Directional Blue Micro-LEDs With DBR Optical Cavities for Compact AR Displays

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Solution Overview

Problem

Current AR display technologies face challenges with large size and weight due to optics, low brightness, aspect contrast ratio, high pixel density requirements, and issues with directionality and color mixing, particularly in outdoor conditions.

Innovation Solution

The integration of freestanding InGaN-based blue LEDs, distributed Bragg reflectors, and diffractive optics in AR displays, utilizing remote epitaxy and DBR layers to achieve highly directional and monochromatic blue light emission, with quantum dots converting red and green light for full-color displays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional AR display technologies (LCoS, digital light processor, LBS) are used, then display functionality is achieved, but device size and weight become large and cumbersome

Engineering Contradiction:

Improvedisplay brightnessVSAvoiddevice weight

Core Design Contradiction:

Illumination intensityVSWeight of moving object

Solution Approach 1:

The patent changes the fundamental parameters of the light source by using micro-LEDs with integrated DBR structures instead of conventional display technologies. This parameter change enables high brightness (luminance) while simultaneously reducing device size and weight, as the micro-LED approach eliminates the need for large optical components required by LCoS, digital light processors, and laser beam scanning systems

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite structure combining micro-LEDs with distributed Bragg reflectors (DBRs) integrated into a single device. This composite approach allows the light source to achieve both high brightness emission and directional control without requiring separate large optical components, thereby reducing overall device weight and size while maintaining display functionality

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If OLED on Si technology is used, then display functionality is achieved, but brightness and aspect contrast ratio are low making display hard to see on sunny days

Engineering Contradiction:

Improvedisplay brightnessVSAvoidoutdoor visibility

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent changes the material parameter from organic OLED to inorganic micro-LED technology, which inherently provides orders of magnitude higher luminance. This parameter change enables the display to achieve sufficient brightness for outdoor sunny day visibility while maintaining the compact form factor required for wearable AR devices

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If high pixel density is implemented in compact space, then AR display resolution is improved, but directionality and color mixing issues from nearby pixels occur

Engineering Contradiction:

Improvepixel densityVSAvoiddirectionality control

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent merges the light emission function with directional control by integrating distributed Bragg reflectors directly into the micro-LED structure. This combination allows high pixel density to be achieved in compact space while the integrated DBR ensures that each pixel's light is emitted in a controlled direction, preventing color mixing from nearby pixels without requiring complex manufacturing processes

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach provides high luminance, directionality, and monochromaticity, enabling compact and lightweight AR devices with enhanced image quality and usability.

Implementation Method 1

distributed Bragg reflectors (DBRs)... The light generated by blue LEDs is reflected within the optical cavity of DBR/LED/DBR, creating a highly directional (Δθ≤±5°) and monochromatic (FWHM≤5 nm) blue light

Methodology Applied

Scientific EffectDistributed Bragg reflector: Bragg Diffraction

Implementation Method 2

quantum dots (QDs) can be used to form red and green light via color conversion

Methodology Applied

Scientific EffectQuantum dot color conversion: Photoluminescence

Implementation Method 3

freestanding InGaN-based blue LEDs... the light generated by blue LEDs

Methodology Applied

Scientific EffectLight emitting diode: Light Emitting Diode

Data Source

PatentUS20250301844A1Directional and monochromatic blue micro-leds and articles comprising the same

Publication Date: 2025.09.25 UNIV OF VIRGINIA PATENT FOUND

AI summary

In one aspect, the disclosure relates to micro-LED based AR displays combining stacked red, green, and blue LEDs, distributed Bragg reflectors, and diffractive optics; methods of making the same; and augmented reality displays using the same. In one aspect, the light generated by the LEDs is reflected within the optical cavity of DBR/LED/DBR, creating a highly directional (Δθ≤±5°) and monochromatic (FWHM≤5≤nm) blue light. In an aspect, the luminance of the disclosed inorganic-based micro-LEDs is orders of magnitude higher than that of organic LEDs while also providing high directionality and monochromaticity, leading to higher image quality. In a further aspect, the small size of the disclosed light source and combiner allows a much more compact and light-weight AR device to be constructed.