Capacitive Sensing Voltage Calibration for Fingerprint Distortion
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Solution Overview
Problem
Capacitive sensing devices experience errors and distortions in image processing due to voltage variation distortions caused by process offset or parasitic capacitance effects, leading to inconsistent capacitance readings.
Innovation Solution
A capacitive sensing system with a calibration unit, comprising a pixel matrix and an analog-to-digital converter, generates control signals to adjust voltage variations using a variable resistor, ensuring that voltage readings fall within the analog-to-digital converter's swing range, thereby reducing distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage variations are directly converted to pixel data values without calibration, then the conversion process is simple and fast, but image distortion and measurement errors occur due to process offset and parasitic capacitance effects
Solution Approach 1:
The patent applies preliminary action by performing voltage calibration before the main measurement process. A calibration unit pre-adjusts the voltage variations from the pixel matrix using control signals generated from reference pixel data, ensuring that subsequent capacitance measurements are free from process offset and parasitic capacitance distortions. This preliminary calibration step eliminates measurement errors before they affect the final image processing.
Solution Approach 2:
The patent introduces a calibration unit as an intermediary component between the pixel matrix and the data processing system. This calibration unit acts as a mediator that receives raw voltage variations, processes them through calibration calculations using reference pixels, and outputs corrected voltage data. The intermediary calibration unit isolates the measurement system from distortion effects while maintaining system modularity.
2Manufacturing precision
If a calibration unit is added to adjust voltage variations, then image processing accuracy is improved, but the device complexity and number of components increase
Solution Approach 1:
The calibration unit is designed with multi-functionality to reduce overall system complexity. It performs multiple functions including: generating control signals from reference pixel data, calculating calibration factors, adjusting voltage variations from active pixels, and compensating for both process offset and parasitic capacitance effects. By consolidating these functions into a single calibration unit, the patent avoids adding multiple separate components while achieving high image processing accuracy.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting voltage parameters through the calibration unit. The calibration unit modifies voltage variations based on calculated calibration factors derived from reference pixel measurements. By changing voltage parameters in real-time based on calibration data, the system achieves high manufacturing precision without requiring complex hardware modifications to the pixel matrix or readout circuitry.
3Reliability
If voltage variations exceed the analog-to-digital converter's swing range, then signal dynamic range is maintained, but distortion occurs in the converted pixel data values
Solution Approach 1:
The calibration unit performs preliminary action by pre-adjusting voltage variations to ensure they fall within the analog-to-digital converter's swing range before conversion occurs. By calculating appropriate calibration factors from reference pixels and applying these factors to active pixel voltage variations, the system prevents signal clipping and distortion at the source, ensuring reliable data consistency throughout the conversion process.
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 system improves the consistency of voltage variations detected by pixel units, reducing distortions in image processing and maintaining accurate capacitance readings.
Implementation Method 1
since a distortion of the conversion voltage variation is caused by process offset or parasitic capacitance effect
Data Source
AI summary
A capacitive sensing system is provided, which includes: a pixel matrix for sensing a plurality of voltage variations generated by pressing of a fingerprint; and a calibration unit coupled to the pixel matrix and used for calibrating the plurality of voltage variation of the pixel matrix according to a control signal generated based on the plurality of voltage variations. The capacitive sensing system according to the present disclosure has advantages of improving the consistency of the voltage variations detected by the pixel units and reducing the occurrence of distortion.