Keypad Light Guide Film Uniform Illumination
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Solution Overview
Problem
Conventional keypad light guide films with a dome shape cause uneven light distribution, leading to hotspots and reduced tactility, requiring higher energy consumption and increasing the complexity of the keypad assembly.
Innovation Solution
A planar light guide film and dome sheet carrier are used, eliminating the dome effect, which improves light diffusion and reduces energy requirements, allowing for a lower intensity light source and enhanced tactility by positioning the printed circuit board and dome switches within cavities, creating a compact and efficient keypad assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a dome shaped light guide film is used to accommodate dome switches, then the light path is non-linear and causes uneven light distribution with hotspots and dull spots, but the dome shape was necessary to cover the dome switches
Solution Approach 1:
The light guide film is segmented into a planar base layer and separate dome-shaped optical elements positioned above it. This allows the light guide film itself to remain flat for uniform light distribution, while dome switches are covered by individual translucent domes that redirect light locally without creating the problematic non-linear path through the entire light guide film.
Solution Approach 2:
The solution moves the dome shape from the light guide film plane to a separate vertical dimension. The planar light guide film remains in its original plane, and dome-shaped translucent covers are added in a second dimension above it, allowing light to be redirected upward through these domes without distorting the light path through the light guide film itself.
2Illumination intensity
If a dome shaped light guide film is used, then light seeps and erroneously highlights other keys, but the dome shape was intended to illuminate keys
Solution Approach 1:
Each dome switch is covered by its own dedicated translucent dome that is positioned and sized to illuminate only that specific key. This localizes the light redirection function, preventing light from one key area from seeping into adjacent key areas, thereby maintaining accurate light direction and preventing erroneous key highlighting.
3Illumination intensity
If a dome shaped light guide film is used, then a light source of greater intensity is required, but this increases energy consumption
Solution Approach 1:
The planar light guide film acts as an efficient intermediary that distributes light uniformly across the keypad area before light reaches the dome switches. This intermediate uniform distribution step reduces light loss and inefficiency, allowing a lower intensity light source to achieve the same overall illumination effect that would require a higher intensity source with a dome-shaped light guide film.
4Shape
If a dome shaped light guide film is used, then tactility restricting forces increase, but the dome shape was necessary to cover dome switches
Solution Approach 1:
The light guide function is segmented from the dome switch structure. The planar light guide film remains flat and does not interfere with dome switch operation, while separate translucent dome covers are placed over individual switches. This segmentation eliminates the tactility restriction problem because the light guide film no longer needs to conform to the dome shape, allowing dome switches to maintain their full tactile feedback capability.
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 significantly improves keypad luminance, reduces energy consumption, and enhances tactility by providing a more uniform and efficient light distribution while maintaining a compact design.
Implementation Method 1
A light guide film or panel is often used to deflect, reflect or channel light from a light source to illuminate the keypad
Implementation Method 2
A reflective pattern may be provided on a surface of the light guide film in communication with the light source
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
Keypad apparatus and methods are described herein. An example keypad includes a keypad support (306) having a first surface defining a cavity, and an electrical switch assembly coupled to the keypad support. The electrical switch includes a printed circuit board (322) having at least a portion repositioned relative to a second surface of the printed circuit board (322). The repositioned portion (328) is located in the cavity and the second surface is located on the first surface of the keypad support (306) when the printed circuit board (322) is coupled to the keypad support (306). The repositioned portion (328) is attached to the second surface of the printed circuit board (306). A dome switch (324) is aligned with the repositioned portion (328) of the printed circuit board (306) and is at least partially positioned in the cavity of the keypad support (306).