Micro-Reflector Array for Micro-LED Light Divergence Control
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Solution Overview
Problem
Conventional projection systems based on passive imager devices like LCD and DMD suffer from low efficiency due to light loss and require complex optics, while micro-LED arrays with large divergence angles lead to reduced brightness and contrast in projection systems.
Innovation Solution
Integration of a micro-reflector array with each micro-LED in an active-matrix LED micro-display panel to reduce light divergence and suppress inter-pixel crosstalk, enhancing light collection and directionality for high-brightness and power-efficient displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a projection lens with limited numerical aperture is used to collect light from micro-LEDs with large divergence angle, then the system structure is simplified, but light collection efficiency is significantly reduced
Solution Approach 1:
The patent divides the optical control function into two parts: the micro-reflector array integrated with each micro-LED pixel to pre-collimate light at the source, and the projection lens to collect and project the already directional light. This segmentation allows each component to operate more efficiently within its capabilities.
Solution Approach 2:
The micro-reflector array performs preliminary light direction control before the light reaches the projection lens. By collimating light at the micro-LED level first, the system reduces the burden on the projection lens and improves overall light collection efficiency.
2Device complexity
If micro-LEDs with large divergence angle are used for self-emissive display, then device simplicity is improved, but inter-pixel light crosstalk increases and image sharpness is reduced
Solution Approach 1:
Each micro-LED pixel is equipped with its own micro-reflector structure that is specifically designed to control light emission in that local region. This local optical control prevents light from spreading into adjacent pixel regions, eliminating crosstalk while maintaining device simplicity.
3Illumination intensity
If microlens array is used to reduce light divergence from micro-LEDs, then light directionality is improved, but only the central portion of light is manipulated effectively
Solution Approach 1:
Instead of using lenses to converge light from all directions (which misses oblique light), the patent uses micro-reflectors to redirect oblique and peripheral light toward the central emission direction. This inverted approach of controlling light from the edges inward is more effective for LED emission patterns.
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 micro-reflector array significantly improves projection brightness and contrast, reduces power consumption, and enhances privacy by improving light-emission directionality in direct-view applications.
Implementation Method 1
A micro-reflector is integrated with each micro-LED or each display pixel... The micro-reflector typically is responsible for manipulating the oblique-angle light
Data Source
AI summary
A display panel with integrated micro-reflectors. The display panel also includes an array of pixel light sources (e.g., micro-LEDs) electrically coupled to corresponding pixel driver circuits (e.g., FETs). The micro-LEDs produce light and the micro-reflectors reduce the divergence of the light produced by the micro-LEDs. Different designs are possible. The micro-reflectors can have different shapes, include the shape of their sidewalls and the shape of their plan cross-section. The array schemes can also vary, including the number of LEDs per micro-reflector. Different fabrication approaches are also possible. In one approach, a support structure is integrated between micro-LEDs. The sides of the support structure are reflective and serve as the reflective sidewalls of the micro-reflector. Alternately, the LED mesa itself can serve as the support structure.