This PDF file contains the front matter associated with SPIE Proceedings Volume 12449, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

On the path to consumer-oriented augmented reality devices, the development of lightweight and unobtrusive waveguides with high optical quality is essential for the acceptance of a device in order to access a broader market. Optical-grade polymers with application-specific refractive index are key components in this development and are used to manufacture and enhance diffractive, reflective or holographic waveguide combiners.

Polymers with high mass-productivity are the best material for waveguide in AR/VR/MR smart glasses, for which demand is increasing year by year. However, polymer waveguides are difficult to obtain a wide field of view because of its lower refractive index compared to glass. Since a wide field of view can be obtained even with polymer waveguides by dividing the field of view, we performed optical design, mold design, mold processing, and injection molding of an injection moldable surface relief grating type waveguide. We used a polymer with relatively high refractive index and good flowability to improve the transferability of diffraction grating and design flexibility. The diffraction gratings manufactured on a trial basis were measured and fed back into the optical design to improve the efficiency of the waveguide. Waveguide and laser beam scanning module were combined to image the projection image. The captured image looks like a projected image through a screen door because the tiling length is larger than the pupil size. The future challenge is to improve the quality of the projected image by achieving thinner thickness and higher precision molding.

Nano-Imprint lithography (NIL) is a powerful technology for low-cost, large area patterning of complex nano-features, including surface relief gratings and meta-structures for AR optical components. A full layer patterning module that includes a NIL process suited for mass manufacturing requires multiple capabilities: nano-imprint tools, materials, template fabrication, potentially pre- or post-imprint material deposition or removal and extensive metrology. Through its longstanding history in the semiconductor industry, imec has developed advanced mastering, deposition, and etch capabilities that can be paired with NIL process development for fully integrated patterning. In this talk, recent developments in integrated surface relief patterning on transparent 300 mm substrates will be presented. Because the fabrication itself is substrate agnostic, this capability can be transferred to other substrate material available at 300 mm to match the design requirements of a variety of diffractive optical components, such as refractive index tuning.

Over the last two decades, the need for high-throughput and high-fidelity fabrication technology for micro and nano surface topologies designed for various photonic and optoelectronic devices has steadily driven the advancement of nanoimprint lithography technology (NIL). The availability of a functional high refractive index resin can enable high-volume and lowcost production of micro and nano-optical devices. However, available NIL-compatible resists have not kept up with the consumer industry's growing performance, processability, and reliability demands. In particular, for Augmented and Mixed Reality (AR and MR) devices, for the best optical performance (i.e., enhanced user experience) and reasonably low-cost production, a refractive index higher than 1.80 in the NIL resin is often desired. HighRI Optics, Inc. has developed two classes of materials with ultra-high refractive index, from 1.8 to 2.00 at 590 nm, for the nanoimprinting of photonic devices: 1) purely organic polymers and 2) nanocomposites consisting of polymeric matrix containing inorganic nanocrystals. The purely organic materials with a 1.8 refractive index do not contain nanoparticles, exhibit high transparency in the visible wavelength, and are NIL processable. The organic formulation has the highest refractive index ever reported among the organic polymers for nanoimprint lithography. The nanocomposites exhibit tunable refractive index values between 1.8 ~ 2.0 at 590 nm, with high optical transparency and low haze. These materials can become an essential part of the ecosystem to enable the mass production of future photonic devices.

Nanoimprinting of surface-relief grating-based waveguides has the potential to result in the best performing Augmented Reality (AR) smart glasses, but there are still many challenges in the design, scaling, and reproducibility of these imprinted waveguides. We presented a promising path toward mass manufacturing of optical waveguide combiners via large-area nanoimprinting at SPIE AR/VR/MR 2022. This alternative route for manufacturing surface-relief gratings on a larger area generated much interest. This follow-up paper presents a further optimized design based on the lessons learned from the previous paper, with a particular focus on quality. The complete value chain with partners is involved throughout the process of this iterative update: from design, mastering, and materials to imprinting and metrology, to prove that this method improves not only the manufacturing throughput but also the waveguide quality. We demonstrate that both the replication and image quality is true to the intended design using large area, high refractive index (1.9 RI), square (300 x 300mm) glass substrates with high refractive index resins (1.9 RI). Our objective is to further establish this new approach towards high-volume and low-cost manufacturing of waveguides based on surface relief gratings as a viable path forward for enabling the Metaverse.

We have been developing Scanning Overlapped Phase Interference Lithography (SOPHIL) system which can provide an excellent grid pitch uniformity, 380 nm+-0.005 nm over the entire 200 mm diameter substrate. The SOPHIL method consists of two steps. As the first step, a spot fringe pattern generated by two-beam interference is scanned direction along the grid on the wafer. As the second step, the spot is moved just the integer multiple length of its fringe period, then the spot is exposed again over the 1st fringe pattern. We achieved the pitch uniformity of +-0.002%, and also 180 nm pitch pattern was confirmed.

Improving the efficiency and performance of Augmented Reality (AR) headsets is a key technical challenge for enhancing user experiences and catalyzing AR market growth. Current AR headsets are bulky and present a limited field of view (FOV), compromised image quality, and short battery life. In principle, high-refractive-index optical components could be integrated to create next-generation headsets with form factors that simultaneously deliver improved performance. Glass manufacturers have recently announced the availability of new, high-index substrates (n = 2.0+) to assist the technical development of these advanced devices. The materials required to manufacture high-index structures on these substrates, however, are not commercially available. Phosio Corporation has recently developed new solution-based, UV-curable inorganic coatings with customizable indexes (n = 1.6 – 2.35) and non-yellowing low absorbance across the visible spectrum. The formulations are compatible with incumbent imprinting tools, enabling waveguide fabrication on high-index glass. Consequently, Phosio’s technology provides a unique path to elevating FOV and image quality beyond current state-of-the-art AR headsets.

