Reflective Polarizer Films for Low-Reflection Head-Mounted Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical systems in head-mounted displays suffer from reduced contrast due to undesired reflections from reflective polarizers with high pass-state reflectance, which degrade image quality.
Innovation Solution
The use of a reflective polarizer with a low pass-state reflectance (Rp ≤ 1%) and controlled reflectance in the block state (50% ≤ Rs ≤ 95%) combined with a partial reflector, along with index matching layers and antireflection coatings, to minimize higher-order reflections and enhance contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a reflective polarizer with high pass-state reflectance is used, then the device complexity is reduced, but the contrast ratio deteriorates due to undesired reflections
Solution Approach 1:
The patent converts the harmful effect of reflections by using a reflective polarizer with controlled reflectance characteristics. The polarizer reflects unwanted polarized light (converting harm into benefit) while maintaining desired light transmission, thereby improving contrast ratio without significantly increasing device complexity
Solution Approach 2:
The patent changes the optical parameters of the reflective polarizer, specifically controlling the pass-state reflectance (Rp ≤ 1%) and block-state reflectance (50% ≤ Rs ≤ 95%). By adjusting these reflectance parameters, the system achieves high contrast ratio while maintaining reasonable device complexity
2Object-affected harmful factors
If a reflective polarizer with low pass-state reflectance (Rp ≤ 1%) is used, then the contrast ratio improves, but the block-state reflectance control becomes more difficult
Solution Approach 1:
The patent precisely controls the optical parameters of the reflective polarizer, achieving Rp ≤ 1% and 50% ≤ Rs ≤ 95%. This requires high manufacturing precision in the polarizer fabrication process to ensure the reflectance characteristics meet the specified ranges for optimal contrast performance
Solution Approach 2:
The patent uses a partial reflector with reflectance of at least 30% to create a controlled reflection path. This partial reflection serves as a reference or copy of the light path, allowing precise control over the overall system reflectance characteristics while maintaining image quality
3Object-affected harmful factors
If index matching layers and antireflection coatings are added, then the contrast ratio improves by minimizing reflections, but the device complexity increases
Solution Approach 1:
The patent introduces index matching layers and antireflection coatings as intermediary elements between optical components. These layers act as mediators that reduce reflections at interfaces by matching refractive indices, thereby minimizing higher-order reflections and improving contrast ratio
Solution Approach 2:
The patent employs composite optical structures combining multiple materials with different refractive indices. The index matching layers and antireflection coatings form a composite system that optimizes light transmission while minimizing reflections, achieving high contrast ratio through material composition rather than complex structural arrangements
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 configuration achieves a higher contrast ratio (Ib/Id ≥ 50) by reducing unwanted reflections, resulting in improved image quality for head-mounted displays.
Implementation Method 1
the reflective polarizer has an average optical reflectance Rs for a first polarization state, an average optical transmittance Tp for an orthogonal second polarization state, and an average optical reflectance Rp for the second polarization state, where Tp≥80%, Rp≤1%, and 50%≤Rs≤95%
Implementation Method 2
the partial reflector has an average optical reflectance of at least 30%
Implementation Method 3
an optical film including a plurality of alternating first and second polymeric layers numbering between 200 and 500. Each first and second polymeric layer has an average thickness less than about 500 nm. For each pair of adjacent first and second polymeric layers: the first layer has an index n1x along a first axis in a plane of the optical film, an index of refraction n1y along an orthogonal second axis in the plane of the optical film, and an index n1z along a z-axis orthogonal to the first and second axes; and the second layer has an index n2x along the first axis, an index of refraction n2y along the second axis, and an index n2z along the z-axis
Data Source
AI summary
Optical films, such as reflective polarizer films, and optical systems including the optical films are described. An optical system includes one or more optical lenses having at least one curved major surface, a partial reflector, and a reflective polarizer. For a substantially normally incident light in a predetermined wavelength range extending at least from about 450 nm to about 600 nm: the partial reflector has an average optical reflectance of at least 30%, and the reflective polarizer has an average optical reflectance Rs for a first polarization state, an average optical transmittance Tp for an orthogonal second polarization state, and an average optical reflectance Rp for the second polarization state, where Tp≥80%, Rp≤1%, and 50%≤Rs≤95%.