PBP Micro-Lens Beam Tuning for Dense Micro-OLED Arrays
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Solution Overview
Problem
Near-eye displays face challenges in efficiently directing light emitted by micro-LEDs due to their small size and high packing density, leading to non-uniform brightness and reduced light extraction efficiency, as well as difficulties in fabricating plano-convex micro-lenses with small pitches, which can cause crosstalk and defects.
Innovation Solution
The use of polarization diffraction micro-lenses, specifically Pancharatnam-Berry Phase (PBP) lenses made from liquid crystal polymer layers, which are planar, diffract light of different polarization states differently, allowing for collimation and deflection of light beams without physical displacement, reducing Fresnel reflections, and maintaining alignment with micro-LEDs to avoid crosstalk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If plano-convex micro-lenses are fabricated with small pitches to match high packing density micro-LEDs, then light extraction efficiency is improved, but manufacturing complexity increases and defects such as crosstalk occur
Solution Approach 1:
The patent replaces traditional mechanical/plano-convex micro-lenses with polarization diffraction optical elements. Instead of using physical lens curvature to focus and extract light, the invention uses polarization-sensitive diffraction patterns created by sub-wavelength gratings or liquid crystal structures. This substitution eliminates the need for complex fabrication of small-pitch convex lenses while maintaining high light extraction efficiency through polarization-selective diffraction.
Solution Approach 2:
The invention changes the optical parameters by introducing polarization sensitivity into the light extraction process. By using polarization diffraction micro-lenses that selectively diffract specific polarization states, the system achieves efficient light extraction without requiring precise mechanical alignment or complex lens geometries. The parameter change from geometric optics to polarization optics resolves the manufacturing complexity issue.
2Manufacturing precision
If micro-LEDs are packed at high density to increase resolution, then display quality is improved, but light extraction efficiency decreases due to limited space
Solution Approach 1:
The patent applies local quality by making the light extraction properties polarization-dependent rather than uniformly geometric. Each micro-LED region is equipped with polarization diffraction structures that locally optimize light extraction for specific polarization states. This allows high-density packing because each location can be independently optimized for its specific emission characteristics without requiring physical space for large lens structures.
Solution Approach 2:
The invention transitions from two-dimensional geometric lens design to three-dimensional polarization state control. By utilizing the polarization dimension of light, the system can extract light efficiently from densely packed micro-LEDs without increasing physical footprint. The polarization degree of freedom provides an additional dimension for optimizing light extraction independent of spatial packing density.
3Loss of energy
If polarization diffraction micro-lenses are used to collimate and deflect light beams, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The polarization diffraction micro-lens structure performs multiple functions simultaneously: it acts as a collimating element, a beam deflector, and a polarization selector all in one integrated component. The sub-wavelength grating or liquid crystal structure provides lensing, diffraction, and polarization control in a single element, reducing overall device complexity compared to separate optical components.
Solution Approach 2:
The patent introduces polarization as an intermediary mechanism to achieve light beam control. Instead of directly manipulating light paths with complex mechanical lenses, the system uses polarization-sensitive diffraction structures as intermediaries that convert polarization states into spatial beam patterns. This intermediary approach simplifies the optical structure by using polarization conversion rather than direct geometric manipulation.
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 enhances light extraction efficiency and overall system efficiency by uniformly directing light from micro-LEDs across the display, improving image quality and reducing manufacturing complexities.
Implementation Method 1
polarization diffraction micro-lenses... diffract light of different polarization states differently
Implementation Method 2
Pancharatnam-Berry Phase (PBP) lenses made from liquid crystal polymer layers
Implementation Method 3
diffract light of different polarization states differently
Implementation Method 4
reducing Fresnel reflections
Implementation Method 5
collimation and deflection of light beams
Implementation Method 6
deflect chief rays of light beams emitted by the array of micro-LEDs by different deflection angles
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A micro-light emitting diode device includes a backplane including drive circuits formed thereon, an array of micro-LEDs bonded to the backplane and electrically coupled to the drive circuits, an array of polarization diffraction micro-lenses bonded to the array of micro-LEDs and including a planar surface, and a cover glass bonded to the planar surface of the array of polarization diffraction micro-lenses. A center of each polarization diffraction micro-lens of the array of polarization diffraction micro-lenses aligns with a center of a respective micro-LED of the array of micro-LEDs.