This PDF file contains the front matter associated with SPIE Proceedings Volume 11304, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

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

We proposed a full-color three-dimensional holographic waveguide-type augmented-reality display system based on integral imaging using the holographic optical element-mirror array. As same as the conventional holographic waveguide, two holographic optical elements are utilized as in- and out-couplers that are located at the input and output parts of the waveguide. The main roles of these films are that reflecting the light beams come from the microdisplay into the waveguide, transmitting the reconstructed by the HOE-MA, three-dimensional image while a reflecting to the observer’s eye. In the experiment, the augmented-reality feature has been successfully verified that the real-world scene and reconstructed virtual three-dimensional image were observed simultaneously.

In this work, we aim to realize a wide viewing-angle and a space saving configuration in a projection-type integral 3D display composed of a projector and lens array. In the conventional method, for a wide viewing-angle, light rays should be incident on the lens array at a large incident angle. In order to achieve a large incident angle, projectors are installed diagonally behind the lens array. This requires a large space for projectors behind the display. We propose a projection method that realizes a wide viewing-angle using a space saving configuration in which one projector is installed behind the lens array. In the proposed configuration, two mirrors are arranged facing each other between the projector and the lens array. Light rays enter the lens array from the mirror image positions of the projector through multiple reflections between these two mirrors. The proposed method requires no projector other than the projector installed directly behind the lens array. In this way, wide viewing angle is achieved with a downsized system. First, the proposed configuration was simulated and its feasibility was evaluated. Second, based on the simulation results, the specifications of the proposed configuration were evaluated in the experiment. The actual display system was then prepared for the experiment. As a result of the simulation and experiment, a viewing-angle that requires a configuration employing three or more projectors was realized using a configuration employing one projector.

This article present a design method- a triple coating surface waveguide for augmented reality (AR). Recently, with its blooming developments over decades, AR has established distinguishing features that makes it widely applicable among various fields. Overlapping virtual images onto the external view, AR has contributed to applications, such as education, medical surgery, engineering, entertainment, image-guided navigation and even military. However, there are still two major challenges for AR: (1) The inconvenience brought by the bulkiness of AR head mounted display (HMD) devices; (2) The limited magnitude of the field of view (FOV). To improve the drawbacks above, we propose a triple coating surface waveguide that is thinner than the traditional designs of the AR HMD devices, We separate our waveguide into two parts: (1) The free-form surface collimator based on the n0n-pupil forming system, constructed by four high order term extended polynomial surfaces, (2) The triple coating surface directly attached at the end of the waveguide. Traditionally, the FOV relies on the size of the single couple out surface as the single surface determines all wave reflections. Our triple coating surface allows more flexibility on the reflections of optical rays. Each coating possess a critical angle that filters and reflects the optical rays that have a matching incident angle. In other words, the optical rays with different incident angles are reflected at corresponding coating surfaces. We have achieved a large FOV of 40 degree with a 3 mm thick waveguide.

Due to the degenerate spectral response of the human vision system, different sets of primary colors can cover the same color space. Thus, we propose to generate multiple focal planes in head-mounted displays to mitigate the vergence accommodation conflict (VAC) through wavelength multiplexing, making use of another dimension of light as the information channel for cascading 2D images to 3D scenes.

Conventional approaches based on space- or time- multiplexing can provide multifocal functionality but with a significant sacrifice in resolution or frame rate. As a novel alternative, polarization multiplexed methods can avoid these drawbacks, but they can only achieve two focal depths since there are only two orthogonal polarization states. The wavelength multiplexing proposed here is intrinsically free from all the limitations mentioned above.

Firstly, as a proof of concept, we built a dual-focal near-eye display using off-the-shelf optical components. The prototype is designed based on a birdbath architecture with an extra spectral notch filter as the wavelength-sensitive depth separation element. The optical powers for the two wavelength sets are determined by the distance between the reflector and notch filter. Our benchtop demo can generate two focal depths simultaneously, which are located at 1 m and 2 m away from the optical combiner.

Moreover, another compact optical design of a wavelength-multiplexed dual-focus light engine for lightguide type AR displays is also presented. Also, we analyze the implementation of full-color operation and demonstrate an angle insensitive multi-notch filter design based on optical multi-layer coatings. Finally, we discuss practical limitations and potential improvement of the proposed wavelength multiplexing method for overcoming the VAC issue.

