Optical Fingerprint Sensor Segmented Filtering for Living Signal Detection
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Solution Overview
Problem
Conventional optical fingerprint sensors fail to differentiate between real and fake fingerprints, leading to reduced recognition rates and security risks.
Innovation Solution
An optical fingerprint sensor design featuring a substrate with photoelectric conversion units, a light-shielding layer, and an optical material layer with distinct filtering and non-filtering portions, which utilize IR and visible light to differentiate between living signals and fingerprint signals through specific distribution patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional optical fingerprint sensors only use visible light filtering, then the device complexity is low, but the living identification capability is insufficient leading to security risks
Solution Approach 1:
The optical material layer is segmented into multiple portions: a first optical material layer with first wavelength filtering (e.g., IR cut filter for visible light), a second optical material layer with second wavelength filtering (e.g., visible light blocking for IR transmission), and a third optical material layer with third wavelength filtering. This segmentation enables simultaneous detection of both visible light fingerprint patterns and IR living signals through separate photoelectric conversion units, resolving the contradiction by dividing the optical filtering function into specialized sections.
Solution Approach 2:
Different photoelectric conversion units are assigned different optical filtering characteristics tailored to their specific detection function. Some units have IR cut filtering optimized for visible light fingerprint capture, while others have visible light blocking optimized for IR living signal detection. This local quality differentiation allows each unit to excel at its specific task, achieving both fingerprint recognition and living identification without compromising overall device complexity.
2Measurement precision
If the sensor uses multiple optical material layers with different wavelength filtering, then the living signal detection accuracy is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The optical material layer is divided into multiple discrete filtering layers, each with a specific wavelength filtering function. This segmentation allows for modular manufacturing where each layer can be independently produced and characterized, then assembled in a controlled sequence. The through-holes in the light-shielding layer align with specific photoelectric conversion units to ensure proper optical path alignment, reducing the overall manufacturing precision burden compared to a single complex layer.
Solution Approach 2:
The light-shielding layer with through-holes acts as an intermediary structure that facilitates precise alignment between the optical material layers and the photoelectric conversion units. The through-holes provide physical guides and alignment references that simplify the assembly process, ensuring that each optical layer is correctly positioned relative to the underlying photoelectric conversion units without requiring extremely tight tolerances across all layers simultaneously.
3Measurement precision
If the optical material layer is disposed between the substrate and light-shielding layer, then the optical path optimization is improved, but the device structure complexity increases
Solution Approach 1:
The sensor structure is segmented into distinct functional layers: substrate, photoelectric conversion units, light-shielding layer with through-holes, and multiple optical material layers with different filtering characteristics. This segmentation allows each layer to be optimized for its specific function while maintaining a relatively simple overall architecture. The optical material layers are positioned to receive light through the through-holes directly onto the corresponding photoelectric conversion units, optimizing the optical path without requiring complex intermediate structures.
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
Enhances the living identification function and recognition correctness rate by optimally comparing IR and visible light signals, improving the security and accuracy of fingerprint identification.
Implementation Method 1
the substrate includes a plurality of photoelectric conversion units
Implementation Method 2
the optical material layer includes a non-filtering portion and a filtering portion
Data Source
AI summary
An optical fingerprint sensor is provided. The optical fingerprint sensor includes a substrate, a light-shielding layer and an optical material layer. The light-shielding layer is disposed on the substrate. The optical material layer is in contact with the light-shielding layer. The optical material layer includes a non-filtering portion and a filtering portion.