Under-Display Fingerprint Sensing via Liquid Crystal Light Path Control
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Solution Overview
Problem
Existing under-display fingerprint sensing technologies suffer from low sensitivity, low resolution, and slow recognition speed due to interference from the touch screen.
Innovation Solution
The method involves an electronic device with a liquid crystal display (LCD) and an optical sensing unit, where a sensing light is emitted and reflected by a biometric object. The arrangement of liquid crystal molecules in the LCD controls light paths to ensure only filtered light with predetermined wavelengths reaches the optical sensing unit, enhancing detection sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If under-display sensing is used to enable fingerprint recognition, then integration and aesthetics are improved, but sensitivity and resolution deteriorate due to light interference from the touch screen
Solution Approach 1:
The patent segments the optical path by introducing a light guide plate with specific refractive index regions. The light guide plate divides the light transmission path into different zones: a first light guide region for sensing light and a second light guide region for display light, preventing interference between the two optical paths while maintaining under-display integration
Solution Approach 2:
The light guide plate acts as an intermediary component between the touch screen and the fingerprint sensing module. It mediates the light interaction by guiding sensing light through the touch screen while blocking display light from reaching the sensing module, thus resolving the interference problem without sacrificing integration
2Device complexity
If conventional under-display sensing structure is used, then device integration is improved, but recognition speed deteriorates due to light interference
Solution Approach 1:
The light guide plate is segmented into different refractive index regions that selectively guide different types of light. This segmentation enables the system to maintain integration while improving recognition speed by ensuring only relevant sensing light reaches the detector without interference from display light
Solution Approach 2:
The patent changes the refractive index parameter of the light guide plate material in different regions. By adjusting the refractive index, the light guide plate optimizes light transmission for sensing while blocking display light, thereby improving recognition speed without compromising device integration
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 improves the sensitivity of fingerprint sensing by reducing interference from unwanted light wavelengths, resulting in higher resolution and faster recognition speeds.
Implementation Method 1
The arrangement of liquid crystal molecules in the LCD controls light paths to ensure only filtered light with predetermined wavelengths reaches the optical sensing unit
Implementation Method 2
The LCD includes a liquid crystal layer disposed between the first and second transparent substrates
Implementation Method 3
a backlight unit disposed at a side opposite to the liquid crystal layer for emitting a sensing light
Implementation Method 4
a sensing light is emitted and reflected by a biometric object
Data Source
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AI summary
A method for sensing a biometric object (100) using an electronic device includes the steps of: (a) emitting a sensing light (L1) from a backlight unit (24) upon the biometric object contacting a sensing region (212) on a display surface (211), and allowing the sensing light (L1) to pass through a color filter unit (214) and then reach and be reflected by the biometric object (100) to return as a reflected light (L2) ; and (b) controlling arrangement of liquid crystal molecules (231) located in a first region of a liquid crystal layer (23) to define a first light path, and allowing the reflected light (L2) having predetermined wavelengths to pass through the color filter unit (214) and the first light path to reach and be detected by an optical sensing unit (3).