The visual performance, in terms of both the resolution and the field of view (FOV), of a single near-eye display (NED), is often restricted by its pixel density. There are plenty of attempts to solve this issue in the research literature, but those solutions would adversely affect the system’s form factor. This paper discusses an advanced foveated imaging system using a dual display with a built-in tilting feature, which allows efficient integration with external eye-tracking systems. One of the displays generates a super-resolution foveal image when it experiences optical minimization upon reflection on a fabricated tilting concave mirror (TCM). Besides that, the TCM capable of up to eight-directional actuation with its mechanism governed by four hydraulic pressure-driven membrane-formed cavities (MFCs). The other display that does not undergo any optical modification creates a low-resolution peripheral view. Subsequently, a foveated image with a wide FOV is projected through an eyepiece lens when images from both displays are combined. Here, the apparent foveal image experiences about five times enhancement at a system dimension of 12 x 10 x 5 cm. Furthermore, the achieved tilting range of the TCM reaches about 20° in both the x and y-direction. This system design, which aims to mimic the perception of a human eye to provide a realistic viewing in a NED, has challenged the conventional trade-off issue between resolution and FOV as well as the relative form factor.

Augmented reality (AR) display having vergence-accommodation conflict (VAC) problem which causes dizziness and motion sickness to viewers. It occurs because of the way of displaying a stereoscopic image. This is a severe disadvantage and must be managed for the popularization of AR. Implementing an integral imaging into the AR system can solve this VAC problem, but this system still has a limited depth problem originated from integral imaging. By using focus tunable lens array instead of an ordinary fixed one, the depth limitation of the integral imaging system can be overcome. Electrowetting lens can be implemented into focus tunable microlens array for AR integral imaging with the advantage of small form factor, fast response time and precise focal length control. By using a hexagonal arrangement and solid lens attach, the lens array with high fill-factor for AR display is fabricated. Its specification is well optimized for AR display and focus tunable integral imaging display is constructed with this lens array. Micro display with small sized pixel is loaded with elemental images, and the tunable lens array makes an image of object inside the panel which has a depth of few centimeters. And magnifying lens and beam splitter makes meter scale object into the air. By adjusting the applied voltage for the liquid lens array, the position of central depth plan can vary from tens of centimeters to meter scale, which satisfies enough range for typical AR usage. With the system, objects with various distant can be displayed clearly with some technical implementation.

We will present a prototype of head-mounted holographic display designed to be of multi-depth. The system employed the modified Gerchberg-Saxton algorithm to produce the phase-only functions on different types of spatial light modulators. Furthermore, our system could achieve multi-depth by using human-eye focusing and zooming mechanism. Finally, the quality of images are also analyzed and evaluated.

In standard phase spatial light modulators (SLM), showing a phase modulation of 2π radians, there is a limit to the shortest focal length of an encoded lens. This Nyquist focal length limit is caused by the aliasing originated by the SLM pixelated structure. In this work we show that SLMs with very large phase modulation (in our case about five cycles of 2π radians) can be used to surpass this effect and efficiently encode lenses with focal lengths much lower than the Nyquist limit. We include experimental results showing that this limit is reduced by a factor of about 1/10.

In this work we investigate design parameters of a stereoscopic head-worn augmented reality display that would facilitate a wider uptake of technology by enterprise and professional users. The emphasis is put on mimicking a way of how naturally the ambient world is perceived by human visual system. To solve this, we propose a solid-state multi-focal display architecture, which is tailored for near-work oriented tasks. The core of the proposed technology is a solid-state multi-plane volumetric screen, with four physical image depth planes which form the secondary image source. The volumetric screen utilizes electrically controllable liquid-crystal based diffuser elements, which receive the image information from the primary source – a pico projection unit. The volumetric screen is coupled with a bird-bath type optical image combiner/eyepiece to yield a 40-degree horizontal field of view covering a representable depth space of 0.35m to infinity where no effects of vergence-accommodation conflict are experienced.

