Liquid Crystal Waveguide Pixel Extraction for Low-Loss Microdisplays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing microdisplays suffer from high energy consumption and optical losses due to diffraction gratings that diffract light into superfluous orders, impacting compactness and resolution.
Innovation Solution
A display device with a substrate, lighting module, addressing waveguides, and light extraction structures, utilizing liquid crystal refractive index changes and total internal reflection to enhance directivity and reduce energy loss, featuring a matrix of extraction structures with high-index regions and holograms for beam control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diffraction gratings are used to extract light at emission points, then light extraction is achieved, but optical losses occur due to superfluous diffraction orders and spurious images
Solution Approach 1:
The patent changes the extraction mechanism from diffraction-based to refraction-based by using prismatic structures. The prisms are configured with specific apex angles (e.g., 60 degrees) and refractive indices to control light extraction angles, eliminating the formation of superfluous diffraction orders while maintaining efficient light extraction at emission points.
Solution Approach 2:
The patent extracts only the necessary function of light extraction from the diffraction grating by using selective prismatic structures. Each prism is positioned at specific locations corresponding to emission points and is configured to extract light in specific directions, removing the harmful side effects of diffraction gratings while preserving the beneficial light extraction function.
2Volume of moving object
If diffraction gratings are used for light extraction, then emission points can be activated, but compactness is negatively impacted due to the length required for efficient light extraction
Solution Approach 1:
The patent uses prismatic structures with optimized geometric parameters (apex angles, base dimensions) that enable efficient light extraction over much shorter lengths compared to diffraction gratings. The prisms are configured to provide the necessary phase and direction control in a compact footprint, allowing the microdisplay to achieve high light extraction efficiency without compromising compactness.
Solution Approach 2:
The patent transitions from the diffraction mechanism that requires extended grating lengths to a refraction-based prismatic approach that achieves light extraction in a more compact, three-dimensionally optimized configuration. The prisms utilize angular geometry rather than extended linear patterns, enabling efficient light extraction in a smaller volume.
3Productivity
If light extraction directivity is increased to reduce energy loss, then luminous efficiency improves, but device complexity increases
Solution Approach 1:
The patent divides the light extraction function into discrete, independently optimized prismatic structures positioned at each emission point. Each prism is a simple geometric element that provides directional control, and the collective array of prisms achieves high overall directivity without requiring complex individual components. This segmentation allows for straightforward manufacturing and assembly while maintaining high luminous 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
The solution achieves a compact, low-energy-consuming microdisplay with improved luminous efficiency and resolution by optimizing light extraction and beam directionality.
Implementation Method 1
an intermediate waveguide of a liquid crystal extending parallel to the top face from an input face of the intermediate waveguide to an output face of the intermediate waveguide, the intermediate waveguide being arranged between the addressing electrode and the common electrode so as to flip a refractive index of the liquid crystal along a polarization direction, from a first level to a second level strictly higher than the first level, when a variation of an electrical potential difference is applied between the addressing electrode and the common electrode
Implementation Method 2
an optical mode from the lighting module and guided in the addressing waveguide is coupled at least in part, by evanescent coupling of the addressing waveguide to the intermediate waveguide, only when the refractive index of the liquid crystal is equal to the second level so as to generate an emitted beam
Implementation Method 3
the angle β is greater than or equal to a strictly positive minimum tilt angle beyond which the emitted beam is reflected by total internal reflection on the input face of the adjacent extraction structure into a reflected beam, to be extracted from the display device into a pixel beam corresponding to the display of a pixel of the image
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
The invention relates to an image display device comprising an array of extraction structures and sets of waveguides and addressing electrodes extending respectively along axes xi and ya, ya making an angle β with an axis yi orthogonal to xi. Each extraction structure includes an intermediate liquid crystal waveguide arranged between an addressing electrode and a common electrode so as to switch its refractive index from a first level to a second level. An entrance face of the intermediate waveguide makes an angle γ greater than 30 degrees with the substrate and an angle equal to β with the axis yi. In operation, a mode of the addressing waveguide is coupled to the intermediate waveguide only when the liquid crystal refractive index is equal to the second level to extract a beam corresponding to the display of a pixel, after total internal reflection on the entrance face of the adjacent extraction structure.