Staircase Grating Waveguide Display for Efficient Light Coupling
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Solution Overview
Problem
Existing electronic devices with displays, such as headsets, often have bulky optical elements that do not exhibit desired optical performance, leading to inefficient image light delivery to the user's eye box.
Innovation Solution
The use of a waveguide system with a staircase surface relief grating (SRG) input coupler and a binary SRG output coupler, which maximizes in-coupling efficiency by diffracting image light into and out of the waveguide, ensuring effective pupil expansion and uniform image delivery to the eye box.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional optical elements are used in headsets, then the display can be implemented, but the optical elements become bulky and optical performance is poor
Solution Approach 1:
The patent replaces traditional bulk mechanical optical elements with a waveguide system that uses diffractive optical elements (DOEs) and surface relief gratings (SRGs) to manipulate light. This substitution of mechanical optical components with diffractive structures enables compact form factor while maintaining or improving optical performance through precise light diffraction and waveguide confinement.
Solution Approach 2:
The patent employs staircase surface relief gratings with multiple height levels (first height, second height, third height) to precisely control light diffraction angles and coupling efficiency. By varying the grating depth parameters and using binary or grayscale SRG profiles, the system optimizes light extraction and pupil expansion while keeping the device compact.
2Productivity
If conventional input couplers are used, then light can be coupled into the waveguide, but in-coupling efficiency is not maximized
Solution Approach 1:
The patent applies local quality variation through staircase surface relief gratings where different regions of the grating have different heights (first, second, and third steps) to optimize light coupling at specific locations. This localized optimization of grating depth allows precise control over diffraction efficiency and light direction, maximizing in-coupling performance.
Solution Approach 2:
The patent transitions from binary (two-level) to grayscale (multi-level) surface relief gratings, adding a vertical dimension to the grating structure. The staircase SRG introduces intermediate height levels between the highest and lowest points, enabling continuous variation of diffraction efficiency and improving overall light coupling into the waveguide.
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 enhances the efficiency of image light delivery to the eye box, reducing ghosting and increasing the overall optical performance of the display system, making it more comfortable and efficient for users.
Implementation Method 1
The input coupler may include a first surface relief grating (SRG) in the medium. The first SRG may be a non-binary staircase SRG.
Implementation Method 2
A waveguide may guide the light
Implementation Method 3
The output coupler or the interleaved coupler may include a second SRG in the medium. The second SRG may be a binary SRG
Data Source
AI summary
An electronic device may have a waveguide, an input coupler that couples light into the waveguide, and an optical coupler that couples the light out of the waveguide. A medium may be layered onto the waveguide. The input coupler may include a first surface relief grating (SRG) and the optical coupler may include a second SRG in the medium. The first SRG may be a non-binary staircase SRG having ridges with multiple steps. The second SRG may be a binary SRG having troughs that extend to the height of the lowest steps of the first SRG. A reflective layer may fill the first SRG. Forming the input coupler using a staircase SRG may serve to maximize the in-coupling efficiency of the input coupler, thereby maximizing the efficiency with which the light is provided to an eye box.