Microlens Stack for LED Light Extraction in Thin Displays
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Solution Overview
Problem
Existing light-emitting diode (LED) displays face inefficiencies in light extraction, leading to reduced display performance due to the thickness required for optimal microlens spacing, which increases the overall thickness of the display.
Innovation Solution
A microlens stack is formed over the light-emitting diode, comprising an array of microlenses made from high refractive index inorganic materials and a single microlens from a lower refractive index organic material, with an additional low-index layer and overcoat to enhance lens power and light recycling without increasing the display's thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a microlens stack with array of microlenses and additional single microlens is formed over the light-emitting diode, then light extraction efficiency is improved, but the thickness of the display increases
Solution Approach 1:
The patent implements a microlens stack where an array of microlenses is positioned over the light-emitting diode, and an additional single microlens is positioned over the array of microlenses. This nested configuration allows multiple lens elements to occupy a compact vertical space, increasing lens power and light extraction efficiency without proportionally increasing display thickness.
Solution Approach 2:
The patent employs composite material construction for the microlens stack, using an inorganic material for the array of microlenses and an organic material for the additional single microlens. This composite approach enables optimization of each lens layer's optical properties while maintaining overall structural compactness and achieving high light extraction efficiency within limited thickness.
2Power
If the additional single microlens is formed from organic material with lower refractive index, then lens power is increased without increasing thickness, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by using different materials with different refractive indices for different parts of the microlens system. The inorganic material in the array of microlenses provides high refractive index for strong light bending, while the organic material in the additional single microlens provides lower refractive index for complementary optical effects. This localized material differentiation optimizes lens power distribution and reduces overall manufacturing complexity.
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 solution improves light extraction efficiency by increasing lens power and recycling efficiency, maintaining the display's thinness while enhancing light collimation and redirecting light from sidewalls, thereby improving overall display performance.
Implementation Method 1
The array of microlenses may be formed from an inorganic material having a high index of refraction such as 2.0. The additional single microlens may be formed from an organic material having an index of refraction lower than that of the array of microlenses
Implementation Method 2
An additional low-index layer may be interposed between the light-emitting diode and the array of microlenses. The low-index layer may increase the lens power of the microlens stack and may improve recycling efficiency for the display
Implementation Method 3
A diffusive layer may be formed around the light-emitting diode to capture light emitted from the light-emitting diode sidewalls
Data Source
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AI summary
To extract light from a light-emitting diode (and thereby improve efficiency of the display), a microlens stack may be formed over the light-emitting diode. The microlens stack may include an array of microlenses that is covered by an additional single microlens. Having stacked microlenses in this way increases lens power without increasing the thickness of the display. The array of microlenses may be formed from an inorganic material whereas the additional single microlens may be formed from an organic material. The additional single microlens may conform to the upper surfaces of the array of microlenses. An additional low-index layer may be interposed between the light-emitting diode and the array of microlenses. A diffusive layer may be formed around the light-emitting diode to capture light emitted from the light-emitting diode sidewalls.