Waveguide Device Polarization Control for AR Efficiency
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Solution Overview
Problem
Conventional waveguides with diffraction gratings have low efficiency due to light being reflected out of the waveguide when the diffraction angle is smaller than the critical angle, requiring multiple waveguides to transmit three primary colors, which results in reduced image display quality in augmented reality devices.
Innovation Solution
A waveguide device and optical engine incorporating two diffractive optical elements and polarizing units that reflect one polarization characteristic and transmit another, allowing light with diffraction angles below the critical angle to be guided and filtered, improving efficiency and eliminating ghost images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional waveguides with diffraction gratings are used to transmit light, then light can be diffracted to propagate with different diffraction angles, but when the diffraction angle is smaller than the critical angle, the light cannot be reflected based on total reflection and will transmit out of the waveguide, resulting in low waveguide efficiency
Solution Approach 1:
The patent changes the polarization state of light as a parameter to control its interaction with the waveguide. By converting linearly polarized light to circularly polarized light and back, the system enables light with diffraction angles below the critical angle to be reflected back into the waveguide, thereby improving waveguide efficiency and preventing light loss.
Solution Approach 2:
The patent introduces a polarization conversion element as an intermediary between the diffraction grating and the waveguide. This element converts the polarization state of diffracted light, enabling controlled reflection of light that would otherwise escape the waveguide, thus mediating the interaction between light and waveguide boundaries.
2Adaptability or versatility
If multiple waveguides are used to transmit three primary colors, then color transmission can be achieved, but the device complexity increases and image display quality is reduced
Solution Approach 1:
The patent makes a single waveguide capable of transmitting multiple colors by using polarization conversion. The waveguide can handle different wavelengths (colors) of light through the same physical structure by manipulating polarization states, eliminating the need for multiple separate waveguides and reducing device complexity while maintaining color transmission capability.
Solution Approach 2:
The patent merges the functions of multiple waveguides into a single waveguide structure. By combining color separation and polarization control in one integrated system, the patent achieves multi-color transmission through a unified optical path, simplifying the overall device architecture.
3Measurement precision
If diffraction gratings are used to separate colors, then spectral separation can be achieved, but light of certain wavelengths transmits out of the waveguide when diffraction angle is below critical angle
Solution Approach 1:
The patent changes the polarization parameter of light to control its reflection and retention within the waveguide. By converting linear polarization to circular polarization and back, the system ensures that light of all wavelengths, including those with sub-critical diffraction angles, remains confined within the waveguide, preventing energy loss while maintaining spectral separation.
Solution Approach 2:
The patent converts the harmful effect of light escaping the waveguide (when diffraction angle is below critical angle) into a beneficial effect. By using polarization conversion, the escaping light is redirected back into the waveguide, transforming potential energy loss into useful light transmission that maintains both spectral separation and energy efficiency.
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
Enhances the efficiency of waveguide devices by guiding light with diffraction angles below the critical angle and filtering out unwanted polarization characteristics, ensuring effective augmented reality image display without affecting external light propagation.
Implementation Method 1
Each of the diffractive optical elements has a grating configured to diffract light of a wavelength to propagate with a diffraction angle
Implementation Method 2
Each of the polarizing units is configured to reflect light of a first polarization characteristic and transmit light of a second polarization characteristic
Implementation Method 3
the efficiency of the waveguide is low... based on the principle of total reflection
Data Source
AI summary
A waveguide device includes two diffractive optical elements, a waveguide element, and two polarizing units. Each of the diffractive optical elements has a grating configured to diffract light of a wavelength to propagate with a diffraction angle. The waveguide element is configured to guide light propagated from one of the diffractive optical elements to the other of the diffractive optical elements. The polarizing units are at opposite surfaces of the waveguide element and optically coupled between the diffractive optical elements. Each of the polarizing units is configured to reflect light of a first polarization characteristic and transmit light of a second polarization characteristic.