Optical Proximity Sensors Using Triangulation for Touch Detection
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Solution Overview
Problem
Existing light-based touch screens require numerous light emitters and detectors around the entire screen, making it difficult to integrate them into existing devices without significant layout changes and increasing costs.
Innovation Solution
A light-based touch detection system using a one-dimensional array of alternating light emitters and detectors, where emitters project collimated light beams and detectors detect reflections to determine object location through triangulation, allowing for reduced component placement and cost-effective integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light-based touch screens use numerous light emitters and detectors along all four edges of the screen, then touch detection accuracy is improved, but device complexity and bill-of-materials costs increase
Solution Approach 1:
The patent extracts the touch detection functionality from requiring light emitters and detectors along all four edges, concentrating them instead at only two opposite edges. This extraction reduces the total component count while maintaining the ability to detect touches across the entire screen surface through triangulation geometry.
Solution Approach 2:
The patent introduces triangulation in the vertical dimension (z-axis) to complement the horizontal (x-axis) and vertical (y-axis) screen coordinates. By measuring angles from two different edges, the system adds a depth dimension to the detection geometry, enabling full 2D screen coverage with fewer components than traditional grid approaches.
2Measurement precision
If light-based touch screens surround the screen borders with light emitters and detectors, then comprehensive touch detection is achieved, but integration into existing devices becomes difficult without significant layout changes
Solution Approach 1:
The patent extracts the light emitter and detector arrays from surrounding all four screen borders, relocating them to only two opposite edges. This extraction simplifies the physical layout requirements, making integration into existing devices more feasible without requiring modifications to all four device edges.
Solution Approach 2:
The patent makes the light emitter and detector systems multi-functional by using them for both touch location detection and determining the orientation of the device. This universality allows the same reduced component configuration to serve multiple purposes, enhancing ease of manufacture while maintaining comprehensive detection capability.
3Quantity of substance
If the number of light emitters and detectors is reduced, then bill-of-materials costs decrease, but maintaining accurate two-dimensional coordinate determination becomes more challenging
Solution Approach 1:
The patent replaces the mechanical/grid-based approach of having light emitters and detectors at every intersection point with an optical triangulation system. This substitution uses geometric relationships and angle measurements from fewer components to calculate precise 2D coordinates through trigonometric computations, maintaining accuracy while reducing component quantity.
Solution Approach 2:
The patent adds the angular measurement dimension to the coordinate determination process. By measuring the angles of reflected light from two different edges and combining this with the known geometry of the emitter-detector arrangement, the system can accurately calculate 2D screen coordinates with fewer components than traditional planar grid 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
Enables efficient two-dimensional touch detection with reduced component count, facilitating integration into various devices while maintaining effective touch detection capabilities.
Implementation Method 1
a light guide in front of the LEDs and the PDs, for collimating light from the LEDs and for focusing light reflected by an object onto the PDs
Implementation Method 2
when this light is reflected by an inserted object, such as a finger or a stylus, the reflected light is detected by the PDs
Implementation Method 3
a plurality of photodiodes (PDs) arranged along one edge... for detecting the light emitted by the light sources
Data Source
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AI summary
A proximity sensor including a housing, a plurality of light pulse emitters for projecting light out of the housing along a detection plane, a plurality of primary light detectors for detecting reflections of the light projected by the emitters, by a reflective object in the detection plane, a plurality of primary lenses oriented relative to the emitters and primary detectors in such a manner that for each emitter-detector pair, light emitted by the emitter of that pair passes through one of the primary lenses and is reflected by the object back through one of the primary lenses to the detector of that pair when the object is located at a position, from among a primary set of positions in the detection plane, that position being associated with that emitter-detector pair, and a processor for co-activating emitter-detector pairs, and configured to calculate a location of the object in the detection plane.