Lens Inner Depression for Bubble-Tolerant Light Extraction
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Solution Overview
Problem
Existing light-emitting modules face challenges in maintaining high light extraction efficiency due to air bubbles trapped within the sealing liquid, which cause total reflection and reduce the effectiveness of light emission.
Innovation Solution
A light-emitting device design featuring a lens with a recessed depression on its inner surface positioned above the optical axis, accommodating air bubbles and preventing them from overlapping the light-emitting element, thereby ensuring that light is extracted without passing through the bubbles, utilizing a fluorine-based oil as the sealing liquid and optimizing the lens shape to minimize refractive index differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inner space of the package is filled with sealing liquid to seal the light-emitting element, then the light-emitting element is protected and sealed, but air bubbles may be mixed in and cause total reflection at the interface, decreasing light extraction efficiency
Solution Approach 1:
The lens inner surface is segmented into different regions: a first region with a first refractive index and a second region with a second refractive index. This segmentation allows the light to be extracted through multiple paths with different refractive indices, reducing the impact of air bubbles on light extraction efficiency
Solution Approach 2:
Different regions of the lens inner surface are assigned different refractive indices to create local quality variations. The first region has a higher refractive index while the second region has a lower refractive index, allowing optimized light extraction in different areas and reducing total reflection caused by air bubbles
2Quantity of substance
If air bubbles are present in the sealing liquid, then the sealing is complete, but total reflection occurs at the air-liquid interface, reducing light extraction efficiency
Solution Approach 1:
The invention converts the harmful effect of air bubbles into a beneficial structure by creating a second region with lower refractive index that mimics the optical properties of air bubbles. This allows the lens to handle light extraction as if air bubbles were present, reducing total reflection and maintaining high light extraction efficiency even when sealing liquid is fully filled
3Illumination intensity
If the lens material has a high refractive index to improve light extraction, then light extraction efficiency increases, but the refractive index difference with sealing liquid increases, causing more total reflection
Solution Approach 1:
The lens is divided into regions with different refractive indices. The first region has a higher refractive index for strong light extraction, while the second region has a lower refractive index closer to the sealing liquid, reducing total reflection and energy loss at the lens-sealing liquid interface
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 configuration effectively suppresses the decrease in light extraction efficiency by keeping air bubbles away from the optical axis, allowing for enhanced light emission with reduced total reflection, and maintains high extraction efficiency even with small refractive index differences between the sealing liquid and the lens material.
Implementation Method 1
an air bubble is included in at least a portion of the depression
Implementation Method 2
a height of the inner surface monotonically increases from the point on the optical axis to the depression
Implementation Method 3
light emitted from the light-emitting element can be totally reflected at the interface between the air bubbles and the liquid, hence, light extraction efficiency decreases
Data Source
AI summary
A light-emitting device includes a light-emitting element mounted on a substrate, a lens disposed on the substrate so as to cover the light-emitting element, and a sealing liquid disposed in a space defined under the lens to seal the light-emitting element. An inner surface of the lens includes a depression that is recessed upward at a position not overlapping an optical axis of the light-emitting element. A position of the depression is higher than a position of a point on the inner surface that is located on the optical axis. A height of the inner surface monotonically increases from the point on the optical axis to the depression.