Dome Lens Refraction for Visual Alarm LED Arrays
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Solution Overview
Problem
Visual alarm devices (VADs) using a set of ten light emitting diodes (LEDs to provide strobe light output often require a configuration that minimizes the number of LEDs while maintaining a threshold minimum amount of lighting, as using fewer LEDs is desirable for compactness and efficiency.
Innovation Solution
A dome lens design for VADs that covers an array of LEDs, featuring a unique geometry with convex inner and outer surfaces, optimized to refract light effectively, ensuring aberration-free light distribution and meeting or exceeding minimum light output standards, such as UL 1971, by concentrating light intensity in directed locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fewer LEDs are used in the VAD configuration, then the device achieves compactness and efficiency, but the light output intensity may fall below the threshold minimum
Solution Approach 1:
The patent introduces a specially designed dome lens as an intermediary optical element between the reduced LED array and the external environment. This lens mediates the light transmission by refracting and concentrating light from fewer LEDs to achieve the required illumination intensity, thus resolving the contradiction between using fewer LEDs and maintaining sufficient light output.
Solution Approach 2:
The patent changes the optical parameters of the system by introducing a dome lens with specific geometric parameters (radius, thickness, refractive index). This parameter change allows the light distribution characteristics to be optimized, enabling fewer LEDs to produce the required light output intensity through improved optical efficiency.
2Illumination intensity
If a dome lens is introduced to concentrate light from fewer LEDs, then the light output intensity increases, but the device complexity increases
Solution Approach 1:
The patent employs a dome-shaped lens with spherical or aspherical curvature to achieve light concentration. This curved geometry naturally focuses light rays through refraction, providing the required illumination intensity enhancement without requiring complex multi-element optical systems, thus minimizing device complexity while achieving the optical goal.
3Illumination intensity
If the lens geometry is optimized for light concentration, then light directionality and intensity improve, but manufacturing precision requirements increase
Solution Approach 1:
The dome lens design utilizes spherical or aspherical surfaces which can be manufactured using standard molding techniques. While precision is required, the spherical geometry is more manufacturable than complex freeform surfaces, as it can be produced using conventional injection molding or compression molding processes with appropriate tooling.
Solution Approach 2:
The patent specifies particular parameter ranges for the lens (radius, thickness, refractive index) that balance optical performance with manufacturability. By optimizing these parameters within practical ranges rather than pursuing extreme precision, the design achieves good light concentration while remaining manufacturable with standard tolerances.
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 lens design enhances light directionality and intensity, allowing a packed seven LED board to meet or exceed the luminosity of a ten LED board, ensuring effective alerting capabilities, especially for hearing-impaired individuals, while being compact and efficient.
Implementation Method 1
A dome lens design for VADs that covers an array of LEDs, featuring a unique geometry with convex inner and outer surfaces, optimized to refract light effectively
Data Source
AI summary
A dome lens extending upwardly about a center axis A and outwardly in a radial direction R, having: a first portion forming a first annular ring about the center axis A that includes a first inner surface that is convex, and being oriented so that a first tangent to the first inner surface is at a first angle to the center axis A that is less than forty-five degrees; a second portion being continuous with the first portion and forming a second annular ring about the center axis A and including a second inner surface that is convex, and being oriented so a second tangent to the second inner surface is canted toward the center axis A; a third portion being continuous with the second portion to enclose the lens, forming an annular solid disk about the center axis A, and including a third inner surface that is convex.