Multi-Polarization Pixel Selection for Vein Imaging
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Solution Overview
Problem
Existing imaging devices for biometric authentication face challenges in accurately extracting vein patterns under high external light conditions, as intense external light can cause saturation and local high-brightness regions, leading to difficulties in signal extraction and requiring measures like artificial shading or limited external light use.
Innovation Solution
An imaging device equipped with a multi-polarization image sensor, where each pixel is structured with polarizing plates of different polarization directions, allowing for the selection of the lowest brightness pixel in each group to reduce regular reflection light and enhance image quality by using the properties of polarizing plates to filter out S-polarized light, thereby reducing the impact of external light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exposure is decreased to avoid saturation under intense external light, then saturation is avoided, but the difference between images taken with self-illuminating device on and off decreases, making vein pattern extraction difficult
Solution Approach 1:
The pixel group is segmented into multiple pixels with different polarization directions. By selecting only the pixel with the lowest brightness from each segmented group, the patent isolates the most reliable signal while filtering out saturated or overexposed pixels, thus maintaining measurement precision without requiring reduced exposure.
Solution Approach 2:
Different pixels within the same pixel group are assigned different polarization directions, creating local quality variations. This allows each pixel to respond differently to external light based on its polarization orientation, enabling the selection of the optimal pixel (lowest brightness) that provides the best signal quality for vein pattern extraction.
2Device complexity
If only external light is used for illumination, then self-illuminating device complexity is reduced, but local high-brightness regions occur due to incident angle, affecting signal extraction
Solution Approach 1:
The patent changes the polarization direction parameter of pixels within each pixel group. By having pixels with different polarization directions (e.g., 0°, 45°, 90°, 135°), the system can select the pixel that receives minimal external light based on its polarization orientation, thereby eliminating local high-brightness regions without modifying the illumination system.
3Measurement precision
If polarizing plates with different polarization directions are arranged for each pixel, then regular reflection light is reduced and image quality is enhanced, but device structure becomes more complex
Solution Approach 1:
The patent merges multiple pixels with different polarization directions into a single pixel group structure. This integration allows the system to process multiple polarization directions simultaneously while maintaining a compact design, reducing the per-pixel complexity burden while achieving the benefit of polarization-based glare reduction.
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 solution enables the acquisition of high-quality palm images without local high-brightness regions, even under intense external light, by effectively reducing regular reflection light and maintaining image continuity, thus improving the accuracy of vein pattern extraction.
Implementation Method 1
polarizing plates arranged to have a different polarization direction for each pixel in a pixel group
Implementation Method 2
a part of the infrared lights is reflected on a surface of the palm
Implementation Method 3
a part thereof passes through the skin and is absorbed by hemoglobin of veins inside the hand
Data Source
AI summary
An imaging device includes: an image sensor that images an object to be imaged through polarizing plates arranged to have a different polarization direction for each pixel in a pixel group that includes a plurality of pixels corresponding to each of points of the object to be imaged; a pixel selecting unit that selects a pixel having a lowest brightness for each of the pixel group corresponding to each of the points; and an image output unit that outputs a captured image of the object to be imaged that is generated from pixels selected by the pixel selecting unit.