Multilayer Dielectric Infrared Reflector for Angle-Stable LIDAR
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Solution Overview
Problem
Existing LIDAR reflectors for autonomous driving suffer from reduced reflectance at large incident angles, leading to signal sensitivity deterioration and limited viewing angles, especially in near-infrared wavelengths, due to materials like aluminum and silver, which are not suitable for near-infrared reflection and are prone to oxidation.
Innovation Solution
A multilayer dielectric film composed of alternating low-refractive and high-refractive layers, primarily SiO2 and TiO2, is applied to an optical glass substrate, ensuring high reflectance independent of incident angle by optimizing layer thickness and configuration to maintain reflectance above 99% across a wide wavelength band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum or silver is used as reflector material to achieve high reflectance, then reflectance is improved, but the material is prone to oxidation and not suitable for near-infrared wavelengths
Solution Approach 1:
The patent uses a composite dielectric film structure consisting of multiple layers with different refractive indices (e.g., SiO2, TiO2, HfO2) deposited in alternating sequences. This composite structure achieves high reflectance for near-infrared wavelengths without the oxidation problems of metallic materials, while maintaining stability in air environments.
2Reliability
If aluminum is deposited to increase reflectance, then reflectance is improved, but reflectance varies significantly according to incident angle
Solution Approach 1:
The patent optimizes the thickness and refractive index parameters of each dielectric layer to achieve angle-independent reflectance. By carefully selecting layer thicknesses (e.g., quarter-wave or half-wave thicknesses) and refractive indices, the reflector maintains high reflectance across a wide range of incident angles (0° to 80°), eliminating the angle-dependent performance degradation of metallic reflectors.
3Reliability
If metal deposition layer is used to increase reflectance, then reflectance is improved, but light is absorbed by free electrons
Solution Approach 1:
The patent replaces metallic reflection mechanisms (which involve free electron absorption) with dielectric reflection mechanisms based on refractive index differences. The alternating low-and high-refractive-index dielectric layers create constructive interference for reflected light, achieving high reflectance without the energy absorption losses inherent in metal-free electron interactions.
4Object-affected harmful factors
If multiple oxide deposition layers are added to protect aluminum, then oxidation is prevented, but reflectance changes significantly with incident angle
Solution Approach 1:
The patent extracts and removes the problematic metallic aluminum layer entirely, replacing it with a dielectric film structure that inherently provides both protection and optimal optical performance. The dielectric layers themselves serve as the protective barrier against oxidation while simultaneously providing angle-independent reflectance, eliminating the need for separate protective coatings.
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 maintains high reflectance and minimizes light loss across a wide range of incident angles, enhancing LIDAR signal sensitivity and viewing angle, crucial for autonomous driving applications.
Implementation Method 1
a multilayer dielectric film deposited on the substrate, in which the multilayer dielectric film includes a first plurality of low-refractive layers each having a relatively lower refractive index than a high-refractive layer
Implementation Method 2
a first plurality of low-refractive layers each having a relatively lower refractive index than a high-refractive layer
Data Source
AI summary
The present disclosure provides an infrared reflector for a LIDAR, the infrared reflector including a substrate, and a multilayer dielectric film deposited on the substrate, in which the multilayer dielectric film includes a first plurality of low-refractive layers each having a relatively lower refractive index than a high-refractive layer, and a second plurality of low-refractive layers each having a relatively lower refractive index than the low-refractive layer, and the first plurality of low-refractive layers and the second plurality of low-refractive layers are alternately and repeatedly stacked. According to the present disclosure, the infrared reflector may be independent of an incident angle, i.e., have high reflectance while having the reflectance that does not vary depending on the incident angle.