We propose a novel technique to synchronize elemental images and audio signal and the transmission technique for a glass-free 3D TV system based on integral imaging in real time. The main idea behind the method is to generate real time 3D video based on elemental images synchronized with audio stream. The system uses the depth information and RGB data of per frame of a video through Intel RealSense 3D camera and the audio stream from microphone. The audio file is sampled according to per frame of the video and kept in different buffers but having same index. The frames are divided into elemental images using Elemental Image Generation algorithm and the audio data is synchronized according to the index. Then the stream of elemental images and corresponding audio data is transmitted to data server. The display device fetches and decodes this data to produce video which is viewed as 3D using multi-array of lenses.

MicroLED is considered as the next generation display technology, since MicroLED display has high brightness, wide color gamut, high aperture ratio, and good reliability. In additional to traditional display applications, MicroLED display can be used for innovative display technology. Based on our proprietary PixeLED^® display technology and SMAR·TechTM repair solution, we have demonstrated various new applications, such as borderless transparent display, ultra-high brightness wearable device, and ultra-thin flexible display.

Micro-scale light emitting diode (micro-LED) with a chip size less than 100 μm has improved light extraction efficiency due to increased sidewall emission. However, it causes mismatched angular distributions between AlGaInP-based red micro-LED and InGaN-based blue/green counterparts because of the epitaxial material difference. As a result, color shift of RGB micro-LED displays may become visually noticeable. To address this issue, the angular distributions of RGB micro-LEDs are analyzed theoretically and experimentally. In addition, a device structure with top black matrix and taper angle in micro-LEDs is proposed, which greatly suppresses the color shift while keeping a reasonably high light extraction efficiency.

Sheet-type liquid crystal displays (LCDs) using plastic substrates have many advantages such as ultra-thin, light-weight and unbreakable and have attracted significant interest as a promising technology for new display applications. We have developed the foldable LCDs using nano-phase-separated LCs. By introducing the nano-size polymer network into the LCs and controlling the viscoelasticity of LC materials, we successfully suppressed the flow of LCs and improved the luminance uniformity by in the bending process. In addition, we established the control method of the polymer aggregation structure by using the polymerization inhibitor and developed the foldable LCDs with a small radius of curvature.

In this paper, flexible coplanar top-gate p-type SnO TFTs are demonstrated. The TFT performance was optimized by adjusting the post-deposition annealing temperature of the SnO channel. The on/off current ratio of the TFT first improves and then degrades as the channel annealing temperature increases. With an optimized annealing temperature of 175C, the flexible SnO TFT exhibits a field-effect mobility of 0.71 cm²/V-s, threshold voltage of 5.2 V, subthreshold swing of 1.6 V/decade, and on/off current ratio of 1.6 x 10³. The gate-bias stress stability of the optimized TFT was then investigated. When the TFT is at flat state, the threshold voltage shifts after bias-stressed at +10 V and -10 V for 10000 s are 0.2 V and nearly 0 V, respectively. The electrical stability degrades slightly when the TFT is subjected to both mechanical tensile and compressive strains. At a compressive strain of 0.25%, the threshold voltage shifts increase to 0.8 V and -0.3 V for positive and negative bias stress, respectively. At a tensile strain of 0.25%, the corresponding values are 0.7 V and -0.2 V. Compared with unpassivated bottom-gate SnO TFTs, the gate-bias stress stability is greatly improved.

Holographic display is known as the most realistic 3D display by creating real 3D image in front of observer. But there are tremendous technical hurdles in realizing electronic hologram. It is required to achieve very small pixel pitch SLM (spatial light modulator) for realizing electronic hologram using flat panel display. All the components of the unit pixel should be carefully redesigned and improved to maintaining same performance in spite of reduction of pixel pitch. The size of hologram image depends on the size of SLM. Therefore, the resolution of the SLM increases very fast as the reduction of pixel pitch in SLM. The driver chip and architecture should be developed to manage the large number of pixels with high speed.

Novel unit pixel design for achieving 1μm pixel pitch will be presented. VST (vertically stacked transistor) structure will be introduced. In VST structure, the driving TFT is stacked on the data line. VST structure has the merits for reducing horizontal pixel pitch without introducing expensive high-definition lithography tool. The technology compatible with 0.5μm critical dimension can be used for fabrication of 1μm pixel pitch SLM.

