Apodized Broadband Partial Reflectors for Spectral Ringing
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Solution Overview
Problem
Broadband polymeric multilayer optical films face challenges in achieving a smooth spectrum for in-band transmitted and reflected light due to in-band spectral ringing, which leads to undesired color issues in applications like visual displays.
Innovation Solution
The implementation of apodized broadband reflectors with differing optical packets, featuring a graded layer thickness profile that monotonically and exponentially deviates from a baseline profile, reduces in-band spectral ringing by minimizing spectral features associated with layer profile discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a broadband multilayer optical film is designed with a graded layer thickness profile to provide intermediate reflectivity and transmission, then the film can achieve broadband optical performance, but in-band spectral ringing occurs causing color issues in visual displays
Solution Approach 1:
The optical film is divided into multiple discrete layers with varying thicknesses, where each layer contributes to the overall spectral response. By segmenting the film into many thin layers rather than using a continuous gradient, the design achieves broadband performance while controlling spectral ringing through discrete thickness transitions.
Solution Approach 2:
Different regions of the film (different layers) have locally optimized thickness values to achieve the desired spectral response. The layer thicknesses are specifically tailored to provide intermediate reflectivity and transmission across the broadband spectrum while minimizing color issues at specific wavelengths.
2Stability of the object's composition
If the layer thickness profile is monotonically increased from first side to second side, then the film provides graded optical properties for broadband operation, but spectral ringing occurs due to discontinuities in the layer profile
Solution Approach 1:
The layer thickness profile transitions from a static monotonic gradient to a dynamic design where the thickness variations follow a sinusoidal or apodized pattern. This dynamic approach allows the profile to maintain graded optical properties while eliminating the sharp discontinuities that cause spectral ringing.
Solution Approach 2:
The layer thickness profile is modified to follow a curved, sinusoidal, or apodized pattern rather than a straight linear or monotonic gradient. This curvature in the thickness profile smooths out discontinuities and reduces spectral ringing while maintaining the broadband graded optical properties.
3Manufacturing precision
If a single packet of microlayers with carefully tailored layer thickness profile is used, then manufacturing control is maximized, but in-band spectral ringing cannot be reduced
Solution Approach 1:
The optical film uses a composite structure combining multiple materials with different refractive indices in a multilayer configuration. This composite approach allows simultaneous optimization of manufacturing control through extrusion processes and spectral performance through material selection, while the specific thickness profiling eliminates spectral ringing.
Solution Approach 2:
The design changes the thickness parameter of each layer according to a specific mathematical profile (sinusoidal, apodized, or other smooth variation). This parameter change strategy maintains manufacturing feasibility while eliminating spectral ringing that occurs with uniform or linear thickness profiles.
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 approach substantially eliminates in-band spectral ringing, resulting in a smooth spectrum for both transmitted and reflected light, thereby reducing undesired color and enhancing the optical performance of broadband partial reflectors.
Implementation Method 1
the reflection and transmission characteristics of the optical film are determined in large part by constructive and destructive interference of light reflected from the layer interfaces
Implementation Method 2
the relative refractive index differences for adjacent microlayers
Data Source
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AI summary
A broadband partial reflector includes a first multilayer polymeric optical film having a total number of optical repeating units from a first side to a second side of the first multilayer polymeric optical film and a second multilayer polymeric optical film having a total number of optical repeating units from a first side to a second side of the second multilayer polymeric optical film and an intermediate layer on the second side of the multilayer polymeric optical film separates the first multilayer polymeric optical film from the second multilayer polymeric optical film. The first multilayer polymeric optical film has a first baseline optical repeating unit thickness profile and a first apodized optical repeating unit thickness profile monotonically deviating from the first baseline optical repeating unit thickness profile and defining the second side of the first multilayer polymeric optical film. The second multilayer polymeric optical film has a second baseline optical repeating unit thickness profile and a second apodized optical repeating unit thickness profile monotonically deviating from the second baseline optical repeating unit thickness profile and defining the first side of the second multilayer polymeric optical film.