Aspherical Dome Lens for Quadrangular LED Packages
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Solution Overview
Problem
In light emitting device packages, the mismatch between the quadrangular LED chip and hemispherical lens leads to increased angle of incidence, causing total internal reflection and optical loss, which hinders miniaturization and efficiency, especially when using large-area chips.
Innovation Solution
An optical device with a dome structure featuring a quadrangular first surface and a convex curved second surface, with an aspherical shape in one cross-section and a semicircular shape in another, reduces the angle of incidence by incorporating a flange part and a lens part with a linear section, preventing total internal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a hemispherical lens is used with a quadrangular LED chip, then the lens structure is simple and easy to manufacture, but the angle of incidence increases causing total internal reflection and optical loss
Solution Approach 1:
The patent applies asymmetry by transitioning from a symmetric hemispherical lens to an asymmetric lens shape that adapts to the quadrangular LED chip geometry. The lens surface is modified with different curvatures in different regions, creating an asymmetric profile that reduces the angle of incidence at chip corners while maintaining manufacturing feasibility through injection molding processes.
Solution Approach 2:
The patent implements local quality by applying different surface characteristics to different regions of the lens. The lens surface includes a first region with a first curvature radius and a second region with a second curvature radius, where the curvature varies locally to optimize light extraction at specific areas such as chip corners versus center regions, thereby reducing optical loss where it occurs most.
2Loss of energy
If the lens size is enlarged to adjust the angle of incidence, then optical efficiency improves, but miniaturization of the package becomes difficult
Solution Approach 1:
The patent applies parameter changes by modifying the curvature radius parameters of the lens surface. Instead of increasing lens size, the invention optimizes the angle of incidence by adjusting the curvature radius in different regions of the lens. This allows the use of smaller lenses while maintaining or improving optical efficiency, thereby enabling package miniaturization.
3Power
If a large-area chip is used to increase capacity, then light output increases, but optical loss due to total internal reflection increases
Solution Approach 1:
The asymmetric lens design specifically addresses the corner regions of large-area quadrangular chips where total internal reflection is most problematic. By creating an asymmetric profile that extends further at corners compared to the center, the lens reduces the angle of incidence at these critical regions, enabling large-area chips to maintain high light output without proportionally increased optical loss.
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 design minimizes optical loss and enables the use of large-area chips in compact, high-efficiency packages by reducing the angle of incidence below the critical angle, facilitating miniaturization without enlarging the lens.
Implementation Method 1
an optical device with a dome structure featuring a quadrangular first surface and a convex curved second surface, with an aspherical shape in one cross-section and a semicircular shape in another, reduces the angle of incidence
Implementation Method 2
in accordance with a structure in which the angle of incidence exceeds a critical angle in a portion adjacent to a corner of the LED chip, total internal reflection (TIR) may occur, thereby leading to optical loss
Data Source
AI summary
An optical device may include a first surface having a shape of a quadrangle; and a second surface disposed to be opposite to the first surface and comprising a convex curved surface. The optical device has an aspherical shape in a cross-section taken along a diagonal direction of the quadrangle and has a semicircular shape in a cross-section taken along a direction connecting a central portion of a first side of the quadrangle and a central portion of a second side opposite to the first side of the quadrangle. In a cross-sectional view of the optical device, the second surface is continuously varied between the semicircular shape of the cross-section and the aspherical shape of the cross-section.