Optical Touch Screen Using Total Internal Reflection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional touch screen technologies, such as resistive and capacitive systems, face limitations including non-transparency, readability issues in direct sunlight, deterioration of pressure-sensitive layers, need for periodic recalibration, and inability to discern multiple touches or accurately measure touch pressure.
Innovation Solution
A touch sensitive apparatus utilizing a top plate with multiple touch detection regions and integrated light sources, where light is transmitted with total internal reflection, and detectors beneath the top plate detect light coupled out due to touches, allowing for accurate detection of touch presence, pressure, and multiple touches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive or capacitive overlay is placed over LCD display surface, then touch sensitivity is achieved, but transparency and readability in direct sunlight deteriorate
Solution Approach 1:
The patent replaces the mechanical resistive overlay system with an optical field-based detection system. Light sources illuminate the touch surface from below, and sensors detect changes in light patterns caused by touch, eliminating the need for opaque resistive or capacitive overlays and thereby maintaining transparency and readability.
Solution Approach 2:
The patent introduces light as an intermediary medium between the touch surface and the detection system. By using light sources and optical sensors, the system detects touch interactions through light pattern changes rather than through opaque conductive layers, resolving the contradiction between touch sensitivity and optical transparency.
2Reliability
If pressure sensitive layers are used for touch detection, then touch detection is achieved, but deterioration occurs over time requiring periodic re-calibration
Solution Approach 1:
The patent replaces mechanical pressure-sensitive layers with an optical detection system using light sources and sensors. This substitution eliminates the deterioration issues inherent in mechanical and electrical components, providing a more durable solution with extended service life and no periodic re-calibration requirements.
3Reliability
If conventional touch screen technology is used, then basic touch detection is achieved, but multi-touch and pressure intensity discrimination are not possible
Solution Approach 1:
The patent segments the touch detection capability by using multiple independent light sources and sensors distributed across the touch surface. This segmentation allows independent detection of multiple touch points simultaneously and enables measurement of pressure intensity through analysis of light pattern disturbances at different locations.
Solution Approach 2:
The optical detection system serves multiple functions: it detects single and multi-touch events, determines touch location, measures pressure intensity, and maintains transparency. This multi-functionality resolves the contradiction between basic touch detection and advanced touch capabilities.
4Ease of operation
If overlay layers are added for touch sensitivity, then touch input capability is achieved, but device complexity increases
Solution Approach 1:
The patent replaces multiple mechanical overlay layers with an integrated optical system where light sources and sensors are positioned behind the transparent touch surface. This substitution reduces structural complexity while maintaining or enhancing touch input 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 provides a transparent and reliable touch screen system capable of accurately detecting touch presence, pressure, and multiple touches, enhancing usability and functionality compared to conventional systems.
Implementation Method 1
a top plate comprising a plurality of touch detection regions, and having one or more light sources associated therewith, such that light from the one or more light sources is transmitted within the top plate with total internal reflection
Implementation Method 2
The top plate and the detectors are arranged such that if an external body touches a first surface of the top plate in a touch detection region, then light is coupled from a second surface of the top plate to the associated detector(s)
Data Source
AI summary
A touch sensitive apparatus comprises: a top plate comprising a plurality of touch detection regions, and having one or more light sources associated therewith, such that light from the one or more light sources is transmitted within the top plate with total internal reflection; a plurality of detectors for detecting light from the one or more light sources, wherein each detector is associated with a touch detection region; wherein the top plate and the detectors are arranged such that if an external body touches a first surface of the top plate in a touch detection region, then light is coupled from a second surface of the top plate to the associated detector(s); the touch sensitive apparatus further comprising processing means to determine at least the presence or absence of a touch in any of the touch detection regions of the top plate.