Diffusive Light Guide for Optical Touch Sensing
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Solution Overview
Problem
Existing above-surface optical touch systems relying on collimated light are cumbersome and expensive due to precise alignment requirements, making them difficult to implement in mass production and increasing system complexity.
Innovation Solution
A touch-sensing apparatus using a diffusive transmissive or reflective light guide that directs and receives light around the edge of a panel, eliminating the need for precise alignment of emitters and detectors, and incorporating features like diffusive surfaces, reflective coatings, and angular filters to enhance light transmission and reduce system complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If collimated light is used for above-surface optical touch systems, then light transmission efficiency is improved, but alignment precision requirements increase and system complexity increases
Solution Approach 1:
The patent changes the optical parameter from collimated light to diffusive light. The light guide uses diffusive surfaces and reflective coatings to scatter and redirect light, eliminating the need for precise collimation while maintaining adequate light transmission for touch sensing operation.
Solution Approach 2:
The patent replaces expensive precision optical components (collimators, precise alignment mechanisms) with simpler, cheaper diffusive light guide components that are easier to manufacture and assemble, reducing system cost and complexity.
2Measurement precision
If collimated light systems are implemented, then optical performance is improved, but device complexity increases
Solution Approach 1:
The patent merges the light guiding, diffusing, and reflecting functions into a single integrated light guide component. This eliminates the need for separate collimators, mirrors, and alignment mechanisms, reducing device complexity while maintaining optical performance through the combined diffusive and reflective surfaces.
Solution Approach 2:
The light guide acts as an intermediary component between the light source and the touch surface, using diffusive and reflective properties to manage light distribution without requiring precise optical alignment, thereby simplifying the overall system.
3Manufacturing precision
If precise alignment of emitters and detectors is required, then light path control is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent changes the light propagation parameter from directional collimated light to omnidirectional diffusive light. This allows the light guide to control light paths through geometric design and surface properties rather than precise component alignment, greatly easing manufacturing and assembly.
4Use of energy by moving object
If collimated light paths are used, then optical efficiency is improved, but system cost increases
Solution Approach 1:
The patent replaces expensive precision optical components with simpler, cheaper diffusive light guide components that are easier to manufacture and assemble, reducing system cost while maintaining adequate optical efficiency for touch sensing.
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 simplifies the manufacturing process, reduces costs, and results in a more compact and reliable touch-sensing system by using diffusive and reflective light guides to manage light paths, improving optical tolerances and suppressing ambient light noise.
Implementation Method 1
The second surface may be diffusively transmissive
Implementation Method 2
The light guide may further comprise a reflective surface configured to internally reflect light travelling in the light guide
Data Source
AI summary
A touch sensing apparatus is provided comprising: a light transmissive panel that defines a touch surface, a plurality of light emitters and detectors arranged along a perimeter of the light transmissive panel, a plurality of optical components arranged along the perimeter of the light transmissive panel, wherein the light emitters are arranged to emit a respective beam of emitted light and the optical components are configured to direct the emitted light to a path across the light transmissive panel. Optionally, optical components comprise a light guide arranged to receive light from the light emitters through a first surface and couple out light travelling in the light guide to the touch surface through a second surface. The second surface may be diffusively transmissive. The light guide may further comprise a reflective surface configured to internally reflect light travelling in the light guide from the first surface to the diffusive surface. The reflective surface may be diffusely reflective, partially diffusely reflective, or specularly reflective.