Optical Waveguide Output Coupler for RGB Diffraction Efficiency
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Solution Overview
Problem
In polarization volume grating-based waveguide systems, it is challenging to couple light out with desired qualities due to the presence of various wavelengths, requiring optimization of polarization volume gratings for primary colors to achieve high-efficient out-coupling of visible light.
Innovation Solution
The optical waveguide system employs a stack of polarization volume gratings and color filters optimized for each primary color, using achromatic quarter-wave plates and polarization color filters to convert and separate light polarization states, enabling efficient out-coupling of red, green, and blue light through transmissive or reflective polarization volume gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single polarization volume grating is used for out-coupling, then the device complexity is reduced, but the diffraction efficiency for multiple wavelengths cannot be optimized simultaneously
Solution Approach 1:
The patent divides the out-coupling function into multiple polarization volume gratings, each optimized for a specific wavelength range (red, green, blue). This segmentation allows each grating to achieve high diffraction efficiency for its designated color while maintaining overall system simplicity through functional specialization.
Solution Approach 2:
Each polarization volume grating is designed with locally optimized properties (refractive index modulation, grating period, thickness) tailored to specific wavelength requirements. This local quality optimization enables maximum diffraction efficiency for each color component while keeping the overall device architecture relatively simple.
2Reliability
If polarization volume gratings are optimized for each primary color, then the diffraction efficiency is improved, but the device complexity increases due to multiple gratings and filters
Solution Approach 1:
The patent combines multiple polarization volume gratings and color filters into an integrated output coupler assembly. This merging approach achieves high diffraction efficiency for multiple wavelengths while managing device complexity through functional integration and compact arrangement of components.
Solution Approach 2:
The output coupler is designed as a universal component that handles multiple wavelength ranges (RGB) simultaneously through the combination of multiple polarization volume gratings and color filters. This multi-functionality approach improves diffraction efficiency across the visible spectrum while avoiding the need for separate out-coupling systems for each color.
3Illumination intensity
If color filters are added to separate wavelengths, then the light transmission quality is improved, but the loss of light intensity increases
Solution Approach 1:
The patent uses polarization state changes induced by quarter-wave plates and color filters to separate wavelengths. By exploiting polarization parameter changes rather than purely absorptive filtering, the system achieves wavelength separation with reduced light intensity loss, as polarization manipulation is non-absorptive and preserves energy.
4Adaptability or versatility
If the waveguide system supports wide viewing angles, then the adaptability is improved, but the polarization maintenance becomes more difficult
Solution Approach 1:
The patent introduces quarter-wave plates before the polarization volume gratings to pre-convert linearly polarized light into circularly polarized light. This preliminary action ensures that the light maintains its polarization state across wide viewing angles, as circular polarization is less sensitive to angle variations, thereby preserving polarization integrity while enabling wide adaptability.
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 enhances the performance of the optical waveguide system by effectively separating and coupling out different wavelengths of light, maintaining polarization integrity and achieving high diffraction efficiency across a wide angle range, thereby improving the overall light transmission and display quality.
Implementation Method 1
the rays/lights emerged from displays that with certain field of view (FOV) are in-coupled to the waveguide by an input coupler grating (ICG), undergo total internal reflection (TIR) and pupil expansion
Implementation Method 2
a first polarization volume grating, which couples the first color component out of the waveguide; a second polarization volume grating, which couples the second color component out of the waveguide
Implementation Method 3
using achromatic quarter-wave plates and polarization color filters to convert and separate light polarization states
Data Source
AI summary
An optical waveguide system and an electronic device are disclosed. The optical waveguide system comprises: a waveguide; an input coupler, coupling a light including a first and a second color component into the waveguide; and an output coupler, including: a first polarization color filter, converting the first color component of a first polarization state into the first color component of a second polarization state without changing the second color component of the first polarization state; a first polarization volume grating, coupling the first color component out of the waveguide; a second polarization color filter, converting the second color component of the first polarization state into the second color component of the second polarization state without changing the first color component of the first polarization state; a second polarization volume grating, coupling the second color component out of the waveguide.