Under-screen Fingerprint Sensing via Dynamic Illumination Pattern
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Solution Overview
Problem
Conventional capacitive fingerprint sensors on portable electronic devices occupy excessive space, making it difficult to increase the screen-to-body ratio, and under-screen optical fingerprint sensors face low light transmittance issues leading to low contrast fingerprint images and recognition failures.
Innovation Solution
An electronic device with a display panel that emits an illumination beam to enhance the contrast of fingerprint images by displaying a base fingerprint image to illuminate the finger, allowing the sensing module to capture a second image with improved contrast, thereby increasing recognition accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an under-screen optical fingerprint sensor is used, then the screen-to-body ratio is improved, but the light signal strength deteriorates resulting in low contrast fingerprint images
Solution Approach 1:
The system performs a preliminary fingerprint capture to obtain a base fingerprint image, then uses this image to generate a light pattern that illuminates the finger in a second capture. This preliminary action creates a customized illumination pattern that compensates for the low light transmittance of the display panel, thereby improving the contrast of the fingerprint image without requiring additional hardware that would reduce the screen-to-body ratio.
Solution Approach 2:
The system changes the illumination parameters by displaying the base fingerprint image as a light pattern on the display panel. This dynamic adjustment of illumination parameters (brightness distribution matching fingerprint patterns) compensates for the low light transmittance environment, enabling high-contrast fingerprint capture while maintaining the under-screen configuration that preserves screen-to-body ratio.
2Reliability
If conventional capacitive fingerprint sensor is used, then fingerprint recognition is achieved, but the area occupied on the front of the device increases
Solution Approach 1:
The patent merges the display panel and fingerprint sensing functions into a single integrated structure. The display panel serves dual purposes: as the user interface and as the illumination source for fingerprint capture. This merging eliminates the need for separate capacitive sensor areas on the front, thereby maintaining fingerprint recognition capability while maximizing the screen-to-body ratio.
3Adaptability or versatility
If display panel light transmittance is low, then under-screen fingerprint sensing is enabled, but the fingerprint image contrast deteriorates
Solution Approach 1:
The system uses feedback from the base fingerprint image to generate an optimized light pattern. The base image provides information about the finger's fingerprint structure, which is then used to create a customized illumination pattern that enhances contrast in the second capture. This feedback mechanism compensates for the low light transmittance environment, enabling high-precision fingerprint imaging through the display panel.
Solution Approach 2:
The system effectively creates a composite illumination approach by combining ambient light transmission through the display panel with the projected light pattern from the base fingerprint image. This composite lighting strategy overcomes the limitations of low light transmittance materials, enabling high-contrast fingerprint capture while maintaining the under-screen sensing configuration.
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 method effectively enhances the contrast between bright and dark lines in fingerprint images, improving the success rate and accuracy of fingerprint recognition.
Implementation Method 1
The display panel displays a bright area in a fingerprint sensing area to emit an illumination beam to the finger
Implementation Method 2
a sensing module sensor disposed under a display panel reads a fingerprint of a finger pressing on the display panel
Data Source
AI summary
An electronic device, having fingerprint sensing function, is provided. The electronic device includes a display panel and a sensing module. The display panel has a surface configured to be pressed by a finger of a user. The sensing module is disposed under the display panel. The display panel displays a bright area in a fingerprint sensing area to emit an illumination beam to the finger. The sensing module obtains a base fingerprint image correspondingly. The display panel then displays the base fingerprint image in the fingerprint sensing area, so as to use the base fingerprint image as a light pattern to illuminate the finger. The sensing module obtains a second fingerprint image correspondingly. A fingerprint sensing method is also provided.