Reflective Polarizer With Variable Layer Thickness
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Solution Overview
Problem
Conventional reflective polarizers used in optical devices such as VR headsets and display devices suffer from optical artifacts like ghosting and low contrast ratio due to high reflectivity in the pass polarization state and low transmissivity in the block polarization state, which affects their efficiency and performance.
Innovation Solution
A reflective polarizer is designed with alternating polymeric first and second layers, each with an average thickness less than 300 nanometers, and an intermediate layer thicker than 500 nanometers, optimized through co-extrusion and co-stretching processes to achieve very low reflectivity in the pass polarization state and high transmissivity in the block polarization state, reducing optical artifacts and improving contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional reflective polarizers are used, then they provide basic polarization function, but they generate optical artifacts like ghosting and have low contrast ratio due to high reflectivity in pass polarization state and low transmissivity in block polarization state
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of each polymeric layer (alternating layers of 20-300 nm and 20-300 nm) to achieve specific optical path differences. This parameter optimization enables the polarizer to maintain low reflectivity in pass state and high transmissivity in block state, eliminating optical artifacts while preserving manufacturing feasibility through co-extrusion processes.
Solution Approach 2:
The patent uses composite materials by combining multiple polymeric layers with different refractive indices and optical properties. The alternating structure of different polymeric materials creates constructive and destructive interference patterns that selectively transmit or block polarized light, achieving high contrast ratio and eliminating ghosting effects while maintaining ease of manufacture through integrated co-extrusion of the composite structure.
2Device complexity
If conventional reflective polarizers are used, then they are easier to manufacture with simpler structures, but they exhibit high reflectivity in pass polarization state which causes optical artifacts
Solution Approach 1:
The patent applies segmentation by dividing the polarizer into multiple alternating polymeric layers with different optical properties. Each layer is thin (20-300 nm) and segmented to create specific interference effects. This segmented structure achieves low reflectivity in pass state while maintaining a relatively simple overall device architecture that can be manufactured through co-extrusion processes.
Solution Approach 2:
The patent changes structural parameters by optimizing the thickness of each segmented layer to 20-300 nm, which creates the necessary optical path differences for destructive interference of reflected light in pass state. This parameter optimization reduces optical artifacts while keeping the device structure simple enough for practical manufacturing through integrated co-extrusion of the multi-layer structure.
3Device complexity
If conventional reflective polarizers are used, then they have simpler layer structures, but they show low transmissivity in block polarization state which reduces efficiency
Solution Approach 1:
The patent segments the layer structure into alternating thin polymeric layers (20-300 nm each) with different refractive indices. This segmentation creates multiple interfaces that produce constructive interference for transmitted blocked light, significantly improving transmissivity efficiency in block polarization state while maintaining a relatively simple overall layer structure that can be manufactured through co-extrusion processes.
Solution Approach 2:
The patent employs composite materials with alternating polymeric layers having different optical properties. This composite structure enhances transmissivity in block state through controlled interference effects, improving energy efficiency while keeping the layer structure simple enough for practical manufacturing. The composite nature allows optimization of light transmission without requiring complex multi-step fabrication processes.
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 solution significantly reduces optical artifacts like ghosting and enhances the contrast ratio of optical devices, ensuring high performance in applications such as VR headsets by maintaining very low reflectivity in the pass polarization state and high transmissivity in the block polarization state across various wavelengths.
Implementation Method 1
A reflective polarizer includes a plurality of polymeric first layers and a plurality of polymeric second layers. The polymeric first layers and the polymeric second layers have different average layer thicknesses. For a first wavelength range extending from about 400 nm to about 700 nm, the pluralities of polymeric first and second layers, in combination, have, for a first polarization state and an incident angle of less than about 5 degrees, an average optical reflectance of greater than about 95%
Implementation Method 2
The plurality of polymeric first layers includes a polymeric first end layer at each end thereof. The polymeric first end layers and each layer therebetween have an average layer thickness less than about 300 nanometers (nm). The plurality of polymeric second layers includes a polymeric second end layer at each end thereof. The polymeric second end layers and each layer therebetween have an average layer thickness less than about 300 nm.
Data Source
AI summary
The present disclosure provides a reflective polarizer including a plurality of polymeric first layers and a plurality of polymeric second layers. A plot of an average layer thickness versus a layer number for the pluralities of polymeric first, but not second, layers includes a knee region separating a left region including at least 50 sequentially arranged polymeric first layers. The polymeric first layers have lower layer numbers, and the average layer thickness increases with increasing layer number from a right region including at least 5 sequentially arranged polymeric first layers. The polymeric first layers have higher layer numbers and the average thickness increases with increasing layer number, such that linear fits to the at least 50 sequentially arranged polymeric first layers and to the at least 5 sequentially arranged polymeric first layers have respective positive slopes S1 and S2, S2/S1≥5.