Graded Waveguide Coating for Uniform Holographic Emission

Solution Overview

Problem

Conventional waveguides for pupil expansion in holographic projection systems suffer from non-homogeneous emission, leading to variability in brightness and reduced image quality due to complex and costly manufacturing processes that are difficult to scale up.

Innovation Solution

A waveguide with a graded coating comprising alternating layers of dielectrics with controlled thickness variations, allowing for uniform emission across specific wavelengths, manufactured using a shadow mask and multiple targets to achieve consistent intensity and spectrum in replicas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional coating processes are used on waveguides, then manufacturing is simpler, but emission becomes non-homogeneous leading to brightness variability

Engineering Contradiction:

Improveemission uniformityVSAvoidcoating structure complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The coating is divided into multiple discrete layers (at least two layers) with different optical properties. Each layer can have controlled thickness and material composition, allowing independent optimization of light transmission and reflection characteristics to achieve homogeneous emission across the waveguide output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the waveguide coating are designed with locally optimized properties. The coating structure varies spatially to compensate for non-uniform light distribution within the waveguide, ensuring that each region contributes appropriately to achieve uniform overall emission brightness.

Inventive Principle:

Principle #3Local quality

2Reliability

If complex manufacturing processes are used to achieve homogeneous emission, then image quality improves, but manufacturing cost and scalability worsen

Engineering Contradiction:

Improveimage qualityVSAvoidmanufacturing scalability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

By segmenting the coating into discrete layers, the manufacturing process becomes more controllable and scalable. Each layer can be deposited using standard techniques with precise thickness control, replacing complex monolithic coating processes that are difficult to scale.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention controls key parameters such as layer thickness, material composition, and number of layers to achieve homogeneous emission. These parameters can be precisely adjusted during manufacturing using conventional techniques, enabling scalable production while maintaining high image quality and consistent brightness.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If single-layer coating is used, then manufacturing is easier, but emission uniformity and brightness consistency worsen

Engineering Contradiction:

Improvecoating process simplicityVSAvoidemission homogeneity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The coating is divided into multiple discrete layers (at least two layers) with different optical properties. Each layer can have controlled thickness and material composition, allowing independent optimization of light transmission and reflection characteristics to achieve homogeneous emission across the waveguide output.

Inventive Principle:

Principle #1Segmentation

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

The solution provides spatially homogeneous emission, enhancing image quality and reducing manufacturing complexity and cost, while maintaining consistent brightness across different viewing angles.

Implementation Method 1

A waveguide with a graded coating comprising alternating layers of dielectrics with controlled thickness variations, allowing for uniform emission across specific wavelengths, manufactured using a shadow mask and multiple targets

Methodology Applied

Scientific EffectShadow mask blocking: Shadow

Implementation Method 2

A waveguide with a graded coating comprising alternating layers of dielectrics with controlled thickness variations, allowing for uniform emission across specific wavelengths, manufactured using a shadow mask and multiple targets

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 3

A waveguide with a graded coating comprising alternating layers of dielectrics with controlled thickness variations

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentEP4715083A2Variable gradient thickness coating

Publication Date: 2026.03.25 ENVISICS LTD

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AI summary

A coating device comprising a sample carrier, a source, shadow mask and coating driver. The source comprises a plurality of targets such as a first target and second target. The source is arranged to coat at least one sample housed in the sample carrier. The shadow mask is disposed in a line-of-sight between the sample carrier and source. The shadow mask is arranged such that the first target provides a first coating contribution. The shadow mask is further arranged such that the second target provides a second coating contribution. The second coating contribution is different to the first coating contribution. At least one of the first and second coating contributions is non-uniform in a first dimension of the sample. The coating driver is arranged to independently control the first coating contribution and second coating contribution such that a thickness gradient of the coating in the first direction is variable.