Optical Touch Screen Multi-Touch Detection Using Edge Emitters
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Solution Overview
Problem
Light-based touch screens face challenges in accurately recognizing multiple points of contact due to ambiguity and 'ghosting' effects, which hinder their ability to support multi-touch gestures and are cumbersome to integrate into devices due to the extensive arrangement of light emitters and detectors.
Innovation Solution
A light-based touch screen system with a reduced component count, utilizing a rectangular arrangement of light emitters and detectors along two edges, where each emitter's beam is detected by multiple detectors, and a method to calculate touch locations by marking pixels as fully blocked, partially blocked, or unblocked, connecting adjacent blocked pixels to identify touch locations, and using a lens to enhance light collimation and detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light emitters and detectors are arranged along all four edges to create a complete light beam grid, then touch detection coverage is improved, but device complexity and component quantity increase
Solution Approach 1:
The patent extracts the light emitters and detectors from all four edges and relocates them to only two opposite edges. This extraction removes unnecessary components while preserving the essential function of creating light beams across the touch surface, thereby reducing device complexity without sacrificing touch detection coverage.
Solution Approach 2:
The patent makes each light emitter serve multiple functions by having its light detected by multiple detectors across the opposite edge. Similarly, each detector receives light from multiple emitters. This multi-functionality allows the reduced component arrangement to maintain comprehensive touch detection coverage that would otherwise require more components.
2Device complexity
If emitters and detectors are arranged along two opposite edges with each emitter detected by multiple detectors, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The patent transitions from a one-dimensional linear arrangement of emitters and detectors to a two-dimensional detection matrix by having multiple detectors receive light from each emitter and multiple emitters illuminate each detector. This dimensional change creates a grid of light beams that maintains measurement precision while reducing the total number of components needed.
Solution Approach 2:
The patent segments the light detection function across multiple detector elements rather than relying on a single detector per emitter. By dividing the detection task among multiple detectors that each measure light from specific emitters, the system maintains accurate touch location measurement with fewer total components.
3Reliability
If extensive arrangements of light emitters and detectors are used, then touch detection capability is improved, but ease of manufacture and integration deteriorate
Solution Approach 1:
The patent extracts unnecessary emitters and detectors from the traditional four-edge arrangement and removes them entirely, keeping only the essential two-edge configuration. This extraction simplifies the manufacturing process and integration requirements while preserving the core touch detection capability through the multi-detector-per-emitter approach.
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
Enables unambiguous multi-touch detection, reduces the number of components needed, and allows for more flexible integration into devices, improving the accuracy and efficiency of touch recognition while minimizing material costs.
Implementation Method 1
utilizing a rectangular arrangement of light emitters and detectors along two edges, where each emitter's beam is detected by multiple detectors, and a method to calculate touch locations... and using a lens to enhance light collimation and detection
Implementation Method 2
each emitter's beam is detected by multiple detectors
Data Source
AI summary
Activating a plurality of light emitters and light detectors around a screen, each emitter-detector pair corresponding to a light path crossing the screen, wherein some of the light paths are blocked when one or more objects touch the screen, providing a look-up table, listing, for each cell from a plurality of cells, those light paths that traverse that cell when no object is touching the screen, wherein the cells partition the screen, for each cell: accessing the look-up table to identify those light paths that traverse that cell, determining whether the thus-identified light paths are blocked during the activating and, if affirmative, recognizing that cell as being a touched cell, and combining adjacent touched cells into a common touch location, thereby calculating one or more touch locations wherein each touch location is a combination of one or more constituent touched cells.