High-dynamic-range Foveated Near-eye Display System

Wearable near-eye display has found widespread applications in education, gaming, entertainment, engineering, military training, and healthcare, just to name a few. However, the visual experience provided by current near-eye displays still falls short to what we can perceive in the real world. Three major challenges remain to be overcome: 1) limited dynamic range in display brightness and contrast, 2) inadequate angular resolution, and 3) vergence-accommodation conflict (VAC) issue. This dissertation is devoted to addressing these three critical issues from both display panel development and optical system design viewpoints. A high-dynamic-range (HDR) display requires both high peak brightness and excellent dark state. In the second and third chapters, two mainstream display technologies, namely liquid crystal display (LCD) and organic light emitting diode (OLED), are investigated to extend their dynamic range. On one hand, LCD can easily boost its peak brightness to over 1000 nits, but it is challenging to lower the dark state to \u3c 0.01 nits. To achieve HDR, we propose to use a mini-LED local dimming backlight. Based on our simulations and subjective experiments, we establish practical guidelines to correlate the device contrast ratio, viewing distance, and required local dimming zone number. On the other hand, self-emissive OLED display exhibits a true dark state, but boosting its peak brightness would unavoidably cause compromised lifetime. We propose a systematic approach to enhance OLED\u27s optical efficiency while keeping indistinguishable angular color shift. These findings will shed new light to guide future HDR display designs. In Chapter four, in order to improve angular resolution, we demonstrate a multi-resolution foveated display system with two display panels and an optical combiner. The first display panel provides wide field of view for peripheral vision, while the second panel offers ultra-high resolution for the central fovea. By an optical minifying system, both 4x and 5x enhanced resolutions are demonstrated. In addition, a Pancharatnam-Berry phase deflector is applied to actively shift the high-resolution region, in order to enable eye-tracking function. The proposed design effectively reduces the pixelation and screen-door effect in near-eye displays. The VAC issue in stereoscopic displays is believed to be the main cause of visual discomfort and fatigue when wearing VR headsets. In Chapter five, we propose a novel polarization-multiplexing approach to achieve multiplane display. A polarization-sensitive Pancharatnam-Berry phase lens and a spatial polarization modulator are employed to simultaneously create two independent focal planes. This method enables generation of two image planes without the need of temporal multiplexing. Therefore, it can effectively reduce the frame rate by one-half. In Chapter six, we briefly summarize our major accomplishments

Large-angle and high-efficiency tunable phase grating using fringe field switching liquid crystal

We propose a switchable phase grating using fringe field switching (FFS) cells. The FFS phase grating possesses several attractive features: large diffraction angle, high diffraction efficiency, fast response time, and high contrast ratio. It can diffract \u3e 32% light to +/- 2nd orders with a large diffraction angle of 12.1 degrees. Meanwhile, its response time remains relatively fast even at -40 degrees C. A simulation model is developed to explain the experimental results and good agreement is obtained. We also demonstrate a blazed phase grating to achieve tunable beam steering between 0th, 1st and 2nd orders

FORECASTING METHOD OF VEHICLE ENGINE RELIABILITY LIFE TEST DATA

Aiming at the problem of long time of vehicle engine reliability life test,the grey system forecasting theory is used to forecast vehicle engine reliability life test data,and the unbiased grey GM（ 1,1） power model for engine reliability life test data is proposed. By examining the overall distribution function equality of test data sequence and forecasted data sequence,it is confirmed that the proposed unbiased grey GM（ 1,1） power model can be effectively used for the prediction of engine reliability life test data. The example results show that the grey theory forecasting method for the prediction of engine reliability life test data has high precision,and distribution function parameters of test data sequence and forecasted data sequence are very close. Using the proposed method can shorten engine reliability life test time and save test cost

Ambient Contrast Ratio Of Lcds And Oled Displays

We systematically analyze the ambient contrast ratio (ACR) of liquid crystal displays (LCDs) and organic light-emitting diode (OLED) displays for smartphones, TVs, and public displays. The influencing factors such as display brightness, ambient light illuminance, and surface reflection are investigated in detail. At low ambient light conditions, high static contrast ratio plays a key role for ACR. As the ambient light increases, high brightness gradually takes over. These quantitative results set important guidelines for future display optimization. Meanwhile, to improve an OLED’s ACR at large oblique angles, we propose a new broadband and wide-view circular polarizer consisting of one linear polarizer and two biaxial films. Good performance is realized

Multi-Angle Beam Steering For Head-Mounted Displays

We propose a switchable multi-angle grating for steering the light between nine different angles from 0° to 16° with an interval of 2°, It shows great promises for eye-tracking applications in head-mounted displays

Functional Reflective Polarizer For Augmented Reality And Color Vision Deficiency

We report a functional reflective polarizer that can be incorporated into a compact augmented reality system. The design principle of the functional reflective polarizer is explained and two design examples are illustrated. In the first example, with the specially designed functional reflective polarizer, the transmittance of the augment reality system is relatively high as compared to a polarizing beam splitter or a conventional reflective polarizer. Such a functional reflective polarizer can also be used for vehicular displays. For the second example, the functional reflective polarizer is specially tailored to help those people with color vision deficiency