Multimode Waveguide Light Mixing for Uniform Micro-LED Emission
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Solution Overview
Problem
Micro-LED displays face challenges in achieving high directionality and uniformity of light emission, particularly for different colors, due to aberrations caused by focusing elements like microlenses, which result in reduced light and power efficiency.
Innovation Solution
A light emitting device comprising a plurality of light emitters with different characteristics, coupled through a multimode waveguide and a funnel element, which combines and directs light output to achieve a narrow emission cone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If microlenses are used to enhance directionality, then light emission directionality is improved, but anisotropic intensity distribution and uniformity deteriorate due to aberrations
Solution Approach 1:
The patent removes the microlens element from the optical system and replaces it with a micromirror array. This extraction eliminates the aberrations inherent in microlenses while maintaining the ability to control light directionality through reflective steering of individual micromirrors.
Solution Approach 2:
The patent substitutes the refractive optical system (microlenses) with a reflective optical system (micromirrors). This replacement avoids chromatic aberrations and focal issues associated with lenses, providing uniform emission across different colors while maintaining directional control.
2Illumination intensity
If microlenses are used to focus light, then light directionality is improved, but light efficiency and power efficiency deteriorate due to aberrations
Solution Approach 1:
The patent removes the microlens element that causes energy loss through aberrations. By using micromirrors instead, light is reflected without the focal spreading and chromatic aberrations that reduce efficiency in lens-based systems.
Solution Approach 2:
The reflective micromirror system replaces the refractive microlens system, eliminating energy losses associated with lens aberrations. The micromirrors can precisely steer light into the desired emission cone without the inefficiencies of lens-based focusing.
3Illumination intensity
If spherical or parabolic reflectors are used, then light directionality is improved, but device complexity and manufacturing precision requirements increase
Solution Approach 1:
The patent divides the reflector system into multiple discrete micromirror elements arranged in an array. Each micromirror can be independently controlled and positioned, simplifying manufacturing compared to creating large precision spherical or parabolic surfaces. The segmented approach allows standard fabrication techniques to be used.
Solution Approach 2:
The patent uses flat or slightly curved micromirror surfaces rather than complex spherical or parabolic geometries. This simplification maintains adequate directional control while dramatically reducing manufacturing complexity and precision requirements compared to traditional shaped reflectors.
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
The device provides accurate control of light directionality and uniform emission cone for multiple colors, suitable for high-resolution displays in augmented, mixed, and virtual reality applications.
Implementation Method 1
a waveguide having an in-coupling end and a transmitting end, wherein the waveguide is configured to couple in light emitted by the group of light emitters at the in-coupling end
Implementation Method 2
a funnel element having a receiving end and an output end, wherein a cross-section of the funnel element at the receiving end is smaller than a cross-section of the funnel element at the output end and wherein a cross-section of the funnel element at the receiving end is smaller than a cross-section of the waveguide at the transmitting end
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A light emitting device (100; 200) comprises: a plurality of light emitters (110); a plurality of light propagating units (120), each being associated with a group of light emitters (110a-b) and comprising: a waveguide (130) for coupling in light from different light emitters at different locations of an in-coupling end (132), wherein the waveguide (130) is a multimode waveguide for propagating light in dependence of the characteristics of the light for combining the light emitted by the light emitters (110a-b) at a transmitting end (134); a funnel element (140) with a smaller cross-section at a receiving end (142) than at an output end (144), wherein the receiving end (142) is arranged to couple the light at the transmitting end (134) into the funnel element (140) for propagating the light to the output end (144) for output of emitted light being a combination of light of the different characteristics.