Optical Touch Sensing via Light Scattering in Transparent Displays
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Solution Overview
Problem
Current touch-screen technologies face challenges such as high cost, limited scalability, inability to sense stylus input, and inadequate sensitivity to light touch events, while also struggling with robustness and transparency.
Innovation Solution
A touch-sensitive display system that includes a transparent touch glass layer with a light source and light sensing elements, where light is directed through the glass layer and scattered light is measured to determine touch positions, using a control circuit to process signals and compute touch locations, while minimizing reflections with edge suppression mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive touch-screen technology is used, then sensitivity to light touch events and multi-touch capability are improved, but cost and manufacturing complexity increase
Solution Approach 1:
The patent replaces the complex capacitive sensing system with a simpler optical system. Instead of using capacitive traces and mutual capacitance measurement, the invention uses light sources, photodetectors, and light scattering detection to sense touch events. This mechanical/optical substitution maintains high touch sensitivity while significantly reducing manufacturing cost and complexity.
Solution Approach 2:
The patent changes the sensing parameter from electrical capacitance to optical properties (light scattering, absorption, or transmission). By detecting changes in light parameters when an object touches the display, the system achieves capacitive-level sensitivity without requiring complex capacitive trace patterns, thereby simplifying manufacturing.
2Ease of manufacture
If resistive touch-screen technology is used, then cost is reduced, but ability to sense stylus input and light touch events deteriorates
Solution Approach 1:
The patent replaces the mechanical pressure-based resistive sensing system with an optical detection system. Instead of relying on physical contact between conductive layers, the invention uses photodetectors to detect light scattering or absorption changes caused by any object (finger, stylus, or other implements) touching the display surface.
Solution Approach 2:
The optical sensing system is universally responsive to different types of touching implements. Whether it's a finger, stylus, pen, or other object, the system detects the optical interaction (scattering, absorption, or reflection) caused by the object, providing versatile input capability while maintaining low cost.
3Reliability
If ITO coating is applied for conductivity, then electrical conduction is improved, but transparency and mechanical robustness deteriorate
Solution Approach 1:
The patent eliminates the need for brittle ITO conductive coatings by substituting electrical sensing with optical sensing. The system uses photodetectors and light sources instead of conductive traces, removing the mechanical weakness of brittle ITO coatings while maintaining sensing functionality.
Solution Approach 2:
The patent extracts and removes the problematic ITO conductive coating layer from the touch-screen structure. By transitioning to an optical sensing architecture, the system no longer requires conductive coatings on the touch surface, thereby eliminating the transparency and robustness issues associated with ITO.
4Ease of operation
If plastic film is used for touch sensing, then flexibility is improved, but susceptibility to damage increases
Solution Approach 1:
The patent replaces the mechanical flexing-based resistive sensing in plastic films with an optical sensing system. Instead of requiring the plastic film to flex and contact conductive layers, the invention uses photodetectors to detect optical changes, eliminating the mechanical stress and damage risk to the plastic film.
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 solution provides a cost-effective, scalable, and sensitive touch-screen technology capable of detecting stylus input and light touch events with improved robustness and transparency, enabling accurate multi-touch capabilities.
Implementation Method 1
at least one light sensing element in communication with the transparent layer and operating to receive scattered light in response to an object touching a surface the transparent layer and disturbing the propagation of the light therethrough
Data Source
AI summary
Methods and apparatus provide for a touch sensitive display, in which a transparent layer is disposed over a display layer; light is directed to propagate into and/or through the transparent layer; scattered light is measured in response to an object touching a surface the transparent layer and disturbing the propagation of the light therethrough; and one or more positions at which the object touches the transparent layer are computed based on signals obtained by the step of measuring the scattered light.