Partially Overlapping Microlens Arrays for Dense Micro-LED Light Coupling
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Solution Overview
Problem
Ultra-dense micro-LED arrays face inefficiencies in light collection due to broad angular distribution of emitted light, with much of the light being unusable as it exits at angles outside the specified acceptance cone, leading to wasted energy and reduced system performance.
Innovation Solution
The use of partially overlapping microlenses of varying sizes, which do not cover the entire display area, is introduced to compress emitted light into desirable acceptance angles, maximizing light directionality and compensating for differences in efficiency among red, green, and blue emitters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If micro-LED arrays use ultra-dense emitter arrangements with small pixel pitch, then display resolution and density are improved, but light collection efficiency deteriorates due to broad angular distribution
Solution Approach 1:
A microlens array is introduced as an intermediary optical element between the micro-LED emitters and the viewing direction. Each microlens corresponds to one or more emitters and focuses their broadly distributed light into a concentrated beam within the acceptance cone, thereby resolving the contradiction between high emitter density and efficient light collection
Solution Approach 2:
The solution transitions from a two-dimensional emitter arrangement problem to a three-dimensional optical path control problem by introducing microlenses with specific curvature and focal length. This adds the dimension of optical focusing in the vertical direction, enabling light from ultra-dense emitters to be collected efficiently despite their small pitch
2Loss of energy
If microlenses are made larger to collect more light, then light collection efficiency is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
Rather than using a single large microlens for each emitter, the system segments the optical function across multiple smaller microlenses, each serving one or more adjacent emitters. This segmentation allows for standardized, smaller lens units that are easier to manufacture and align, while collectively achieving the required light collection efficiency
Solution Approach 2:
The patent optimizes microlens parameters including diameter (1.5-3.0 μm), focal length (3-6 μm), and curvature radius (2-4 μm) to achieve the balance between light collection efficiency and manufacturing feasibility. These parameter changes enable effective light focusing without requiring excessively large or complex lens structures
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 increases optical performance by coupling more light into the acceptance cone, achieving a boost of up to 10% higher efficiency, which translates to longer battery life in battery-operated displays and improved resolution in high-density applications.
Implementation Method 1
microlenses... compress emitted light into desirable acceptance angles
Data Source
AI summary
In micro-LED displays, emitters may be arranged to form an array of pixels. Examples of emitters include a micro-LED alone, or a combination of a micro-LED and a color converter. The color converter may be based on quantum dots or other quantum confined nanostructures. Each emitter is served by a corresponding microlens. Rather than using microlenses that fully overlap so that there are no areas of the display devoid of microlenses, optical performance may be increased by using smaller microlenses that partially overlap with each other but which do not cover the entire area of the display.