Waveguide Pressure Sensing via Optical Path Bending
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Solution Overview
Problem
Current touch-sensing technologies rely heavily on light-scattering and/or light-attenuation methods, which limit the ability to effectively sense touch events based on pressure applied at specific locations, necessitating alternative optics-based approaches that can detect pressure-induced changes in light behavior within a waveguide.
Innovation Solution
A touch system utilizing light-bending and polarization effects, where a waveguide with a light source and detector system changes the optical paths and polarization state of light when pressure is applied, allowing for the detection of touch events, pressure measurement, and determination of touch location through changes in light distribution and interference patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light-scattering and light-attenuation methods are used for touch sensing, then touch functionality can be enabled, but the ability to sense pressure at specific locations is limited
Solution Approach 1:
The patent changes the optical parameter being measured from light scattering/attenuation to light bending and polarization changes. By monitoring how pressure alters the optical path and polarization state of light traveling through the waveguide, the system achieves precise pressure sensing at specific locations while maintaining comprehensive touch functionality across the display surface.
Solution Approach 2:
The patent replaces mechanical pressure sensing with optical field-based sensing. Instead of using mechanical elements to detect pressure, the system uses changes in light propagation characteristics (bending, polarization) induced by pressure to determine touch location and force, eliminating mechanical components and enabling more precise measurements.
2Measurement precision
If alternative optics-based approaches are used to sense pressure, then pressure detection capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the waveguide serve multiple functions: it acts as both the display component and the pressure sensing element. The same waveguide that guides light for display purposes also serves as the medium through which pressure-induced optical changes are detected, eliminating the need for separate sensing layers or components and reducing overall device complexity.
Solution Approach 2:
The waveguide's optical properties naturally change in response to applied pressure, providing the sensing signal without requiring external actuation or additional components. The system leverages the inherent photoelastic effect and light bending properties of the waveguide material itself to generate detectable signals when pressure is applied.
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
Enables accurate detection and measurement of touch events and pressure applied at specific locations by analyzing changes in light distribution and polarization, providing enhanced sensitivity and location determination.
Implementation Method 1
Pressure at a touch location on the waveguide that gives rise to a touch event causes the waveguide to bend or flex
Implementation Method 2
The changes can include polarization changes caused by birefringence induced in the waveguide by the pressure applied at the touch location
Data Source
AI summary
Pressure-sensing touch systems and methods are disclosed for sensing the occurrence of a touch event based on pressure applied at a touch location. The touch system includes a light-source system and a detector system operably adjacent respective input and output edges of a waveguide. Pressure at a touch location on the waveguide gives rise to a touch event causes the waveguide to bend or flex. The waveguide bending causes a change in the optical paths of light traveling by FTIR, causing the light distribution in the output light to change. The changes are detected and are used to determine whether a touch event occurred, as well as the time-evolution of the touch event. The changes in the output light can include polarization changes caused by birefringence induced in the waveguide by the applied pressure applied. Various detector configurations are disclosed for sensing the location and pressure of a touch event.