Biometric Optical Antispoofing via Angular Filter
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing biometric fingerprint sensors face challenges in distinguishing between live and spoof fingers, particularly due to the need for additional filters for liveness detection, which complicates integration and increases costs.
Innovation Solution
A biometric imaging arrangement with an optical filter assembly that incorporates an infrared cut-off wavelength and an angle-dependent visible cut-off wavelength, allowing for simultaneous infrared protection and spoof detection using a single filter, thereby eliminating the need for additional dedicated filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional dedicated filters are used for liveness detection, then anti-spoofing capability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent combines the infrared cut-off function and the visible range liveness detection function into a single optical filter. This single filter has an infrared cut-off wavelength to block infrared light and a first cut-off wavelength in the visible range that depends on the angle of incidence, eliminating the need for separate dedicated filters for each function.
Solution Approach 2:
The optical filter is designed to perform multiple functions simultaneously: it provides infrared protection for the image sensor while also enabling liveness detection through its angle-dependent visible range cut-off wavelength. This multi-functional filter simplifies the overall optical system architecture.
2Reliability
If multiple separate filters are used for infrared protection and liveness detection, then functional performance is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent merges the functionality of multiple separate filters (infrared cut-off filter and liveness detection filter) into a single integrated optical filter. This reduces the number of manufacturing steps, alignment operations, and assembly operations required, thereby improving ease of manufacture.
3Device complexity
If a single filter is used for both infrared protection and liveness detection, then device complexity is reduced, but measurement precision may deteriorate
Solution Approach 1:
The optical filter exhibits different optical properties at different angles of incidence. The first cut-off wavelength in the visible range is angle-dependent, creating different filtering characteristics for different spatial regions of the image sensor. This local variation in filter properties enables liveness detection while maintaining infrared protection.
Solution Approach 2:
The filter's cut-off wavelength is not fixed but dynamically varies with the angle of incidence of incoming light. This dynamic property allows the single filter to provide different filtering functions for different light paths, achieving both infrared protection and angle-resolved liveness detection simultaneously.
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 integration of optical components, providing effective anti-spoofing capabilities while maintaining cost-efficiency by utilizing a single filter for both infrared protection and liveness detection, improving the accuracy of distinguishing between live and spoof biometric objects.
Implementation Method 1
an optical filter assembly comprising at least an optical interference filter
Implementation Method 2
the optical filter assembly having an infrared cut-off wavelength to at least partly block infrared light from reaching the photodetector pixel array, the optical filter assembly further having at least a first cut-off wavelength in the visible range of wavelengths, wherein the first cut-off wavelength depends on the angle of incidence of the received light on the optical filter assembly
Data Source
AI summary
A biometric imaging arrangement configured to acquire an image of an object comprising: an image sensor comprising a photodetector pixel array configured to detect light transmitted from the object for capturing an image, an optical filter assembly comprising at least an optical interference filter, the optical filter assembly being arranged to cover the photodetector pixel array, and the optical filter assembly having an infrared cut-off wavelength to at least partly block infrared light from reaching the photodetector pixel array, the optical filter assembly further having at least a first cut-off wavelength in the visible range of wavelengths, wherein the first cut-off wavelength depends on the angle of incidence of the received light on the optical filter assembly.