Under-screen optical fingerprint sensor spatial period adjustment
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Solution Overview
Problem
Under-screen optical fingerprint systems face interference from moiré fringes due to the similar structural forms of OLED screens and optical sensors, affecting fingerprint identification performance.
Innovation Solution
The fingerprint identification apparatus adjusts the spatial period of the optical sensing array to ensure it is less than half the spatial period of the light-emitting pixel array divided by the zoom ratio, avoiding moiré fringes by configuring the optical sensing array or the light-emitting pixel array to reduce the size or distance between units, or using a lens to alter the zoom ratio, thereby improving fingerprint identification accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the optical sensor and OLED screen have similar structural forms, then the imaging system can be simplified, but moiré fringes are generated affecting fingerprint identification performance
Solution Approach 1:
The patent changes the spatial period parameter of the optical sensing array to be less than half the spatial period of the light-emitting pixel array divided by the zoom ratio. This parameter adjustment eliminates moiré fringes while maintaining the simplified imaging system structure, thus resolving the contradiction between device complexity and measurement precision.
2Measurement precision
If the spatial period of the optical sensing array is reduced, then moiré fringes are eliminated, but the manufacturing precision requirements increase
Solution Approach 1:
The patent establishes a specific mathematical relationship for the spatial period parameter that can be implemented through standard manufacturing processes. By defining the spatial period as less than half the spatial period of the light-emitting pixel array divided by the zoom ratio, the solution achieves moiré elimination with feasible manufacturing precision requirements.
3Measurement precision
If the sampling frequency of the optical sensing array is increased, then moiré fringes are avoided, but the device complexity and cost increase
Solution Approach 1:
The patent optimizes the spatial period parameter to achieve the minimum required sampling frequency that satisfies the Nyquist criterion (less than half the spatial period of the light-emitting pixel array divided by the zoom ratio). This avoids moiré fringes while minimizing device complexity and cost by not oversampling beyond what is necessary.
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 adjustment effectively eliminates moiré fringes in the imaging system, enhancing the performance of fingerprint identification by ensuring the sampling frequency of the fingerprint image is twice that of the sampling pattern, thus improving recognition accuracy.
Implementation Method 1
an optical sensor mounted underneath the display, the optical sensor being parallel to a second primary direction along a second axis
Implementation Method 2
an organic light-emitting diode (OLED) screen
Implementation Method 3
using a lens to alter the zoom ratio
Implementation Method 4
the optical sensor will generate moiré fringes when imaging based on light transmitted through the display screen
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A fingerprint identification apparatus and an electronic device (200). The fingerprint identification apparatus includes: a fingerprint sensor (231); and the fingerprint sensor (231) including an optical sensing array, whererin a spatial period N of the optical sensing array satisfies N<M/2K; wherein M is a spatial period of a light-emitting pixel array, and K is a zoom ratio between an image displayed in a sensing area of the fingerprint sensor (231) and an image captured in the sensing area by the fingerprint sensor (231). By clarifying the relationship between the spatial period of the light-emitting pixel array in the display screen and the spatial period of the optical sensing array in the fingerprint sensor (231), it can avoid the sensor from generating moire fringes when imaging based on light received by transmitting through the display screen, thereby improving fingerprint identification performance.