Top-fire LED Key Assembly with Optical Mask for Uniform Backlighting
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Solution Overview
Problem
Electronic devices face issues with light leak and unbalanced backlighting of keys due to the use of side-fire LEDs, which are costly and difficult to integrate in shallow key assemblies, leading to uneven illumination and aesthetic concerns.
Innovation Solution
The implementation of a top-fire LED with an optical mask and a light guide foil that is directly atop the LED, without a significant gap, to ensure uniform light distribution and prevent light from exiting through non-decorative areas, combined with a cover tape to block light leakage, results in a thinner and more evenly illuminated key assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If side-fire LEDs are used to inject light into the light guide foil, then uniform light distribution is achieved, but device cost increases and assembly depth increases
Solution Approach 1:
The patent inverts the conventional side-fire LED approach by using a top-fire LED positioned above the light guide foil. Instead of injecting light from the side, the light is directed downward through an optical mask onto the foil, achieving uniform distribution while reducing assembly depth and cost
2Device complexity
If top-fire LEDs are used to inject light into the light guide foil, then assembly depth is reduced, but uniform light distribution becomes difficult to achieve
Solution Approach 1:
The patent introduces an optical mask as an intermediary component between the top-fire LED and the light guide foil. This mask shapes and directs the light from the LED, ensuring uniform distribution across the foil while maintaining the shallow depth profile of the top-fire configuration
3Device complexity
If light guide foil is used to spread light from a single source, then cost is reduced compared to individual light sources per key, but light leakage from non-decorative areas occurs
Solution Approach 1:
The patent applies local quality control by using an optical mask with specific aperture patterns that correspond to decorative areas. The mask allows light to pass only through designated regions, creating localized illumination zones that prevent light leakage from non-decorative areas while maintaining the cost benefits of a single light source
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 provides a cost-effective and aesthetically pleasing solution by ensuring uniform backlighting of keycaps, reducing light leakage, and maintaining a shallow depth, thus enhancing the user experience and device design.
Implementation Method 1
a light guide foil is positioned underneath a set of keys and the light guide foil functions to spread out the light from the light source
Implementation Method 2
an optical mask and a light guide foil that is directly atop the LED, without a significant gap, to ensure uniform light distribution and prevent light from exiting through non-decorative areas
Data Source
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AI summary
A key assembly (200, 300) for an electronic device (100) that includes a keycap defining a key that has a non-opaque portion to identify the key that is backlit. The assembly includes a light guide (204) positioned in spaced relation to the keycap. An optical radiation source (202), such as top-fire light emitting diode, is mounted below the lower surface of the light guide (204). A mask (250) is disposed on the top surface (218) of the optical radiation source (202). The mask (250) includes an aperture (252) to allow light from the optical radiation source (202) to pass into the light guide (204), and the mask (250) blocks at least a portion of the light from the optical radiation source (202). The mask (250) blocks a portion of the top surface (218) of the optical radiation source that emits tinted light (212, 214). The light guide (204) is affixed atop the opaque mask (250) such that it is nearly directly affixed to the optical radiation source (202).