Optical Waveguide Polarization Splitting for Higher Display Capacity
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Solution Overview
Problem
The capacity of optical waveguides is limited by the number of discernible angular directions and refractive index differences, restricting image size and resolution, especially when using gratings for image guidance.
Innovation Solution
The use of orthogonal or partially orthogonal polarization states to split an image into two parts, allowing each location in the waveguide to convey two images independently, with equal intensity changes, and accounting for polarization rotation in the out-coupling design to combine them correctly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional optical waveguide arrangements are used, then the structure is simple, but the capacity is limited due to constraints in angular directions and refractive index differences
Solution Approach 1:
The patent applies polarization dimensionality by introducing orthogonal polarization states (first and second polarizations) as an additional degree of freedom. The in-coupling structure diffracts incoming light into two versions with orthogonal polarizations, allowing independent signal paths within the same waveguide, thereby doubling capacity without adding physical waveguide layers
Solution Approach 2:
The patent segments the light signal into two distinct polarization components (first version with first polarization, second version with second polarization) at the in-coupling structure. Each polarization component is independently guided and can be separately recovered at the out-coupling structure, enabling parallel information channels within the same physical medium
2Productivity
If the waveguide capacity is doubled using orthogonal polarizations, then image size and resolution improve, but polarization rotation may cause cross-talk between channels
Solution Approach 1:
The out-coupling structure is pre-designed with knowledge of the polarization rotation that occurs during waveguide propagation. The patent states that the out-coupling structure is arranged to compensate for rotation of polarization state, meaning the compensation mechanism is built into the design before operation, allowing accurate separation of polarization channels despite rotation effects
Solution Approach 2:
The system incorporates polarization state compensation as a feedback mechanism. The out-coupling structure detects the rotated polarization state and applies compensatory transformation to restore the original orthogonal relationships, ensuring that first and second polarization components remain distinguishable and preventing cross-talk
3Ease of operation
If gratings are used for image guidance, then light coupling is achieved, but the number of discernible angular directions is limited
Solution Approach 1:
The patent changes the parameter used for signal differentiation from angular direction to polarization state. Instead of relying on multiple discernible angular directions provided by gratings, the system uses orthogonal polarization states as the distinguishing parameter, thereby bypassing the angular direction limitation while maintaining efficient light coupling through the same grating structures
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 approach doubles the waveguide capacity by enabling separate recovery of partial images with orthogonal polarization states, improving image size and resolution without cross-talk.
Implementation Method 1
an in-coupling structure arranged to diffract an incoming light signal having a spectral characteristic in visible spectrum into a first version of the light signal with a first polarization and a second version of the light signal with a second polarization
Implementation Method 2
the optical waveguide arranged to convey the first version of the light signal with the first polarization and the second version of the light signal with the second polarization towards an eye
Implementation Method 3
the optical waveguide arrangement further comprises an out-coupling structure arranged to compensate for rotation of polarization state of the first version and the second version of the light signal, said rotation occurring when the first version and the second version of the light signal are conveyed in the optical waveguide
Data Source
AI summary
According to an example aspect of the present invention, there is provided an optical waveguide arrangement comprising an in¬coupling structure (103) arranged to diffract an incoming light signal having a spectral characteristic in visible spectrum into a first version of the light signal with a first polarization and a second version of the light signal with a second polarization, wherein the first polarization is at least partially orthogonal compared to the second polarization, and the in-coupling structure (103) is further arranged to diffractively couple the first and the second versions of the light signal into an optical waveguide (110) and the optical waveguide (110) arranged to convey the first version of the light signal with the first polarization and the second version of the light signal with the second polarization towards an eye (120), to generate a waveguide-based display.