Capacitive Force Touchpad with Haptic Feedback
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Solution Overview
Problem
Conventional capacitive touchpads face challenges in accurately detecting user input due to variability in touch threshold caused by factors like skin humidity and environmental conditions, leading to awkward or non-intuitive methods for performing cursor-position associative functions such as clicks and gestures.
Innovation Solution
The implementation of capacitive force-sensing technology that determines the X/Y/Z position of a user's finger on a touchpad, providing active tactile feedback to enhance the illusion of pressing on-screen buttons, allowing for intuitive single-, double-, or right-click operations without the need for additional buttons or gestures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch sensors are used to detect user input, then the touchpad can detect finger position on the surface, but the touch threshold varies widely due to skin humidity and environmental conditions leading to inaccurate detection
Solution Approach 1:
The patent changes the detection parameter from surface capacitance (which varies with environmental conditions) to subsurface capacitance at a fixed depth (which remains stable). By measuring capacitance at a consistent depth below the touchpad surface, the system achieves reliable and consistent touch detection thresholds regardless of skin humidity or environmental variations.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using multiple capacitive sensors at different depths to indirectly measure the force applied. Instead of directly measuring surface capacitance which is affected by environmental factors, the system measures the displacement of the touchpad surface through subsurface capacitance changes, providing a more reliable indicator of intentional user input.
2Adaptability or versatility
If additional buttons or complex gestures are added to perform cursor-position associative functions, then more functions can be achieved, but the device complexity increases and usability decreases
Solution Approach 1:
The patent makes the touchpad surface itself multi-functional by enabling it to detect both position and force application. This allows the same surface to perform multiple cursor-position associative functions (click, double-click, right-click, drag) without requiring separate buttons or complex gesture sequences, simplifying the user interface while maintaining versatility.
Solution Approach 2:
The patent merges the functions of separate physical buttons into the capacitive touchpad surface by detecting force magnitude and duration. This combination allows single-click, double-click, and other cursor operations to be performed through variations of the same basic interaction (pressing the surface), eliminating the need for additional buttons or complex gesture systems.
3Ease of operation
If the touchpad surface is made more sensitive to detect light touches, then lighter input is possible, but accidental touches increase
Solution Approach 1:
The patent applies preliminary discrimination by measuring both the position and force characteristics before registering a touch input. By evaluating the magnitude and duration of the applied force as preliminary conditions, the system can distinguish between intentional light touches and accidental contacts, allowing sensitive detection while filtering out false inputs.
Solution Approach 2:
The patent uses feedback from multiple capacitive sensors to analyze the characteristics of each touch event. By continuously monitoring capacitance changes at different depths and comparing them against established thresholds and patterns, the system provides real-time discrimination between deliberate user input and accidental touches, adjusting recognition based on the measured force characteristics.
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 solution improves user interaction by providing precise and intuitive input methods, reducing errors from accidental touches and enhancing the tactile feedback experience, thus simplifying cursor-position associative functions on touchpads.
Implementation Method 1
conventional capacitive touchpads...sense the position of a user's finger (or fingers) on its surface...sensing the changes in an electrical field using, for example, capacitance or conductance
Implementation Method 2
an electrostatic actuation mechanism that provides tactile feedback to the user's finger
Data Source
AI summary
Described herein are techniques related to a touchpad with capacitive force sensing. The described techniques may determine the point or region of a user-engagement surface contacted by a user. In addition, the described techniques may also determine a force of the user's finger press on the user-engagement surface using one or more capacitance force-sensors. Furthermore, the described techniques may offer active tactile feedback (i.e., haptics) to the user's finger touching the user-engagement surface. This Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.