 to circular (1:1) at the output side. Output powers of >1mW are measured and depend on the laser diodes used. The described assembly approach facilitates wafer level laser diode integration and wafer level hermetic packaging for scalable volume manufacturing.

Laser beam scanners are of strong interest, as they offer a compact and low-power consumption solution for head-worn AR-displays and, more in general, for efficient and focus-free projection displays. In this framework, EXALOS has been leading the research and development of active light sources, focusing on optimizing red, green, and blue edge-emitting devices, including superluminescent diodes (SLEDs) and laser diodes (LDs). This work provides an overview of the performance achieved by single-emitter SLEDs and low-threshold LDs based on GaN, as well as AlGaInP, III-V semiconductors. Furthermore, we report on the development of emitter arrays. In particular, narrow-pitch devices with an emitter-to-emitter spacing of 10 μm and also a novel device design featuring both anodes and cathodes on the top chip surface are reported. The individual cathodes are fully independent and electrically insulated, ensuring an emitter-to-emitter resistance close to 1MOhm. Compared to conventional arrays with common cathode, the new architecture allows for integration with industry-standard current-sink drivers for efficient multi-LD modulation.

Microelectronics have evolved from mainframe computers to desktop PCs to tablets and mobile devices, and now to wearables. For many optics applications, there is also a trend to move from conventional optics to micro-optics and nanooptics. These two trends meet at optical see-through augmented reality, both from the user experience and the underlying technology. With our sights on eventual high-volume manufacturing of waveguide combiners, such as surface relief gratings, we take what we have learned from technology development and present challenges that must be overcome to achieve high yields in high volume production. In this report we discuss inline metrology and inspection challenges and opportunities starting with processes related to the transparent substrates: slicing, edge grinding lapping, polishing, marking and cleaning. Resulting challenges include roughness, scratches, particles, thickness variation, flatness, bow, warp, wedge and the like. Similarly for waveguide patterning on the substrate, whether it is with optical lithography or nano-imprint lithography, there are challenges that must be overcome. These include film thickness variations, maintaining critical dimensions such as feature width, height, pitch and profile, as well as defectivity resulting from particles, scratches, residue/stains, etc. Finally, diced eyepiece inspection challenges include scratches, particles, residue, color variation, chips and cracks. We describe both inline process control and impact on downstream optical properties such as modulation transfer function. While there are many similarities between augmented reality waveguide combiner manufacturing and silicon IC semiconductor manufacturing, there are many important unique challenges.

Bayfol® HX photopolymer films prove themselves as easy-to-process recording materials for volume holographic gratings (VHGs) and are available in customized grade at industrial scale. Their full-color (RGB) recording and replay capabilities are two of their major advantages. Moreover, the adjustable diffraction efficiency, tunable angular and spectral selectivity of VHGs recorded into Bayfol^® HX as well as their unmatched optical clarity enables superior invisible “Off-Bragg” optical functionality. As a film product, the replication of VHGs in Bayfol^® HX can be carried out in a highly cost-efficient and purely photonic roll-to-roll (R2R) process. Utilizing thermoplastic substrates, Bayfol^® HX was demonstrated to be compatible to state-of-the-art plastic processing techniques like thermoforming, film insert molding and casting, which opened up using a variety of industry-proven integration technologies for VHGs. Therefore, Bayfol^® HX makes its way in applications in the field of augmented reality such as Head-up-Displays (HUD) and Head-mounted-Displays (HMD), in free-space combiners, in plastic optical waveguides, and in transparent screens. Also, VHGs made from Bayfol^® HX are utilized in highly sophisticated spectrometers in astronomy as well as in narrow band notch filters for eyeglasses against laser strikes and retail optics. See through applications such as, HMD and HUD, have demanding performance requirements on combiner and imaging technologies such as efficiency, optical function, and clarity. The properties of Bayfol^® HX make it well suited to solve these challenges in primary display, and near-infrared imaging applications such as eye-tracking, while maintaining the requirements on optical performance. Using our novel free space Bragg matching technique introduced two years ago we demonstrate the recording of a complete set of grating couplers to achieve a 2-D eye-box expansion in a representative waveguide based near-eye display. In addition, using our novel NIR sensitized Bayfol^® HX grade, we demonstrate a free space holographic grating combiner working at 940 nm but exposed at 850 nm.

