Capacitive Pointing Stick Structure for Low-Profile Force Sensing
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Solution Overview
Problem
Existing input devices, such as pointing sticks and touchpads, face challenges in providing a low-profile, cost-effective solution for sensing lateral and vertical forces to control user interface indicators in electronic devices, particularly in embedding them within other input devices like keyboards without compromising accuracy or increasing manufacturing costs.
Innovation Solution
A low-profile capacitive pointing stick is developed using an elastomeric material mechanically coupled to a substrate with sensor electrodes, where the area of contact between the elastomeric material and the electrodes changes in response to applied forces, allowing for capacitance measurements that control user interface indicators, utilizing transcapacitive and absolute capacitive excitation schemes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional pointing stick design is used, then the sensing accuracy is maintained, but the profile height increases and manufacturing cost increases
Solution Approach 1:
The patent replaces traditional mechanical sensing mechanisms with capacitive sensing. The elastomeric material deforms under applied force, changing the capacitance between sensor electrodes and the elastomeric material, thereby eliminating the need for complex mechanical structures and reducing profile height while maintaining sensing accuracy.
Solution Approach 2:
The patent uses an elastomeric material as a flexible thin film that serves as both the sensing element and the structural component. This thin elastomeric layer allows for low-profile construction while still providing adequate mechanical deformation for accurate force sensing in both lateral and vertical directions.
2Length of stationary object
If a low-profile design is implemented, then the device can be embedded in other input devices, but the sensing capability for lateral and vertical forces is compromised
Solution Approach 1:
The patent divides the sensing function into multiple independent sensor electrodes arranged in arrays. By segmenting the sensing area into multiple electrodes, the system can independently measure capacitance changes in different regions, enabling accurate detection of both lateral and vertical force components even within a compressed profile height.
Solution Approach 2:
The patent transitions from traditional single-dimensional mechanical displacement sensing to multi-dimensional capacitive field sensing. By measuring capacitance changes across multiple electrodes in both lateral and vertical arrangements, the system captures force information from multiple dimensions simultaneously, maintaining full sensing capability in a low-profile configuration.
3Measurement precision
If complex sensing mechanisms are used to maintain accuracy, then the measurement precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces complex mechanical sensing mechanisms with simpler capacitive sensing using basic sensor electrodes and elastomeric material. This substitution dramatically reduces device complexity while maintaining or improving measurement precision through electronic capacitance measurement, which is inherently more accurate and easier to implement than mechanical displacement sensing.
Solution Approach 2:
The patent measures physical force by detecting changes in capacitance parameters rather than mechanical displacement. By monitoring capacitance values between electrodes and the elastomeric material, the system converts mechanical force into electrical parameter changes that are easier to measure precisely with simpler electronics, thereby reducing overall device complexity.
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 enables accurate and efficient sensing of user input forces, allowing for precise control of user interface indicators with a low-profile design suitable for integration into other devices, reducing manufacturing costs and maintaining high accuracy.
Implementation Method 1
The elastomeric material includes an inner portion disposed such that an area of contact between the inner portion and at least some of the plurality of sensor electrodes changes in response to at least one of a lateral force or a vertical force applied to the elastomeric material
Implementation Method 2
The elastomeric material is mechanically coupled to the substrate and overlaps the plurality of sensor electrodes
Data Source
AI summary
In an example, an input device includes a substrate and an elastomeric material. The substrate includes a plurality of sensor electrodes disposed thereon. The elastomeric material is mechanically coupled to the substrate and overlaps the plurality of sensor electrodes. The elastomeric material includes an inner portion disposed such that an area of contact between the inner portion and at least some of the plurality of sensor electrodes changes in response to at least one of a lateral force or a vertical force applied to the elastomeric material.