Near-Infrared Touch Screen With Collimating Structure
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Solution Overview
Problem
Conventional rear projection touch screen technologies face accuracy issues due to light interference from layers such as Fresnel lenses and diffusers, which cause non-uniform reflections or 'hot spots' that can be misinterpreted as screen touches, especially in curved or non-planar surfaces.
Innovation Solution
A screen design with a collimating structure on one side and near-IR emitting stripes on the other side, where near-IR light is emitted in response to an electrical or photoluminescence excitation source, allowing for accurate touch detection by processing reflected light through a diffusion layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional IR/near-IR elements and cameras are placed inside the projector away from the screen, then touch detection capability is achieved, but light interference from Fresnel lenses and diffusers causes non-uniform reflections and hot spots that reduce detection accuracy
Solution Approach 1:
The patent extracts the near-IR emitting elements from the projector interior and positions them on the viewer side of the screen, removing them from the path of light that passes through the Fresnel lens and diffuser. This extraction eliminates the source of non-uniform reflections and hot spots that plagued the conventional approach, thereby resolving the contradiction between achieving touch detection capability and maintaining detection accuracy.
Solution Approach 2:
The patent introduces a near-IR emitting element that operates at a wavelength where the screen materials (Fresnel lens, diffuser) are transparent or have minimal interaction. This intermediary element emits light that passes through the screen layers without causing the non-uniform reflections that occur with conventional IR wavelengths, thus enabling accurate touch detection despite the presence of these light-directing layers.
2Ease of manufacture
If a single illuminated curtain approach is used for touch detection, then touch detection is feasible on planar surfaces, but it becomes infeasible on curved or non-planar surfaces
Solution Approach 1:
The patent creates a touch detection system that universally works on both planar and curved surfaces by positioning near-IR emitting elements on the viewer side of the screen. This configuration allows the emitted near-IR light to conform to the screen's geometry, enabling the same basic approach to function across diverse surface types without requiring different implementation strategies.
Solution Approach 2:
The patent changes the operational parameters of the touch detection system by using near-IR wavelengths and positioning emitters on the viewer side, which allows the light to interact with curved surfaces differently than conventional IR approaches. This parameter change enables the system to adapt to various screen geometries while maintaining the fundamental principle of light interruption detection.
3Measurement precision
If total internal reflection (TIR) is maintained in edge-injected light approaches, then touch detection works on planar surfaces, but screen curvatures eliminate the ability to maintain adequate TIR
Solution Approach 1:
The patent inverts the conventional approach by instead of injecting light from the edge and relying on TIR, it positions near-IR emitting elements on the viewer side of the screen. This inversion eliminates the dependency on TIR maintenance, which is problematic on curved surfaces, and allows the system to function on various geometries by directly emitting light toward the front surface where touch interruption occurs.
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 enhances touch accuracy by minimizing light interference and maintaining effective touch detection on both planar and curved surfaces, reducing false positives and requiring less complex signal processing.
Implementation Method 1
The first side includes a collimating structure to direct the beam from the first side through first striped regions of the screen to the second side
Implementation Method 2
near-IR light is emitted in response to an electrical or photoluminescence excitation source
Implementation Method 3
near-IR light is emitted in response to an electrical or photoluminescence excitation source
Implementation Method 4
The second side includes a diffusion layer. The first side is viewable to detect a portion of the emitted near-IR light reflected back from the second side through the first striped regions to the first side
Implementation Method 5
detect a portion of the emitted near-IR light reflected back from the second side
Data Source
AI summary
A screen has first and second sides to receive at least one beam on the first side and to display an image on the second side opposite the first side. The beam represents the image. The first side includes a collimating structure to direct the beam from the first side through first striped regions of the screen to the second side. The screen includes second striped regions, positioned between the first and second sides, to emit near-IR light to the second side in response to an excitation source that is selected from a group consisting of an electrical excitation source and a photoluminescence excitation source. The second side includes a diffusion layer. The first side is viewable to detect a portion of the emitted near-IR light reflected back from the second side through the first striped regions to the first side. The detected portion is processable to determine a position touch on the second side.