Optical Waveguide Grating Layout to Reduce Screen Door Effect
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Solution Overview
Problem
The optical waveguide technology in augmented reality devices experiences uneven light transmission due to the use of one-dimensional and two-dimensional gratings, leading to the 'screen door effect' and reduced comfort through bright and dark regions, affecting user experience.
Innovation Solution
A light guide device with a first diffraction structure featuring unequal periods in two vector directions, combining with a second diffraction structure to optimize light coupling and reduce the 'screen door effect', ensuring consistent lighting and improved user comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If one-dimensional grating and two-dimensional grating are used together in the optical waveguide device, then the light coupling function is improved, but the transmittance of ambient light becomes uneven and the screen door effect occurs
Solution Approach 1:
The patent applies local quality by making the grating period direction-dependent. Specifically, the grating period in the first direction is set to a first value while the grating period in the second direction is set to a second value that is different from the first value. This allows different regions of the grating structure to have different periodicity characteristics, optimizing light coupling in certain directions while maintaining ambient light transmittance in other directions, thereby resolving the contradiction between coupling function and transmittance uniformity.
2Adaptability or versatility
If diffraction structures are added to the optical waveguide device, then the virtual image display capability is improved, but the brightness uniformity and visual comfort deteriorate due to screen door effect
Solution Approach 1:
The patent applies asymmetry by introducing direction-dependent grating periods. The grating structure is designed with asymmetric periodicity where the period along the first direction differs from the period along the second direction. This asymmetric design enables the diffraction structure to selectively couple light while minimizing the formation of regular interference patterns that cause screen door effect, thus improving virtual image display while reducing brightness non-uniformity and visual discomfort.
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 unequal period design enhances visual clarity and comfort by minimizing light and dark differences, improving the overall lighting effect and user experience in augmented reality devices.
Implementation Method 1
The substrate is configured for totally reflecting the incident light from the second diffraction structure to the first diffraction structure
Implementation Method 2
The second diffraction structure is configured for coupling incident light into the substrate; the first diffraction structure is configured for coupling out light
Data Source
AI summary
Disclosed are a light guide device, an optical display system, and a display device. The light guide device includes a substrate and a first diffraction structure provided at the substrate. The first diffraction structure includes a first grating. The first grating includes a plurality of first grating units provided at intervals of a first period P1 along a first vector direction u1 and at intervals of a second period P2 along a second vector direction u2. The first vector direction u1 is intersected with the second vector direction u2, the first period P1 is longer than the second period P2, forming unequal periods in two vector directions, and the first period P1 is at least 1.5 times the second period P2.