The productivity of waveguide combiner is crucial for augmented reality (AR) devices. Nanoimprint technology is one of options to produce Surface Relief Grating (SRG) waveguides today. This technology enables fabricating SRG patterns by pressing a mold with the desired SRG patterns into High Refractive Index (HRI) resins, and UV curing, then released the mold from HRI resins. The mold used in this process is known as a master mold, and these master molds are expensive to be used as stamps for production itself directly. Working stamps made by resins, a copy of the master molds, are used repeatedly to prevent damage to the master molds and reduce process costs. In this method, high durability is desirable for the working stamp over repeated cycles. We evaluated the formability and durability of working stamps through repeated using that influences the productivity of SRG waveguides. In this process, we investigated the compatibility between HRI resins (RI = 1.8 and RI = 1.9 respectively) and working stamps by fabricating grating patterns 50 times repeatedly to examine the influence of the material types on the durability of working stamps. The result showed that there are no defects and significant deformation on the patterns of each HRI resins after fabricated repeatedly more than 50 times using one working stamp respectively. This suggests that working stamps have capability to improve the productivity of SRG waveguides.

The optics and photonics fields have been greatly developed in recent years leading to novel devices and applications for organic light emitting devices (OLEDs), high performance screens and virtual and augmented. The further development of these areas will be greatly advanced with the design, synthesis, and engineering of new optical materials with enhanced performance and excellent properties including high refractive index. The development of high refractive index materials is very challenging due to the high light absorption of the molecules and atoms required in the design of the molecular structure. Besides high refractive index and transparency, the synthesized materials must be easily processable, cost-effective, have long shelf-life and durability under extreme l conditions. These materials need to be easily nanopatterned with high resolutions and fidelity with a high throughput. We present the development of purely organic polymers with high refractive index for nanoimprint lithography. They are the organic polymers with the highest refractive index commercially available. The proposed materials are transparent in visible wavelengths, can be nanoimprinted with high resolution and have good durability for promising long service life stability. They can be spin-on or solvent-free materials. The developed high refractive index polymers can serve as an organic matrix for inorganic nanocrystals to create nanocomposites with even higher refractive indices. These materials represent the state-of-the-art in functional materials for nanoimprint lithography with applications in advanced photonics and will push the progression of several fields requiring high refractive index configurations including virtual and augmented reality.

Non-sequential Monte Carlo ray trace is used to simulate light propagation through complex optical systems. When a ray is traced, the ray splits at surfaces and generates multiple out going ray segments. A large power threshold or a probabilistic split approach is typically used to limit the number of segments. However, these approaches reduce accuracy by either losing low power segments or reducing the number of segments in low power paths. In this paper we examine the use of sequence ray tracing to generate stray light distributions. When a ray is propagated from one surface to the next surface in a sequence, the ray can be transmitted and/or reflected/TIRed (total internal reflection). It can also be specular or diffuse and can be blocked by a surface that is not part of the sequence. The traditional sequence definition is enriched to define what type of rays are allowed to propagate and allow rays to be blocked by surfaces that are not part of the sequence. Stray light analysis usually contains multiple stray light paths. Identifying these paths and creating sequences from them for an optical model is an art that requires significant optical expertise. To make this easier, a stray light sequence generation algorithm can be used to create the initial stray light sequences. Once the sequences are specified, the illuminance distribution of the specified stray light paths can be quickly traced. A ray trace algorithm to trace multiple sequences simultaneously without limiting the power threshold or using probabilistic split has been implemented. In typical cases, we see greater than 10X speed improvements with no loss in accuracy. Examples illustrating typical use cases will be shown.

