Optical Film Stack Layout for Low-Leakage Polarizing Beam Splitters
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Solution Overview
Problem
Conventional polarizing beam splitters face challenges in achieving high reflectivity and low transmission leakage over a broad wavelength range with a limited number of interference layers, leading to inefficiencies and potential image contamination.
Innovation Solution
The development of optical films with alternating polymeric interference layers, configured to reflect and transmit light of different polarization states, utilizing a two-packet structure with thicker and thinner layers aligned to optimize reflectivity and transmission, and incorporating a dichroic polarizer to reduce multiple reflections and scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a limited number of interference layers is used, then device complexity is reduced, but reflectivity and transmission leakage performance deteriorate
Solution Approach 1:
The optical film is divided into multiple packets of interference layers, where each packet consists of alternating thick and thin layers. This segmentation allows the system to achieve high reflectivity and low transmission leakage without requiring a single large number of layers, thereby reducing overall device complexity while maintaining performance.
Solution Approach 2:
Different regions of the optical film have different layer thicknesses (thick and thin layers alternating within each packet). This local variation in quality allows optimized optical interference patterns that achieve high reflectivity for one polarization state and low transmission leakage for the orthogonal state with fewer total layers.
2Reliability
If more interference layers are added to improve reflectivity and reduce transmission leakage, then optical performance improves, but device complexity increases
Solution Approach 1:
Instead of using a single long sequence of interference layers, the design segments the film into multiple packets with alternating thick and thin layers. This segmentation achieves the required optical performance (high reflectivity and low transmission leakage) more efficiently, reducing the total number of layers needed and thus device complexity.
Solution Approach 2:
The optical film uses composite polymeric layers with different refractive indices arranged in alternating thick and thin patterns. This composite structure creates multiple interference patterns that work together to achieve high reflectivity and low transmission leakage with a reduced total number of layers compared to a single-material design.
3Ease of manufacture
If conventional polarizing beam splitter design is used, then manufacturing simplicity is maintained, but image quality deteriorates due to contamination and increased point spread function
Solution Approach 1:
The patent segments the optical film into multiple packets of alternating thick and thin interference layers. This segmented structure reduces multiple reflections and scattering that cause image contamination and increase point spread function, while still using polymeric materials that can be manufactured with standard techniques, thus maintaining ease of manufacture while improving image quality.
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 films provide high reflectivity (>95%) for one polarization state and low transmission leakage (<0.05%) over a broad wavelength range, improving image quality and reducing point spread function in imaging systems.
Implementation Method 1
Each interference layer reflects or transmits light primarily by optical interference for at least one wavelength in a predetermined wavelength range
Implementation Method 2
the plurality of interference layers has an average optical transmittance greater than about 85% for a first polarization state, an average optical reflectance greater than about 95% for an orthogonal second polarization state
Data Source
AI summary
Optical films and polarizing beam splitters including the optical films are described. In some cases, the optical film includes a first optical stack disposed on, and spaced apart by one or more spacer layers from, a second optical stack, each optical stack comprising a plurality of polymeric interference layers reflecting and transmitting light primarily by optical interference in a same predetermined wavelength range. Each optical stack has interference layers closer to the one or more spacer layers that reflect longer wavelengths and interference layers farther from the one or more spacer layers that reflect shorter wavelengths.