Alternative structure for achieving small pitch pixel is the adopting VTFT (vertical channel thin film transistor). VTFT means that the channel direction is vertical to SLM plane. The footprint of VTFT is very small, for required area is only the overlap region of active layer and source/drain layer.

Cross-talk between adjacent pixels can interfere the rotation of LC molecule. This phenomenon will be very critical for accurate phase modulation for 1μm pixel pitch SLM. Novel concept for reducing cross-talk will be also presented with experimental results.

A suitable model for OLED simulation is provided. We included the tail state model, field dependent model, and triplet conversion model at heterojunction interface into our developed simulator to provide academic free TCAD simulator for research society. The details of simulator, algorithm, and fitting to experimental results will be provided.

A emission mode based on triplet-triplet annihilation up conversion (TTAUC) was proposed as follows: when the electrons and holes recombined at the sensitizer layer with a lower energy bandgap, the triplet exciton of sensitizer can transfer the energy to the triplet-triplet annihilation (TTA) emitter and emit a higher energy blue photon. TTAUC-OLEDs had proved to have a higher device efficiency with tris(8-hydroxyquinolinato)aluminum (Alq3) as sensitizer and 9,10-Bis(2-naphthyl)anthraces (ADN) as TTA emitter. In this research, we employed Bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) to replace Alq3 which had a higher electron mobility and resulted in a better electrical properties. It showed a higher current density at constant voltages and the turn-on voltage (at 1 cd/m2) decreased 0.3V compared to Alq3 as sensitizer. Bebq2 as sensitizer achieved a higher efficiency with 3.26% in overall EQE, together with 1.91% and 1.35% in blue and green EQE at J=6.71 mA/cm2 compared to Alq3

This Conference Presentation, Highly efficient, transparent, and near-infrared organic up-conversion devices, was recorded at Photonics West 2020, San Francisco, United States

An extended depth-of-field projection is needed for spatial augmented reality. However, conventional projectors are often designed with a small F/#, which causes a narrow depth-of-field. This paper presents a new system consisting of a variable focus optical path and 1000-fps 8-bit high-speed projector. This system oscillates the focal length of the lens at high speed and synchronizes it with the projection. High speed performance contributes to project clear images even under the oscillated focal length and to realize all-in-focus projections on more than 10 targets at different depths.

The purpose of this research is to investigate the different requirements and design parameters and thus the challenges of digital RGB LEDs for automotive interior lighting and signage. Challenges are for instance scalability and driving of a large number of LEDs. The optical performance is ruled by temperature dependencies of LEDs, production tolerances of LEDs and integration into light guides. All these and some more parameters determine at the very end the uniformity in terms of luminance and color coordinate; a potential non-uniformity should be in a range that is not perceived by observers or limited to a non-disturbing value. For this purpose, commercially available digital RGB LEDs (WS2812B) and professional automotive RGB LEDs (ISELED) were evaluated with regard to optical parameters such as spectra, uniformity and temperature dependencies. The optical measurements reveal the importance of calibration, temperature compensation and production tolerances (binning). It also shows how essential an efficient protocol for RGB data communication is for addressing a large number of LEDs without noticeable lag or sluggish animations.

Intermediate pupil mask is adopted for synthesis of computer-generated holograms via Fourier ptychographic method. The problem of the conventional Fourier ptychographic method is that the exact target images cannot be created, when it utilized to synthesize computer-generated holograms. In the previous study, the diffraction effect on target images is ignored, and the target images are generated by light-field scheme. However, the mismatched target images degrade the quality of holographic images. The degradation can be mitigated by choosing the optimal size of the sub-regions. The optimal size of the sub-regions can be derived by considering the all-in-focus condition. It is also shown that the computation load can be reduced by setting the pupil mask to Gaussian function. The proposed method has an advantage in computation load for their image quality compared with other hologram synthesis algorithms. The proposed method is verified by numerical simulation.

