Capacitive Touch Electrode Layout Around Openings Without Ghost Points
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Solution Overview
Problem
Projected-capacitive touch detection systems face limitations in multi-touch recognition and spatial resolution due to geometric deviations from a strictly regular electrode pattern, particularly in large diagonal touchpads and vehicle applications, where single and dual touch recognition are common, and 'ghost points' can occur, limiting the design variety and increasing installation space.
Innovation Solution
An arrangement with electrically conductive surfaces of alternating types on an insulating substrate, where surfaces of one type are connected in rows and the other in columns, maintaining a minimum distance to form a regular pattern, even with non-compliant surfaces around openings, ensuring retained sensitivity and resolution through optimized surface design and software compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If through-holes for fasteners or orientation aids are located outside the contact surface to avoid impairing resolution, then the touch detection resolution is maintained, but the design flexibility is limited and installation space increases
Solution Approach 1:
The patent applies local quality by allowing geometric deviations from the regular electrode pattern specifically in regions surrounding through-holes, while maintaining regular patterns in other areas. This localized adaptation enables through-holes to be positioned within the contact surface without compromising overall touch detection resolution, as the regular pattern is preserved in regions where high precision is critical.
Solution Approach 2:
The patent resolves the spatial conflict by transitioning to a mutual capacitance measurement approach that operates in the electromagnetic field dimension rather than relying solely on physical electrode spacing. This allows the system to detect touches even when electrode patterns are disrupted by through-holes, effectively decoupling the physical layout constraints from the measurement capability.
2Measurement precision
If a strictly regular electrode pattern is maintained, then touch detection resolution is optimized, but design variety and placement flexibility of orientation aids are reduced
Solution Approach 1:
The patent implements local quality by permitting geometric deviations from the regular electrode pattern in specific local regions, particularly around through-holes and orientation aids. The evaluation unit is configured to account for these known deviations, maintaining accurate touch detection despite the irregular patterns. This allows diverse designs with strategically placed orientation aids and fasteners within the contact surface.
Solution Approach 2:
The patent applies preliminary action by pre-configuring the evaluation unit with information about expected geometric deviations and their locations. This preliminary setup allows the system to compensate for irregular electrode patterns before touch detection begins, enabling design flexibility without sacrificing measurement precision.
3Area of stationary object
If geometric deviations from regular pattern occur around through-holes, then design flexibility and space utilization improve, but resolution and sensitivity at affected points deteriorate
Solution Approach 1:
The patent applies parameter changes by modifying the evaluation criteria in the evaluation unit to account for altered electrode geometries around through-holes. The system adjusts measurement parameters and thresholds locally in affected regions, compensating for the reduced electrode area and irregular patterns. This maintains acceptable resolution and sensitivity even where geometric deviations occur, enabling effective space utilization.
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 approach enables user-friendly, space-saving, and clear multi-touch detection with improved resolution and sensitivity, reducing 'ghost points' and allowing for optimal placement of orientation aids, suitable for vehicle controls, while maintaining sensitivity and resolution even with geometric deviations.
Implementation Method 1
Projected capacitive technology detects touch by measuring the electrical capacitance at each addressable electrode. When a finger or conductive stylus approaches an electrode, its electromagnetic field is disturbed, changing its electrical capacitance.
Implementation Method 2
When a finger or conductive stylus approaches an electrode, its electromagnetic field is disturbed, changing its electrical capacitance.
Implementation Method 3
Mutual capacitance refers to the intended or unintended electrical capacitance between two charged objects. In projected capacitive touchpads (pcap touch), a counter-capacitance is intentionally created between the elements of rows and columns located near each intersection point.
Data Source
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Figure 5~6
AI summary
The invention relates to an arrangement for spatially resolved projected capacitive touch detection comprising an electrically insulating substrate (5) with several electrically conductive surfaces of the first type (1) and the second type (2) arranged side by side on the substrate, wherein the surfaces within a type regularly have a uniform surface structure, and wherein the surfaces of the first type (1) are electrically connected to each other to form several transmitting electrodes and the surfaces of the second type (2) are electrically connected to form several receiving electrodes, and are arranged forming an essentially regular pattern due to their generic, regular surface structure and placement, wherein an opening (4) is formed in the substrate (5), wherein the receiving electrodes are connected column-wise and the transmitting electrodes are connected row-wise.that the surfaces of the first type (1) and the surfaces of the second type (2) are arranged alternately, that the surface of one type (6) is surrounded by several surfaces of the other type (7) maintaining a minimum distance (3), and that at least one first surface (1b, 2a) of the first type (1) or second type (2) adjacent to the opening (4) is provided, which is not designed in accordance with the standard surface configuration and/or placement in such a way that the specified minimum distance (3) to at least two nearest adjacent surfaces (1a, 1a') of the other type is achieved, characterized in that the surfaces not designed in accordance with the standard are designed in such a way that they have the same outer perimeter as the standard surfaces, in particular the same outer perimeter as the standard surfaces of the same type.