Optical Layer Microlens Mask Stray Light Control
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Solution Overview
Problem
Liquid crystal displays with refractive components behind them can split reflected fingerprint light into multiple beam segments, reducing the quality of the optical image incident on the fingerprint sensor.
Innovation Solution
An optical system comprising a lens layer with microlenses arranged along orthogonal directions, an optically opaque first mask layer, and an optically opaque second mask layer, where the mask layers define through openings that correspond to the microlenses, ensuring that greater than 35% of incident image light is transmitted through the second opening, thereby reducing image quality degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a refractive component is placed behind the liquid crystal display, then the display structure is completed and light guiding is enabled, but the reflected fingerprint light is split into multiple beam segments reducing image quality
Solution Approach 1:
The patent divides the optical path into multiple segments by introducing a microlens array that splits the incident light into multiple beam segments, each directed toward corresponding sensor elements. This segmentation approach transforms the harmful single-beam refraction into a controlled multi-beam system that maintains image quality while achieving the desired optical functionality
Solution Approach 2:
The patent applies different optical properties to different regions of the optical system. The microlens array creates localized focal points for different beam segments, and the mask layer selectively blocks or transmits light in specific regions. This local quality adjustment ensures that each beam segment is properly directed while maintaining overall image quality
2Object-affected harmful factors
If the mask layer openings are made smaller to block stray light, then stray light blocking is improved, but less image light is transmitted reducing signal strength
Solution Approach 1:
The patent uses multiple mask layers with progressively smaller openings, where each layer provides partial blocking of stray light while allowing sufficient image light transmission. The cumulative effect of multiple partial blocking actions achieves superior stray light rejection without excessively reducing the image light signal
Solution Approach 2:
The patent introduces intermediate microlens structures between the incident light and the sensor that act as mediators. These microlenses focus the light in a way that allows smaller mask openings to effectively block stray light while the focused beam maintains sufficient intensity for detection
3Object-affected harmful factors
If multiple mask layers are added to improve stray light blocking, then stray light rejection is enhanced, but device complexity increases
Solution Approach 1:
The patent combines multiple functional layers (microlens array, multiple mask layers with different opening patterns) into a single integrated optical element. This merging approach achieves superior stray light rejection through the combined action of multiple layers while reducing overall device complexity compared to separate discrete components
Solution Approach 2:
The patent designs the optical element with multi-functionality, where the microlens array serves both as a focusing element and as a structural support for the mask layers. The mask layers simultaneously block stray light and define the optical path for the beam segments. This multi-functionality reduces the need for additional separate components
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 optical system effectively reduces image quality degradation by ensuring that a significant portion of incident image light is transmitted, improving the clarity of the fingerprint image at the sensor.
Implementation Method 1
a lens layer including a plurality of microlenses arranged along orthogonal first and second directions
Data Source
AI summary
An optical system includes a lens layer including a plurality of microlenses arranged along orthogonal first and second directions, and at least one optically opaque mask layer spaced apart from the lens layer and defining a plurality of through openings therein arranged along the first and second directions. There is a one-to-one correspondence between the microlenses and the openings, such that for each microlens, the microlens and corresponding openings are substantially centered on a straight line making a same oblique angle with the lens layer. An optical layer can include the lens layer and the optically opaque mask layer embedded in the optical layer.