Nanoparticles such as titanium dioxide (TiO2) with high refractive index values of 2.0 in the visible light spectrum are increasingly being sought after for applications in XR waveguide designs for improvements in field of view (FOV). Pixelligent’s PixNIL® formulations with PixClear® TiO₂ nanocrystals can create diffractive optical elements and planarized films with refractive index values of up to 2.0 at 520 nm. With the introduction of high refractive index formulations with PixCor™, a new line of nanocrystals using Pixelligent’s proprietary "Core-Shell" technology, we offer significantly improved resistance to near-UV and UVA light exposures in nanoimprintable formulations. The films containing PixCor™ technology maintain very high transparency and low haze in the visible light spectrum and demonstrate high refractive index of 1.9 at 520 nm, and low absorbance, all while maintaining nanoimprintability at commercial scale.

Nano-photonic applications are on the brink of disrupting the optics we know. Examples are augmented reality glasses based on diffractive waveguide combiners (DWC) using surface relief gratings and meta-lenses consisting of high aspect ratio pillars. The challenge will be fabricating 100’s of millions of these large area devices with high yield and low cost. In this paper we will demonstrate the direct replication of nano-photonic patterns using a nanoimprint method in combination with inorganic functional optical resist materials. SCIL Nanoimprint solutions always developed the materials, processes and nanoimprint hardware as an integral system for optimal results. The same imprint technology scales from 100mm up to 300mm wafers. A unique approach of SCIL is to directly pattern inorganic materials with single-nm precision and keep this accuracy for over the full stamp lifetime. For nanophotonic applications the direct replication of nano-patterning in materials with a high refractive index (1.7 – 2.0) is highly desired. With this slow and expensive process steps such as optical- and hard mask layer deposition and reactive ion etching of these materials after the lithography step can be omitted. As another example augmented reality glasses with a high efficiency require 3 slanted gratings with varying orientations, resulting in 2 additional lithography and etching steps. We will show the direct nanoimprint patterning of slanted gratings in all orientations with a refractive index up to n=1.92 (@550nm). For these nano-photonic devices to work within specification, the absolute size of the patterns needs to be within 1-5nm variation and the refractive index to be controlled to the 3rd decimal (depending on the application). To verify the full nanoimprint production process in a close-coupled manner a fast non-destructive test method based on Fourier imaging scatterometry will be introduced. This method can determine the relevant sub-micron feature sizes with single nmprecision.

The production of surface relief gratings (SRG) plays a crucial role in nano-structuring. Applications range from laser mirrors to manufacturing of waveguides for mixed and augmented reality. In order to fabricate lightweight near eye displays SRGs are used for coupling the light from the source into the waveguide and out of the waveguide towards the eye. Ion Beam Trimming is a well-established method in the MEMS industry to locally change the thickness of a functional layer on a substrate and was adapted as a very flexible approach for the production of SRGs with varying slant angles and varying trench depth.

AR architectures based on TIR waveguides require surface diffraction gratings to couple light in and out. Traditionally, the spectral response of a grating is tuned by blazing, i.e., creating faceted grooves with precise angles. However, blazed facets are difficult to achieve using resist-based techniques such as e-beam lithography. In this talk I will describe a new approach to making blazed AR grating masters by mechanical ruling, in which grooves are created by deforming a metallic surface with a diamond stylus.

Many optical systems such as cameras and XR displays suffer a loss of performance when ambient temperature changes due to distortion of optics. A focusing actuator can compensate for distortion and therefore maintain system performance. Existing actuators require always-on power consumption, which is undesirable. Here we will present a novel SMA actuator which utilizes the unique characteristics of SMA to provide temperature compensation without compromising power consumption.

We demonstrate a silicon-nitride Photonic Integrated Circuit based RGB light engine. The engine uses a flip chip laser diode assembly process for hybrid integration of the Red, Green and Blue laser diodes, as well as power monitoring detectors. The lasers are flip chip soldered in etched recesses in the silicon nitride PIC for optimal coupling. Small formfactor 5x10x1 mm³ (width x length x thickness) devices have been realized. Output powers of ~1mW are measured and depend on the laser diodes used. Typical coupling losses are 1.5 dB for the actively aligned implementations. The described assembly approach facilitates wafer level laser diode integration and wafer level hermetic packaging for scalable volume manufacturing.

Realization of augmented reality (AR) solutions is key towards the much-needed integration of digital content into the real world. This seamless integration of digital content with the real world in AR devices is achieved by displaying the information using a suitable projector in the field-of-view (FOV) of the user. One of the most practical solutions to realize this is a laser beam scanner (LBS) projector combined with a diffractive optical waveguide. Features such as a small form factor, high brightness, large color gamut, and low power-consumption make LBS a popular choice as the light engine for the emerging consumer market for AR displays where the primary focus is on obtaining a stylish wearable rather than an unwieldly head mounted device. As should be the case for any AR/VR/MR display, LBS plus waveguide solution must be evaluated against the IEC 60825- 1:2014 standard for a typical use case. In this manuscript, we will first describe a typical AR solution, a TriLite Trixel® 3 LBS plus a waveguide combiner. We will discuss the operating principle of such a device. Based on that we shall highlight stepwise the key considerations in such a system for ensuring a Class 1 operation in a typical AR use case as per the IEC 60825-1:2014 requirements.

This paper reviews recent developments in software, materials, processes and fabrication tools that can enable a rapid transition from design, modeling and simulation to fabricating cost effective test parts and prototypes for Augmented Reality and Mixed Reality displays. Using the approaches detailed here, display systems can be laboratory and field tested in a matter of days after establishing design goals and production criteria. Robust and industry-ready Imageguides® (aka planar optical elements) produced from this short run rapid design/fabrication cycle can result in directly printed one-offs for inclusion in evaluation systems or lead directly to the production of masters for additive NIL or etch masks for subtractive processes which are required for production level quantities.

