Mutual Capacitive Sense Array Edge Positioning Accuracy
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Solution Overview
Problem
Conventional capacitive touch screens experience significant position tracking errors near the edges due to mutual capacitance array designs, which limit the usable area and accuracy in edge interactions.
Innovation Solution
The implementation of a mutual capacitive sense array configuration that minimizes edge errors by using a combination of complete and partial sense elements, along with virtual sense elements and additional transmit/receive elements, to accurately detect user inputs and improve tracking accuracy at the edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mutual capacitance array design is used, then the touch screen can be manufactured with standard elements, but position tracking accuracy deteriorates near the edges
Solution Approach 1:
The sense array is segmented into different element types: complete sense elements for central regions and partial sense elements for edge regions. This segmentation allows each region to be optimized independently, improving position tracking accuracy at edges while maintaining manufacturability through standardized manufacturing processes.
Solution Approach 2:
Different regions of the touch screen are assigned different qualities: complete sense elements with full capacitance sensing capability are placed in central areas, while partial sense elements with reduced capacitance are placed at edges. This local differentiation optimizes measurement precision for each region's specific requirements.
2Area of stationary object
If the touch screen area is maximized, then the usable area increases, but position tracking accuracy deteriorates at the edges
Solution Approach 1:
The patent introduces a new dimension to the sense element design by adding virtual sense elements that extend beyond the physical array boundaries. These virtual elements compensate for the reduced capacitance signal at physical edges, enabling accurate position tracking across the entire maximized touch screen area including edge regions.
Solution Approach 2:
Virtual sense elements act as intermediaries between the physical sense array and the edge regions where capacitance signals are weak. These virtual elements provide the additional sensing capability needed to maintain measurement precision at edges while allowing the physical array to be maximized.
3Measurement precision
If additional sense elements are added to improve edge accuracy, then position tracking accuracy improves, but device complexity increases
Solution Approach 1:
Virtual sense elements are created as computational copies of physical sense elements. Rather than adding physical components, the system creates virtual representations that can be processed through the existing capacitance measurement infrastructure, improving edge accuracy while avoiding the complexity of additional physical hardware.
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 configuration effectively reduces edge errors and enhances the accuracy of input tracking, allowing for a more reliable and efficient use of the touch screen's edge areas, thereby increasing the usable touch screen area while maintaining uniform position tracking accuracy.
Implementation Method 1
When a conductive object, such as a finger, comes in contact or close proximity with the touch-sensing surface, the capacitance of one or more capacitive touch sense elements changes.
Data Source
AI summary
A mutual capacitive sense array configured to improve edge performance in tracking user inputs is described. A mutual capacitive sense array comprises a first and second plurality of sense elements and a visual display configured below the sense array. The display is configured to contact the first plurality of sense elements, where each of the first and second plurality of sense elements has a first area and second area, respectively, and wherein the second area is less than the first area. A method is described to scan a mutual capacitive sense array for a user input, the array comprising a first, second, and third plurality of sense elements, wherein the third plurality of sense elements are arranged in parallel along the exterior edge of the mutual capacitive sense array. The third plurality of sense elements effectively reduces the tracking error occurring at the edges of the mutual capacitive sense array.