Capacitive Fingerprint Detection Matrix With Integrated Storage Capacitors
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Solution Overview
Problem
Traditional fingerprint detection methods face limitations in speed, force, and accuracy due to strip-shaped designs and interference from external static electricity, and require multiple detecting units for large-area detection.
Innovation Solution
A capacitive fingerprint detection device with specially designed detecting units, including a fingerprint electrode and storage capacitor, uses a driving circuit to charge an equivalent capacitor and a reading circuit to determine capacitance, minimizing mutual interference and external static electricity, while also enabling touch control functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a strip-shaped detecting area is used, then the device complexity is reduced, but the measurement precision and detection accuracy deteriorate due to the need for sweeping scanning and image recombination
Solution Approach 1:
The detecting area is divided into multiple detecting units arranged in a matrix, where each unit independently detects a portion of the fingerprint. This segmentation eliminates the need for sweeping scanning and image recombination, thereby improving detection accuracy while maintaining device simplicity.
Solution Approach 2:
The detecting area transitions from a one-dimensional strip shape to a two-dimensional matrix arrangement of detecting units. This dimensional change enables simultaneous detection of the entire fingerprint area, eliminating the need for sweeping motion and improving both accuracy and speed.
2Measurement precision
If multiple detecting units are used to form a large-area detecting matrix, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
Multiple detecting units are merged into a single integrated detecting matrix, where all units work simultaneously to detect the entire fingerprint. This merging approach improves detection accuracy while avoiding the complexity of coordinating multiple separate detection systems.
Solution Approach 2:
Each detecting unit in the matrix is designed with identical structure and function, enabling them to perform the same detection task. This universality simplifies the overall system design and reduces complexity compared to using different types of detecting units.
3Reliability
If traditional capacitive detecting units are used, then the detection capability is achieved, but the reliability deteriorates due to mutual interference between neighboring units and external static electricity
Solution Approach 1:
The harmful effects of mutual interference and static electricity are extracted and isolated from the detection process. By designing shielding structures and isolation mechanisms around each detecting unit, the interference factors are separated from the fingerprint detection signal, thereby improving reliability.
Solution Approach 2:
Shielding structures and isolation layers are introduced as intermediary elements between the detecting units and external static electricity sources. These intermediaries block or reduce the harmful effects of interference, protecting the detection process and improving reliability.
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 accuracy and speed of fingerprint detection by simplifying hardware circuits and reducing interference, allowing for simultaneous fingerprint and touch control capabilities.
Implementation Method 1
a sense capacitor formed between the fingerprint electrode and a finger is parallel connected to the storage capacitor
Implementation Method 2
capacitive fingerprint detector can determine whether the detected fingerprint is the furrow or ridge
Data Source
AI summary
A fingerprint detection device and method and an associated touch control device with fingerprint detection are disclosed. The fingerprint detection device includes special detecting units for upgrading the accuracy of fingerprint detection. The fingerprint detection device comprises a plurality of detecting units, a driving circuit and a reading circuit. Each detecting unit includes a fingerprint electrode and a storage capacitor coupled to the fingerprint electrode. A sense capacitor can be formed between the fingerprint electrode and a finger, where the sense capacitor is parallel connected to the storage capacitor. The driving circuit is coupled to the detecting units and provides a charging signal to charge an equivalent capacitor of each detecting unit, where the capacitance of the equivalent capacitor is determined according to whether the sense capacitor is formed within the detecting unit. The reading circuit is coupled to the detecting units and reads the voltage of the storage capacitor after the equivalent capacitor is charged, so as to determine whether the detecting unit detects a portion of fingerprint and the detected portion is a furrow or ridge.