Chemical-Diffusion Treated Volume Holograms for Side-Lobe Control

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Solution Overview

Problem

Manufacturing optical gratings with certain optical properties, such as well-defined angular diffraction efficiency, is challenging due to side lobes in the angular diffraction efficiency curve leading to crosstalk and image artifacts.

Innovation Solution

A method involving a layer of photopolymerization material placed between two material transfer layers, with polymerization inhibitors or absorptive materials, to create a non-uniform refractive index profile, reducing side peaks and crosstalk through diffusion processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional methods are used to manufacture optical gratings, then the manufacturing process is simpler, but side lobes appear in the angular diffraction efficiency curve causing crosstalk and image artifacts

Engineering Contradiction:

Improveangular diffraction efficiency profileVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The manufacturing process is segmented into distinct stages: placing photopolymerization material between material transfer layers, exposing to interference patterns, and allowing diffusion during polymerization. This segmentation enables precise control over the refractive index profile to suppress side lobes while maintaining manufacturing feasibility

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Material transfer layers with polymerization inhibitors are placed in contact with the photopolymerization material before exposure. This preliminary action creates a controlled diffusion gradient during subsequent polymerization, which pre-establishes the non-uniform refractive index profile needed to eliminate side lobes

Inventive Principle:

Principle #10Preliminary action

2Reliability

If material transfer layers with polymerization inhibitors are used, then side peaks are suppressed and crosstalk is reduced, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvecrosstalk suppressionVSAvoidease of manufacture

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Material transfer layers containing polymerization inhibitors serve as intermediary components between the photopolymerization material and the external environment. These intermediaries control the diffusion of inhibitors into the photopolymerization material, creating the desired non-uniform refractive index profile that suppresses side peaks and reduces crosstalk

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If a non-uniform refractive index profile is created through diffusion, then image artifacts are minimized, but the manufacturing process requires additional steps

Engineering Contradiction:

Improverefractive index profile uniformityVSAvoidmanufacturing efficiency

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The refractive index profile is controlled by changing chemical parameters during polymerization. By adjusting the concentration and distribution of polymerization inhibitors through diffusion, a non-uniform refractive index profile is created that minimizes image artifacts while the polymerization process itself drives the material redistribution

Inventive Principle:

Principle #35Parameter changes

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

Optical gratings with suppressed side peaks and reduced crosstalk, enhancing image quality by minimizing artifacts, suitable for use in image optics, particularly in head-mounted displays for virtual and augmented reality.

Implementation Method 1

exposing the layer of photopolymerization material to two beams that overlap with each other over at least a portion of the layer of photopolymerization material to form a volume hologram

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

allow material transfer between the layer of photopolymerization material and the first and second material transfer layers by diffusion

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS12405409B2Chemical diffusion treated volume holograms and methods for making the same

Publication Date: 2025.09.02 META PLATFORMS TECHNOLOGIES LLC

AI summary

A method for making an optical grating having a non-uniform refractive index profile along a direction substantially perpendicular to a plane defined by the optical grating includes placing a layer of photopolymerization material having a first surface and a second surface that is opposite to the first surface between a first material transfer layer and a second material transfer layer so that the first surface of the layer of photopolymerization material is in contact with the first material transfer layer and the second surface of the layer of photopolymerization material is in contact with the second material transfer layer to allow material transfer between the layer of photopolymerization material and the first and second material transfer layers by diffusion.