Small projector units for Near-To-Eye (NTE) displays such as AR glassed are currently a field of intensive research and development activity. To industrialize the first generation of user-friendly consumer smart glasses we propose using LED based solutions. LED illuminated DLP/LCoS pico-projectors are a mature technology which can be further optimized for the use in AR glasses. This article paper will share some updates on recent LED based NTE activities, and describe important design challenges such as etendue match, integration size and power efficiency.

Augmented Reality (AR) or smart glasses might be the next big thing in the field of wearable consumer electronics. Ideas, concepts and even products exist since a while but still they are all quite far away from being perfect. AR glasses act as an add-on to the smartphone or -watch, bringing the visual content to the line of sight with no need to look at the mobile device’s display. All-day-use glasses need to look fashionable, need to provide a high level of wearing comfort (weight, heat dissipation) and should provide a reasonable battery live time which enables several hours of operation. Laser Beam Scanning (LBS) might be the display technology of choice for such consumer AR glasses because it enables ultra-small optical engine sizes of below 1cc and the laser diodes can be switched off for image areas without content. But there are also many technical challenges to overcome. Beside the complexity of the scanning itself the interaction of the coherent laser light with the optical combiner optics can lead to image artefact. In this paper we present the ams- Osram laser source solution and give an outlook how to further improve system performance.

We present a method to rapidly and accurately measure the eye box of Augmented Reality (AR) and Virtual Reality (VR) eyewear. We demonstrate that this rapid method measures the eye box with a fidelity comparable to slower, traditional methods. The presented rapid method uses a lens that mimics the human eye in core aspects like pupil position, pupil size and field of view to get an impression of the eyewear performance as it appears to a human user with single image capture. By combining as few as three such image captures with such a lens, one can rapidly and accurately measure the entire eye box geometry of any given AR or VR eyewear. We further demonstrate the advantages of adopting this new method by referencing the display metrology industry, where this method has already been adopted as the new metrology standard.

A current challenge for VR headsets producers is to reduce the weight and size of headsets. One very promising approach is the use of pancake lenses that help reducing the weight of the VR lens system but at the same time significantly increase the optical quality. Due to their complexity pancake lenses confront manufacturers with many challenges in testing and fabrication. TRIOPTICS´ expertise in active alignment and optical metrology enable our customers to create better pancake lenses for the challenges of tomorrow.

Porotech is delivering novel microLED display technology using its porous gallium nitride (PoroGaN®) platform technology in combination with complimentary epitaxial design. This has enabled blue, green and (most critically) red emission from the same InGaN material platform, delivering monochrome displays with very low wavelength shift (<10nm for blue, <2nm for green and <30nm for red). Further still, Porotech have used the same approach to deliver microLEDs with deliberately high wavelength shift (<150nm), allowing the wavelength emission of individual LED emitters to be tuned. This DynamicPixelTuning® technology enables all colors from red to blue to be emitted from identical pixels/emitters on the same wafer, removing significant roadblocks to full color display manufacture - particularly in the case of microdisplays for AR/MR applications. In terms of the display engine and system level design the technology can be exploited further by simplifying the driving, light extraction, waveguide design etc… since only one ‘type’ of pixel needs to be designed for. In general, much greater design freedom can be employed at all stages in the manufacture of the final product in order to meet consumer performance requirements.

Natural and comfortable visual experience is critical to the success of metaverse, which has recently drawn worldwide attention. However, due to the vergence-accommodation conflict (VAC), most augmented reality (AR) or virtual reality (VR) displays on the market today can easily cause visual discomfort or eyestrain to users. Being able to resolve the VAC, light field display is commonly believed to be the ultimate display for metaverse. Similar to conventional near-eye AR displays, a near-eye light field AR display consists of three basic components: light source, projection unit, and eyepiece. Although the same light source can be used in both kinds of displays, the projection unit and the eyepiece of a near-eye light field AR display call for a new design to preserve the structure of light field when it reaches user’s retina. The primary focus of this paper is on the eyepiece design for a near-eye light field AR display. In consideration of the compact form factor and wide field of view, the birdbath architecture, which consists of a beam splitter and a combiner, is selected as the basis of our eyepiece design. We optimize the birdbath eyepiece for the light field projection module produced by PetaRay Inc. The birdbath eyepiece receives the light field emitted from the light field projection module and projects it fully into the user’s eye. Our design preserves the structure of light field and hence allows virtual objects at different depths to be properly perceived. In addition, the eyepiece design leads to a compact form factor for the near-eye light field AR display. Specifically, our eyepiece is designed by optimizing the tradeoff between the eyebox and the depth of focus (DOF) of the near-eye light field AR display. The resulting DOF allows the user to have a clear and sharp perception of any virtual object in the working range, which is from 30 cm to infinity. In addition, we optimize the entrance pupil position and the F-number of the eyepiece according to the exit pupil position and the divergence angle of the light field projection module. This way, the eyepiece is able to preserve the structure of light field, meaning that the angular relation between light rays coming from the same object point in space is preserved. To demonstrate the performance of our birdbath eyepiece, we use the Human Eye Model-Liou & Brennan (JOSA A 08/97) to simulate the image formation process.

Polarized catadioptric optics systems are an emerging solution for virtual reality (VR) head mounted displays (HMD). A good VR optical system should have a large pupil volume to tolerate multiple interpupillary distances and to accommodate eye rotation as the user scans across the field of view (FOV). In this paper we review the 3M™ High Acuity Reflective Polarizer (HARP) optical lens and module. We present empirical and modeling data for lens module performance including MTF as functions of pupil rotation, decenter, and diopter adjustment range. The large eye box and decentering tolerance yields a natural viewing experience. 3M™ HARP optics demonstrates the promise of pancake optic designs to deliver realistic immersive VR experience.