Waveguide displays are a popular architecture for optical see-through augmented reality (AR) devices because they provide a large eyebox while maintaining a compact form factor. However, they typically suffer from some drawbacks, including low optical efficiency and limited image quality, especially toward the edges of the field of view. Low optical efficiency reduces the brightness seen by the user and makes AR devices difficult to use in brighter environments, particularly outdoors. Poor image quality reduces the amount of detail that can be displayed through an AR device, limiting their range of application to showing large text and low-resolution figures. High efficiency and sharp image quality are difficult to achieve simultaneously in waveguide displays, requiring tradeoffs in the design process and the system specifications. In this work, we investigate how these parameters are impacted by the waveguide's geometry and choices about the diffractive gratings used. We show an example of a starting architecture and how to optimize performance by dividing the in-coupler into multiple zones without altering the overall waveguide geometry. Splitting the in-coupler into multiple zones opens a new dimension for exploring and expanding the waveguide design space.

Rendering of the virtual environment in VR devices is computationally expensive. Foveated rendering uses eye tracking to reduce this by only rendering the portion of virtual environment where the user is looking at. The eye tracking module has multiple near-infrared (NIR) LEDs to illuminate the eye homogenously and a camera to track the direction of gaze and eye movement. However, NIR illumination is potentially harmful to the human eye and skin. On the other hand, the safety assessment of eye tracking systems is not straight forward because it is not clear what standard and measurement recommendations to use. The international photobiological safety standard IEC 62471 provides guidelines for evaluating the photobiological hazards of incoherent broadband light sources for illumination purposes. The technical report CIE 245 is tailored for eye tracking systems, but provides only advisory information which is not mandatory. We have evaluated the hazards of a VR eye tracking module according to IEC 62471 and CIE 245. A measurement set up was designed and the classification scheme was used to classify the module. The number of LEDs, their geometrical orientation, optical power and duration of the exposure and the proximity to the eye are among the important parameters that could increase the damage to the cornea, lens and retina. Furthermore, since these modules have multiple IR sources in close proximity to the eye and are meant for prolonged use, the long-term hazard assessment must be thoroughly investigated. Our safety assessment was done on a VR module and opens up possibilities to extend this safety assessment for other eye tracking modules used in AR, VR and MR.

Very few research works featuring AR and Brain-Computer Interface (BCI) systems considered integrating cognitive state of the user in their applications. Additionally, even fewer projects explored the wearable, everyday solutions to help the user in their everyday tasks beyond the lab setup. In this project, we propose a wearable, wireless pair of glasses with a monocle-like heads-up display by including information about the current attentional state of the wearer by adapting their environment accordingly. We first introduce a our solution for AR-BCI integration. An application was designed, which adapted to the user’s state of attention measured via electroencephalography (EEG) and electrooculography (EOG). The system only responded if the attentional orientation was classified as "internal". Fourteen users tested the attention-aware system; we show that the adaptation of the interface improved the usability of the system. We conclude that more systems would benefit from awareness of the user’s ongoing attentional state as well further efficient integration of AR and BCI headsets.

Augmented Reality (AR) waveguide metrology requires placing the measurement camera next to the projection optics, thereby complicating system referencing, which requires the camera to be opposite to the projection optics, not next to it. The traditional mechanical solution of rotating and repositioning the camera is expensive and error-prone. This paper introduces an innovative optical technique that eliminates physical adjustments, thus reducing risk, cost and complexity in AR waveguide metrology referencing. We demonstrate that this new optical method provides referencing equal to the classical mechanical approach. This innovative technique has the potential to significantly simplify AR waveguide metrology, providing a cost-effective and risk-reduced method for quality control metrology.

