Optical Touch Display Segmented Illumination for Reflection Reduction
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Solution Overview
Problem
Optical multi-touch displays face challenges in accurately detecting user input due to illumination-related changes in the environment, such as ambient light frequency, direction, and reflectance, which can lead to undesired reflections from non-contacting objects interfering with the detection of touch points.
Innovation Solution
An interactive display system with a touching surface illuminated by alternating invisible light sources, where touch detection units capture images of these regions and a processor controls the light sources to reduce reflections from non-contacting objects, allowing for precise detection of contact areas by making some light sources operable while others are not.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If all invisible light sources are kept operable to illuminate the entire touching surface, then the coverage and detection capability are improved, but undesired reflections from non-contacting objects increase
Solution Approach 1:
The touching surface is divided into multiple sub-regions, each illuminated by a separate invisible light source. The system activates only the light sources corresponding to sub-regions where touch detection is needed, rather than illuminating the entire surface. This segmentation allows localized illumination that reduces reflections from non-contacting objects while maintaining detection capability in active areas.
Solution Approach 2:
The invisible light sources are activated alternately in a periodic manner, with different light sources being turned on at different time intervals. This alternating activation pattern allows the system to illuminate different sub-regions sequentially, reducing the overall presence of active light sources and thereby minimizing undesired reflections while maintaining continuous monitoring capability across the entire surface.
2Adaptability or versatility
If multiple invisible light sources are activated simultaneously to cover the entire surface, then the touch detection coverage is improved, but the complexity of controlling individual light sources increases
Solution Approach 1:
The control system is segmented to manage individual light sources independently. Each invisible light source can be controlled separately based on detection needs, allowing the system to activate only specific regions rather than managing all light sources simultaneously. This reduces control complexity while maintaining comprehensive detection coverage through selective activation.
Solution Approach 2:
The system activates only the necessary portion of light sources at any given time rather than all light sources simultaneously. By applying partial action—activating only the light sources needed for current detection requirements—the system reduces control complexity while still achieving adequate detection coverage for active touch regions.
3Measurement precision
If invisible light is used to illuminate the touch surface, then the accuracy of touch detection is improved, but reflections from non-contacting objects interfere with detection
Solution Approach 1:
The harmful reflections from non-contacting objects are extracted and eliminated by selectively deactivating light sources that would cause such reflections. The system identifies and removes the problematic light sources from active operation, keeping only those necessary for detecting actual touch contact, thereby maintaining detection accuracy while reducing interference.
Solution Approach 2:
The system converts the potential harm of reflections into a benefit by using the reflection pattern itself as information. By analyzing which light sources produce reflections versus which illuminate actual touch points, the system distinguishes between harmful reflections and useful touch signals, turning the reflection issue into a means of enhancing detection accuracy through differential analysis.
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 approach effectively reduces undesired reflections, enhancing the accuracy of touch detection by controlling the invisible light sources, thereby improving the ability to identify contact areas on the surface.
Implementation Method 1
the reflecting or shadowing of the IR light is measured
Implementation Method 2
The invisible light may be infrared light
Data Source
AI summary
An interactive display device (100) has an image layer (102) for presenting user perceivable visual content and a touching surface (101) covering the image layer (102) or formed by the image layer (102). Further, there are a plurality of invisible light sources (110) for illuminating alternatingly different sub-regions of the touching surface (101) and a plurality of touch detection units (107) for capturing images of illuminated sub-regions from behind the image layer (102). From the captured images contact areas are detected where a pointing object (112) contacts the touching surface (101) and thus causes correspondingly one or more marks in the captured images. The remaining ones of the invisible light sources (110) are controlled to be operable while adjacent touch detection units and associated invisible light sources are controlled to be non-operable so as to reduce undesired reflections of invisible light from non-contacting objects in the vicinity of the touching surface.