Light Emitting Device Lens Extension for Leakage Reduction
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Solution Overview
Problem
Conventional light emitting devices experience reduced light extraction efficiency due to light leakage to the mounting surface, as the refractive index difference between the lens and the substrate leads to absorption of light by the substrate, rather than reflection and extraction.
Innovation Solution
A light emitting device design where the lens is extended beyond the substrate with an inclined portion at its end, allowing light to be reflected back into the lens and enhancing extraction efficiency by minimizing contact with the substrate, which has a higher refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the lens is disposed on the substrate to cover the light emitting element, then the light emitting device can be compact and easy to manufacture, but significant amount of light is absorbed by the substrate due to refractive index difference, reducing light extraction efficiency
Solution Approach 1:
The lens is extended in the vertical dimension beyond the substrate surface, creating a protruding structure. This dimensional extension allows the lens to interact with air (lower refractive index) rather than substrate material, enabling total internal reflection and improving light extraction efficiency without complicating the manufacturing process
2Loss of energy
If the bottom surface of the lens is extended to outside of the substrate, then light extraction efficiency is improved by contact with air, but the device structure becomes more complex
Solution Approach 1:
The lens and substrate are merged into a single integrated structure where the lens protrudes from the substrate. This combining approach achieves the optical benefit of air contact while avoiding the need for separate components or complex assembly processes, thus minimizing device complexity
3Loss of energy
If the lens is made to extend beyond the substrate, then light leakage to the mounting surface is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The lens is designed with a curved spherical surface rather than flat surfaces. This curvature provides optical benefits for light redirection and total internal reflection while being manufacturable using standard spherical lens fabrication techniques, balancing light leakage reduction with achievable manufacturing precision
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 significantly reduces light leakage to the mounting surface, improving light extraction efficiency, particularly at the upper surface of the lens, by utilizing the low refractive index of air to enhance total reflection and redirect light outward.
Implementation Method 1
A significant amount of light emitted from the light emitting element is refracted by the lens and directed from the upper surface of the lens toward the desired direction
Implementation Method 2
The air has a small refractive index, so that the difference between the refractive index n1 of the light transmissive material such as glass or a resin which constituting the lens and the refractive index nair of the air can be large and which leads a small value of the critical angle for total reflection. As a result, most of the light reaching the bottom surface of the lens 502 is reflected
Data Source
AI summary
A light emitting device has a lens, extended to outside of the mounting substrate on which a semiconductor a light emitting element is mounted, and leakage of light is reduced. A light emitting element, a substrate having the light emitting element mounted on its upper surface, and a lens, having a curved upper surface encloses the light emitting element and the upper surface of the substrate is included. From the bottom surface of the lens, a lower surface of the substrate is exposed. In a top view from a perpendicular direction to the upper surface of the substrate, the bottom surface of the lens includes an outer extending portion where the bottom surface is extended to outside of the substrate, and a inclined portion, which inclines with respect to a direction approximately in parallel to the upper surface of the substrate, at an end portion of the outer extending portion.