Under-Display Biometric Sensor Using Segmented Microlens Array
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Solution Overview
Problem
Existing optical fingerprint sensors with microlenses are complex to manufacture and sensitive to spatial variations in transmissivity, making them challenging to integrate under display panels while maintaining high resolution and durability.
Innovation Solution
A biometric imaging device with a transparent substrate, an opaque layer having separate openings, and microlenses arranged in the same plane as the opaque layer, redirecting light onto a subarray of pixels in the image sensor, allowing for sparse microlens arrangement and reduced sensitivity to spatial variations in the display panel's transmissivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If microlenses are made small and arranged closely to increase image resolution, then measurement precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The sensor is divided into multiple independent subarrays, each corresponding to a microlens. This segmentation allows each microlens-subarray pair to be optimized independently, simplifying the overall manufacturing process while maintaining high resolution through the array of segmented units.
Solution Approach 2:
The patent implements local quality by assigning specific subarrays to specific microlenses, creating localized functional units. This allows for optimized light collection and image formation in each local region, improving measurement precision without requiring all microlenses to be uniformly small and complex.
2Measurement precision
If microlenses are made small to achieve high resolution, then measurement precision is improved, but the sensor becomes more sensitive to spatial variations in transmissivity
Solution Approach 1:
By segmenting the sensor into multiple subarrays, each with its own microlens, the system can independently optimize light collection for each segment. This reduces the impact of spatial variations in transmissivity on the overall image quality, as each subarray processes light from a localized region.
3Measurement precision
If an opaque layer with separate openings is introduced to prevent light mixing between microlenses, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The opaque layer is segmented into separate openings that correspond to each microlens position. This segmentation physically separates the light paths from adjacent microlenses, preventing light mixing and improving measurement precision while maintaining a relatively simple overall structure.
Solution Approach 2:
The patent extracts the light-blocking function into a separate opaque layer with defined openings. This extraction allows for precise control of light paths without complicating the microlens or substrate structures, improving light separation accuracy while keeping the device structure manageable.
4Ease of manufacture
If microlenses are arranged in the same plane as the opaque layer, then ease of manufacture is improved, but light collection efficiency may be reduced
Solution Approach 1:
The microlenses are merged with the opaque layer by placing them in the same plane, with each microlens positioned within or adjacent to its corresponding opening. This merging simplifies manufacturing and alignment while the careful design of opening sizes and microlens positions ensures adequate light collection efficiency is maintained.
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 simplifies the manufacturing process, enhances light collection, and minimizes stray light, enabling high-resolution fingerprint imaging under a display panel without degrading display performance, and is compatible with large-scale processing technologies.
Implementation Method 1
a plurality of microlenses, each microlens being located in a respective opening of the opaque layer in the same plane as the opaque layer; wherein each microlens is configured to redirect light through the transparent substrate and onto a subarray of pixels in the photodetector pixel array
Implementation Method 2
The operating principle of the described biometric imaging device is that light emitted by pixels in the display panel will be reflected by a finger placed on the sensing surface
Implementation Method 3
an image sensor comprising a photodetector pixel array
Data Source
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AI summary
There is provided a biometric imaging device (100) configured to be arranged under an at least partially transparent display panel (102) and configured to capture an image of an object in contact with an outer surface (106) of the display panel. The biometric imaging device comprises: an image sensor (108) comprising a photodetector pixel array (109); a transparent substrate (112) arranged to cover the image sensor; an opaque layer (114) covering an upper surface of the transparent substrate, wherein the opaque layer further comprises a plurality of separate openings (116); and a plurality of microlenses (118), each microlens being arranged in alignment with a respective opening of the opaque layer; wherein each microlens is configured to redirect light through the transparent substrate and onto a subarray (120) of pixels in the photodetector pixel array.