The production of a VR headset is a complex process with several steps. At each step, various measurements are taken to verify quality or to characterise the component for later use. The visual system is the key component of a VR headset and consists in general of a microdisplay and an optical lens, which form the near eye display. In a first step, the properties like luminance and chromaticity of the microdisplay are determined. In the second step, the properties like distortion of the near eye display as combination of microdisplay and lens are measured. In the last step, the final VR headset is characterised for calibration and quality control. Exemplary measurements are shown for each step using imaging and spot light measuring devices.

Introduction. Proper fitting and left to right eye ocular alignment is necessary to maintain user performance and comfort with the use of binocular head-worn displays (HWDs). Towards that objective, measuring alignment of binocular HWDs for performance was investigated. Methods. A new, deployable, ruggedized Helmet-Mounted Display Binocular Alignment measurement tool (HMD BAMT) was developed that provides accurate alignment measurements to 15 microns. The tool was developed for measurement of any HWD/HMD in use in the field. Validation of the tool was accomplished using a commercially available binocular HMD. The HMD was provided to the U.S. Army C5ISR Center Research and Technology Integration Directorate at Fort Belvoir, VA for additional validation against the Near-Eye Display Test Station (NDTS), a much larger and more expensive system designed for laboratory measurement of HWDs. Results. Measurements showed the BAMT has very good accuracy and repeatability (i.e. milliradian accuracy). The BAMT capability and comparison to the NDTS measurements are described in this paper. Discussion. Further development of the alignment tool is ongoing and expanding the capability to include other measurements such as but not limited to uniformity, contrast, modulation transfer function (MTF) and distortion. The tool has been ruggedized for field support of binocular displays. The tool design updates have 3-axis capability and will provide fast, automated testing capability for production rate measurements. The new alignment tool will enable measurements to characterize quality of alignment of binocular HWDs in use in the field which will, in turn, support research concerning individual tolerance to representative levels of misalignment.

When designing camera systems, (for instance, in a cell phone), one important source of image degradation can come from stray light. This can result in ghost images caused by unwanted reflections off internal lens surfaces, or by out of field light being scattered from spacers or other surfaces in the optical system. In this paper, we demonstrate a method for characterizing the glare spread function (GSF) of an optical system using ray trace simulations. The GSFs can then be interpolated at angles and wavelengths that were not traced. Interpolated GSFs are applied to in-field image points as well as out of field points and then combined with the primary imaging path image. The result accurately predicts the detector illuminance.

Multi-layer bonded structures play an important role in AR/VR systems. Parallelism between layers and the consistency of thin gaps is critical for the function of these devices. Opto-Alignment has developed a system that provides rapid, non-contact measurement of these types of structures. In this presentation, we will share measurements of components from a commercially available AR headset. Thickness maps of the different layers as well as overall profile data will be presented.

Pancake lens has been widely used in mixed reality (MR) due to its compact formfactor. However, using a half mirror to fold the optical path results in a tremendous optical loss. To break this optical efficiency limit while keeping a compact formfactor, we present a new folded optical system incorporating a nonreciprocal polarization rotator. In our proof-of-concept experiment using a commercial Faraday rotator, the theoretically predicted 100% efficiency is validated. Meanwhile, the ghost images can be suppressed to undetectable level if the optics are with anti-reflection coating. Our novel pancake optical system holds great potential for revolutionizing next-generation MR displays.

The measurement and evaluation methods for the optical characteristics of near-eye displays, including augmented reality (AR) and virtual reality (VR) display devices, are specified in IEC 63145-20-10. Although 2D imaging light measuring devices (LMDs) such as 2D spectroradiometers are mentioned as one type of measurement equipment, only the point measurement with a spot LMD is incorporated in the measurement procedure in that standard. Since display panels in AR/VR display devices have become smaller and had higher resolution in recent years, the point measurement with spot LMDs has become difficult to be accurately performed. Therefore, 2D imaging light spectrometry measurements are desired in the measurements for AR/VR display devices. We performed the 2D spectrometry measurement for various commercially available AR/VR display devices using our spectroradiometer (SR-5100 HM). The optical characteristics of AR/VR display devices specified in IEC 63145-20-10; luminance uniformity, chromaticity non-uniformity and contrast ratio were measured. This paper reports and compares the measurement results of the four AR/VR display devices. Our SR-5100 HM 2D spectroradiometer is capable of highly accurate evaluation of AR/VR display devices with spectral data that filter-type LMDs cannot provide.

