Depolarization Beam-Splitting Structure with Gradient-Index Protection
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Solution Overview
Problem
Existing Pancake lens-based VR and MR devices suffer from ellipticity issues due to inconsistent transmittance and reflectance of polarized components at large incident angles, leading to stray light and ghosting, particularly with micro OLED displays.
Innovation Solution
An optical structure incorporating a beam splitting film with a metal layer and a light-transmitting protective film featuring a refractive index that gradually decreases along a reference direction, protected by a base layer, to maintain consistent transmittance and reflectance across varying angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional beam splitting film is used in Pancake lens-based VR/MR devices, then the device can achieve compact optical path, but the transmittance and reflectance of polarized components become inconsistent at large incident angles, causing ellipticity issues and stray light
Solution Approach 1:
The patent changes the material parameters of the beam splitting film by introducing a metal layer with specific optical characteristics. The metal layer has different optical properties compared to conventional dielectric materials, enabling consistent beam splitting performance across various incident angles while maintaining the compact Pancake lens structure.
Solution Approach 2:
The patent employs a composite structure combining metal layer and dielectric layers to form the beam splitting film. This composite material approach allows optimization of both the beam splitting function and the protection function, achieving reliable performance at large incident angles while keeping the device compact.
2Reliability
If a metal layer is added to the beam splitting film to improve beam splitting effectiveness, then the beam splitting performance at large angles improves, but the protective function of the beam splitting film deteriorates
Solution Approach 1:
The patent divides the beam splitting film into multiple functional layers: a metal layer for beam splitting and multiple dielectric protective layers for protection. This segmentation allows each layer to perform its specific function optimally without compromising the other, solving the contradiction between beam splitting effectiveness and protective function.
Solution Approach 2:
The dielectric layers act as intermediary protective coatings between the metal layer and the external environment. These intermediary layers protect the metal layer from damage while allowing the metal layer to maintain its beam splitting function, thus resolving the contradiction between functionality and protection.
3Strength
If a protective film is added to protect the beam splitting film, then the protective function improves, but the optical performance and beam splitting effectiveness deteriorate
Solution Approach 1:
The patent carefully controls the optical parameters (refractive index, thickness) of the protective dielectric layers to minimize their impact on optical performance. By optimizing these parameters, the protective layers provide necessary protection while maintaining high beam splitting effectiveness and optical performance.
Solution Approach 2:
The patent applies different material properties to different layers: the metal layer provides beam splitting functionality while the dielectric protective layers provide protection. Each layer is designed with local quality optimized for its specific function, allowing the system to achieve both protection and optical performance simultaneously.
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 enhances the ellipticity of light to near-circular polarization, reducing stray light and ghosting, and maintains the beam splitting effectiveness even at large incident angles, improving the viewing experience in VR and MR devices.
Implementation Method 1
a light-transmitting protective film, located on a side of the beam splitting film away from the first surface and in contact with the beam splitting film; a phase retardation film, located on a side of the second surface away from the first surface
Implementation Method 2
a beam splitting film, located on a side of the first surface away from the second surface; the beam splitting film includes a metal layer
Implementation Method 3
a phase retardation film, located on a side of the second surface away from the first surface
Data Source
AI summary
An optical structure, a display device and a depolarization beam splitting structure. The optical structure has a light incident side and a light-exiting side; and the optical structure includes a lens structure, a beam splitting film, a light-transmitting protective film, a phase retardation film and a polarizing reflective film. The lens structure includes a first surface and a second surface, the beam splitting film is located on a side of the first surface; the light-transmitting protective film is located on a side of the beam splitting film away from the first surface and in contact with the beam splitting film. The beam splitting film includes a metal layer; the light-transmitting protective film includes a structure layer; a refractive index of the structure layer gradually decreases along a reference direction; and the reference direction is a direction in which the beam splitting film points towards the light-transmitting protective film.