Waveguide AR Grating Layout for Rainbow Effect Reduction
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Solution Overview
Problem
Augmented reality (AR) display devices, such as AR glasses, suffer from a rainbow effect caused by external ambient light being dispersed into a rainbow pattern, which affects user experience and can harm the eyes, particularly in outdoor conditions.
Innovation Solution
The AR display device incorporates a waveguide substrate with an in-coupling grating, a turn grating, and an out-coupling grating, where the grating vectors form a closed vector triangle, with the angle between the out-coupling grating vector and the horizontal direction ranging from −45° to 45°, to minimize the rainbow effect by converting −1st order transmitted light into an evanescent wave or deflecting it outside the user's eye movement range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional waveguide AR display devices are used, then virtual images can be displayed, but external ambient light is dispersed into a rainbow pattern that enters the user's eyes
Solution Approach 1:
The patent changes the orientation parameter of the out-coupling grating by defining its grating vector to form a closed vector triangle with specific angular relationships (−45°≤A≤45°) relative to the horizontal direction. This parameter adjustment redirects the diffracted light path so that the rainbow pattern exits at angles that do not enter the user's field of view, while maintaining the virtual image display function.
Solution Approach 2:
The patent utilizes the angular dimension of light propagation by orienting the out-coupling grating's diffraction direction away from the user's line of sight. The closed vector triangle configuration of grating vectors (K1, K2, K3) creates a three-dimensional light path control mechanism that separates the virtual image output direction from the ambient light dispersion direction, effectively eliminating the rainbow effect in the user's field of view.
2Object-affected harmful factors
If the out-coupling grating is oriented to eliminate the rainbow effect, then user experience is improved, but the device complexity increases due to specific grating vector configuration requirements
Solution Approach 1:
The out-coupling grating serves multiple functions simultaneously: it couples light out of the waveguide substrate to form the virtual image, and it redirects ambient light dispersion away from the user's field of view through its specific angular orientation. The closed vector triangle configuration (K1+K2+K3=0) integrates both functions into a single optical element, avoiding the need for additional components and reducing overall system complexity.
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 or eliminates the rainbow effect, allowing the AR display device to be used outdoors without significant impact on user experience and eye safety, by minimizing the entry of diffracted light into the user's field of view.
Implementation Method 1
The in-coupling grating is disposed on the waveguide substrate and is configured to couple light into the waveguide substrate. A grating vector of the in-coupling grating is a first vector K1.
Implementation Method 2
The turn grating is disposed on the waveguide substrate and is configured to perform pupil expansion on the light coupled into the waveguide substrate by the in-coupling grating. A grating vector of the turn grating is a second vector K2.
Implementation Method 3
The out-coupling grating is disposed on the waveguide substrate. The out-coupling grating is configured to receive the light that is subject to the pupil expansion by the turn grating and couple the light out of the waveguide substrate. A grating vector of the out-coupling grating is a third vector K3.
Data Source
AI summary
An augmented reality (AR) display device and a near-eye display device are provided. The AR display device includes a waveguide substrate, an in-coupling grating, a turn grating, and an out-coupling grating. The in-coupling grating is disposed on the waveguide substrate. A grating vector of the in-coupling grating is a first vector K1. The turn grating is disposed on the waveguide substrate. A grating vector of the turn grating is a second vector K2. The out-coupling grating is disposed on the waveguide substrate. A grating vector of the out-coupling grating is a third vector K3. The first vector K1, the second vector K2, and the third vector K3 form a closed vector triangle. An angle A between the third vector K3 and a horizontal direction X satisfies: −45°≤A≤45° when the AR display device 1 is used.