Touch Sensor Calibration via Cell-Specific Capacitance Ratios
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Solution Overview
Problem
Conventional touch sensing circuits experience significant accuracy degradation due to varying process variations and other factors, leading to inconsistent capacitance change readings across different sensor cells, which affects navigation data accuracy.
Innovation Solution
A touch controlling apparatus coupled to a touch sensor array, featuring a memory circuit for recording calibration ratios associated with different process variations and a controlling circuit that adjusts sensed capacitance changes using these ratios to generate resultant capacitance changes, thereby calibrating cell sensitivities and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional touch sensing circuits are used without calibration, then the device complexity is low, but the measurement precision of capacitance change readings is significantly degraded due to process variations
Solution Approach 1:
The patent applies preliminary action by pre-calibrating each sensor cell during the manufacturing process and storing its unique calibration ratio in a lookup table. This preliminary calibration action eliminates the need for complex real-time calibration mechanisms during operation, thereby improving measurement precision without significantly increasing operational device complexity.
Solution Approach 2:
The patent uses copying by creating a lookup table that stores pre-determined calibration ratios for each sensor cell. Instead of implementing complex real-time calibration algorithms, the system copies and applies the appropriate calibration ratio from the lookup table based on the sensor cell's position, simplifying the calibration mechanism while maintaining high measurement precision.
2Measurement precision
If different calibration ratios are stored for different sensor cells, then the measurement precision is improved, but the quantity of data stored in memory increases
Solution Approach 1:
The patent applies parameter changes by storing calibration ratios as simple multiplicative factors rather than complex calibration curves or lookup matrices. This parameter transformation reduces the quantity of calibration data needed while maintaining the ability to correct for process variations, thereby improving navigation data accuracy without significantly increasing memory requirements.
3Reliability
If calibration ratios are applied to each sensor cell, then the reliability of touch sensing is improved, but the use of energy for calibration calculations increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing calibration ratios during manufacturing, so that during operation, the system only needs to perform simple multiplication operations rather than complex real-time calibration calculations. This dramatically reduces the energy required for calibration while maintaining reliable and consistent touch sensing across all sensor cells.
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 calibration mechanism effectively reduces the impact of process variations, enhancing the accuracy of touch sensing data by generating consistent and accurate navigation curves, as demonstrated by reducing undesired S curves in finger navigation examples.
Implementation Method 1
sense the capacitance change amount of a sensor cell
Implementation Method 2
employ the self-capacitive or mutual-capacitive sensing mechanism to sense the capacitance change amount
Data Source
AI summary
A touch controlling apparatus to be coupled to a touch sensor array is disclosed. The apparatus comprises a memory circuit and a controlling circuit. The memory circuit is used for recording different calibration ratios associated with different process variations. The controlling circuit is coupled to the memory circuit, and is used for calibrating or adjusting sensitivities of a plurality of cells by respectively using the different calibration ratios to calibrate or adjust sensed capacitance changes of the plurality of cells to generate and output resultant capacitance changes of the plurality of cells.