Fingerprint Sensor Charge Removal Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fingerprint image generation methods face challenges in optimizing the removal of electric charge from detection circuits, leading to suboptimal signal-to-noise ratios and reduced image quality due to limited integrations and unnecessary charge removal.
Innovation Solution
A method that determines the optimal quantity of electric charge to be removed from each detection circuit based on amplifier characteristics, such as input offset voltage, by adjusting current source values and switch turn-on times, and integrates this charge to generate a fingerprint image beyond predetermined threshold values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electric charge is removed from detection circuits to reduce offset voltage, then image quality improves, but signal-to-noise ratio deteriorates due to excessive charge removal
Solution Approach 1:
The patent applies local quality by determining the quantity of electric charge to be removed individually for each detection circuit based on its specific amplifier characteristics (input offset voltage). This allows each detection circuit to receive a customized charge removal amount, optimizing both image quality and signal-to-noise ratio for each local region rather than applying a uniform charge removal across all circuits.
Solution Approach 2:
The patent changes the parameter of electric charge quantity dynamically based on amplifier characteristics. By calculating the required charge removal amount as Q = I × t (where I is current and t is turn-on time), and adjusting this quantity according to each detection circuit's input offset voltage, the system optimizes the balance between offset voltage reduction and signal-to-noise ratio preservation.
2Manufacturing precision
If the number of integrations is increased to improve image quality, then manufacturing precision improves, but the complexity of charge management increases
Solution Approach 1:
The patent applies preliminary action by determining and setting the optimal quantity of electric charge to be removed before the integration process begins. By calculating the required charge removal based on amplifier characteristics and integrating this into the detection circuit design, the system eliminates the need for complex dynamic charge management during multiple integrations, simplifying the overall system while maintaining high image quality.
3Device complexity
If uniform charge removal is applied to all detection circuits, then device complexity is reduced, but image quality deteriorates due to not accounting for individual amplifier characteristics
Solution Approach 1:
The patent implements local quality by transitioning from uniform charge removal to individualized charge removal for each detection circuit. The system determines the specific input offset voltage of each amplifier and calculates the corresponding optimal charge removal quantity, thereby optimizing image quality for each local detection circuit while managing complexity through systematic calculation methods.
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 enhances the quality of fingerprint images by increasing the number of integrations and improving signal-to-noise ratios, resulting in higher resolution and better image representation.
Implementation Method 1
determining a quantity of electric charge to be removed from each of a plurality of detection circuits based on an amplifier characteristic of each of the plurality of detection circuits; obtaining a second electrical quantity by removing the quantity of electric charge from a first electrical quantity that is input to each of the plurality of detection circuits
Implementation Method 2
The predetermined threshold value may correspond to an input offset voltage of an amplifier included in each of the plurality of detection circuits
Data Source
AI summary
A method of generating a finger image includes determining a quantity of electric charge to be removed from each of a plurality of detection circuits connected to a fingerprint sensor, based on an amplifier characteristic of each of the plurality of detection circuits; obtaining a second electrical quantity by removing the quantity of electric charge from a first electrical quantity that is input to each of the plurality of detection circuits; integrating the second electrical quantity to obtain an integrated value; and generating the fingerprint image based on comparison between the integrated value of the second electrical quantity and a predetermined threshold value.