Night Vision Touchscreen Using Modulated Visible Light
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Solution Overview
Problem
Existing touchscreen technologies face challenges in accurately detecting touch inputs in high ambient light conditions and are not compatible with night vision systems, leading to interference and reduced performance in noisy optical environments.
Innovation Solution
The development of a touchscreen system using optical emitters and detectors with synchronized modulation and detection circuitry, capable of emitting wavelengths compatible with night vision systems, and featuring a tone detection mechanism to distinguish self-emitted energy from external sources, ensuring reliable detection even in dynamic ambient light environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional IR touchscreens use standard IR LEDs and phototransistors, then touch detection function is achieved, but compatibility with night vision systems is lost due to interference in the night vision spectrum
Solution Approach 1:
The patent changes the optical parameters by using visible light wavelengths (400-700nm) instead of conventional IR wavelengths, and implements intensity modulation of the light source. This allows the touchscreen to operate in the visible spectrum while being distinguishable from ambient light through modulation detection, achieving night vision compatibility without suffering from ambient light interference
Solution Approach 2:
The light source is modulated at a specific frequency to create periodic light emission. The detection system is synchronized to detect only this modulated signal, which allows differentiation between the touchscreen's intentional light source and unmodulated ambient light, thereby eliminating ambient light interference while maintaining night vision compatibility
2Measurement precision
If light intensity is increased to improve touch detection in ambient light, then detection capability improves, but interference with night vision systems increases
Solution Approach 1:
Instead of increasing light intensity, the patent uses intensity modulation at a specific frequency. This allows the use of low-intensity light that does not interfere with night vision, while achieving reliable touch detection through synchronous detection of the modulated signal. The modulation frequency acts as a signature that distinguishes the touchscreen light from ambient light regardless of intensity
Solution Approach 2:
The detection system uses synchronous detection that references the modulation frequency of the light source. This feedback mechanism continuously monitors for the specific modulated signal pattern, enabling accurate touch detection at low light intensities without generating harmful interference to night vision systems
3Device complexity
If unmodulated light sources are used, then device complexity is reduced, but ability to distinguish self-emitted energy from ambient light is lost
Solution Approach 1:
The patent implements modulation of the light source at a specific frequency, creating a temporal signature that enables discrimination from ambient light. While this adds modulation circuitry, it provides robust ambient light rejection that would be impossible with unmodulated sources, achieving reliable operation in varying ambient light conditions
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 enhances touch detection accuracy and immunity to ambient light interference, achieving higher reliability and compatibility with night vision systems, making it suitable for critical applications such as avionics and life-critical uses.
Implementation Method 1
one or more optical emitters to create the beams, and one or more optical detectors to provide detection signals
Implementation Method 2
IR transmitters (LEDs) being placed opposite to IR receivers (Usually IR phototransistors) where a touch is detected by pulsing a series of LEDs
Implementation Method 3
drive circuitry to modulate the emitters, and detection circuitry to detect the same modulation in the detection signals
Implementation Method 4
a demodulation circuit for detecting the received light, wherein the presence of a light interruption is determined on the basis of the output of the demodulation circuit. The demodulation involves comparing the output signal of the light receiving element and the output signal of the oscillator
Data Source
AI summary
A touchscreen system for locating an opaque object in a target region, detects interruption of light beams. Each of the touchscreens have one or more optical emitters to create the beams, and one or more optical detectors to provide detection signals arranged to use emission wavelengths which are compatible with night vision apparatus, and having an NVIS radiance smaller than 1.7×10−11 NR.