Under-screen Optical Fingerprint Detection with Micro Lens Array
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current lens-type under-screen optical fingerprint products face challenges in miniaturization, requiring thicker depths for higher imaging quality, which results in low light utilization and susceptibility to aliasing, leading to poor contrast and resolution in fingerprint images.
Innovation Solution
A fingerprint detection apparatus with a micro lens array and light shielding layers is used, where the micro lens array converges oblique light signals to optical sensing pixels, and the light shielding layers with small holes restrict structure parameters to avoid aliasing, ensuring sufficient light and improved contrast, signal-to-noise ratio, and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If collimating holes with greater depth are used to achieve higher imaging quality, then the imaging quality is improved, but the light utilization is reduced
Solution Approach 1:
The patent changes the optical parameters by introducing a micro lens array with specific focal lengths and aperture ratios. The micro lenses are designed with a focal length f and aperture diameter D such that the ratio D/f is optimized to achieve both high imaging quality and high light utilization. This parameter optimization allows the system to capture light more efficiently while maintaining sharp fingerprint images.
Solution Approach 2:
The micro lens array acts as an intermediary optical element between the light source and the sensing pixels. These micro lenses focus oblique light signals from the finger onto the optical sensing pixels, improving light utilization while maintaining imaging quality. The micro lenses serve as a mediator that optimizes the light path without requiring deep collimating holes.
2Loss of energy
If micro lens focusing is used to improve light utilization, then light utilization is improved, but aliasing occurs for light signals at different positions resulting in low contrast
Solution Approach 1:
The patent applies local quality by designing each micro lens with specific local optical properties tailored to its position in the array. Each micro lens has optimized focal length and aperture characteristics that are locally adapted to focus light from specific regions of the finger onto corresponding sensing pixels. This local optimization prevents aliasing while maintaining high contrast for light signals at different positions.
Solution Approach 2:
The system dynamically adjusts the optical focus by utilizing the focal length of the micro lenses to converge oblique light signals from different depths and positions onto the sensing pixels. This dynamic focusing capability allows the system to maintain high contrast across varying light signal positions without introducing aliasing artifacts.
3Volume of moving object
If the fingerprint detection apparatus is miniaturized to reduce thickness and volume, then the device size is reduced, but the imaging quality and light utilization deteriorate
Solution Approach 1:
The patent implements nesting by integrating the micro lens array directly onto the sensing pixel array, creating a compact nested structure where optical elements are packed closely together. This nested configuration achieves miniaturization while maintaining high imaging quality through the optimized optical design of each micro lens and its correspondence to sensing pixels.
Solution Approach 2:
The system changes critical optical parameters including micro lens focal length, aperture diameter, and spacing between lenses to optimize the balance between device miniaturization and imaging quality. By carefully selecting these parameters, the patent achieves high-resolution fingerprint imaging in a compact, thin-profile device suitable for modern smartphones.
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 solution enhances fingerprint image brightness, resolution, and identification accuracy by optimizing light transmission and reducing spherical aberration, allowing for thinner and more integrated fingerprint detection systems.
Implementation Method 1
the micro lens array converges the received oblique light signals to the optical sensing pixel array
Implementation Method 2
an array of small holes of a bottom light shielding layer of the Z light shielding layers... a light signal returned from a finger above the display screen is transmitted to the optical sensing pixel array through arrays of small holes provided in the Z light shielding layers
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A fingerprint detection apparatus and an electronic device are provided. The fingerprint detection apparatus is applied below a display screen to implement under-screen optical fingerprint detection, and the fingerprint detection apparatus includes: a micro lens array disposed below the display screen; Z light shielding layers disposed below the micro lens array, each of the Z light shielding layers being provided with an array of small holes, where Z is a positive integer; and an optical sensing pixel array disposed below an array of small holes of a bottom light shielding layer of the Z light shielding layers; where an array of small holes of each of the Z light shielding layers satisfies 0≤Xi/Zd≤3. By restricting structure parameters of small holes in an array of small holes, aliasing of transmission of light signals returned via different positions of a finger could be avoided. That is, on the basis of a guarantee of contrast of a fingerprint image, brightness of the fingerprint image is improved, a signal-to-noise ratio and a resolution of the fingerprint image are increased, and a fingerprint identification effect and identification accuracy are improved.