Grating-Coupled Light Guide for Plate Waveguide Alignment
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Solution Overview
Problem
Existing light coupling technologies for plate light guides require exacting manufacturing and precise alignment of separate light couplers, leading to increased costs and complexity, and often fail to achieve desired propagation characteristics efficiently.
Innovation Solution
A combination of an optical concentrator and a grating coupler with a diffraction grating is used to couple light into a plate light guide, transforming uncollimated light into guided light with predetermined propagation characteristics, such as collimated beams with controlled spread angles, by diffractively redirecting light within the guide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional light couplers (lenses, baffles, mirrors) are used to introduce light into the plate light guide, then light coupling is achieved, but manufacturing complexity and alignment precision requirements increase significantly
Solution Approach 1:
The patent combines the light coupling function and the plate light guide into a single integrated structure. The diffraction grating is directly formed on the input surface of the plate light guide, eliminating the need for separate light couplers and their precise alignment. This integration resolves the contradiction by simplifying manufacturing while maintaining coupling effectiveness.
Solution Approach 2:
The patent replaces traditional mechanical optical elements (lenses, baffles, mirrors) with a diffractive optical element (diffraction grating). This substitution eliminates complex mechanical manufacturing and alignment requirements, as the diffraction grating can be directly patterned on the light guide surface using standard semiconductor fabrication techniques.
2Ease of manufacture
If separate light couplers are manufactured and affixed to the plate light guide, then light coupling is achieved, but production cost and manufacturing complexity increase
Solution Approach 1:
The patent merges the light coupler function into the plate light guide itself by forming the diffraction grating directly on the input surface. This eliminates separate manufacturing steps for light couplers and their subsequent assembly, reducing both production cost and manufacturing complexity.
Solution Approach 2:
The plate light guide serves multiple functions: it guides light through total internal reflection and simultaneously acts as the light coupling element through its integrated diffraction grating. This multi-functionality eliminates the need for separate light coupler components, simplifying the overall device structure and manufacturing process.
3Productivity
If traditional light couplers are used, then light introduction is achieved, but coupling efficiency and propagation characteristic control are insufficient
Solution Approach 1:
The patent uses the diffraction grating to precisely control the angular distribution of coupled light by adjusting grating parameters (period, depth, profile). This enables high coupling efficiency while maintaining reliable control over propagation characteristics such as beam direction and spread angle, which are difficult to achieve with traditional couplers.
Solution Approach 2:
The replacement of mechanical optical elements with a diffractive element enables more precise control over light propagation characteristics. The diffraction grating can be designed to produce specific angular distributions and beam patterns, improving both coupling efficiency and reliability of propagation control.
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 achieves high coupling efficiency, with up to 70% in reflection configurations, and provides controlled propagation characteristics, reducing manufacturing complexity and costs while enhancing light distribution in applications like multiview displays.
Implementation Method 1
a grating coupler with a diffraction grating configured to receive the concentrated light and diffractively redirect the concentrated light into the plate light guide as guided light
Implementation Method 2
an optical concentrator configured to receive uncollimated light from the light source and concentrate the uncollimated light to provide concentrated light
Data Source
Figure 1A~1B
Figure 2~3A
Figure 3B~4
AI summary
A grating-coupled light guide concentrates light and diffractively redirects the concentrated light at a non-zero propagation angle as guided light having a predetermined spread angle. The grating-coupled light guide includes a light guide, an optical concentrator, and a grating coupler. The optical concentrator is configured to concentrate light from a light source as concentrated light and the grating coupler is configured to diffractively redirect the concentrated light into the light guide as the guided light. Characteristics of the optical concentrator and grating coupler are configured in combination to determine the non-zero propagation angle and predetermined spread angle. A grating-coupled display system further includes an array of light valves configured to modulate emitted light as a displayed image.