We have developed augmented reality (AR) glasses that can be used outdoors for long periods of time. To enable this outdoor usage, both high light utilization efficiency and high transmittance are required. Polarizing beam splitter coatings with characteristics that correspond to the visible wavelength range are used to achieve 75% transmittance and 2% light utilization efficiency. In addition, it is necessary to reduce the burden on the wearer’s nose to allow them to use the device for extended periods of time. The combiner and the lenses are made from plastic, and an anamorphic optical system is used in which the position of the pupil of the incident optical system differs in two cross-sections oriented perpendicular to the optical axis. As a result, the weight of the entire optical system is only 20 g for both eyes, despite the full-color imaging capability.

Recently, an increasing interest in utilizing 2D gratings on the waveguide for exit pupil expander (EPE) designs has been observed. However, to the best of author’s knowledge, most of these designs use only hexagonally arranged lattice for the 2D grating and do not investigate how varying lattice vector angle can help the optimization. In this paper, we will first discuss the consideration of non-orthogonal lattice vectors in Rigorous Coupled Wave Analysis (RCWA), provided by Ansys Lumerical RCWA. We will explain how a hexagonal 2D grating can be simulated with a set of orthogonal lattice vectors and why the same trick does not work for non-hexagonal 2D grating with arbitrary lattice vector angle. We will explain what it means when the grating is non-hexagonal in k-space and real space, and the consequent benefits. Based on the concept, initial simulation results, using dynamic link between Ansys Lumerical RCWA and Ansys Zemax OpticStudio, will be demonstrated. The simulation with different lattice vector angle are performed for understanding the system behavior. Finally, we set up an optimization workflow in Ansys optiSlang, considering lattice vector angles as one of variables. The optimization results will be discussed.

The roughness of sidewalls on slanted etched diffraction gratings needs to be minimized to avoid compromising their optical efficiency. Sidewall roughness usually does not significantly alter the overall features of gratings reflectance, however, narrow spectral features that are due to strong Fabry–Perot resonances can be strongly affected by roughness1,2. The complication in performing these roughness measurements is to access the slanted sidewall by Atomic Force Microscope (AFM) tips on a typical etched feature with Critical Dimension (CD) of 100 nm, 200 nm pitch and on a steep angle of 45 degrees. Usually, to address this challenge, expensive long AFM tips and non-standard AFMs capable of measuring samples on a certain angle are used2. Alternatively, a post process on the wafer is required3,4,5. We present a simple method to measure the gratings’ sidewall roughness without any physical and/or chemical process and optical analysis needed before or after the measurement and which is also done on a standard AFM. The method could, in principle, be applied to measure sidewall roughness on any etched trench sidewalls or deposited features. Diffraction gratings were processed by an Oxford Instruments Plasma Technology’s Large (30cm) Ion Beam Etch Source. Patterned SiO2 and Silicon slanted sidewalls roughnesses were measured by an in-house conventional Asylum Research - Jupiter XR - AFM allowing a speedy sidewall roughness assessment and development. Feasibility tests for SiO2 slanted diffraction gratings processed by the Oxford Instruments Plasma Technology Ion Beam Etch System showed a very low roughness of 1.3nm for the trench sidewall.

