Biometric Capture Using Semi-Transparent Mirror
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Solution Overview
Problem
Existing biometric facial image capture systems are either expensive, high-maintenance, or compromise on achieving frontal recordings, which are essential for effective biometric comparison algorithms, and often struggle with reflections from glasses that degrade image quality.
Innovation Solution
A device using a semi-transparent mirror and adjustable mirror arrangements with automatic coupling to maintain constant optical distance and illumination, ensuring frontal images of consistent size and quality without moving the camera, while minimizing reflections through adaptive lighting control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple cameras are used to achieve frontal recording, then the quality of biometric capture is improved, but the device complexity and cost increase
Solution Approach 1:
A semi-transparent mirror is introduced as an intermediary optical element between the person and the camera. This mirror allows the camera to capture frontal images by reflecting light from the person's face while remaining transparent enough to see the person directly. This single-mirror solution replaces the need for multiple cameras or complex mechanical positioning systems, thereby improving biometric capture quality while reducing device complexity
Solution Approach 2:
The semi-transparent mirror creates an optical copy or reflection of the person's face that the camera can capture. Instead of using multiple physical cameras to achieve different viewing angles, the system uses the mirror to create a virtual frontal view that the single camera can record, effectively copying the frontal appearance without requiring multiple physical sensing devices
2Measurement precision
If the recording system is displaced to achieve frontal positioning, then the biometric capture accuracy is improved, but the ease of operation and maintenance worsen
Solution Approach 1:
The optical path is segmented into multiple sections using the semi-transparent mirror and additional mirrors. Instead of moving the entire recording system to achieve frontal positioning, the light path is divided and redirected through stationary mirror elements, allowing the camera to remain fixed while still capturing frontal images. This segmentation of the optical path eliminates the need for system displacement and simplifies operation
Solution Approach 2:
Stationary mirrors serve as intermediaries that redirect light from the person to the fixed camera. These mirror elements mediate between the stationary camera and the moving person, enabling frontal capture without requiring the camera or entire system to be displaced. This eliminates mechanical complexity and operational difficulties associated with moving the recording system
3Measurement precision
If a semi-transparent mirror is used to enable frontal recording, then the biometric capture quality is improved, but reflections from glasses may degrade image quality
Solution Approach 1:
The system uses locally optimized mirror arrangements with specific orientations and positions. By carefully controlling the angle and position of the semi-transparent mirror and additional mirrors, the optical path is configured to minimize the incidence of reflections from glasses while maintaining frontal image quality. This local optimization of mirror properties at specific positions in the optical path addresses the reflection problem without sacrificing capture quality
4Adaptability or versatility
If the person's position varies, then adaptability is improved, but maintaining constant image size and quality becomes more difficult
Solution Approach 1:
The system uses multiple mirrors arranged in a folded optical path configuration. When the person moves, the mirror arrangements can be adjusted to redirect light along different paths while maintaining the effective optical distance. This dimensional flexibility in the optical path configuration allows adaptation to different person positions while keeping the image size and quality constant on the camera sensor
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
Enables cost-effective, high-quality, and reliable biometric feature detection with frontal images of consistent size, regardless of the person's position, and minimizes reflections for improved image quality.
Implementation Method 1
the beam path of light incident on the semi-transparent mirror is parallel to the beam path of the part of this light reflected back by the semi-transparent mirror
Implementation Method 2
the first mirror arrangement being arranged in such a way that this transmitted part of the light directed onto the first mirror arrangement is reflected onto the camera
Data Source
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AI summary
The invention relates to a device (100) for recording biometric features of a person's face (110), the device (100) comprising a camera (102) for recording the biometric features and a semi-transparent mirror (108), the semi-transparent mirror (108) being arranged between the person and the camera (102), the semi-transparent mirror (108) being aligned such that, on the side (112) of the semi-transparent mirror (108) facing the person, the path (114) of the light incident on the semi-transparent mirror (108) is parallel to the path (116) of the portion of said light reflected back by the semi-transparent mirror (108).