Optical Fingerprint Sensor with Force Sensing
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Solution Overview
Problem
Conventional fingerprint recognition methods, such as password authentication, are prone to security vulnerabilities and user inconvenience, and existing fingerprint sensors face challenges in accurately distinguishing between live fingers and non-living materials, especially in varying environmental conditions.
Innovation Solution
The development of an optical fingerprint sensor module that incorporates an optical sensor array and collimator array to detect fingerprint patterns and biometric markers, utilizing probe light at multiple wavelengths to differentiate between live and non-live inputs, and featuring a design that minimizes water interference and enhances signal contrast through refractive index matching and light path compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fingerprint recognition methods are used, then user authentication can be achieved, but security vulnerabilities and false access risks increase due to inability to distinguish live fingers from non-living materials
Solution Approach 1:
The optical sensor array is divided into multiple independently controllable light sources emitting at different wavelengths (e.g., first wavelength for fingerprint imaging, second wavelength for liveness detection). This segmentation allows the system to perform multiple authentication functions using a single sensor structure, improving reliability without proportionally increasing device complexity.
Solution Approach 2:
The optical sensor array serves multiple functions: capturing fingerprint spatial patterns at one wavelength and detecting liveness indicators (such as blood flow or tissue properties) at another wavelength. This multi-functionality enables the system to distinguish live fingers from non-living materials while maintaining a unified sensor design.
2Measurement precision
If optical sensor array with multiple wavelengths is used, then liveness detection capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines multiple light sources with different wavelengths into a single integrated optical sensor module. The light sources are positioned in close proximity and share common optical paths and detection circuits, allowing manufacturing processes to treat them as a unified structure rather than separate components, thereby reducing manufacturing complexity.
Solution Approach 2:
The sensor system uses the reflected light from the finger itself to perform both fingerprint capture and liveness detection. The finger's biological properties (such as blood flow, tissue density, or moisture content) naturally modulate the reflected light at different wavelengths, eliminating the need for additional active components or complex illumination systems.
3Loss of information
If probe light is used to detect fingerprint patterns, then spatial pattern recognition is achieved, but water interference and signal contrast are reduced
Solution Approach 1:
The system changes the wavelength parameter of the probe light to optimize penetration through water layers and enhance contrast between fingerprint ridges and valleys. By selecting specific wavelengths that are less affected by water absorption or scattering, the sensor maintains high signal quality even in the presence of moisture on the finger surface.
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 provides enhanced security by accurately distinguishing between live and non-live fingerprints, improving user authentication and reducing false access risks, while maintaining a compact and cost-effective sensor design suitable for integration into mobile devices.
Implementation Method 1
an optical sensor array positioned to receive reflected probe light that carries information of the received contact input
Implementation Method 2
an optical collimator array of optical collimators located between the display panel and the optical sensor array to spatially select returned probe light to enter the optical sensor array
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A device is provided to include a display panel and an optical sensor module. The optical fingerprint sensor can detect an contact input and generate a signal indicative of an image of the fingerprint and to generate a signal indicative of a biometric marker different form the fingerprint. The generated sensor signal includes the signal indicative of the image of the fingerprint and the signal indicative of the biometric marker different from the fingerprint. The optical sensor module can capture different fingerprint patterns at different times to monitor time-domain evolution of the fingerprint ridge pattern deformation that indicates time-domain evolution of a press force from the contact input. The sensing circuitry can process the generated sensor signal to determine whether the contact input associated with the fingerprint belongs to a finger of a live person.