Capacitive Touch Screen Stylus Signal Stability

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Solution Overview

Problem

Capacitive touch screens using passive pens often experience discontinuous and jittery strokes due to low signal magnitude, which is exacerbated by noise interference, leading to an unpleasant user experience.

Innovation Solution

Implementing a processing system that selectively activates a subset of transmitters based on predicted stylus motion, improving the signal-to-noise ratio and reducing latency by scanning only the transmitters closest to the stylus contact point, thereby enhancing the stability and clarity of stylus signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If all transmitters are scanned to detect stylus signals, then detection coverage is improved, but signal-to-noise ratio deteriorates due to noise interference from unnecessary transmitters

Engineering Contradiction:

Improvestylus signal detection accuracyVSAvoidnoise interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The transmitter scanning process is segmented into two phases: an initial full scan to locate stylus contact, followed by focused scanning of only those transmitters in the vicinity of detected contact points. This segmentation eliminates noise from distant transmitters while maintaining detection accuracy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The scanning intensity and transmitter activation are made local rather than uniform. Transmitters near the stylus contact point are actively scanned with higher priority, while transmitters far from contact points are excluded or scanned minimally, creating a localized detection zone that reduces noise interference.

Inventive Principle:

Principle #3Local quality

2Reliability

If all transmitters are scanned to ensure complete coverage, then detection reliability is improved, but latency increases due to scanning unnecessary transmitters

Engineering Contradiction:

Improvestylus signal detection reliabilityVSAvoidscanning latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

An initial comprehensive scan is performed to preliminarily identify stylus contact locations. Based on this preliminary information, subsequent scans are optimized to focus only on relevant transmitters, thereby reducing latency while maintaining detection reliability through the initial thorough assessment.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The transmitter scanning strategy is made dynamic rather than static. The set of active transmitters changes based on real-time detection needs: all transmitters are scanned when no contact is detected, but only vicinity transmitters are scanned when contact is detected, optimizing the balance between reliability and latency adaptively.

Inventive Principle:

Principle #15Dynamics

3Productivity

If a subset of transmitters is scanned to reduce latency, then scanning speed is improved, but detection precision deteriorates due to missed signals

Engineering Contradiction:

Improvescanning speedVSAvoidstylus signal detection precision

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The system uses feedback from initial scans and detected contact points to dynamically adjust which transmitters are scanned subsequently. This feedback mechanism ensures that the subset of scanned transmitters is always relevant to current stylus activity, maintaining detection precision while improving scanning speed.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

A preliminary full scan establishes the baseline detection coverage and identifies contact regions. This preliminary action provides the information needed to subsequently scan only the necessary subset of transmitters, ensuring no signals are missed while achieving faster scanning.

Inventive Principle:

Principle #10Preliminary action

4Measurement precision

If all transmitters are excited to maximize signal detection, then signal magnitude is improved, but energy consumption increases

Engineering Contradiction:

Improvesignal detection capabilityVSAvoidtransmitter excitation energy

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

Instead of excessively exciting all transmitters continuously, the system applies partial action by exciting only the necessary subset of transmitters based on detected stylus contact locations. This reduces energy consumption while maintaining sufficient signal detection capability through targeted excitation.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system dynamically changes the parameter of transmitter activation state: all transmitters are excited when no contact is detected, but only a subset is excited when contact is detected. This parameter change optimizes the balance between signal detection capability and energy consumption based on real-time conditions.

Inventive Principle:

Principle #35Parameter changes

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 approach results in cleaner, more stable stylus signals with improved signal-to-noise ratio and reduced latency, providing a smoother user experience by optimizing the number of transmitters scanned during touch screen interactions.

Implementation Method 1

Capacitive touch surfaces determine the position of an object, such as a finger or stylus, by detecting a change in capacitance due to a distortion in an electrostatic field that occurs when the touch screen is touched.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

Methodology Applied

Scientific EffectElectrostatic field: Electric Field

Data Source

PatentUS10606419B2Touch screen control

Publication Date: 2020.03.31 INTEL CORP

AI summary

An apparatus and method for display control are described. In one embodiment, the apparatus comprises: a touch screen surface comprising a plurality of transmitters and a plurality of receivers; and a processing system coupled to the touch screen surface to excite all transmitters in the plurality of transmitters or a subset of transmitters in the plurality of transmitters during different scanning periods when scanning the plurality of transmitters to obtain input signals from the touch screen surface, the subset of transmitters being less than all transmitters in the plurality of transmitters.