Capacitive Sensing Air Gap Calibration via Baseline Comparison
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Solution Overview
Problem
The unpredictable variation in air gap thickness between a cover lens and a capacitive sensing device affects input sensing signals in proximity sensor devices, leading to inconsistent performance.
Innovation Solution
A processing system that determines a capacitive image, compares it to a baseline, and calculates calibration values to compensate for the air gap between the cover lens and common electrodes, ensuring accurate input sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If transparent electrodes are used to prevent the sensing region from obscuring the user's view, then display visibility is improved, but the air gap between the electrode and cover lens causes unpredictable effects on input sensing signals
Solution Approach 1:
The system performs preliminary calibration by determining baseline capacitance values and saturation capacitance values before normal operation. This preliminary measurement allows the system to calculate calibration values that compensate for air gap variations, ensuring consistent input sensing performance without requiring physical modification of the air gap structure.
Solution Approach 2:
The system changes the electrical parameters by applying calibration values to the capacitance measurements. By adjusting the interpreted capacitance values based on the determined calibration parameters, the system compensates for the unpredictable effects of air gap variations while maintaining the transparent electrode design.
2Ease of manufacture
If the air gap thickness is allowed to vary as a function of location, then manufacturing tolerance is improved, but input sensing signal accuracy deteriorates
Solution Approach 1:
The system determines calibration values at different locations across the sensing region by comparing baseline and saturation capacitance values at multiple positions. This allows the system to account for local variations in air gap thickness, with each location having its own calibration characteristics, thereby maintaining accuracy despite manufacturing tolerances.
Solution Approach 2:
The system uses feedback from capacitance measurements at multiple locations to determine calibration values. By measuring baseline and saturation capacitance values across the sensing region and comparing them, the system obtains feedback information about air gap variations and adjusts calibration parameters accordingly to maintain signal accuracy.
3Measurement precision
If calibration values are determined through complex comparison processes, then sensing accuracy is improved, but processing complexity increases
Solution Approach 1:
The calibration process is segmented into distinct steps: determining baseline capacitance values, determining saturation capacitance values, comparing the two to find differences, and using these differences to calculate calibration values. This segmentation makes the complex process more manageable and implementable while maintaining accuracy.
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 enhances the performance of capacitive sensing devices by compensating for air gap variations, improving the accuracy and reliability of input detection.
Implementation Method 1
the air gap may act as a dielectric layer, affecting input sensing signals which are transmitted and received by the device
Implementation Method 2
the processing system determines a first capacitive image based on the resulting signals, compares the first capacitive image to a baseline capacitive image
Data Source
AI summary
Embodiments of the present invention generally provide a processing system for a display device integrated with a capacitive sensing device. The processing system includes a driver module, a receiver module, and a determination module. The driver module is coupled to a plurality of common electrodes configured to be driven for display updating and capacitive sensing. The receiver module is coupled to a plurality of receiver electrodes and configured for receiving resulting signals with the receiver electrodes. The determination module is configured for comparing a delta capacitive image to one or more saturation capacitance values and replacing the saturation capacitance values with one or more capacitance values from the delta capacitive image. The determination module is further configured for determining calibration values based on the saturation capacitance values. The calibration values calibrate for an air gap defined between a cover lens of a display device and the plurality of common electrodes.