Diffraction Optical Element for Uniform Biometric Illumination
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Solution Overview
Problem
Existing biometric authentication systems face challenges in achieving uniform intensity distribution of illumination over larger regions than the illumination device, leading to reduced authentication accuracy due to varying biometric capturing targets and inefficient light usage.
Innovation Solution
A biometric authentication apparatus utilizing a diffraction optical element to diffract light from LEDs into a uniform intensity distribution across a larger illuminating region, preventing light intensity decrease and maintaining authentication accuracy without increasing the size of the illuminating optical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the illuminating optical system is formed by a plurality of light emitting diodes arranged two-dimensionally to a size greater than or equal to a biometric region, then the illumination light can be irradiated on a relatively large biometric region, but the size of the illuminating optical system becomes large and it is difficult to apply to compact biometric authentication apparatus
Solution Approach 1:
The illuminating optical system is divided into multiple light emitting diodes arranged in a matrix pattern, where each LED illuminates a specific sub-region. This segmentation allows the system to cover a large illuminating region while maintaining a compact overall structure, as the LEDs can be arranged in a space-efficient matrix configuration rather than requiring a large planar array.
Solution Approach 2:
The light emitting diodes are arranged in a nested matrix structure where multiple LEDs are positioned in a compact configuration. The matrix arrangement allows for efficient space utilization, with LEDs positioned at different levels or in a space-filling pattern that maximizes the illuminating region while minimizing the footprint of the illuminating optical system.
2Device complexity
If conventional illuminating systems are used, then the structure is simple, but the light intensity distribution on the illuminating region is non-uniform and intensity decreases in regions farther from the light source
Solution Approach 1:
Each light emitting diode in the matrix arrangement is positioned to illuminate a specific local region of the biometric target. The collective arrangement of multiple LEDs with locally optimized positions creates a globally uniform illumination pattern across the entire illuminating region, compensating for the inverse square law effects and maintaining consistent intensity distribution.
Solution Approach 2:
Multiple light emitting diodes are combined in a matrix configuration to collectively illuminate the entire illuminating region. By merging the illumination contributions from numerous LEDs positioned at different locations, the system achieves uniform light intensity distribution across the region, with each LED contributing to multiple areas and overlapping illumination patterns ensuring even coverage.
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 ensures a stable and high-accuracy biometric authentication by maintaining uniform light intensity across larger regions, accommodating varying biometric targets and preventing authentication accuracy deterioration.
Implementation Method 1
A biometric authentication apparatus utilizing a diffraction optical element to diffract light from LEDs into a uniform intensity distribution across a larger illuminating region
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3~4B
AI summary
An illumination device includes a light source provided on a surface of a substrate and configured to emit light, and a diffraction optical element having a plurality of diffraction gratings with different pitch and rotating direction, and configured to diffract the light into illumination light that illuminates an illumination region of an illuminating target. The illuminating region is larger than an area occupied by the diffraction optical element and the light source provided on the surface of the substrate.