Optical Fingerprint Light-Path Layout to Suppress Moiré
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Solution Overview
Problem
Optical in-display fingerprint identification systems face challenges with poor fingerprint image quality due to the 'Moiré effect' caused by capturing unwanted screen elements, leading to increased difficulty in identification and reduced accuracy.
Innovation Solution
The system incorporates a light path adjusting element, such as a wedge prism, between the photo sensor and the light emitting layer, along with a condenser lens element and a collimator unit, to alter the light path and reduce the angle of incidence, thereby preventing unwanted image capture and enhancing image quality. Additionally, a light interference filter layer and a light absorption filter layer are used to filter light at large incident angles, and a touch layer is integrated for live fingerprint confirmation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the screen is used as a light source to emit light onto the fingerprint and the light is reflected to a photo sensor disposed under the screen, then the fingerprint can be sensed and identified, but unwanted images of screen elements are captured causing Moiré effect and poor fingerprint image quality
Solution Approach 1:
The patent extracts and removes the harmful Moiré effect by introducing a light path adjusting element that redirects light to prevent the capture of screen element images. The light path adjusting element selectively blocks unwanted light paths from screen elements while maintaining the useful light path from the fingerprint, effectively separating the harmful optical paths from the useful ones.
Solution Approach 2:
The light path adjusting element acts as an intermediary component between the light emitting layer and the photo sensor. It mediates the light transmission by adjusting the light path to redirect light from the fingerprint while blocking light from screen elements, thus resolving the conflict between capturing fingerprint images and avoiding Moiré effects.
2Measurement precision
If a light path adjusting element is introduced to prevent Moiré effect and improve fingerprint image quality, then identification accuracy increases, but device complexity increases
Solution Approach 1:
The light path adjusting element is designed to perform multiple functions: it adjusts the light path to prevent Moiré effects, maintains light transmission from the fingerprint, and integrates with the existing display structure. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving improved identification accuracy.
3Measurement precision
If the light emitting element is disposed away from the light path adjusting element and photo sensor in a sideway direction, then unwanted image capture is prevented and image quality is enhanced, but device structure becomes more complex
Solution Approach 1:
The patent transitions from a vertical stacking arrangement to a lateral (sideway) arrangement of components. By disposing the light emitting element away from the light path adjusting element and photo sensor in a sideway direction, the system uses horizontal space instead of vertical stacking, which prevents unwanted image capture while managing device complexity through spatial reorganization rather than adding more layers.
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 configuration significantly improves fingerprint image quality, reduces identification time, and increases accuracy by minimizing unwanted light interference and enhancing the alignment of light with the photo sensor, resulting in higher compatibility with thin electronic devices.
Implementation Method 1
The light emitting element is disposed away from the light path adjusting element and the photo sensor in a sideway direction that is different from a stack direction of the optical fingerprint identification system
Implementation Method 2
The screen can be a light source to emit light onto user's fingerprint, and then the light can be reflected to a photo sensor disposed under the screen
Implementation Method 3
The optical fingerprint identification system further includes a light path adjusting element between the photo sensor and the cover
Implementation Method 4
a light path adjusting element, such as a wedge prism, between the photo sensor and the light emitting layer, along with a condenser lens element and a collimator unit, to alter the light path and reduce the angle of incidence
Implementation Method 5
a light interference filter layer and a light absorption filter layer are used to filter light at large incident angles
Implementation Method 6
a light interference filter layer and a light absorption filter layer are used to filter light at large incident angles
Data Source
AI summary
An optical fingerprint identification system includes a base, a photo sensor, a light emitting layer and a cover. The photo sensor is disposed on the base. The light emitting layer is disposed above the photo sensor, and the light emitting layer includes a light emitting element. The cover is disposed above the light emitting layer. The optical fingerprint identification system further includes a light path adjusting element between the photo sensor and the cover. The light emitting element is disposed away from the light path adjusting element and the photo sensor in a sideway direction that is different from a stack direction of the optical fingerprint identification system.