Fingerprint Sensor Light Path Adjustment for Contrast
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Solution Overview
Problem
Current under-screen fingerprint identification technologies face challenges in achieving high contrast between fingerprint peaks and troughs due to the direct reception of light beams, resulting in a greater burden on post-end image processing.
Innovation Solution
The use of a light path adjustment element, such as an optical diffraction plate or prism array, to adjust the light path of inclined image beams, combined with an optical filter layer and image sensor, enhances contrast by directing the inclined image beams to the image sensor, which senses image information with improved contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct reception of light beam is used, then device complexity is reduced, but contrast between fingerprint peaks and troughs deteriorates
Solution Approach 1:
The patent introduces a light path adjustment element as an intermediary component between the fingerprint and the image sensor. This element modifies the light paths from different height regions (peaks and troughs) to achieve greater separation at the sensor plane, thereby improving contrast without significantly complicating the overall device structure.
Solution Approach 2:
The patent transforms the problem from a two-dimensional imaging challenge to a three-dimensional light path manipulation task. By adjusting light paths in the vertical dimension (using inclined reception angles), the system achieves better separation of fingerprint features that are closely spaced in the horizontal plane, thus improving contrast.
2Measurement precision
If inclined image beam is received, then contrast between fingerprint peaks and troughs is improved, but device complexity increases
Solution Approach 1:
The light path adjustment element serves as a mediator that enables inclined beam reception while maintaining a relatively simple device architecture. This intermediary component handles the complexity of light path manipulation, allowing the rest of the system to remain straightforward.
Solution Approach 2:
The patent replaces complex mechanical adjustments with an optical element (light path adjustment element) that inherently performs the light path modification function. This substitution eliminates the need for mechanically adjustable components while achieving the desired inclined beam reception.
3Device complexity
If normal image beam is used, then device complexity is minimized, but image processing burden increases
Solution Approach 1:
The light path adjustment element performs preliminary action by pre-processing the light paths before they reach the image sensor. It enhances the contrast of fingerprint features in the optical domain, which reduces the amount of post-processing required in the digital domain, thereby decreasing the overall image processing burden.
Solution Approach 2:
The patent substitutes digital image processing operations with optical preprocessing performed by the light path adjustment element. This substitution shifts work from the computational domain to the optical domain, reducing the burden on post-end image processing systems.
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 results in a fingerprint identification effect with good contrast and reduced image processing burden, as the inclined image beams maintain higher intensity and provide clearer image information compared to normal direction illumination.
Implementation Method 1
The light path adjustment element is an optical diffraction plate. The optical diffraction plate is configured to enable the inclined image beam to be incident to the optical diffraction plate in a reverse tracking manner of first-order light of the optical diffraction plate.
Implementation Method 2
The inclined image beam is incident from the side surface of each prism, and is reflected by the inclined surface to sequentially penetrate the bottom surface and the transparent substrate to emit out of the light path adjustment element.
Implementation Method 3
The inclined image beam is incident from the side surface of each prism, and is reflected by the inclined surface to sequentially penetrate the bottom surface and the transparent substrate to emit out of the light path adjustment element.
Data Source
AI summary
A fingerprint identification apparatus, including a light path adjustment element, an optical filter layer, and an image sensor, is provided. The light path adjustment element is disposed on a transmission path of an image beam from a fingerprint of a user. The optical filter layer is disposed on a transmission path of the image beam from the light path adjustment element. The optical filter layer has openings. An inclined image beam in the image beam is obliquely incident to the light path adjustment element. The light path adjustment element adjusts a light path of the inclined image beam to be transmitted to the openings along a normal direction. The image sensor is disposed on a transmission path of the image beam from the optical filter layer. The image sensor has pixels. Positions of the pixels respectively correspond to positions of the openings.