Light-Based Touch Screen Using Optical Beam Interruption
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Solution Overview
Problem
Conventional touch screens, such as resistive and capacitive systems, face limitations including non-transparency, sensitivity to pressure, readability issues in sunlight, susceptibility to scratches and interference, and inability to detect multi-touch inputs, making them unsuitable for versatile use in consumer electronic devices.
Innovation Solution
A light-based touch screen system utilizing infra-red or near infra-red light-emitting diodes and photo diodes arranged along the perimeter, where light beams are projected across the screen and detected by receivers to determine touch points, enabling multi-touch detection and operation without overlays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resistive or capacitive overlays are placed over LCD surfaces, then touch detection functionality is achieved, but transparency of the screen is reduced
Solution Approach 1:
The patent replaces mechanical/electrical overlay systems (resistive or capacitive layers) with an optical system using light beams, emitters, and receivers. This substitution eliminates the need for physical overlays that block light, thereby maintaining screen transparency while achieving touch detection functionality through optical interruption methods.
2Reliability
If pressure is applied to resistive touch screens for touch detection, then touch input is detected, but finger touches without sufficient pressure go undetected
Solution Approach 1:
The patent replaces the pressure-dependent mechanical contact detection of resistive screens with an optical detection system. Light beams are projected across the screen surface, and any interruption of these beams (regardless of pressure applied) is detected by receivers, enabling detection of light touches, finger touches, and multi-touch gestures without requiring pressure.
Solution Approach 2:
The patent introduces light beams as an intermediary between the user's touch and the detection system. Instead of directly measuring pressure or capacitance changes, the system uses light beams as a mediator that can be interrupted by any object touching the screen, providing a more sensitive and versatile detection mechanism.
3Ease of manufacture
If conventional resistive touch screens are used, then cost and power consumption are reduced, but multi-touch detection capability is lost
Solution Approach 1:
The patent segments the touch detection function into multiple independent light beam channels, with emitters and receivers positioned at different locations. Each light beam represents an independent detection channel, allowing the system to detect multiple simultaneous touch points by monitoring interruptions in different beams, thereby enabling multi-touch capability.
4Reliability
If overlays are placed on touch screens, then touch detection is enabled, but readability in direct sunlight is reduced
Solution Approach 1:
The patent replaces overlay-based touch detection with a projected light beam system that operates independently of display transparency. The emitters project light beams across the screen, and receivers detect beam interruptions. This system works effectively in direct sunlight because the projected light beams are intense enough to be detected even in bright environmental conditions, and no opaque overlays are required.
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 light-based system provides transparent, durable, and interference-resistant touch detection, capable of accurately identifying multiple touch points and gestures, enhancing usability across various device sizes and environments.
Implementation Method 1
A light-based touch screen system utilizing infra-red or near infra-red light-emitting diodes and photo diodes arranged along the perimeter, where light beams are projected across the screen and detected by receivers
Implementation Method 2
photo diodes arranged along the perimeter, where light beams are projected across the screen and detected by receivers to determine touch points
Data Source
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AI summary
A touch screen system, including a near-infrared transparent screen including a plurality of reflective elements embedded therein, a circuit board including circuitry for controlled selective activation of electronic components connected thereto, at least one light source connected to the circuit board, for emitting light, and at least one light detector connected to the circuit board, for detecting light emitted by the at least one light source and reflected by the reflective elements.