Direct Optical Fingerprint Scanner Ambient Light Compensation
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Solution Overview
Problem
Current optical systems for recording fingerprints and handprints, especially for forensic and border control applications, face challenges in achieving high quality and miniaturization while dealing with ambient light interference and complex mechanical components, and existing solutions either fail to meet FBI standards or are cumbersome and expensive.
Innovation Solution
A direct optical scanner method using a controllable illumination array and image processing algorithms to generate an adapted illumination pattern, which minimizes ambient light interference and ensures high-quality imaging without the need for passive shading, allowing for the detection of finger falsification and simultaneous capture of multiple fingers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a prism is used for frustrated total internal reflection to achieve high image quality, then imaging quality meets FBI standards, but device size and mass increase significantly
Solution Approach 1:
The patent extracts and removes the prism component from the optical system, replacing it with a flat sensor surface that directly contacts the finger. This eliminates the need for frustrated total internal reflection while maintaining fingerprint capture capability, thereby significantly reducing device mass and size.
Solution Approach 2:
The patent replaces the mechanical prism-based optical system with a direct contact sensor system using a flat placement surface. This substitution eliminates complex mechanical components while achieving the same fingerprint detection function through direct optical contact between the sensor and skin ridges.
2Measurement precision
If a prism is used for frustrated total internal reflection, then high image quality is achieved, but device complexity and assembly difficulty increase
Solution Approach 1:
The patent extracts and removes the prism component from the optical system, replacing it with a flat sensor surface that directly contacts the finger. This eliminates the need for frustrated total internal reflection while maintaining fingerprint capture capability, thereby significantly reducing device mass and size.
Solution Approach 2:
The patent replaces the mechanical prism-based optical system with a direct contact sensor system using a flat placement surface. This substitution eliminates complex mechanical components while achieving the same fingerprint detection function through direct optical contact between the sensor and skin ridges.
3Ease of operation
If ambient light is present during recording, then device operation is simplified, but image quality and contrast deteriorate
Solution Approach 1:
The patent changes the illumination parameters by using structured light patterns projected onto the finger surface. This allows the system to operate in ambient light conditions while maintaining image quality, as the structured illumination creates sufficient contrast between ridges and valleys despite the presence of ambient light.
Solution Approach 2:
The patent implements dynamic illumination control where the light source intensity and pattern can be adjusted based on ambient light conditions. This allows the system to adapt to varying environmental lighting while maintaining consistent fingerprint image quality.
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
The solution enables high-resolution, high-quality direct optical recording of fingerprints and handprints that meet FBI standards, excluding ambient light interference and simplifying the detection of falsification, while reducing the device's size and complexity.
Implementation Method 1
a light source is provided and is formed such that light components of the light source from the direction of the sensor layer can be coupled through the placement surface into the skin area to be recorded
Implementation Method 2
reading out and storing image data of a calibration image from the sensor array, which calibration image is generated under homogeneous illumination from an areal source and ambient light that may be present, calculating an adapted illumination pattern through application of image processing algorithms to the stored calibration image
Data Source
AI summary
A device and method for direct optical recording of live skin areas, particularly of fingerprints or handprints, is disclosed. A novel possibility for direct optical recording of human skin prints with forensic quality where interference through ambient light is excluded is achieved in that, from a skin area to be recorded, image data of a calibration image generated under homogeneous illumination from an areal source and ambient light that may be present are read out from the sensor array, an adapted illumination pattern is calculated by means of the stored calibration image such that, through application of the adapted illumination pattern, a two-dimensionally structured illumination pattern is generated to minimize the influence of the ambient light and to homogenize the illumination at least of the deposited skin print, wherein an illumination array is controlled in individual light-emitting elements or in groups of light-emitting elements with the calculated illumination pattern.