Capacitive Force Sensor Integration for Touch Input

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Solution Overview

Problem

Current touch devices can only detect the location of a touch, limiting the ability to differentiate and measure the force of a touch, which is advantageous for providing multiple types of user input, such as controlling virtual objects or simulating real-world interactions in applications like flight simulators or virtual reality.

Innovation Solution

Integration of a capacitive force sensor within a touch device that uses a compressible element and capacitive plates to detect changes in capacitance as force is applied, allowing for the measurement and differentiation of various force levels applied to the device's surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a traditional touch sensor is used, then the device can detect touch location, but it cannot measure the force of the touch

Engineering Contradiction:
Improveforce measurement capabilityVSAvoidsensor structure complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the touch location detection function and force measurement function into a single integrated sensor system. The capacitive sensor array simultaneously detects both the position and force magnitude of touches by measuring capacitance changes, eliminating the need for separate sensors and reducing overall system complexity despite enhanced functionality.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The capacitive sensor array performs multiple functions: it detects touch location coordinates and simultaneously measures touch force magnitude. This multi-functional approach allows a single component to replace what would traditionally require separate sensors, addressing the contradiction between enhanced measurement capability and device complexity.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If only touch location is detected, then the device structure remains simple, but the ability to provide nuanced user input is limited

Engineering Contradiction:
Improveuser input differentiationVSAvoidsensor system complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent utilizes changes in capacitance parameters to encode multiple types of information. By monitoring both the magnitude and distribution of capacitance changes across the sensor array, the system can differentiate between various touch forces and locations, providing nuanced user input capability through parameter variation rather than additional hardware complexity.

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

Enables the detection and measurement of force levels applied to a touch device, enabling more nuanced user input and interaction with virtual objects, enhancing applications in gaming, virtual reality, and other interactive systems.

Implementation Method 1

a capacitive force sensor integrated into a device for detecting and measuring an amount or a magnitude of a touch applied to a surface of the device

Methodology Applied
Scientific EffectCapacitance: Capacitance

Data Source

PatentEP3072040B1Force determination employing sheet sensor and capacitive array
Publication Date: 2021.12.29 APPLE INC
  • EP3072040B1 patent drawingFigure 1
  • EP3072040B1 patent drawingFigure 2A
  • EP3072040B1 patent drawingFigure 2B

AI summary

A device configured to sense a touch on a surface of the device. The device includes a cover and a force-sensing structure disposed below the cover. The force-sensing structure may be positioned below a display and used in combination with other force-sensing elements to estimate the force of a touch on the cover of a device.