Thin film couplers for optical waveguide touch sensing
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Solution Overview
Problem
Existing touch-sensitive technologies face challenges in scaling to larger screen sizes due to increased manufacturing costs and difficulties in handling multitouch events efficiently, leading to ambiguities in signal detection and high computational requirements.
Innovation Solution
An optical touch-sensitive device utilizing an optical waveguide with emitters and detectors, coupled with optical couplers and reflectors, that directs and redirects optical beams via total internal reflection to detect touch events across a surface, allowing for efficient multitouch event resolution and scalable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optical coupling techniques are used for waveguides, then light can be coupled into the waveguide, but the manufacturing cost increases significantly
Solution Approach 1:
The patent changes the geometric parameters of the coupler structure, specifically using a thin film coupler with thickness between 1-10 micrometers, and optimizes the refractive index parameters of the coupling layer to achieve efficient optical coupling without complex manufacturing processes. This resolves the contradiction by achieving good coupling efficiency through parameter optimization rather than complex structures.
Solution Approach 2:
The patent employs a thin film coupler structure that is flexible and easy to manufacture, replacing traditional bulky optical coupling components. The thin film approach allows for simpler fabrication processes and reduced manufacturing costs while maintaining effective optical coupling between the light source and waveguide.
2Area of stationary object
If screen size is increased linearly by a factor of N, then the display area increases, but the manufacturing complexity and cost increase by a factor of N2 due to scaled processing requirements
Solution Approach 1:
The patent creates a universal thin film coupler design that can be applied to waveguides of any size without requiring scaled processing. The same coupler geometry and material properties work for both small and large displays, eliminating the need to re-optimze or re-process manufacturing techniques when scaling up the display area.
Solution Approach 2:
The patent segments the optical coupling function into a separate thin film component that can be independently manufactured and then integrated with waveguides of various sizes. This modular approach allows the coupler to be produced once and applied to different scale waveguides, avoiding the need to scale the entire optical system together.
3Adaptability or versatility
If more special elements are added to handle multitouch events, then touch detection capability improves, but computational requirements and processing time increase
Solution Approach 1:
The patent replaces complex computational signal processing with optical physics-based signal separation. By using waveguides with specific elevation angles and optical path geometries, the system naturally separates multitouch signals through optical interference patterns and path differences, reducing the computational burden compared to electronic signal processing methods.
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
The solution enables cost-effective and efficient detection of touch events on larger surfaces by redistributing optical beams across the active area, reducing the need for extensive surface processing and special elements, while effectively handling multitouch events with improved computational efficiency.
Implementation Method 1
configured to direct at least some of the optical beams to propagate via total internal reflection (TIR) through the waveguide
Implementation Method 2
The optical reflector reflects optical beams propagating in the waveguide, wherein incident optical beams propagate through the waveguide at an initial elevation angle and reflected optical beams propagate through the waveguide at a modified elevation angle
Data Source
AI summary
An optical touch-sensitive device is able to determine the locations of multiple simultaneous touch events. The optical touch-sensitive device can include an optical waveguide, an emitter, and an emitter coupler. The emitter produces optical beams, and the emitter coupler is on a surface of the waveguide and is configured to direct at least some of the optical beams to propagate via total internal reflection (TIR) through the waveguide as coupled optical beams. Touches on the top surface of the waveguide disturb the coupled optical beams, and the touch-sensitive device determines touch events based on the disturbances.