Waveguide Display Structure for Interference-Free Pupil Expansion
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Solution Overview
Problem
Conventional waveguide-based display devices using laser light sources face image quality disturbances due to the high temporal coherence of laser light, which causes interference issues when replicated beams of light converge at the same location via different propagation paths.
Innovation Solution
The display structure incorporates a waveguide, an in-coupling structure for coupling input beams into the waveguide, a diffractive exit pupil expansion structure to form multiple sets of guided beams, and a diffractive retardation and out-coupling structure with an out-coupling grating to manage beam propagation and reduce interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If pupil replication is used to increase output image size, then the exit pupil size is expanded, but image quality deteriorates due to interference between replicated beams
Solution Approach 1:
The patent divides the replicated beams into multiple groups, where each group contains beams with non-overlapping propagation paths. This segmentation prevents interference between beams from different groups while still achieving pupil expansion, thereby resolving the contradiction between increasing exit pupil size and maintaining image quality
Solution Approach 2:
The patent utilizes the spatial dimension by directing different groups of replicated beams through different propagation paths in three-dimensional space. By separating beams along spatial dimensions rather than keeping them in the same plane, the patent eliminates interference while maintaining pupil expansion
2Measurement precision
If laser light sources are used, then image sharpness and energy efficiency are improved, but temporal coherence causes interference issues
Solution Approach 1:
The patent converts the harmful temporal coherence property of laser light into a beneficial feature by carefully controlling the propagation paths. Instead of trying to eliminate coherence, the patent uses it to create well-defined, non-overlapping beam groups that maintain sharpness while avoiding interference, thus turning the harmful coherence into a useful characteristic for precise beam 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 configuration effectively reduces image quality disturbances by managing beam interference and enhancing image sharpness, while maintaining the benefits of lower energy consumption and smaller form factors associated with laser light sources.
Implementation Method 1
an in-coupling structure configured to couple a set of input beams into the waveguide as a set of in-coupled beams
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 at least three sets of guided beams
Implementation Method 3
an annular guided propagation domain associated with the waveguide
Implementation Method 4
an out-coupling grating configured to couple light out of the waveguide as a set of output beams
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 couple a set of input beams (1020) into the waveguide (1100) as a set of in-coupled beams (1021), a diffractive exit pupil expansion structure (1300) configured to diffract the set of in-coupled beams (1021) to form at least three sets of guided beams (1030), and a diffractive retardation and out-coupling structure (1400) configured to receive from the exit pupil expansion structure (1300) a diffracted set of beams (1035) and comprising an out-coupling grating (1420). The retardation and out-coupling structure (1400) is configured to diffract the diffracted set of beams (1035) to form at least one returning set of beams (1040) guided towards the exit pupil expansion structure (1300).