ORCID

0000-0002-2157-0497

Keywords

Augmented reality displays; light engines; power consumption; micro-LED display; perceived image quality

Abstract

Augmented reality displays, which integrate digital information with environmental backgrounds, are emerging in our daily lives. To ensure readability under outdoor environments with intense ambient light, AR displays must achieve high luminance levels suitable for human visual perception. However, severe light leakage in waveguide couplers and significant losses during exit pupil expansion limit the overall system efficiency to approximately 4%, requiring the light engine to reach luminance levels over one million nits. In addition, to match visual acuity while keeping a compact light engine size (< 1cc), full-color pixel pitch must be below 4 µm. This dissertation is devoted to addressing the possibility of existing light engines to meet these demanding requirements.

In Chapter 2, we comprehensively analyze the power consumption of existing commercial light engines from emissive displays (e.g., microLED and micro-OLED) to light modulation technologies (e.g., liquid crystals on silicon and digital light processing), and raster scan displays (e.g., laser beam scan). The analysis includes both electrical and optical losses throughout the projection system. Although microLEDs are regarded as the most promising solution for AR eyeglasses, their efficiency degrades significantly as pixel size decreases due to sidewall defects introduced during mesa etching.

To overcome this limitation, a continuous quantum well (CQW) microLED architecture is proposed in Chapter 3, mitigating surface defects by keeping damaged area from the active layer. Electrical and optical crosstalk between adjacent pixels is further addressed through structural engineering, including moth-eye meta-atom arrays and pixel define layer modulation, which enhance air-mode confinement and reduce refractive index mismatch. Remarkably, incorporating a carbon black matrix reduces optical crosstalk by five times while maintaining high optical efficiency.

In Chapter 4, next-generation nanowire LEDs grown via bottom-up selective epitaxy are explored as an alternative to conventional microLEDs, inherently avoiding sidewall damage. Despite their promising efficiency, nanowire LEDs exhibit angular color shift due to variations in radius and emission wavelength for RGB colors. By optimizing nanowire geometry, the air mode can be maximized with a suppressed angular color shift can be suppressed within ±20°. Such nanowire LEDs are more efficient than traditional microLEDs for high-resolution-density displays, holding strong potential for emerging AR glasses.

Beyond increasing the peak luminance of the display, tong mapping can enhance image readability under strong ambient light. In Chapter 5, a novel tone-mapping method based on dynamic gamma correction, fitted to the human eye function, is proposed to mitigate image washout. Finally, in Chapter 6, we briefly summarize our major accomplishments.

Completion Date

2025

Semester

Fall

Committee Chair

Shin-Tson Wu

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

Optics and photonics

Format

PDF

Identifier

DP0029795

Document Type

Thesis

Campus Location

Orlando (Main) Campus

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