Electrochromic Rearview Mirror Coating for NIR Iris Recognition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrochromic rearview mirrors have limited near-infrared (NIR) transmittance, which hampers eye-scan identification functions by reducing the intensity of infrared light needed for iris recognition, and metal-based transflective coatings inhibit light transmission and return signals.
Innovation Solution
A transflective dielectric coating with an alternating high-index and low-index multi-layer stack is applied to enhance NIR transmittance while maintaining visible reflectance and color neutrality, replacing metal-based coatings to improve light transmission and image capture efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If metal-based transflective coatings are used, then visible reflectance is maintained, but NIR transmittance is limited and light transmission is inhibited
Solution Approach 1:
The patent uses a composite dielectric coating structure with alternating high-index and low-index material layers. This composite structure enables the coating to simultaneously reflect visible light and transmit NIR light by exploiting the different optical properties of each material layer at different wavelengths, resolving the contradiction between maintaining visible reflectance and improving NIR transmittance.
Solution Approach 2:
The dielectric coating is designed with spatially varying properties through the alternating layer structure. Each layer is optimized for specific wavelength ranges, with the high-index and low-index materials distributed in a pattern that creates wavelength-selective optical behavior. This local quality variation allows different parts of the spectrum to be treated differently, achieving high visible reflectance while maintaining NIR transmittance.
2Measurement precision
If conventional electrochromic mirrors are used, then eye-scan identification function is provided, but light intensity for iris recognition is reduced
Solution Approach 1:
The patent changes the optical parameters of the transflective coating by using dielectric materials with specific refractive indices arranged in alternating layers. This parameter optimization allows the coating to transmit more NIR light while maintaining visible reflectance, thereby increasing the infrared light intensity reaching the iris and improving recognition accuracy without sacrificing the eye-scan identification function.
3Illumination intensity
If dielectric coating with alternating high-index and low-index layers is applied, then NIR transmittance is enhanced, but device complexity increases
Solution Approach 1:
The dielectric coating is segmented into multiple alternating layers of high-index and low-index materials. This segmentation allows each layer to contribute differently to the overall optical performance, with the layered structure enabling NIR transmission while maintaining visible reflectance. The segmentation into functional layers makes the complex optical requirements achievable through modular design.
Solution Approach 2:
The patent employs composite dielectric materials with alternating high and low refractive indices. This composite approach allows the coating to achieve superior optical performance that cannot be obtained with single-material coatings. The composite structure manages the complexity by combining materials whose individual properties complement each other to achieve the desired wavelength-selective behavior.
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 achieves NIR transmittance greater than 30%, often exceeding visible transmittance, enabling effective eye-scan identification with improved light intensity and signal capture, while maintaining neutral color appearance and reflectance levels.
Implementation Method 1
an electrochromic element operable to change from a first state to a second state and vice versa in response to an applied potential difference
Implementation Method 2
The transflective dielectric coating may comprise a multi-layer stack comprising alternating high-index (H) and low-index (L) materials
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The disclosure provides for an electrochromic element comprising a first substrate and a second substrate. The first substrate comprises a first surface and a second surface. The second substrate comprises a third surface and a fourth surface. The first substrate and the second substrate form a cavity have an electrochromic medium disposed therein. A dielectric coating is disposed on the fourth surface and is configured to provide for improved transmittance of the electrochromic element in the near infrared (NIR) range, wherein the near infrared transmittance exceeds the visible transmittance.