Current augmented reality (AR) waveguide display technology faces a challenging trade-off between essential factors such as eyebox, efficiency, and image uniformity. Surface relief grating has been a commonly used exit pupil expander (EPE) in waveguides, but it exhibits limitations in efficiency and uniformity. To overcome these shortcomings, polarized volume grating (PVG) with ultra-wide angular bandwidth and high efficiency has been employed as an EPE to enhance efficiency and uniformity. However, the challenge arises when attempting to achieve high uniformity within the eyebox using nematic liquid crystal for controlling each expansion, as the polarization changes of diffracted light contribute to varying diffraction efficiencies, which affects the maintenance of uniformity across the entire field of view. This article introduces an innovative approach by incorporating high-low cover-layers on top of PVG to effectively control the path difference between light rays at various angles. This design modification mitigates unnecessary out-coupling and ensures a remarkably high level of uniformity in the entire AR system, providing a more efficient and uniform expanded eyebox.

The advantages of holographic displays over stereoscopic displays are that they provide both real motion parallax and solve the vergence-accommodation conflict without varifocal lenses and gaze tracking. For large holographic displays, pupil tracking and beam steering are required to ensure that the pupil is within the so-called viewing window or eye box between the diffraction maxima in the Fourier plane of the display system. We present a simulation study of the possibilities when the pupil is precisely tracked and can be considered in an iterative optimization process for hologram computation. Our study focuses on different initial phases and the resulting speckle noise.

Amidst the mixed news surrounding the feasibility of Augmented Reality (AR) smart glasses, the demand for commercially viable mass production of industry-standard optical waveguide combiners remains unwavering. Over the past two years, our consortium of companies has proposed a cost-effective and scalable manufacturing process for Surface Relief Grating (SRG) based waveguides, offering a comprehensive path from concept to fabrication through large-area nanoimprinting. This approach has garnered significant interest from both customers and partners associated with the participating companies. Our aim is to push beyond the established limits of large-area nanoimprinting. In this work we address the obstacles and latest advancements in maintaining imprint quality, fidelity and uniformity during large-area nanoimprinting. We demonstrate various building blocks that are crucial to manufacture high quality and cost-effective AR waveguides, such as the replication of slanted gratings and the possibility of low residual layer thickness using large-area nanoimprint lithography. We employ high refractive index materials, such as resin and glass (1.8, 1.9 and 2.0), and also explore a lighter and flatter version of the RealView 1.9 glass. Our primary objective is to demonstrate that large-area nanoimprinting not only presents itself as a novel method for high-volume manufacturing of SRG waveguides but also enables the production of challenging optics for AR smart glasses.

μThe emergence of adaptive and compact optical and optoelectronic devices, including flexible electronics, wearable displays, and solar panels, has necessitated the use of flexible and fracture-resistant substrates. High refractive index (HRI) polymeric coatings are being explored as promising alternatives to traditional inorganic thin films. In this study, three pure organic platforms were developed that offer tunable refractive indices (1.6 to 1.8 at 550 nm) and high light transmission (>98% at 400 nm for a 2-μm film). These HRI polymers demonstrate excellent compatibility with common processing solvents such as PGMEA, PGME, and acetone, as well as high thermal resistance with a Td of 300-370°C. Furthermore, an extended high-temperature baking study revealed the thermal and optical stability of our HRI polymer coatings, with less than 5% film thickness loss and less than 1% changes in optical properties. Additionally, we have developed photo-imageable formulations based on these HRI polymers, which can yield well-defined small features (<5 Θm) through i-line exposure.

Metalens is optical components that can replace traditional multi-element lens designs, offering the advantages of aberration elimination, high numerical aperture, and wide field-of-view imaging capabilities. However, engineering nano-antennas within metalens, especially in wide-angle configurations at the millimeter scale, presents challenges. These nanostructures must effectively control phase and amplitude to meet the required phase for different angles of incidence, while also achieving focal spot sizes close to the diffraction limit. This study utilizes the Synopsys simulation tool, "MetaOptic Designer," to design and optimize a metalens with a 1mm diameter and a numerical aperture (NA) of 0.37, operating at a 940 nm wavelength.

