Touch Key Assembly Light Guide for Mobile Terminals
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Solution Overview
Problem
Conventional mobile terminals with light-emitting diodes (LEDs) for key illumination suffer from increased thickness due to the space required for LEDs and light obstruction by dome switches, leading to higher power consumption from increased LED numbers.
Innovation Solution
A touch key assembly with an optically transmissive cover and light guide system, where a light source positioned below the touch pad provides light to the keys through apertures, reducing the need for multiple LEDs and minimizing thickness by using an optical waveguide and reflection elements to enhance light distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If LEDs are positioned within the gap between pad and circuit board to illuminate key buttons, then key illumination is achieved, but the gap increases the thickness of the mobile terminal
Solution Approach 1:
The patent introduces a light guide as an intermediary component that redirects light from the LED to the key button area. The light guide receives light from the LED positioned in the gap and guides it to illuminate the key buttons, allowing the LED to be positioned closer to the circuit board while still achieving effective illumination without increasing terminal thickness
Solution Approach 2:
The patent uses a reflective element positioned at an angle (45 degrees) to redirect light in a different spatial dimension. The LED emits light upward, the reflective element redirects this light horizontally toward the key buttons, changing the light propagation path from vertical to horizontal direction, thereby illuminating keys without requiring increased vertical space
2Illumination intensity
If the number of LEDs is increased to compensate for light blocked by dome switches, then sufficient key illumination is achieved, but power requirements increase
Solution Approach 1:
The light guide acts as a mediator that efficiently directs LED light to the key button area, reducing light loss and improving illumination efficiency. This allows fewer LEDs to be used while achieving the same illumination effect, thereby reducing power consumption
Solution Approach 2:
The patent converts the potentially harmful effect of light being blocked by dome switches into a beneficial arrangement by using reflective elements and light guides to redirect and utilize the light that would otherwise be lost, improving overall light utilization efficiency and reducing the number of LEDs needed
3Ease of operation
If dome switches are positioned below key buttons to detect pressing, then key press detection is achieved, but significant portions of light emitted by LEDs are blocked
Solution Approach 1:
The reflective element is positioned at a 45-degree angle to redirect light from the vertical path (where it would be blocked by dome switches) to a horizontal path that reaches the key buttons from the side, changing the light propagation dimension to avoid obstruction by the dome switches while maintaining their detection function
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 reduces the overall thickness of the mobile terminal and decreases power requirements by allowing fewer light sources to effectively illuminate touch keys, while maintaining adequate lighting in dim environments.
Implementation Method 1
a touch pad coupled to the cover and shaped to define at least one aperture which forms a light guide that is associated with the touch key
Implementation Method 2
an optical waveguide positioned relative to the bottom side of the touch pad, the optical waveguide being structured to transmit light
Implementation Method 3
A reflection element operatively associated with the bottom side of the optical waveguide may be used to enhance refection of the light
Data Source
AI summary
A touch key assembly is structured to operate with a cover having at least one touch key, which is defined by an optically transmissive region of the cover. A touch pad is coupled to the cover and is shaped to define at least one aperture which forms a light guide that is associated with the touch key. A light source is positioned relative to the bottom side of the touch pad, and is further positioned relative to the light guide to provide light to the touch key. The assembly may also include an optical waveguide positioned relative to the bottom side of the touch pad, the optical waveguide being structured to transmit light. A reflection element operatively associated with the bottom side of the optical waveguide may be used to enhance refection of the light. The touch key assembly may be implemented in a portable electronic device, such as a mobile terminal or a personal digital assistant (PDA).