Switchable polarization volume hologram gratings and lenses have been developed. The diffraction efficiency can be modulated by a vertical electric field. A small amount of liquid crystal monomer is doped into cholesteric liquid crystal to form a stabilized polymer network to make the unwinding process reversible. The fabricated devices exhibit submillisecond response time, a large range of diffraction efficiency modulation, and high see-through quality. Some potential applications are demonstrated, including a significantly suppressed rainbow effect, enhanced light efficiency for a waveguide-based augmented reality display, and a Maxwellian-view type waveguide with pupil expansion. The unique properties and benefits of these switchable reflective gratings and lenses open a new door for near-eye displays, especially novel optical systems for augmented reality waveguide displays.

Near-eye displays have become a technology of high interest for Augmented, Virtual and Mixed reality due to the unique immersive experience they provide to the user. The majority of these devices use macroscopic optical elements that make them bulky and heavy. Our team has proposed a disruptive near-eye display concept that uses the self-focusing effect to project an image to the user’s retina. To form an image, emissive points are generated from a dense photonic integrated circuit embedded within the lens of a pair of smart glasses. In this work, we present the design of a dense routing architecture that addresses thousands of randomly distributed emissive points from a few hundred inputs. The circuit combines unbalanced waveguide splitter trees with a non-periodical addressing onto a dense waveguide network. We present the design optimization through numerical simulations and estimate the overall device performance based on simulation results. A waveguide interlayer crossing simulation indicates losses better than 0.003 dB/crossing, which guarantees low optical losses over thousands of crossings. By unbalancing correctly the splitter trees, we can obtain homogeneous power profiles over an emissive point distribution. The experimental validation of our design will be a major step towards the elaboration of a first prototype.

We present the design of a dense silicon-nitride photonic integrated circuit applied to a novel concept of unconventional augmented reality display combining holography with integrated photonic circuits embedded in the glass of the display. An integrated projector made of a grid of waveguides and electrodes generates randomly distributed emissive points at the wavelength of 532 nm, from crossings between waveguides and electrodes. These emissive points then interact with a hologram to form a composite plane wave focused on the user’s retina using the self-focusing effect. In this work, we present the design of the entire photonic circuit comprising the projector and the routing architecture to address the emissive points. We define both shapes of waveguides and electrodes by a succession of segments that we approximate by BSplines. We designed the photonic circuits using Matlab, Lumerical and KLayout softwares. We engineer the waveguide architecture on two levels in order to limit optical losses due to the high number of waveguide crossings required for the random addressing. In this contribution, we present the mathematical model used to elaborate our design as well as the technical details. We also evaluate it for our retinal projection project.

Visual confusion occurs when two dissimilar images are superimposed onto the same retinal location. In the context of wearable displays, it can be used to provide multiple sources of information to users on top of the realworld scene. While useful, visual confusion may cause visual rivalry that can suppress one of the sources. If two different images are projected to each eye (i.e., monocular displays), it provokes binocular rivalry wherein visual perception intermittently switches between the two images. When a semi-transparent image is superimposed (i.e., see-through displays), monocular rivalry results, causing perceptual alternations between the foreground and the background images. Here, we investigated how these rivalries influence the visibility of the peripheral target using three configurations of wearable displays (i.e., monocular opaque, monocular see-through, and binocular see-through) with three eye movement conditions (i.e., saccades, smooth pursuit, and central fixation). Using the HTC VIVE Eye Pro headset, subjects viewed a forward vection of a 3D corridor with a horizontally moving vertical grating at 10° above the center fixation. During each trial (∼1 min), subjects followed a fixation cross that varied in location to induce eye movements and simultaneously reported whether the peripheral target was visible. Results showed that the binocular display had significantly higher target visibility than both monocular displays, and the monocular see-through display had the lowest target visibility. Target visibility was also higher when eye movements were executed, suggesting that the effects of rivalry are attenuated by eye movements and binocular see-through displays.

Polarized catadioptric systems (also called folded optics, pancake lenses) are a viable solution for virtual reality (VR) head-mount display applications. Reasons include its high image resolution, wide field-of-view, smaller physical size and lighter weight compared to the conventional refractive optics counterparts. One of the major challenges with folded optics systems is to reduce the light intensities of the ghost images and spurious halos due to multi-bounces, hence improve the overall image contrast. In this paper we discuss a high-quality polarized catadioptric system and present a ghost analysis method and the corresponding results. It can be shown that the many ghosts in the image plane can be coarsely categorized into “local ghosts” and “distant ghosts” according to their proximity to the image. The local ghosts or halos are close to the image itself and they directly decrease image contrast; whereas the distant ghosts are located diagonally away from the image and they can create some distracting faint images under certain display content. The origin of each individual ghost and halo can be traced back to its contributing optical components, which provides targeted information to directly mitigate them on a component level. Experimental results are shown to demonstrate the validity and efficacy of this approach. Furthermore, the ghost analysis information can also be used as additional constraints in the lens design software to perform new rounds of optimization on a system level.

Over 20,000 children experience a cardiac arrest annually in the U.S., only 17-50% survive. There is massive variability in the quality of lifesaving cardiopulmonary resuscitation (CPR) that children receive due to limited availability of pediatric specialized emergency resources, suppressing the survival rate. High quality CPR is performed to replace the function of the beating heart during a cardiac arrest, preventing the asphyxiation of the vital organs, while the inciting process can be investigated. A collaboration between the Johns Hopkins University Applied Physics Laboratory and School of Medicine was developed to address this critical healthcare gap, with the goal of saving the lives of dying children. We developed a novel effective, portable, usable, affordable, and equitable augmented reality system, called AR-CPR, that provides real-time CPR feedback. AR-CPR improves the rate of Pediatric Advanced Life Support guideline adherence to 73% (SD 18%) from 17% (SD 26%) (p<0.001). We engineered a custom array of inertial measurement units (IMU) and microprocessors to sense and analyze the quality of CPR. This information is then wirelessly transmitted to an AR head mounted display. The medical practitioner receives imperative feedback on their performance with actionable guidance. AR-CPR has promise as the preeminent CPR feedback tool and is the first such device being developed for international clinical use. With continued development, AR-CPR could be used anywhere a child may experience a cardiac arrest, including emergency departments, ambulances, and/or malls, households airports, or schools in conjunction with automated external defibrillators (AED). Thousands of children’s lives could be saved.