Maintenance in the railway context has today reached very high safety standards. Still, despite these high standards, the sector's goal remains to continue to use resources and technologies to achieve a total absence of accidents. Our study proposes creating an integrated monitoring system to support the awareness of a planning operator. The system consists of 3 blocks that collect data from the field, process them, and identify anomalies. Subsequently, these data are displayed interactively in a virtual environment that realistically reproduces the piece of railway line we are analyzing. The planning operator can navigate the virtual environment with extreme awareness and plan maintenance interventions. Finally, the prepared maintenance cards will be made available in augmented reality to support the maintainers in locating the intervention area and executing the task.

Despite advancements in global positioning systems (GPS) and related sensor technologies, indoor navigation continues to pose significant challenges due to signal attenuation and scattering caused by surrounding objects. In underground spaces, specialized assisted technologies for mapping, positioning, and navigation are essential for effective search and rescue operations. Augmented reality (AR)-assisted navigation holds promise for enhancing emergency evacuations in such environments. This study aimed to evaluate the performance of AR-assisted navigation in an underground mine and simulate search and rescue scenarios. To accomplish this objective, LIDAR and thermal cameras were integrated onto the Microsoft Hololens using NUC computer and ROS Bridge. The LIDAR-based spatial mapping technique was employed to generate a tessellated model of the surrounding space, which was then rendered as a user interface. The display was updated every 5Hz to provide accurate and temporally relevant visualizations. User performance was assessed by measuring the total time to complete the path. Preliminary results demonstrated that AR-assisted navigation could provide valuable support to first responders and significantly enhance search and rescue operations in emergency situations. By leveraging the combined capabilities of LIDAR and thermal imaging, the proposed approach enables accurate mapping and visualization of the space and the people within, facilitating an efficient evacuation process.

To facilitate Augmented Reality (AR) displays suitable for all-day-long usage, technologies are anticipated to realize compact form factor, low power consumption without compromising key aspects such as field-of-view (FOV), brightness, resolution, and uniformity. The balance among those requirements is crucial for creating a better AR experiences that are both comfortable and visually appealing for extended use. One of the challenges, FOV-resolution-form factor trade-off is addressed by using a MEMS based micro display panel, Digital Micromirror Device (DMD) in diffractive image steering mode. The DMD is paired with synchronized and short laser pulse illumination and a prism array expands FOV. This setup facilitates steering images into one of the multiple diffraction orders in a time sequential manner. The FOV is horizontally increased by fivefold. The vertical FOV is increased by twofold by incorporating illumination multiplexing. The resulting FOV reaches 30 degrees horizontally and 12 degrees vertically, all while sustaining a resolution of 1.86 arc minutes per pixel. This method increases FOV without sacrificing resolution nor increasing the form factor of micro display panel.

This paper proposes a no-reference image quality evaluation model for accurately assessing the quality of real-world images displayed on head-mounted display (HMD) devices. The proposed model employs a simulation of human visual system, providing a reliable measure of image quality. Initially, an efficient convolutional neural network (CNN), specifically designed for noise characteristics, is utilized to obtain a near-perfectly noise-reduced image. The difference between this image and the target image is then calculated in the linear domain. To emulate the contrast sensitivity and masking effects inherent in the human visual system, we introduce a sophisticated frequency-domain filter model in a uniform color space. The resulting multidimensional data from the filters are aggregated and corrected based on the average brightness. Our model's performance is validated against Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index (SSIM) metrics using the TID2013 dataset, revealing superior correlation coefficients. Human factors experiments further confirm the model's reliability and practicality in real-world scenarios.

Tilted diffraction gratings with highly refractive will be an important element for smart glass to realize a metaverse such as AR (Augmented Reality)/VR (Virtual Reality). Nanoimprinting, which can directly process a variety of materials for a variety of shapes, is well suited for mass production of tilted gratings, and many approaches have been reported. In nanoimprinting, one of the keys is to release the gradient grating shape without defects. In this report, we analyzed the strain generated during peeling release and tear release by computer simulation, and investigated a low-damage peeling method for releasing the tilted structure.