Thick Multilayer Bandpass Filter for Zero Angle Wavelength Shift
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Solution Overview
Problem
Optical filters experience performance degradation due to angle of incidence (AOI) deviations, leading to shifts in band edges and inaccurate measurements, especially at high angles, which can result in noise, cross-talk, and measurement errors.
Innovation Solution
An optical filter assembly with a thickness greater than a threshold value and a multilayer structure of alternating high and low refractive index materials, designed to minimize center wavelength shifts to less than a specified threshold, even at high angles of incidence, thereby maintaining precise spectral selectivity and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical filter is used, then the filter can be manufactured with standard thickness, but the center wavelength shifts significantly at high angles of incidence
Solution Approach 1:
The patent changes the thickness parameter of the optical filter from standard thickness to greater than a first threshold value (e.g., greater than 10,000 nm or greater than 1 micrometer). This parameter change fundamentally alters the filter's angular response characteristics, reducing center wavelength shift at high angles of incidence while maintaining spectral selectivity.
2Measurement precision
If the optical filter thickness is increased to reduce angle shift, then center wavelength stability improves, but manufacturing complexity increases
Solution Approach 1:
The patent divides the thick filter into multiple alternating layers of different materials (e.g., high refractive index and low refractive index materials). This segmentation into a multilayer structure allows the filter to achieve the desired thickness and spectral selectivity while managing manufacturing complexity through standardized thin-film deposition processes.
Solution Approach 2:
The patent employs composite material structures with alternating layers of materials having different refractive indices (e.g., silicon nitride and silicon dioxide). This composite approach enables precise control over optical properties and wavelength selectivity, achieving high spectral performance with manageable manufacturing complexity.
3Reliability
If standard optical filter design is used, then manufacturing is simpler, but noise and cross-talk increase due to angle shift
Solution Approach 1:
The patent changes the thickness parameter to greater than a first threshold value, which fundamentally alters the filter's angular response. This parameter change reduces center wavelength shift at high angles of incidence, thereby reducing noise and cross-talk in measurements while maintaining manufacturing feasibility.
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 assembly ensures accurate measurements by minimizing angle shifts, improving signal-to-noise ratio, and reducing cross-talk, enabling energy-efficient and high-performance optical systems.
Implementation Method 1
An optical filter is used to select a spectral band or a spectral component of incoming light
Implementation Method 2
A bandpass filter is a distinct type of filter, which selects light at wavelengths proximate to a center wavelength of the filter within a bandwidth of the filter
Implementation Method 3
an optical filter assembly includes an optical filter disposed on a first side of a substrate, wherein the optical filter has a thickness greater than a first threshold value
Implementation Method 4
a filter stack of alternating layers of a first material with a first refractive index and a second material with a second refractive index
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
In some implementations, an optical filter assembly includes an optical filter disposed on a first side of a substrate, wherein the optical filter has a thickness greater than a first threshold value, and wherein the optical filter is configured to experience a center wavelength shift of less than a second threshold value for a particular operating center wavelength and for a range of angles of incidence from 0 degrees to at least a third threshold value.