The state-of-the-art rendering methods, including path tracing, provide photorealistic images; however, the render time can be too long to be used in real-time applications such as video games and virtual and augmented reality. On the other hand, naive rendering methods such as rasterization can provide high-speed rendering instead of high-quality depiction. This paper exploits insights about human visual characteristics to combine a high-quality rendering method and a high-speed rendering method and achieve photorealistic and real-time animation. To exploit an optical illusion that virtually produces slight motion and deformation by luminance changes, we focus on an animation including small geometrical changes and propose a real-time rendering pipeline to add motion information to a photorealistic scene. We evaluated the render time and animation quality by subjective experiments. As a result, the proposed method achieved up to about 570 times faster rendering than conventional path tracing, and parameters to present the illusion and preserve the animation quality have been revealed.

In this report, a simulation method with an example of optimization and tolerance analysis for an exit pupil expander (EPE) system using 2D grating as out-coupler has been proposed and demonstrated. In this design process, the first step is to establish a simulation workflow to dynamically link a raytracing engine and a rigorous coupled wave analysis (RCWA) solver. The RCWA solver, provided by Ansys Lumerical, can accurately calculate optical response of grating in the EPE system by solving Maxwell’s equations. The raytracing engine, provided by Ansys Zemax OpticStudio, is used to evaluate the whole system’s performance, such as efficiency and uniformity. In this step, the strategy of caching and interpolating the data when linking the RCWA solver and the ray-tracing engine is the key to make the simulation process streamlined and efficient. The second step is to prepare the system for optimization and tolerance analysis. A parametric model of the grating is first constructed. The parameters of this grating model are further considered as a function of position on the waveguide, which means the grating shape varies at different positions. The coefficients of this function are then used as variables during optimization and tolerance analysis by Ansys optiSLang. In this step, the spatial uniformity and the efficiency on the eye box are optimized, and the effect of the imperfect grating geometry and material are investigated.

The creation of new see-through near-eye displays (NEDs) architectures is a topic of intense research focus. A fundamental problem that each design must address is the field of view (FOV) and eyebox of NEDs are limited by etendue conservation for a fixed display optics size. Waveguide architecture provides the solution to increasing the eyebox in NEDs without increasing the optics size through exit pupil expansion. Brightness and uniformity are two key features of waveguide architecture. In this work, we focus on the brightness of the waveguide since the image uniformity can be compensated by the display engine. We show that the geometry of the waveguide sets a fundamental limit on the in-coupling efficiency for a given FOV. This limit can be used as a tool for waveguide designers to benchmark the in-coupling efficiency of their incoupler gratings. With this derived limit, we designed and optimized a metasurface-based grating (metagrating) and a surface relief grating (SRG) as in-couplers. The diffractive efficiencies of the two types of in-couplers were then compared to the theoretical efficiency limit. The metagrating's 28% efficiency surpasses the SRG's 20% efficiency and nearly matches the geometry-based limit of 29% due to the superior angular response control of metasurfaces compared to SRGs. This work provides a new understanding of the brightness efficiency limit of waveguide-based combiners and paves a novel path toward implementing metasurfaces in efficient waveguide AR displays.

A diffractive waveguide-based optical combiner is one of the most commonly used elements to construct head mount AR displays. This paper proposes a design method for a compact and wide field-of-view layout for an AR-applicable diffractive waveguide. The layout design utilizes multiplexed 1D gratings as both the exit pupil expander (EPE) and the out-coupler, combined with minimum-sized 2D grating to improve image uniformity and deliver a better user experience. The design outcome is optimized and simulated in LightTools and RSoft. The result has indicated the feasibility of a compact and 60 degrees FOV design of a diffractive waveguide AR display with a 12 mm × 10 mm eye box.

Bayfol® HX photopolymer films prove themselves as easy-to-process recording materials for volume holographic optical elements (vHOEs) 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 vHOEs 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 vHOEs 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 vHOEs. 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, vHOEs 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. 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. We demonstrate practical examples of Bayfol® HX vHOE’s in see through applications using novel holography techniques for fabricating grating couplers.

For the advancement of XR headset device technology, the projection screen and display technologies are a major focus of discussion. The ToF sensor system used for detecting human viewing area at a given power/space budget is also considered an inevitable feature. We report on the constructed systems and the achieved performances with newly developed refractive-diffractive hybrid lenses, a diffuser (Platanus®) and a dot projector (Ardisia®). These lenses were designed using simulator-based ray tracing and a Maxwell equation analysis, and subsequently fabricated using SCIVAX’ nanoimprinting technology. These lenses were customized with VCSELs to cover the wide range of field of illumination (FOI) from 30 to 150 degrees. Platanus® presented considerably uniform and controllable illumination with high phase uniformity over shorter distances, thus we believe it meets the high-resolution sensing requirements for XR. Ardisia® gave high intensity dots without showing the zeroth order light and any collimation lenses. And its intensity could be even higher with an increased number of VCSEL emitters, without changing the dot count as would be the case for an ordinary DOE, so that long-range illumination is easily achievable. Ardisia® with a FOI of 60x45 degrees enabled illumination over 10 m with an optical power of only 2 W, suggesting that the efficiency and compactness of Ardisia® is suitable for 3D sensing optics for XR applications. And the same can be adopted in automotive applications such as for driver monitoring system (DMS) and potentially LiDAR. In this paper, several experimental results for ToF system are presented.

We have developed a full-color binocular retinal scan AR display, presenting an always-in-focus image to the viewer with a pupil tracking system combined with mechanical movement of an HOE combiner and steering the beam incident angle to the HOE combiner. We achieved high image quality by suppressing dispersion with a relay optical system using a holographic compensator. Our wearable prototype supported a binocular stereoscopic image with 980×560 pixels resolution per eye, 47° diagonal field of view, 6.4×3.2 mm² eyebox, and mechanical IPD adjustment from 55 to 71 mm as an initial setting.

