Touch Panel Controller Hover Palm Input Rejection

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Solution Overview

Problem

Touch panel systems face difficulties in distinguishing between intended touch inputs and spurious inputs such as hover and palm signals, particularly due to variations in finger size and edge responses, leading to inaccurate input recognition.

Innovation Solution

A touch panel controller is designed to implement rule sets for rejecting spurious inputs by processing pixel values, discarding noise, differentiating between hover and touch inputs, and using specific thresholds to distinguish between stylus and finger inputs, thereby improving input accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the touch panel uses capacitance sensing to detect all touches, then it can detect both intended touches and spurious inputs, but it cannot distinguish between hover inputs and actual touch inputs

Engineering Contradiction:

Improveinput detection accuracyVSAvoidinput recognition accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent segments the touch detection process into multiple analysis stages: initial touch detection, hover identification through pixel pattern analysis, palm rejection through centroid analysis, and spurious input filtering. This multi-stage segmentation allows the system to distinguish between different types of inputs by analyzing specific characteristics at each stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic threshold adjustment where the noise threshold and detection parameters are adjusted based on the detected pixel patterns and input characteristics. The system dynamically adapts its sensitivity and rejection criteria based on the analyzed input properties, allowing it to differentiate between hover and touch inputs.

Inventive Principle:

Principle #15Dynamics

2Productivity

If the touch panel detects all capacitance changes, then it captures all input signals, but it also captures spurious signals from palms and hovers

Engineering Contradiction:

Improveinput signal captureVSAvoidspurious input signals

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes spurious signals through multiple filtering mechanisms: discarding pixels below the noise threshold, removing isolated non-zero pixels that are not adjacent to other non-zero pixels, and rejecting inputs that match palm or hover patterns. This extraction process separates the useful touch signals from the harmful spurious signals.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the presence of spurious signals into a beneficial feature by using them as training data for improving the rejection algorithms. The system learns from various input patterns including palms and hovers to refine its discrimination capabilities, turning potential harmful inputs into opportunities for improving overall system accuracy.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If the touch panel uses fixed detection thresholds, then the system is simple to implement, but it cannot adapt to variations in finger size and edge responses

Engineering Contradiction:

Improvesystem implementation simplicityVSAvoidinput variation handling

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent changes the detection parameters dynamically based on the analyzed input characteristics. The noise threshold, adjacency requirements, and rejection criteria are adjusted according to the detected pixel patterns, finger size variations, and edge response characteristics. This parameter adaptation allows the system to handle diverse input scenarios effectively.

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

The solution effectively rejects spurious inputs like hover and palm signals, enhancing the accuracy of touch panel systems by tailoring rejection rules to specific configurations and improving the differentiation between stylus and finger inputs.

Implementation Method 1

Capacitive touch panels are often used with touch screen devices. A capacitive touch panel generally includes an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the panel results in a distortion of the panel's electrostatic field, measurable as a change in capacitance.

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS9081450B1Identifying hover and/or palm input and rejecting spurious input for a touch panel

Publication Date: 2015.07.14 QUALCOMM INC

AI summary

A touch panel controller may include a communications module configured to receive pixel values, where each pixel value represents a capacitance associated with a pixel formed at a drive electrode and a sensor electrode of a touch panel. The touch panel controller may also include a processing module configured to discard pixel values below a noise threshold, discard pixel values for non-zero pixels that are not adjacent to non-zero pixels, reject detected input for pixel values associated with a palm input, compute an initial centroid associated with the pixel values, reject detected input for pixel values associated with a hover input, and provide detected input that is not associated with palm input or hover input.