Optical Fingerprint Sensor Filter Stack for Display Thickness
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Solution Overview
Problem
In display devices with integrated fingerprint recognition, the long distance between optical sensors and the finger contact surface leads to scattered light, resulting in blurred fingerprint patterns and reduced recognition precision due to interfering reflected light.
Innovation Solution
Incorporating filter structures with light-transmitting and light-shielding areas between the sensor and the finger contact surface to collimate and filter out interfering light, featuring a stack of filter layers with specific aspect ratios and displacement of light-transmitting areas to improve light incidence on sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If filter structures are added between the sensor and finger contact surface to collimate light, then fingerprint recognition precision is improved, but device thickness increases
Solution Approach 1:
The filter structures are integrated within the existing display device layers, nesting the light-collimating function within the display stack rather than adding external components. The filter layers are positioned between the array substrate and protecting cover, utilizing the existing device thickness budget.
Solution Approach 2:
The filter structures use vertical stacking of multiple filter layers with progressively smaller light-transmitting areas to achieve light collimation in the vertical dimension, rather than requiring lateral space. This transforms the light-collimating function from a planar to a volumetric solution.
2Manufacturing precision
If multiple filter layers with stacked light-transmitting areas are used to collimate light, then light incidence perpendicularity is improved, but manufacturing complexity increases
Solution Approach 1:
The filter structure is divided into multiple discrete filter layers, each with its own light-transmitting area. This segmentation allows progressive refinement of light direction through each layer, with the second filter layer's light-transmitting area being smaller than the first, creating a funneling effect that improves perpendicularity.
Solution Approach 2:
The light-transmitting areas of successive filter layers are designed with changing parameters - specifically, the area size decreases from the first to the second layer, and the positional relationship changes. This parameter progression systematically controls light propagation to achieve perpendicular incidence.
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
Enhances the precision of optical fingerprint recognition by ensuring nearly perpendicular incidence of reflected light on sensors, thereby improving recognition accuracy and reducing the thickness impact of filter structures.
Implementation Method 1
Incorporating filter structures with light-transmitting and light-shielding areas between the sensor and the finger contact surface to collimate and filter out interfering light
Implementation Method 2
a plurality of filter structures arranged between the protecting cover and the plurality of sensing elements, wherein each of the plurality of filter structures comprises a plurality of filter layers arranged in a stack
Data Source
AI summary
Disclosed are a touch device and a display device, where the touch device includes: an array substrate, a plurality of sensing elements arranged on the array substrate to recognize a fingerprint, and a plurality of filter structures arranged on a side of the plurality of sensing elements; the side is away from the array substrate: each of the plurality of filter structures comprises a plurality of filter layers arranged in a stack, each of the plurality of filter layers comprises light-transmitting areas and light-shielding areas on a periphery of the light-transmitting areas, orthographic projections of any two of the light-transmitting areas of the plurality of filter layers onto the array substrate have an overlapping area; the overlapping area is smaller than an area of an orthographic projection of any one of the light-transmitting areas of the plurality of filter layers onto the array substrate.