Diffractive Waveguide Display Structure for Uniform Brightness
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Solution Overview
Problem
Conventional waveguide-based display structures suffer from high optical losses due to exit pupil expansion methods, which can lead to brightness non-uniformities in the output image.
Innovation Solution
The display structure incorporates a waveguide with an in-coupling structure to couple input beams, a diffractive exit pupil expansion structure to form guided beams, and a diffractive out-coupling structure to efficiently couple light out of the waveguide, reducing optical losses and brightness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If conventional exit pupil expansion structures are used to increase output image size, then the image size is improved, but optical losses increase excessively
Solution Approach 1:
The exit pupil expansion structure is segmented into multiple discrete diffraction gratings arranged in a specific pattern, allowing light to be distributed across multiple guided propagation domains rather than using a single large expansion element, thereby reducing cumulative optical losses while maintaining image size expansion
Solution Approach 2:
The patent utilizes k-space domain transformation by diffracting light into multiple discrete guided propagation domains with different k-vectors, effectively expanding the exit pupil in angular space rather than physical space, which reduces optical losses while maintaining the expanded output image size
2Loss of energy
If the efficiency of exit pupil expansion structure is increased to reduce optical losses, then optical losses are reduced, but brightness non-uniformities appear in the output image
Solution Approach 1:
Each diffraction grating in the array is optimized with locally adapted parameters (grating period, orientation, depth) to control the diffraction efficiency and k-vector distribution for its specific position in the array, ensuring uniform brightness across the entire output image while maintaining high overall efficiency
Solution Approach 2:
The patent systematically varies diffraction grating parameters (such as grating period, groove depth, and orientation angle) across different positions in the array to compensate for position-dependent optical effects, thereby achieving uniform brightness distribution while maximizing overall diffraction efficiency and minimizing optical losses
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 configuration reduces optical losses and minimizes spatial image brightness variations, enhancing the overall performance and efficiency of waveguide-based display structures.
Implementation Method 1
a light beam is coupled into a waveguide such that it propagates towards a first direction through an exit pupil expansion structure
Implementation Method 2
a diffractive exit pupil expansion structure configured to receive the set of in-coupled beams and to diffract the set of in-coupled beams to form a first set of guided beams and a second set of guided beams
Implementation Method 3
a diffractive out-coupling structure configured to receive from the exit pupil expansion structure a first diffracted set of beams and a second diffracted set of beams and the out-coupling structure is configured to couple light from the first diffracted set of beams and light from the second diffracted set of beams out of the waveguide
Data Source
AI summary
A display structure (1000), a display device, and a vehicle are disclosed. The display structure (1000) comprises a waveguide (1100); an in-coupling structure (1200) configured to in-couple a set of in-coupled beams (1021); a diffractive exit pupil expansion structure (1300) configured to receive and diffract the set of in-coupled beams (1021) to form a first set of guided beams (1031) and a second set of guided beams (1032); and a diffractive out-coupling structure (1400) configured to receive from the exit pupil expansion structure (1300) a first diffracted set of beams (1041) and a second diffracted set of beams (1042) and to out-couple light from the first diffracted set of beams (1041) and from the second diffracted set of beams (1042).