Bragg Polarization Grating for High-Efficiency 3D Display Deflection
Solution Overview
Problem
Existing display devices using circular polarization gratings face limitations in achieving high diffraction efficiency and large diffraction angles simultaneously, particularly for thin gratings with small periods, which are technically difficult to produce and result in decreased performance.
Innovation Solution
The use of Bragg polarization gratings with a birefringent layer, capable of deflecting light at angles greater than 20°, combining properties of both volume and polarization gratings, and produced using the bulk photoalignment method, allowing for high diffraction efficiency, large deflection angles, and wide angular and wavelength selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If circular polarization gratings with small periods are used to achieve large diffraction angles, then the diffraction angle increases, but the diffraction efficiency decreases drastically
Solution Approach 1:
The patent changes the grating period parameter from small (conventional) to large (greater than 2 μm), which enables simultaneous achievement of large diffraction angles and high diffraction efficiency. This parameter change fundamentally resolves the trade-off between diffraction angle and efficiency that plagues conventional small-period gratings.
Solution Approach 2:
The patent employs a composite structure combining a polarization grating with a volume grating (Bragg grating). This composite approach leverages the polarization-selective properties of the polarization grating and the high efficiency of the volume grating, achieving both large diffraction angles and high diffraction efficiency that cannot be obtained with single-structure gratings.
2Ease of manufacture
If thin polarization gratings are used to simplify manufacturing, then manufacturing ease improves, but the diffraction efficiency and performance decrease
Solution Approach 1:
The patent creates a composite grating structure that combines thin-film polarization grating technology with volume grating properties. This allows the grating to be manufactured as a thin film (maintaining ease of fabrication) while achieving the high diffraction efficiency of volume gratings through the combined optical effects of both grating types.
Solution Approach 2:
The patent transitions from considering only the thin-film dimension to incorporating the volume dimension through the Bragg grating component. This dimensional extension allows the grating to achieve high efficiency without sacrificing the thin-film manufacturing advantages, as the volume effects are achieved through the composite structure rather than increased physical thickness alone.
3Device complexity
If conventional polarization gratings are used, then the structure is simple, but large diffraction angles greater than 20° cannot be achieved with high efficiency
Solution Approach 1:
The patent combines a polarization grating structure with a volume grating (Bragg grating) to create a composite element that achieves large diffraction angles greater than 20° with high efficiency. The polarization grating provides the angular selectivity and the volume grating provides the high efficiency, creating a structure that outperforms conventional simple gratings.
Solution Approach 2:
The composite grating structure performs multiple functions simultaneously: it provides polarization selection, achieves large diffraction angles, and maintains high diffraction efficiency. This multi-functionality is achieved within a single integrated grating element, avoiding the need for multiple separate components and maintaining reasonable structural simplicity.
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
Bragg polarization gratings provide high diffraction efficiency of up to 100%, large deflection angles, and wide angular and wavelength acceptance, enabling efficient light deflection and improved display performance in three-dimensional scene representation, particularly suitable for augmented and virtual reality applications.
Implementation Method 1
at least one Bragg polarization grating, with incident light being deflectable at a deflection angle, or a diffraction angle, of at least 20°
Implementation Method 2
polarization gratings are based on a spatial periodic variation of the orientation of the liquid crystal molecules, which leads to a local variation of the birefringence
Implementation Method 3
Polarization gratings may, as thin films, have a high diffraction efficiency in a diffraction order, the diffraction efficiency value depending on the polarization of the light
Data Source
AI summary
A display device for representing three-dimensional scenes is provided. The display device comprises at least one illumination device, at least one spatial light modulation device and at least one Bragg polarization grating. The Bragg polarization grating comprises at least one birefringent layer, incident light being deflectable at a deflection angle of at least 20°.