XR devices immerse the user in an augmented world, with digital elements which must be seamlessly blended with the physical world. To achieve this functionality, a perception technology is required. This technology must offer robust operation independently of the environment, must operate within a very tight power budget, and must have very low latency. Existing technologies have been unable to meet all of these demands. VoxelSensors’ sensing and perception technology disrupts the sensorial status quo with the development of unique active event sensors (AES) enabling robust low power and low latency 3D active sensing using laser beam triangulation. This paper will discuss the merits of the proposed sensing paradigm in the context of XR platforms and introduce Switching Pixels® Active Event Sensors.

Hyperspectral and multispectral imaging enable augmented reality experience by collecting spectral information of a scene and mapping it onto a 2D image. This imaging method is especially powerful if done in short-wave infrared (SWIR) because of the unique spectral fingerprints of many molecules found in this region of the spectrum. Despite its high potential, this technology has not been widely adopted due to the high price of standard SWIR cameras. Recently, image sensors based on colloidal quantum dot thin films have gained a lot of attention due to their potential to enable affordable and high-resolution SWIR imaging. In this work, we present the latest results of our efforts to leverage imec's thin-film SWIR imaging platform for spectral imaging. We present the measurement results of our multispectral photodetectors, as well as the results of optical simulations demonstrating new concepts for light filtering in the SWIR region, compatible with the thin-film technology.

Augmented and Virtual Reality (AR/VR) displays differ from regular displays because they hack a human perception system, by creating an illusion of 3D objects that appear to be a part of the real world. Imprecision in implementation of AR system break this illusion and cause us a discomfort or even make us sick. On the other hand, since users are wearing the system on their heads, they are free to move around, their hands are also free, and they want them to stay free to perform the usual tasks. This creates huge and not fully resolved user interface issues - there are no "mouse and keyboard" solution for AR systems. Eye tracking plays a huge role and is one of the cornerstones of what I call high-fidelity Augmented Reality systems that feel comfortable, are easy to use, and do not cause sickness. We will discuss how eye tracking system may help to make better AR, challenges of current eye tracking technologies and what properties of eye tracking systems are important for Hi-Fi AR.

High-accuracy and high-speed 3D sensing technology plays an essential role in VR eye tracking as it can build a bridge to connect the user with virtual worlds. In VR eye tracking, fringe projection profilometry (FPP) can avoid dependence on scene textures and provide accurate results in near-eye scenarios; however, phase-shifting based FPP faces challenges like motion artifacts and may not meet the low-latency requirements of eye tracking tasks. On the other hand, Fourier transform profilometry can achieve single-shot 3D sensing, but the system is highly impacted by the texture variations on the eye. As a solution to the challenges above, researchers have explored deep learning-based single-shot fringe projection 3D sensing techniques. However, building a training dataset is expensive, and without abundant data the model is difficult to make generalized. In this paper, we built a virtual fringe projection system along with photorealistic face and eye models to synthesize large amounts of training data. Therefore, we can reduce the cost and enhance the generalization ability of the convolutional neural network (CNN). The training data synthesizer utilizes physically based rendering (PBR) and achieves high photorealism. We demonstrate that PBR can simulate the complex double refraction of structured light due to corneas. To train the CNN, we adopted the idea of transfer learning, where the CNN is first trained by PBR-generated data, then trained with the real data. We tested the CNN on real data, and the predicted results demonstrate that the synthesized data enhances the performance of the model and achieves around 3.722 degree gaze accuracy and 0.5363 mm pupil position error on an unfamiliar participant.

An immersive augmented reality experience requires adapting the display/optical engine to the human visual system, which introduces many measurement and testing challenges. Near-eye displays often use waveguide combiners to produce superior image quality, thereby placing special demands on the metrology needs. Hence, this challenging application requires robust and state-of-the-art mechanics, and optical setup. In this study, an optical metrology system that can perform various image quality analyses on diced (eyepieces) and undiced (wafer level) waveguides is described. Our novel optical metrology system consists of a human-eye mimicking optical setup, and a multi-axis highly accurate robotics.

Detecting and avoiding collisions during walking is critical for safe mobility. To determine the effectiveness of clinical interventions, a realistic objective outcome measure is needed. A real-world obstacle course with moving hazards has numerous limitations (e.g., safety concerns of physical collision, inability to control events, maintaining event consistency, and event randomization). Virtual reality (VR) platforms may overcome such limitations. We developed a VR walking collision detection test using a standalone head-mounted display (HMD, Meta Quest 2) with the Unity 3D engine to enable subjects’ physical walking within a VR environment (i.e., a busy shopping mall). The performance measures focus on the detection and avoidance of potential collisions, where a pedestrian may (or may not) walks toward a collision with the subject, while various non-colliding pedestrians are presented simultaneously. The physical space required for the system was minimized. During the development, we addressed expected and unexpected hurdles, such as mismatch of visual perception of VR space, limited field of view (FOV) afforded by the HMD, design of pedestrian paths, design of the subject task, handling of subject’s response (detection or avoidance behavior), use of mixed reality (MR) for walking path calibration. We report the initial implementation of the HMD VR walking collision detection and avoidance scenarios that showed promising potential as clinical outcome measures.

Metaforms are novel optical components formed by conforming a metasurface to a freeform substrate. Metaforms can be a powerful solution when designing compact imaging systems such as augmented reality displays. Given the rotationally variant nature of the metaform substrate and the difficulty of metasurface fabrication on curved substrates, the proper alignment of the metasurface nanofeatures to the freeform substrate is essential. Thus, to seamlessly bridge the metaform design, manufacturing, and metrology, we developed a software tool that automatically generates ISO standard highaccuracy CAD models for the designed metaform components.

