Optical Skin Print Recording Device with Light Guide Layer
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Solution Overview
Problem
Current systems for optical direct recording of skin impressions, particularly for FBI-standard quality, face challenges in maintaining high local resolution and contrast due to inadequate illumination and thickness issues, which are exacerbated by the need for additional optical elements and increased device complexity.
Innovation Solution
A device with a layered structure featuring a light guide layer underneath a semi-transparent sensor layer, utilizing LEDs for light coupling with light decoupling structures based on inclination angles and refractive index differences, achieving total internal reflection with a small divergence angle range to ensure high local resolution and allow for user guidance displays without compromising image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional optical elements are introduced to improve illumination quality, then image quality improves, but device complexity and thickness increase
Solution Approach 1:
The patent combines the light source and light guide into a single integrated unit positioned directly beneath the sensor array, eliminating the need for separate optical elements. The light guide layer is integrated with the sensor layer structure, creating a unified illumination system that improves image quality without increasing device complexity.
Solution Approach 2:
The light guide layer serves multiple functions: it provides illumination for the sensor array, acts as a structural support layer, and enables total internal reflection for light coupling. This multi-functionality reduces the need for additional dedicated components, thereby reducing overall device complexity while maintaining high image quality.
2Strength
If the top layer thickness is increased to improve protection and stability, then mechanical strength improves, but resolution and contrast decrease
Solution Approach 1:
The patent introduces an adhesive layer with a specific refractive index (1.4-1.6) between the cover layer and sensor layer. This intermediary layer serves as an optical bridge that enables effective light coupling while allowing the use of thicker cover layers for mechanical protection without significantly degrading resolution and contrast.
Solution Approach 2:
The patent optimizes the refractive index parameter of the adhesive layer to fall within a specific range (1.4-1.6). By carefully controlling this physical parameter, the system achieves effective light coupling that maintains resolution and contrast even when the cover layer thickness is increased for mechanical strength.
3Measurement precision
If homogeneous illumination is achieved across all light-emitting structures, then image quality improves, but device complexity increases
Solution Approach 1:
The light guide layer is divided into multiple light-emitting structures (e.g., LED arrays or light guide fingers) that are independently controllable. This segmentation allows each segment to be optimized for local illumination uniformity while the overall system maintains simplicity through modular design.
Solution Approach 2:
The patent uses the vertical dimension (depth into the light guide layer) to achieve homogeneous illumination. By designing the light guide layer thickness and light coupling geometry to create uniform light distribution in the vertical dimension, the system achieves homogeneous illumination across the contact surface without adding horizontal complexity.
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 high-quality optical direct recording of skin impressions that meet FBI standards while providing user guidance, maintaining high local resolution and contrast without increasing device thickness or complexity.
Implementation Method 1
provide directed light output from the light guide layer at a defined angle, which, after passing through all layers up to the top layer at the contact surface, leads to total internal reflection (TIR) at the interface with air
Implementation Method 2
based on an inclination angle of the light output structures and on the basis of differences in the refractive indices between the neighboring layers of the light guide layer up to the cover layer
Data Source
Figure 1
Figure 2
Figure 3a~3c
AI summary
The invention relates to a device for the direct optical recording of skin impressions. The object of finding a new method for the direct optical recording of skin impressions of human autopodia, which allows for personal identification according to FBI standards with a display layer directly below the contact surface (11), is solved according to the invention by arranging a light guide layer (141) below the sensor layer, which has at least one LED (142) on one narrow side and is provided with light extraction structures (144) that, by means of an inclination angle ε and differences in refractive indices to neighboring layers, allow directed light extraction from the light guide layer (141) at a defined angle, which leads to total internal reflection (TIR) at the contact surface (11) at the interface between the cover layer (12) and air, and with a small divergence angle range of ≤ +/- 15°.wherein first and second adhesion layers (15, 16) are present between the cover layer (12) and the sensor layer (13) and between the sensor layer (13) and the optical fiber layer (141), the refractive indices of which are at least 1% and at most 30% smaller than the refractive indices of the optical fiber layer (141) and the sensor layer (13).