Keypad Waveguide Illumination Uniformity
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Solution Overview
Problem
Conventional keypad assemblies for portable terminals face issues with uneven lighting of key buttons due to the placement of light emitting diodes, which requires a separate AC power source, increasing volume and manufacturing cost, and generating noise.
Innovation Solution
A keypad assembly with a waveguide placed below the elastic layer, featuring reflection patterns to uniformly illuminate key buttons, and light sources integrated into the switch substrate, reducing the need for multiple light emitting diodes and minimizing light loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light emitting diodes are placed on the printed circuit board to illuminate key buttons, then the keypad can be used in the dark, but the lighting becomes uneven and some key buttons are shaded
Solution Approach 1:
A waveguide is introduced as an intermediary component between the light source and the key buttons. The waveguide receives light from LEDs positioned at its side and distributes it uniformly across all key buttons through its structure, eliminating the shading problem caused by direct LED placement near individual keys.
Solution Approach 2:
The lighting approach transitions from a two-dimensional plane arrangement of LEDs near each key to a three-dimensional waveguide structure that distributes light from the side, changing the spatial dimension of light delivery to achieve uniform illumination across the keypad surface.
2Illumination intensity
If inorganic electro luminescence is inserted in the elastic pad to provide uniform lighting, then lighting uniformity is improved, but a separate AC electric source and inverter are required
Solution Approach 1:
The complex AC power source and inverter system required by inorganic electro luminescence is extracted and removed from the device. Instead, the patent uses a simplified DC power source that directly drives LEDs, eliminating the need for DC-to-AC conversion while maintaining uniform lighting through the waveguide structure.
Solution Approach 2:
The patent replaces the expensive and complex inorganic electro luminescence system with a simpler, more economical LED-based solution. Although LEDs have limited lifespan, their low cost and simplicity make them suitable for this application, especially when combined with the waveguide for uniform light distribution.
3Illumination intensity
If DC to AC conversion is implemented to power inorganic electro luminescence, then uniform lighting is achieved, but noise is generated in the portable terminal
Solution Approach 1:
The DC-to-AC conversion process that generates noise is extracted and removed from the system. The patent directly uses DC power to drive LEDs, eliminating the inverter and its associated electromagnetic noise while achieving uniform lighting distribution through the waveguide structure.
4Illumination intensity
If multiple light emitting diodes are placed between switches to illuminate key buttons, then the keypad can be used in the dark, but the volume and manufacturing cost increase
Solution Approach 1:
The waveguide merges multiple light paths into a single integrated structure. Instead of placing multiple separate LEDs between switches, the waveguide consolidates light delivery from a reduced number of LEDs positioned at its side, distributing light uniformly across all keys while reducing overall component count and assembly volume.
Solution Approach 2:
The waveguide serves multiple functions simultaneously: it acts as a light distribution network, a structural component of the keypad assembly, and a space-efficient mounting solution for LEDs. This multi-functionality reduces the need for separate lighting components and reduces overall assembly volume.
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 solution provides uniform key button illumination, reduces the number of light emitting diodes required, and eliminates the need for DC to AC conversion, thereby decreasing the volume and manufacturing cost while minimizing noise.
Implementation Method 1
a waveguide for transmitting and guiding light therethrough
Implementation Method 2
having at least one reflection pattern to reflect light toward a respective key button
Data Source
AI summary
A keypad assembly includes a keypad having at least one elastic layer and at least one key button on the elastic layer, a waveguide for transmitting and guiding light therethrough, the waveguide being placed below the elastic layer and having at least one reflection pattern to reflect light toward a respective key button, and a switch substrate under the waveguide and having at least one switch corresponding to the respective key button.