Dual Touchscreen Modulation for Ambient Light Immunity
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Solution Overview
Problem
Existing touchscreen systems face challenges in achieving high reliability and immunity to ambient light and noise, especially in critical applications like avionics and medical systems, due to interference between multiple touchscreens and sensitivity to ambient conditions.
Innovation Solution
The implementation of dual touchscreens with independent X- and Y-axis scanning, using optical emitters and detectors with synchronized drive and detection circuitry, and modulation techniques to distinguish self-emissions from external sources, along with emission wavelengths compatible with night vision apparatus, ensures increased availability and reduced noise immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple touchscreens are used to provide redundancy, then reliability is improved, but interference between touchscreens increases causing detection errors
Solution Approach 1:
The patent applies periodic action by modulating the optical emitters at different frequencies for different touchscreen layers. Each touchscreen emits modulated light signals at its specific frequency, allowing the detection circuitry to distinguish between signals from different layers through frequency discrimination. This periodic modulation enables multiple touchscreens to operate simultaneously without mutual interference, resolving the contradiction between providing redundancy and avoiding interference.
Solution Approach 2:
The patent changes the frequency parameter of the optical emitters to differentiate between multiple touchscreen layers. By assigning different modulation frequencies to each touchscreen, the system can selectively detect and process signals from specific layers. This parameter change approach allows multiple touchscreens to coexist in the same space without interfering with each other's detection accuracy.
2Measurement precision
If optical emitters operate continuously to detect touches, then detection accuracy is maintained, but sensitivity to ambient light and noise increases
Solution Approach 1:
The patent uses periodic modulation of optical emitters at specific frequencies to distinguish touch-induced signal changes from ambient light variations. By modulating the emitters and detecting only the modulated frequency components, the system can filter out unmodulated ambient light and noise, maintaining detection accuracy while reducing sensitivity to environmental interference.
Solution Approach 2:
The patent implements feedback through synchronized detection circuitry that monitors the modulated optical signals and compares them against reference frequencies. The detection system uses feedback mechanisms to identify and reject signals that do not match the expected modulation patterns, thereby maintaining accurate touch detection while filtering out ambient light and noise interference.
3Object-affected harmful factors
If modulation techniques are used to distinguish self-emissions from external sources, then noise immunity is improved, but device complexity increases
Solution Approach 1:
The patent employs periodic modulation of optical emitters at distinct frequencies, which enables the detection circuitry to use simple frequency-based filtering to distinguish self-emissions from external sources. This approach improves noise immunity while keeping the added complexity manageable, as the modulation and detection can be implemented using standard signal processing techniques.
Solution Approach 2:
The patent introduces modulation frequency as an intermediary parameter that mediates between the optical emitters and the detection circuitry. This intermediary allows the system to clearly distinguish between self-emitted modulated signals and external unmodulated or differently-modulated light sources, improving noise immunity without requiring complex identification algorithms.
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 enhanced reliability and immunity to ambient light and noise, allowing for critical applications without the need for backup systems, and meets stringent NVIS radiance requirements, ensuring stable operation in dynamic environments.
Implementation Method 1
one or more optical emitters to create the beams
Implementation Method 2
one or more optical detectors to provide detection signals
Implementation Method 3
drive circuitry to modulate the emitters, and detection circuitry to detect the same modulation in the detection signals
Data Source
AI summary
A touchscreen system for locating an opaque object in a target region, detects interruption of light beams, using two or more independent touchscreens (TS1, TS2), arranged to provide redundancy, each of the touchscreens having one or more optical emitters (10) to create the beams, and one or more optical detectors (30) to provide detection signals, and circuitry (90) to determine location coordinates of the opaque object from the detection signals. Detection circuitry or software integrates (470) an output of a switching inverter (440, 450), which switches between outputting an inverted or not inverted version of each detection signal, in phase with the modulation of the corresponding emitters. It can use wavelengths compatible with night vision equipment.