Dielectric Optical Filter Layers for Ambient Light Rejection
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Solution Overview
Problem
Ambient light interferes with near-infrared (NIR) light transmission in optical systems, reducing the accuracy of three-dimensional image generation and gesture recognition.
Innovation Solution
An optical filter comprising a set of dielectric thin film layers with alternating high and low refractive index materials, including hydrogenated silicon and other materials, is used to block ambient light and pass NIR light, minimizing interference and maintaining image accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical filter with multiple dielectric layers is used to block ambient light, then the accuracy of three-dimensional image generation is improved, but the device complexity increases
Solution Approach 1:
The optical filter is divided into multiple discrete dielectric layers, each with specific refractive index properties. The filter comprises alternating high-refractive-index layers (e.g., tantalum pentoxide, niobium pentoxide) and low-refractive-index layers (e.g., silicon dioxide, magnesium fluoride), where each layer contributes to the overall interference pattern for selective wavelength transmission
Solution Approach 2:
The optical filter utilizes composite dielectric material structures combining materials with different refractive indices. This composite approach creates constructive interference for NIR wavelengths (700-1700 nm) while producing destructive interference for ambient visible light, achieving spectral selectivity through the combined optical properties of multiple materials
2Reliability
If the optical filter blocks more ambient light, then the signal-to-noise ratio is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The optical filter design specifies precise thickness parameters for each dielectric layer to control the interference conditions. By carefully selecting and controlling the thickness of high and low refractive index layers, the filter achieves maximum blocking of ambient light while maintaining transmission of NIR wavelengths, with thicknesses optimized for the desired spectral response
Solution Approach 2:
The optical filter employs a periodic structure of alternating high and low refractive index layers repeated multiple times. This periodic arrangement creates multiple interference conditions that collectively enhance the blocking of unwanted wavelengths while maintaining transmission of the desired NIR range, with each layer pair contributing to the overall filtering effect
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 optical filter effectively filters out ambient light, enhancing the accuracy of three-dimensional image generation and gesture recognition by reducing the intensity of ambient light interference.
Implementation Method 1
An optical filter may include a set of optical filter layers, the set of optical filter layers including: a first subset of optical filter layers comprising a first material with a first refractive index... a second subset of optical filter layers comprising a second material with a second refractive index... the second refractive index being less than the first refractive index
Data Source
AI summary
An optical filter may include a set of optical filter layers disposed onto a substrate. The set of optical filter layers may include a first subset of optical filter layers comprising a first material with a first refractive index. The first material may comprise at least silicon and hydrogen. The set of optical filter layers may include a second subset of optical filter layers comprising a second material with a second refractive index. The second material is different from the first material and the second refractive index is less than the first refractive index. The set of optical filter layers may include a third subset of optical filter layers comprising a third material different from the first material and the second material.