Multi-scan Touch Sensing for Crosstalk Noise Reduction
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Solution Overview
Problem
Display-to-touch screen crosstalk noise in touch data is a significant issue due to the close proximity of touch and display circuitry, leading to variations in electrical time constants and noise contamination in touch data.
Innovation Solution
Implementing multi-scan touch sensing techniques, including extended touch sensing periods and noise estimation methods, such as bootstrap and non-bootstrap scans, to isolate and remove display-to-touch crosstalk noise by computing differences between scans and up-sampling noise estimates to cover all touch electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If touch sensing is performed with standard sensing period, then touch response time is maintained, but display-to-touch crosstalk noise contaminates the touch data
Solution Approach 1:
The touch sensing operation is divided into multiple separate scans: a first scan during the display refresh period and a second scan during the blanking period. This segmentation allows the system to capture touch data at different times when display-to-touch coupling varies, enabling noise identification and removal through comparison of the scanned results.
Solution Approach 2:
The system performs periodic multi-scan operations at different phases of the display refresh cycle. By scanning during both the active display period and the blanking period, the system creates periodic measurement opportunities that allow differentiation between display-induced noise and actual touch signals through temporal analysis.
2Object-affected harmful factors
If extended touch sensing period is used, then display-to-touch crosstalk noise is reduced, but touch response time increases
Solution Approach 1:
The system performs preliminary scanning during the display blanking period before the main touch sensing operation. This preliminary scan during the extended sensing period allows charge to settle and display-to-touch coupling to minimize, providing a baseline measurement that can be used to subtract noise from the main touch data acquired during the active display period.
Solution Approach 2:
The extended sensing period acts as an intermediary measurement phase that captures the display-to-touch coupling characteristics without the full impact of display signals. This intermediary scan provides reference data that mediates the noise removal process, allowing clean touch data to be extracted from the main sensing operation.
3Measurement precision
If multi-scan techniques are implemented, then noise estimation accuracy is improved, but device complexity increases
Solution Approach 1:
The system uses feedback from multiple scans to continuously refine noise estimation. By comparing results from scans performed at different display phases, the system generates feedback information about display-to-touch coupling characteristics, which is then used to adjust and improve noise removal accuracy for subsequent touch measurements.
Solution Approach 2:
The system creates copies of touch data from multiple scan operations performed under different conditions. By acquiring replicated measurements during both display and blanking periods, the system generates multiple data copies that can be processed and compared to extract and remove noise patterns, improving measurement precision through redundancy.
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 effectively reduces or removes display-to-touch crosstalk noise, providing cleaner touch data for accurate user input detection and operation, even in scenarios where full noise reduction is not possible in a single scan.
Implementation Method 1
capacitive-type touch sensing systems, fringing electrical fields used to detect touch can extend beyond the surface of the display
Implementation Method 2
fringing electrical fields used to detect touch can extend beyond the surface of the display
Implementation Method 3
a large capacitance can be formed between one or more touch electrodes of the touch screen and display circuitry
Data Source
AI summary
In some examples, a touch screen can perform a first touch scan to obtain first touch data and a second touch scan to obtain second touch data. The touch data resulting from the second touch scan may exclude respective noise (e.g., display-to-touch crosstalk (DTX) noise) or may include a reduced amount of the respective noise. In some examples, the electronic device can subtract the second touch data from the first touch data to obtain an estimate of the noise in the first touch data. In some examples, this noise estimate can be subtracted from the first touch data and an action can be performed based on the first touch data with the noise estimate removed.