Moisture-Insensitive Optical Touch Sensors Using Total Internal Reflection
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Solution Overview
Problem
Existing touch sensors in electronic devices, such as capacitive touch sensors, are challenged by moisture, leading to operational issues when exposed to water or moisture, and often fail to function effectively in wet environments.
Innovation Solution
The implementation of a two-dimensional optical touch sensor that utilizes direct illumination or total internal reflection principles, allowing touch input detection even when the device is immersed in water or exposed to moisture, using an array of pixels and light sources that emit light at specific angles to maintain internal reflection within a display cover layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If capacitive touch sensors are used in electronic devices, then touch input functionality is provided, but the sensors fail to operate effectively when exposed to moisture or water
Solution Approach 1:
The patent replaces capacitive touch sensing (electrical field-based) with optical touch sensing (light-based). The optical system uses light sources to illuminate the display surface and light sensors to detect changes in light patterns caused by touch, eliminating dependence on electrical conductivity and making the system immune to moisture interference.
Solution Approach 2:
The patent introduces light as an intermediary medium for touch detection. Instead of directly sensing electrical properties affected by moisture, the system uses light propagation through the display cover glass and detection of light scattering or reflection changes to infer touch events, creating a moisture-independent sensing mechanism.
2Reliability
If optical touch sensors are implemented, then moisture-insensitive touch detection is achieved, but device complexity increases due to additional light sources and light sensors
Solution Approach 1:
The patent makes the display cover glass serve multiple functions: it acts as both the display protective layer and the optical waveguide for touch sensing. The same glass structure that protects the display also guides light for touch detection, eliminating the need for separate waveguide components and reducing overall system complexity.
Solution Approach 2:
The patent combines the display system and touch sensing system into a single integrated structure. The light sources are positioned to serve both display illumination and touch sensing functions, and the light sensors detect both display quality and touch events, merging two separate systems into one unified architecture.
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 optical touch sensor ensures reliable touch input detection in moist conditions by utilizing light scattering from a user's finger to determine location, independent of grounding effects and moisture interference, enabling operation in wet environments.
Implementation Method 1
The light source may supply light to an edge of the display cover layer at an angle that ensures total internal reflection is sustained within the display cover layer when the display cover layer is immersed in water or otherwise exposed to moisture
Implementation Method 2
A light source may illuminate an external object such as a finger of a user when the object contacts a surface of the display cover layer. This creates scattered light that may be detected by an array of light sensors
Data Source
AI summary
An electronic device may have a touch sensitive display that is insensitive to the presence of moisture. An array of pixels in the display may be used to display images. A display cover layer may overlap the array of pixels. A light source may illuminate an external object such as a finger of a user when the object contacts a surface of the display cover layer. This creates scattered light that may be detected by an array of light sensors. The light source may supply light to an edge of the display cover layer at an angle that ensures total internal reflection within the display cover layer is sustained across the display cover layer even when the display cover layer is immersed in water or otherwise exposed to moisture.