3D Diffractive Element for 2D Exit Pupil Expansion
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Solution Overview
Problem
Existing virtual display technologies face challenges in manufacturing and efficiency due to the use of multiple separate linear diffraction gratings, which require precise alignment and are sensitive to polarization, making them complex and space-consuming.
Innovation Solution
A three-dimensional diffractive element with matching pixel periods in both directions on a substrate, allowing for two-dimensional exit pupil expansion of an optical beam through diffraction, enabling compact and efficient beam expansion without the need for multiple gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple separate linear diffraction gratings are used to form virtual images, then the diffraction function can be achieved, but the manufacturing complexity increases and precise alignment is required
Solution Approach 1:
The patent combines multiple separate linear diffraction gratings into a single integrated diffractive element. This element contains multiple diffractive zones with different grating periods arranged in a unified structure, eliminating the need for separate gratings and their precise alignment while maintaining the diffraction function for forming virtual images.
Solution Approach 2:
The single diffractive element performs multiple functions that previously required separate gratings. It simultaneously provides diffraction with different grating periods and orientations within one integrated structure, enabling the system to achieve complex beam manipulation without multiple components.
2Reliability
If multiple separate linear diffraction gratings are used, then diffraction can be achieved, but the space required increases
Solution Approach 1:
By merging multiple diffraction gratings into one integrated element, the patent reduces the overall space required. The diffractive zones are arranged concentrically or in overlapping patterns within a single compact structure, minimizing the area occupied compared to multiple separate gratings that would require individual mounting spaces and alignment clearance.
3Reliability
If separate diffraction elements are used, then diffraction can be achieved, but polarization sensitivity increases
Solution Approach 1:
The patent employs a composite diffractive structure with multiple zones having different grating periods and orientations. This composite design distributes the diffraction function across various zones, reducing the system's sensitivity to polarization effects that would strongly affect any single linear grating orientation, thereby mitigating polarization-dependent performance variations.
4Manufacturing precision
If precise grating period definition is required for separate gratings, then diffraction accuracy improves, but manufacturing difficulty increases
Solution Approach 1:
The patent integrates multiple grating periods into a single diffractive element that can be manufactured as one monolithic structure. This approach allows all grating zones to be fabricated simultaneously using single-step lithography or deposition processes, eliminating the need for multiple separate fabrication and alignment steps, thereby reducing manufacturing complexity while maintaining precise grating period 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 solution simplifies manufacturing, reduces space requirements, and enhances diffraction efficiency, providing high-quality beam expansion suitable for virtual reality displays and other applications.
Implementation Method 1
at least part of the input optical beam is diffracted in the at least one area to provide at least one optical beam substantially within the first and second surfaces
Implementation Method 2
at least part of the at least one optical beam is further coupled out of the first or the second surface of the substrate by diffraction in the at least one further area to provide the at least one output optical beam
Data Source
Figure 1a~1c
Figure 2a~2c
Figure 3a~3b
AI summary
The specification and drawings present a new apparatus and method for using a three-dimensional (3D) diffractive element (e.g., a 3D diffractive grating) for expanding in one or two dimensions the exit pupil of an optical beam in electronic devices. Various embodiments of the present invention can be applied, but are not limited, to forming images in virtual reality displays, to illuminating of displays (e.g., backlight illumination in liquid crystal displays) or keyboards, etc.