Variable Depth Optical Gratings via Planarization for Near-Eye Displays
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Solution Overview
Problem
Conventional lithographic techniques are unable to modulate the vertical dimension (etch depth) of optical gratings relative to the substrate, limiting the manufacturing of optical grating elements with variable depths and duty cycles, which affects the out-coupling efficiency of image light in near-eye displays.
Innovation Solution
A manufacturing system comprising a patterning, deposition, and etching system that creates a surface profile with variable etch depths and duty cycles by using an etch-compatible film, followed by deposition and planarization of a second material, allowing for the formation of optical gratings with adjustable heights and duty cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithography methods are used to produce optical grating elements, then the duty cycle can be varied, but the height of the optical grating cannot be modulated
Solution Approach 1:
The manufacturing process is segmented into multiple sequential steps: depositing etch-compatible film, creating surface profile with variable depths, depositing planarizing material, planarizing to uniform thickness, and etching. This segmentation allows each step to contribute to the final variable-depth grating structure that conventional single-step lithography cannot achieve.
Solution Approach 2:
The invention transitions from two-dimensional planar gratings to three-dimensional variable-depth gratings by introducing vertical dimension modulation through the etch-compatible film profile and subsequent etching process, enabling control over both depth and duty cycle.
2Reliability
If conventional near-eye displays are designed with materials of desired optical properties, then the display can be compact and light weight, but the out-coupling efficiency of image light is very low due to mismatch in the size and shape of the grating element
Solution Approach 1:
The invention changes the physical parameters of the grating elements by controlling the depth and duty cycle through the multi-step manufacturing process, optimizing the grating geometry to match the desired optical properties and improve out-coupling efficiency.
Solution Approach 2:
The etch-compatible film is deposited and profiled before the final grating formation, preliminarily establishing the depth variation pattern that will be transferred to the grating structure during etching, ensuring precise control over the final grating geometry.
3Productivity
If there is no manufacturing system capable of fabricating optical grating elements with variable depths and duty cycles, then conventional lithography can be used, but high throughput production of optimized gratings is not achieved
Solution Approach 1:
The manufacturing system performs multiple functions in a unified process: depositing etch-compatible film, creating surface profiles, depositing planarizing material, planarizing, and etching. This multi-functional system can fabricate gratings with various depth and duty cycle configurations, making it universally applicable to different grating design requirements while maintaining high throughput.
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
Enables the production of optical gratings with variable etch depths and duty cycles, enhancing the out-coupling efficiency of image light and improving the performance of near-eye displays by controlling the power distribution across diffraction orders.
Implementation Method 1
The manufacturing system performs a lithographic patterning of a photoresist deposited over the planarized second material
Implementation Method 2
The manufacturing system performs a deposition of at least one of: an etch-compatible film, a metal, a photoresist, or some combination thereof
Implementation Method 3
The manufacturing system performs an etching of the second material to obtain at least one of the plurality of different etch heights
Data Source
AI summary
A manufacturing system performs a deposition of an etch-compatible film over a substrate. The etch-compatible film includes a first surface and a second surface opposite to the first surface. The manufacturing system performs a partial removal of the etch-compatible film to create a surface profile on the first surface with a plurality of depths relative to the substrate. The manufacturing system performs a deposition of a second material over the profile created in the etch-compatible film. The manufacturing system performs a planarization of the second material to obtain a plurality of etch heights of the second material in accordance with the plurality of depths in the profile created in the etch-compatible film. The manufacturing system performs a lithographic patterning of a photoresist deposited over the planarized second material to obtain the plurality of etch heights and one or more duty cycles in the second material.