The emergence of new immersive AR/VR headsets recently resulted in major improvements in hand-gesturebased user interfaces. Devices such as MS HoloLens II and Oculus Quest II support hand-gestures. Although using hand-gestures increases the sense of presence and ease of natural interactions, it has been shown that hand-gestures require extensive physical activity. Furthermore, it has been shown that the error rate in hierarchical menu selection is much higher when using hand-gestures than when using a desktop environment or the controllers. Therefore, assessing the difficulty of a hierarchical menu design when using hand-gestures and gaze for menu selection will enable UI designers to develop more effective user interfaces. In this work, we provide a validated index for estimating the hierarchical menu selection error using hand-gesture and head-gaze as input modalities. The index is informed by cognitive WAIS data gathered from participants, which measures subjective cognitive performance. The proposed index is the result of a user study that includes hundreds of hierarchical menu selections using MS HoloLens, and is validated against the data of a group of different participants. The results demonstrate that the index can successfully capture the trend of the users’ errors in selecting the hierarchical menu items in immersive environments.

Compact near-eye displays covering a large field of view require complex optical imaging systems. While the optical system is designed to minimize distortion, material, design or production constrains may lead to perceptible residual distortion. Imaging light measurement devices (ILMD) are used to detect distortion for product quality assurance. However, imaging measurement systems, especially with wide-angle lenses, may also add distortion to the measurement. Therefore, the accurate calibration of ILMDs is crucial for the accuracy of AR/VR device distortion measurements. Here, we quantify and validate the accuracy of methods of distortion correction for an imaging light measurement device with a field of view (FOV) of 120° and use calibrated ILMDs to quantify geometric distortion and chromatic aberration of virtual reality (VR) headsets.

A challenge in arthroscopic hip surgery is visualizing patient anatomy beneath the skin's surface, specifically in femoroacetabular impingement (FAI) surgeries. FAI is characterized by a bony deformity and hip pain that leads to osteoarthritis. Due to both poor visualization and under-resection of the bone deformity in FAI surgeries, patients often undergo revision surgeries and/or ongoing pain. During surgery, the patient's preoperative medical images are displayed on a monitor alongside the arthroscope's view. Rather than the surgeon mentally fusing the medical images of the hip anatomy onto the patient, augmented reality (AR) could integrate surgical visualization through a head-mounted display that overlays the patient's virtual anatomy onto the real world. This work presents the results from a preliminary user study, which assessed the functionality and accuracy of our AR live-resection tracking model via Microsoft Hololens 2 with a motion capture (MoCap) system. Our primary objective was to assess the initial accuracy of our live-resection tracking model in a simplified simulation with a physical object compared to our ability to track the resection in a virtual object. Our secondary objective was to obtain user feedback on the current AR system for resection tracking.

Diffractive image steering using a Micro Electro Mechanical System (MEMS) Spatial Light Modulator (SLM) with pulsed illumination decouples display size from field of view (FOV), that reduces a form factor of augmented reality (AR) and virtual reality (VR) display engine, while not sacrificing the resolution of image. In the image steering, pulsed illumination is necessary to access to the transitional period of MEMS SLM. Correlation of average laser power of laser diode driven in a pulsed mode operation is evaluated and compared to the power of the laser diode driven in continuous mode.

Currently, holographic waveguide combiner has been widely used for the augmented reality (AR) and head-up display (HUD) applications because it takes advantage of pupil expansion to increase the size of eye-box without interfering with system’s field of view (FOV). Nevertheless, most of the waveguide substrates are restricted to the flat surface. Indeed, flat geometry is able to avoid unwanted optical power exerting on the image when it propagates inside waveguide, however it lacks the aesthetic perception to the viewer and compatibility to the wearable Near-to-eye Display (NED) applications since none of the glasses or windshield is flat. Here, we propose a 2-D curved holographic waveguide that utilizes the holographic optical element with purposely added optical power to compensate the aberration introduced by the curved geometry. Pupil expansion is achieved by manipulating image have multiple interactions with out-couplers to increase the size of eye-box. Both raytracing model and physical demonstrator will be discussed.

This poster presentation was prepared for the Optical Architectures for Displays and Sensing in Augmented, Virtual, and Mixed Reality (AR, VR, MR) IV Conference at the SPIE AR | VR | MR 2023 Symposium.

Augmented, virtual, and mixed reality (XR) displays require miniature light engines that can be worn near-theeye. Laser beam scanner (LBS) architectures use light from a hermetically-sealed laser beam module (LBM) and scan the light with a MEMS mirror into a combiner. This paper presents an improved method for packaging a red, green, and blue (RGB) LBM using stamped mirror arrays that fold the light beam, correct beam shape, and redirect beam propagation to a MEMS mirror. The mirror array simplifies the optical path and eliminates passive components like dichroic filters and refractive lenses such as those used for slow-axis and fast-axis correction. This new approach reduces the size, weight, and cost of LBMs for XR applications.

Enabling all-day-wearable augmented reality (AR) displays require compact engineering solutions that still satisfy requirements like wide field-of-view (FOV) and high resolution. By using a Digital Micromirror Device (DMD) and a pulsed laser in synchronization we are able to perform diffractive image steering which decouples the FOV of the projected image from the display size while not sacrificing image resolution. This approach reduces, by several factors, the lateral extent of the display panel while retaining image resolution. The diffractive-steering-enabled FOV expansion by the DMD, paired with a prism array placed at the exit pupil of the projection lens, maintains a small form factor by re-distributing a part of the volume from the projector engine to the image transfer optics. Together with diffractive image steering and the prism array we demonstrate a 5x increase in field-of-view. This approach decreases the requirement on the number of pixels to maintain high resolution across a wide FOV, which makes it suitable for eventually installing it in small form factor head mounted displays.