We have proposed the retinal projection type super multi-view head mounted display (HMD). The super multi-view method provides stereoscopic information by inducing the accommodation of the human eye by blurring the retinal image. This method uses the principle of Maxwellian view and reconstruct the blur image by overlapping projected each parallax image on the retina. However, considering only the degree of the overlap of the projected parallax images on the retina is not enough for reconstructing the real blur. In order to overcome this problem, we propose the optimal method considering not only the degree of the overlap of the parallax images projected on the retina but also the light intensity of each parallax image to reconstruct the real blur. From the evaluation experiment, we verified that the proposed method improves the reproducibility of blur compared to the method considering only the degree of superimposition of the parallax images projected on the retina. Furthermore, it was also confirmed that the prototype system can display 3D images in the depth range of human ocular accommodation from 200mm to 2000mm. The super multi-view HMD based on the proposed method can induce the accommodation of the human eye with the high reproducibility blur and provide more natural 3D images.

In 3D displays based on parallax barriers, active parallax barriers that can change the barrier pattern according to the viewing position have been proposed to expand the viewing area. However, the production cost increases because the active barrier requires a special LC panel. Therefore, to lower the cost, we propose a glasses-free stereoscopic display using an active parallax barrier of an LC panel with the same specifications as the image LC panel. The ideal image pattern cannot be formed because the minimum control unit of the LC panel is equal to one subpixel. However, by using an image cycle pitch method (ICPM) that periodically increases the horizontal pitch of one pair of binocular images by one subpixel, we can realize the ideal relationship between the average pitch of the binocular image and the barrier pitch. In our previous research, we could make the average pitch match to the ideal pitch on the discrete optimum viewing distances (OVDs), but we could not follow the viewing position between the discrete OVDs. In this paper, we propose the ICPM that can keep the stereoscopic vision even at any viewing position. In order to verify the effectiveness of the proposed method, we made the prototype displays and evaluated them. As a result, we showed the crosstalk ratio could be suppressed low over a very wide range by using the proposed method. Also, we confirmed we could obtain the stereoscopic vision at the viewing distance from 300 mm to 729 mm by a subjective evaluation.

The visual discomfort caused by vergence-accommodation conflict (VAC) and low angular resolution has been one of the main issues for near eye display devices. Although numerous researches on light-field displays have been presented as possible solutions to reduce the discomfort by reproducing depth cues, the resolution degradation of the system is still a challenging problem. In this paper, we demonstrate a high-resolution light-field near-eye display based on integral imaging using foveated imaging system with two display panels and an optical combiner. The concept of foveated imaging system is based on the fact that human eyes perceives images with the highest sensitivity only in the central vision which covers about 5° of the visual field, and not in the peripheral vision. The first display panel, which is coupled with a lens array, is optically minified to provide resolution-enhanced light-field 3D images with relatively high pixel density for the central foveal area, and the second one offers background images with wide field-of-view (FOV) for the surrounding area. By combining these two images with an optical combiner, it is possible to achieve foveated light-field 3D images concentrated on the central foveal area with highly enhanced resolution while providing wide FOV for the peripheral area. The proposed near eye display effectively reduces VAC for the eye-gazing area.

Commonly, the 3D surface reconstruction is done by analyzing the deformation of the image of binary grating projected onto the relief of an opaque object. The phase of the deformed grating is extracted by Fourier transform and unwrapping the phase by some algorithm. One technique to image grating projection is the Talbot effect that creates self-images of a periodic objects. In this work, one of the self-images is used to be transmitted through a phase object. The difference in thicknesses of the transparent object causes a change in the optical path length of the light beam and deforms the grating lines. This deformation is analyzed to find the 3D shape of this object. Some experimental results are shown.

Three-dimensional images on multiple depth layers of the volumetric display provide the physiological depth cues which ensure the high precision of depth judgements at close viewing distances and enhance the user experience. However, the contribution of physiological cues declines with an increase of viewing distance (egocentric distance), and the human spatial perception varies depending on the inter-stimuli distance (exocentric distance). We conducted a psychophysical experiment to test the perception of three-dimensional images rendered on the volumetric display depending on exocentric and egocentric stimuli distance. The constant angular size visual stimuli were displayed on different depth layers of the optical element at three eccentricities in a random order. In 4AFC tasks, observers were required to indicate the closest stimulus. The decline in performance was evident at the largest tested exocentric distance, and it became more pronounced with an increase of egocentric distance. However, no performance differences manifested themselves when stimuli were located close to each other. Namely, the correct relative depth judgements were given quickly regardless of slight changes in the egocentric distance. We discuss how the viewing distance and spatial layout of stimuli facilitate perception of three-dimensional images on the volumetric display.