Light Guide Plate Optical Layers for Image Quality
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Solution Overview
Problem
Current biometric identification systems face challenges in capturing high-quality images due to disorganized light beams, leading to poor identification results, as existing technologies struggle to effectively address crosstalk issues.
Innovation Solution
The image capturing apparatus employs a light guide plate with two light transmissive layers of lower refractive indices on either side, along with a third light transmissive layer of higher refractive index, to facilitate total internal reflection, reducing stray light and enhancing image quality by ensuring light beams are transmitted and reflected efficiently to the image capturing device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light beams are transmitted directly to the image capturing device, then the structure is simple, but the captured image quality is poor due to disorganized light beams and crosstalk
Solution Approach 1:
A light guide plate is introduced as an intermediary component between the light source and the image capturing device. The light guide plate receives disorganized light beams and guides them through its internal structure to reach the image capturing device in an organized manner, thereby improving image quality without requiring direct alignment between light source and sensor
Solution Approach 2:
The light guide plate is divided into different functional regions including a light transfer region and a light penetration region. This segmentation allows different parts of the light guide plate to perform different functions: guiding light beams in the transfer region and allowing direct light transmission in the penetration region, thereby improving overall light organization and image quality
2Reliability
If light beams are allowed to spread freely, then the light source coverage is maximized, but stray light beams cause crosstalk and reduce identification accuracy
Solution Approach 1:
The light guide plate converts potentially harmful stray light beams into beneficial organized light transmission. By utilizing total internal reflection within the light guide plate, disorganized light beams that would normally cause crosstalk are redirected and channeled properly to the image capturing device, transforming a harmful effect into a useful one
Solution Approach 2:
The refractive indices of different layers in the light guide plate structure are carefully selected and optimized. The light guide plate has a higher refractive index than the adjacent light transmissive layers, creating the conditions for total internal reflection. This parameter optimization ensures that light beams are reflected efficiently within the light guide plate while minimizing stray light leakage, thereby reducing crosstalk and improving identification accuracy
3Object-affected harmful factors
If multiple light transmissive layers are added to control light paths, then stray light is reduced, but the device complexity increases
Solution Approach 1:
Different light transmissive layers are positioned at specific locations with different functional requirements. The first light transmissive layer is disposed on the first surface while the second light transmissive layer is disposed on the second surface, with each layer having specific overlap relationships with light transfer and penetration regions. This localized positioning allows each layer to perform its specific function efficiently without requiring a complex multi-layer structure throughout the entire device
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 significantly reduces stray light beams and improves identification capabilities by ensuring most light beams are transmitted and reflected effectively, resulting in better image quality and identification accuracy.
Implementation Method 1
By providing two light transmissive layers (such as the first light transmissive layer and the second light transmissive layer) having lower refractive indices on both sides of the light guide plate, most of the light beams can be transmitted through total internal reflection in the light guide plate.
Data Source
AI summary
An image capturing apparatus includes a light guide plate, a first light transmissive layer, a second light transmissive layer, a third light transmissive layer, a light source and an image capturing device. The light guide plate has a first surface and a second surface opposite to the first surface. The first light transmissive layer is disposed on the first surface. The second light transmissive layer is disposed on the second surface, wherein the second light transmissive layer is overlapped with a light transfer region of the light guide plate and not overlapped with a light penetration region of the light guide plate. The third light transmissive layer is disposed on the second surface and overlapped with the light transfer region and the light penetration region. Refractive indices of the third light transmissive layer and the light guide plate are higher than those of the first and second light transmissive layers.