As the industrialization of waveguide based Augmented Reality devices is progressing, considerations around design based shaping of the waveguides as well as robustness move into focus. Therefore, automated approaches concerning the cutting of eyepieces made of high index glass is a high priority. A promising approach for scalable free form cutting with high strength and precision is the utilization of ultrashort pulsed lasers. However, the plurality of possible laser process parameters and the different material compositions of high index glasses present a challenging field of optimization opportunities with respect to strength of the glass. SCHOTT AG and 3D-Micromac AG optimized a separation process towards high and predictable bending strength and integrated it into a modular machine concept freely scalable from lab to mass production use.

Incoherent digital holography is a promising idea for holographic teleconferencing because it is free from safety issues by light sources. Here, we propose a fully colored incoherent holographic streaming system that can acquire and reconstruct the incoherent hologram. To capture the real world scene through the natural lights, self-interference incoherent digital holography inferred by the geometric phase optical elements is used. The connection between the hologram pickup system and display system is GPU-based parallel processing which enhances the holographic image quality with phase preserving.

Augmented reality is one of the technologies, which in recent years has been most in the spotlight for communities as diverse as researchers, industrial actors and gamers. A common need in almost any scenarios is to “register” the virtual world with the real one, so that the right virtual objects can be accurately placed in the user's view. Although positioning could be aided by global systems such as GPS, there are situations in which its accuracy or feasibility cannot be guaranteed. Indeed, a few sectors could be prevented from exploring augmented reality as a disrupting technology if this need cannot be adequately fulfilled. In this work, photogrammetry is investigated for scenarios in which a few static already known and well-defined real-world objects can be used for anchoring in a broader area. The goal is to create a solid and reliable augmented reality framework in terms of precise placement of objects with the aim of using it in contexts where other solutions lack the required accuracy. In particular, this work considers as the primary use case a solution developed using Microsoft Hololens 2 for the positioning of digital objects in the context of railway maintenance by exploiting the recognition of real objects in the environment through photogrammetry techniques. Indeed, only a precise positioning of the objects will allow the pervasive diffusion of this technology in sectors such as health, military and in any case in all those contexts where accuracy and reliability are essential elements for ensuring safety of operations.

This poster presentation was prepared for the Optical Architectures for Displays and Sensing in Augmented, Virtual, and Mixed Reality (AR, VR, MR) IV Conference at the SPIE AR | VR | MR 2023 Symposium.

The improvement of fill factor of holographic micromirror array (HMA) with holographic waveguide-type for threedimensional (3D) augmented-reality (AR) display system. Our proposed 3D AR system was created and briefly explain it; there have two the HOE optical film at in-and out coupler of the waveguide. In-coupler HOE is our fabricated HMA, it has a same role with optical microlens-array. HMA is integrate the displaying elemental image set (EIS) from micro display which EIS was generated by the integral imaging technology. The micro display has a 6 mm by 8mm size, 48single elemental images and micro display was located g distance from holographic waveguide which waveguide thickness was 5mm. EIS was displayed by micro display to holographic waveguide. HMA was stick with holographic waveguide and located in opposite side of waveguide and micro display. Micro display was display forward to holographic waveguide and fabricated HMA, then displayed EIS is reflected and integrated at the in-coupler HMA and integrated 3D image was through the holographic waveguide by HMA recorded angle. 3D images of internal reflect in the holographic waveguide was 1 time. 3D image was also reflected at the out-coupler HOE which role was same as optical mirror and reflect to observer’s eye. At least observer as the reconstructed images and real object out and reflects by out-coupler HOE.

Active tracking enables higher precision in tracking the positions, orientations, and states of the virtualized objects. STEAMVR Lighthouse tracking base-stations can be used for tracking specific objects. However, current solutions are bulky and costly. The overall goal of this research work was to reduce the size and cost of active VR trackers to enable their attachment to ever smaller physical tools and objects to be tracked in the real world and displayed in a virtual reality environment.

Glass wafer for AR and MR devices affects directly to image qualities and image properties, such as field of view (FOV), brightness, and so on. The highest index, over 2.10, and high transparent glass for AR and MR devices has been successfully developed. It is expected to realize a wider FOV and a higher sense of immersion by applying this newly developed glass in AR and MR devices.

In stereoscopic extended reality headsets, the distance between optical systems composed of a pair of displays and lenses can be fixed or adjustable. A mismatch between interpupillary distance (IPD) and the distance between optical systems may cause user discomfort and distortions in spatial perception. Nevertheless, little is known about its potential effect on vergence and accommodation. In the study, we explored how visual parameters changed after using the virtual reality headset with a fixed distance between optical systems using routine eye examination tests. Sixty-two subjects (18-33 years of age) were divided into two groups based on the IPD mismatch: 0-5 mm (n = 29) and 6-10 mm (n = 33). Their visual parameters including near point of convergence, amplitude of accommodation, binocular accommodative facility, near horizontal phoria, and fusional reserves were assessed before and after playing 30 minutes of the virtual reality mini-golf game. The data showed considerable changes in the amplitude of accommodation and near point of convergence after the use of virtual reality. Moreover, the prevalence of adverse changes in accommodation and vergence was higher when IPD was mismatched by 6-10 mm compared with the smaller off-alignment. Overall, the findings suggest that the distance between the optical systems in the headsets should be adjustable and matched with the distance between the user’s eyes to lower the demands on the visual system. Moreover, the contribution of IPD mismatch needs to be considered in the user studies investigating the impact of stereoscopic extended reality on the visual system.

We achieved the manufacture of diffraction gratings with line edge roughness of less than 3% at 3σ/ave by utilizing a scanning overlapped phase interference lithography (SOPHIL) system. The SOPHIL method consists of two steps. As the first step, a spot fringe pattern generated by two-beam interference is scanned direction along the grid on the wafer. As the second step, the spot is moved just the integer multiple length of its fringe period, then the spot is exposed again over the 1st fringe. In addition, a 2D-EPE waveguide combiner was fabricated using SOPHIL system. Measured MTF was 0.5 at 0.6 cycles/ milliradian.