Optical Touch System With Diffusive Reflector and Dual Light Paths
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Solution Overview
Problem
Existing touch-sensitive optical systems, particularly FTIR-based systems, face challenges in efficiently detecting multiple touches and are sensitive to contamination, leading to inaccurate readings due to high complexity, cost, and tolerance issues, especially with the use of complex prisms that limit light spread and increase manufacturing costs.
Innovation Solution
A touch-sensing apparatus utilizing a light transmissive element with emitters and detectors arranged around the periphery, where a portion of light propagates internally and another portion reflects above the touch surface, allowing for image reconstruction to determine object position, and using a diffusive reflector surface to reduce sensitivity to tolerances and contamination, with separate emitting and detecting systems for improved signal differentiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If complex prisms are used to couple light above the touch surface, then light coupling is achieved, but manufacturing cost increases and tolerance sensitivity increases
Solution Approach 1:
The patent removes the complex prism component from the optical coupling system. Instead of using a prism to couple light above the touch surface, the system uses a simplified arrangement where light is coupled directly through the edge of the transparent panel without requiring precision-prism components, thereby reducing manufacturing cost and tolerance sensitivity
Solution Approach 2:
The patent separates the optical coupling function from the prism structure and distributes it across multiple simpler components: the transparent panel edge, reflectors, and detectors positioned around the periphery. This segmentation allows each component to be manufactured with standard tolerances rather than requiring a single complex prism with tight tolerances
2Device complexity
If a single optical system is used for both above-surface and in-glass detection, then system complexity is reduced, but signal differentiation becomes difficult
Solution Approach 1:
The patent divides the optical system into two separate detection pathways: one for detecting light reflected from above the touch surface and another for detecting light propagating through the glass. Each pathway has its own set of detectors positioned to receive specific light paths, enabling clear signal differentiation while maintaining manageable system complexity
Solution Approach 2:
The patent uses reflectors as intermediary elements to direct light from above the touch surface into the detection system, while FTIR light propagates through the glass without interacting with these reflectors. This intermediary mechanism allows the system to differentiate between above-surface reflections and in-glass FTIR signals
3Adaptability or versatility
If emitters and detectors are arranged around the periphery, then multi-touch detection is enabled, but the number of components increases
Solution Approach 1:
The patent makes each emitter and detector serve multiple functions: they simultaneously participate in both above-surface optical detection and in-glass FTIR detection. Each emitter projects light that can be reflected above the surface or propagate through the glass, and each detector receives both types of light, thereby enabling multi-touch detection without proportionally increasing the total number of components
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 reduces manufacturing costs, improves tolerance and contamination resistance, and enhances multi-touch detection accuracy by using a diffusive reflector surface and separate optical systems for better signal processing, leading to a more efficient and cost-effective touch-sensitive system.
Implementation Method 1
The apparatus operates by transmitting light inside a transmissive panel 10, from light emitters 30a to light sensors or detectors 30b, so as to illuminate a touch surface 20 from within the transmissive panel 10. The transmissive panel 10 defines an internal radiation propagation channel, in which light propagates by internal reflections.
Implementation Method 2
a second portion of the beams of light pass out of the light transmissive element and are reflected to travel above the touch surface
Implementation Method 3
using a diffusive reflector surface to reduce sensitivity to tolerances and contamination
Data Source
AI summary
An embodiment of the invention provides a touch sensing apparatus, comprising: a light transmissive element (10) that defines a touch surface; a set of emitters (30a) arranged around the periphery of the touch surface to emit beams of light into the light transmissive element, wherein a first portion of the beams (50) of light propagate inside the light transmissive element while illuminating the touch surface such that an object touching the touch surface causes an attenuation of the propagating light, and wherein a second portion of the beams (90) of light pass out of the light transmissive element and are reflected to travel above the touch surface, a set of light detectors (30b) arranged around the periphery of the touch surface to receive light from the set of emitters from the transmissive element and from above the touch surface, wherein each light detector is arranged to receive light from more than one emitter.