Under-screen Fingerprint Reader Specular Reflection Contrast
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Solution Overview
Problem
Conventional fingerprint readers face challenges in obtaining high contrast for skin ridges versus valleys, particularly due to the limitations of Frustrated Total Internal Reflection (FTIR) contrast detection mechanisms, which affect the accuracy and reliability of fingerprint recognition.
Innovation Solution
The implementation of an optical fingerprint reader that utilizes specular reflection as its primary contrast mechanism, leveraging the display's active pixels for illumination and an array of photosensors to detect light reflected via specular reflection, allowing for high-contrast imaging of fingerprint ridges without the need for extensive post-processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Frustrated Total Internal Reflection (FTIR) contrast detection mechanism is used, then fingerprint reader can be implemented, but contrast between skin ridges and valleys is insufficient
Solution Approach 1:
The patent changes the fundamental optical parameter from FTIR to specular reflection. By altering the detection mechanism's physical principle, the system achieves superior contrast between skin ridges and valleys, directly resolving the technical contradiction between measurement precision and reliability.
Solution Approach 2:
The patent replaces the FTIR-based optical system with a specular reflection-based optical system. This substitution of the detection mechanism enables high-contrast imaging of fingerprint ridges, improving both measurement precision and recognition reliability without requiring additional mechanical complexity.
2Measurement precision
If extensive post-processing is used to enhance contrast, then fingerprint image quality improves, but computational costs increase
Solution Approach 1:
The patent applies preliminary action by capturing high-contrast fingerprint images directly during the acquisition process through specular reflection. This eliminates the need for subsequent computational enhancement, reducing energy consumption while maintaining image quality.
Solution Approach 2:
The patent substitutes computational post-processing with an optical solution. By using specular reflection to directly capture high-contrast images, the system replaces energy-intensive computational algorithms with an efficient optical detection mechanism.
3Reliability
If conventional optical fingerprint reader design is used, then fingerprint recognition can be achieved, but device thickness increases
Solution Approach 1:
The patent applies multi-functionality by using the display's active pixels for both illumination and fingerprint detection. This integration eliminates the need for separate illumination components, reducing device thickness while maintaining recognition capability.
Solution Approach 2:
The patent merges the illumination function with the display pixels and integrates the optical detection path through the transparent cover. This consolidation of components achieves fingerprint recognition without increasing device thickness.
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 approach enables the production of high-contrast fingerprint images directly, minimizing computational costs and enhancing the reliability of fingerprint recognition, while also allowing for integration with mobile devices without increasing their thickness, thus providing improved security and user experience.
Implementation Method 1
The active pixels serve as an illuminator of the optical reader apparatus
Implementation Method 2
The array of photosensors is configured to detect light reflected via specular reflection by the transparent cover
Data Source
AI summary
An optical reader apparatus is configured to detect epidermal ridges of a body part using specular reflection contrast detection. The optical reader apparatus comprises a display comprising a transparent cover and a substrate comprising an array of active pixels. The active pixels serve as an illuminator of the optical reader apparatus. The apparatus also comprises a pinhole array and an optical sensor optically coupled to the display via the pinhole array. The optical sensor comprises an array of photosensors arranged on a substrate. The array of photosensors is configured to detect light reflected via specular reflection by the transparent cover. A processor, coupled to the display and the optical sensor, is configured to control reading of signals from the photosensors and to control illumination of selected active pixels in accordance with a predefined scanning pattern that covers a sensing region of the transparent cover during a body part reading operation.