Wavelength Selective Optical Filter for Camouflage
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Solution Overview
Problem
Existing optical filters struggle to effectively manage the transmission of visible and near-infrared light, often resulting in unwanted optical interference and visibility of light emitters or receivers.
Innovation Solution
The development of an optical filter comprising a wavelength selective reflective layer and at least one wavelength selective absorbing layer, which has visible transmittance between 400 nm-700 nm of less than about 30% and near infrared transmittance at 830 nm-900 nm greater than about 30%, effectively reducing visible light transmission while allowing high clarity near-infrared transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If existing optical filters are used to block visible light, then visible light transmission is reduced, but near-infrared transmission is also blocked causing optical interference
Solution Approach 1:
The optical filter is divided into multiple functional layers: a first optical layer (visible wavelength selective layer) that selectively blocks visible light while transmitting near-infrared, and a second optical layer (near-infrared wavelength selective layer) that selectively transmits near-infrared while blocking visible light. This segmentation allows each layer to specialize in specific wavelength management, resolving the contradiction between visible light blocking and near-infrared transmission.
Solution Approach 2:
The filter combines different optical materials with complementary wavelength selectivity properties. The first optical layer uses materials selective for visible wavelengths, while the second optical layer uses materials selective for near-infrared wavelengths. This composite structure enables simultaneous visible light rejection and near-infrared transmission, overcoming the limitations of single-material filters.
2Difficulty of detecting and measuring
If optical filters are used to camouflage light emitters, then visibility is reduced, but optical interference increases
Solution Approach 1:
The camouflage filter is segmented into wavelength-specific functional layers that independently manage different spectral regions. The first layer handles visible light camouflage while the second layer ensures near-infrared transmission for operational functionality. This segmentation prevents the optical interference that would result from using a single broad-spectrum blocking layer.
Solution Approach 2:
Different regions of the filter have different optical properties tailored to specific functions. The first optical layer has visible wavelength selectivity applied locally, while the second optical layer has near-infrared wavelength selectivity applied locally. This local quality differentiation allows the filter to provide camouflage in the visible spectrum while maintaining operational transparency in the near-infrared spectrum, avoiding optical interference.
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 optical filter configuration successfully shields light receivers from visible wavelengths, prevents unwanted interference, and camouflages light emitters, while maintaining high near-infrared transmittance and clarity.
Implementation Method 1
specular reflection may occur on an uppermost surface layer of the material, for example, at an air/material interface
Implementation Method 2
wavelength selective reflective layer configured to transmit near-infrared wavelengths between 830 nm-900 nm
Implementation Method 3
diffusive reflection may occur under a top surface of the material
Implementation Method 4
at least one wavelength selective absorbing layer having visible absorption at 400 nm-700 nm greater than about 30%
Implementation Method 5
The wavelength selective scattering layer scatters visible wavelengths between 400 nm-700 nm and transmits near-infrared wavelengths between 830 nm-900 nm
Data Source
AI summary
An article includes an optical filter that comprises a wavelength selective reflective layer and at least one wavelength selective absorbing layer. The optical filter has visible transmittance between 400 nm-700 nm of less than about 30% and near infrared transmittance at 830 nm-900 nm greater than about 30%.