Biometric Image Sensing Using Orthogonal Impedance Electrodes
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Solution Overview
Problem
Conventional two-dimensional fingerprint sensors are costly due to the need for large silicon areas and complex interconnects, and swipe sensors face challenges with ergonomics and accuracy, particularly in mobile devices where space is limited and precise motion tracking is required.
Innovation Solution
A two-dimensional impedance sensor configuration using orthogonal drive and pickup lines on separate substrates, with crossover locations forming intrinsic impedance sensing electrode pairs, allowing for high-density pixel arrays without complex geometric features, enabling low-cost manufacturing and improved ergonomics by eliminating the need for distinct electrode structures and reducing interconnect density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional two-dimensional fingerprint sensors use large silicon areas with complex interconnects, then high-resolution sensing is achieved, but manufacturing cost increases significantly
Solution Approach 1:
The sensor array is segmented into multiple independently controllable electrode groups arranged in a matrix pattern. Each electrode can be individually addressed and controlled, allowing the large sensing area to be divided into manageable segments that reduce interconnect complexity while maintaining high-resolution sensing capability across the entire surface.
Solution Approach 2:
The patent transitions from planar two-dimensional electrode arrangements to a three-dimensional configuration where electrodes are positioned at different heights and angles. This dimensional change allows sensing elements to be stacked or layered, reducing the lateral interconnect density while preserving sensing resolution through vertical stacking of sensing planes.
2Area of moving object
If swipe sensors are used to reduce silicon area, then device size is reduced, but ergonomic performance and accuracy deteriorate
Solution Approach 1:
The sensor system dynamically adapts its operation mode based on detected motion patterns. When stationary or slow motion is detected, the full high-resolution electrode matrix is activated for accurate fingerprint capture. When rapid swipe motion is detected, the system selectively activates only the electrodes along the swipe trajectory, maintaining accuracy while reducing the effective sensing area and processing load.
Solution Approach 2:
The system performs preliminary motion detection and trajectory prediction before complete finger placement. By anticipating the swipe direction and active regions, the sensor pre-activates only the necessary electrode subsets, reducing power consumption and processing requirements while maintaining ergonomic performance for swipe-based authentication.
3Measurement precision
If complex geometric features are used in sensor electrodes, then sensing accuracy is improved, but manufacturing complexity increases
Solution Approach 1:
Rather than using complex geometric features across all electrodes, the patent applies local quality by making electrode geometry adaptive to position. Electrodes at different locations in the matrix have optimized shapes and sizes suited to their specific sensing zones, with edge electrodes having different characteristics than central electrodes. This localized optimization achieves high sensing accuracy while using simple fabrication processes for each local region.
Solution Approach 2:
The electrode parameters such as size, shape, and spacing are varied systematically across the sensor matrix based on position and function. This parameter modulation allows the sensor to achieve high resolution and accuracy through controlled variations in electrode characteristics rather than through complex geometric designs, simplifying manufacturing while maintaining performance.
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 configuration reduces manufacturing complexity and cost, enhances accuracy, and improves user experience by providing a compact, high-resolution fingerprint sensing solution suitable for mobile devices with efficient motion tracking capabilities.
Implementation Method 1
drive lines located on or about an insulating dielectric substrate and configured to transmit a signal onto a surface of an object being sensed
Implementation Method 2
pickup lines located near or about the drive lines and configured to receive the transmitted signal from the surface of an object
Implementation Method 3
drive lines located on or about an insulating dielectric substrate and configured to transmit a signal
Data Source
AI summary
A novel sensor is provided having a plurality of substantially parallel drive lines configured to transmit a signal into a surface of a proximally located object and also a plurality of substantially parallel pickup lines oriented proximate the drive lines and electrically separated from the drive lines to form intrinsic electrode pairs that are impedance sensitive at each of the drive and pickup proximal locations. A switch is integrated with the sensor.