Light Guiding Apparatus with Layered Refractive Index Gradient

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Solution Overview

Problem

Light guiding apparatus with diffractive optics used in devices like mediated headsets and vehicular displays face challenges with color uniformity due to varying angles of incidence affecting the optical path and brightness of the output.

Innovation Solution

The apparatus comprises a light guiding member with a stack of layers and multiple interfaces, where in-coupling and out-coupling diffractive means are provided on the first layer. The refractive index decreases gradually through the stack, enabling uniform brightness across different angles of incidence.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a light guiding member with diffractive optics is used, then light can be guided through the device, but color uniformity deteriorates due to varying angles of incidence affecting optical path and brightness

Engineering Contradiction:

Improvebrightness uniformityVSAvoidlayer structure complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The light guiding member is divided into multiple layers with different refractive indices. Each layer segment handles specific angle ranges of incident light, with the refractive index decreasing from the first layer through the stack. This segmentation allows different angular components to be guided separately, maintaining brightness uniformity across the output.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different layers are assigned different refractive indices tailored to specific angular ranges. The first layer has a higher refractive index for capturing a broader range of angles, while subsequent layers have progressively lower refractive indices to handle specific angular components. This local optimization of optical properties ensures uniform brightness distribution.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If multiple layers with different refractive indices are used to improve color uniformity, then brightness consistency improves, but manufacturing complexity increases

Engineering Contradiction:

Improvecolor uniformityVSAvoidlayer fabrication difficulty

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The refractive index parameter is systematically varied across the layer stack, decreasing from the first layer through subsequent layers. This parameter change is designed to compensate for the angular dependence of the diffractive optics, ensuring that light at different angles experiences appropriate refractive conditions to maintain uniform color and brightness at the output.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If the refractive index decreases gradually through the layer stack, then brightness uniformity across different angles improves, but the number of layers and interfaces increases

Engineering Contradiction:

Improvebrightness consistencyVSAvoidnumber of layers and interfaces

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The solution transitions from a single-layer structure to a multi-layer vertical stack, adding the dimension of layer depth. By arranging layers with progressively decreasing refractive indices in the vertical direction, the system can handle multiple angular components simultaneously, converting a two-dimensional angular problem into a three-dimensional optical path management solution.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 ensures improved color uniformity and brightness consistency across the output, addressing the issue of uneven brightness caused by varying angles of incidence.

Implementation Method 1

a light guiding member comprising a stack of layers and multiple interfaces between respective layers, wherein the respective layers are arranged to enable light to be guided through the light guiding member via internal reflections

Methodology Applied

Scientific EffectInternal reflection: Reflection

Implementation Method 2

in-coupling diffractive means configured to in-couple one or more input beams of light into the first layer of the light guiding member; out-coupling diffractive means configured to out-couple the one or more beams of light from the light guiding member

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20250189713A1Light Guiding Apparatus

Publication Date: 2025.06.12 NOKIA TECHNOLOGIES OY

AI summary

Light guiding apparatuses include diffractive optics. A light guiding member includes a stack of layers and multiple interfaces between respective layers. The layers are arranged to enable light to be guided through the light guiding member via internal reflections. The apparatus also includes an in-coupling diffractive element configured to in-couple one or more input beams of light into the first layer of the light guiding member and an out-coupling diffractive element configured to out-couple the one or more beams of light from the light guiding member. The in-coupling diffractive element and the out-coupling diffractive element are provided on the first layer of the light guiding member. The light guiding member includes more than three layers and the refractive index of at least one of the respective layers or the respective interfaces decreases from the first layer through the stack of layers.