Micro-prism Array Field Inversion Waveguide for Uniform Eyebox Coupling

Solution Overview

Problem

Existing waveguide technologies, such as helmet-mounted displays, face inefficiencies in coupling collimated light into the eyebox due to diverging light from diffraction gratings or beam splitters, leading to non-uniformity and banding issues with pupil replication techniques.

Innovation Solution

A field inversion waveguide using a micro-prism array, specifically a two-dimensional array of tilted roof prisms or indented prisms, that inverts the field of view by implementing two reflections and refraction, redirecting collimated light efficiently into the eyebox, thereby addressing the inefficiencies and uniformity issues of standard waveguide systems.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If diffraction gratings or beam splitters are used to couple collimated light out of the waveguide, then light can be directed to the user's eye, but the out coupled light is diverging with respect to the eyebox resulting in inefficient coupling

Engineering Contradiction:

Improvelight coupling efficiencyVSAvoideyebox filling efficiency

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent inverts the conventional approach by using a microlens array at the input surface to collimate light before it enters the waveguide, rather than attempting to diverge light from the output surface. This inversion of the optical path approach allows efficient coupling of collimated light into the waveguide while maintaining uniform illumination across the eyebox, resolving the contradiction between light coupling efficiency and eyebox filling efficiency

Inventive Principle:

Principle #13The other way round (Inversion)

2Area of stationary object

If pupil replication techniques are used to fill the eyebox, then a large pupil can be created in both fields of view, but non-uniformity and banding of the replicated pupils occur

Engineering Contradiction:

Improveeyebox sizeVSAvoiduniformity across field

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The patent segments the waveguide into multiple optical paths, each with its own microlens and waveguide section leading to a distinct exit pupil. This segmentation allows each pupil to be independently optimized for uniformity while collectively filling the entire eyebox area, resolving the contradiction between eyebox size and uniformity across field

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each localized pupil region is optimized with specific microlens parameters and waveguide dimensions tailored to that region's requirements. This local optimization ensures uniform illumination in each pupil while maintaining overall eyebox coverage, resolving the contradiction between eyebox size and uniformity across field

Inventive Principle:

Principle #3Local quality

3Area of stationary object

If the original pupil is oversized to fill the eyebox, then the eyebox can be filled with light, but relatively large collimators and waveguide substrates are required

Engineering Contradiction:

Improveeyebox coverageVSAvoidcollimator and waveguide substrate size

Core Design Contradiction:

Area of stationary objectVSLength of stationary object

Solution Approach 1:

The patent transitions from a single large pupil approach to multiple smaller pupils arranged in a two-dimensional array. This dimensional change allows the system to fill the eyebox area using smaller, more compact collimators and waveguide substrates, resolving the contradiction between eyebox coverage and component size

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

The micro-prism array structure enhances the efficiency of light coupling into the eyebox, ensuring a full color functioning display with improved uniformity and reduced banding, allowing for a smaller input pupil size while accommodating larger fields of view and color systems.

Implementation Method 1

The micro-prism array structure enhances the efficiency of light coupling into the eyebox, ensuring a full color functioning display with improved uniformity and reduced banding, allowing for a smaller input pupil size while accommodating larger fields of view and color systems. The micro-prism array structure implements two reflections and refraction

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

The micro-prism array structure enhances the efficiency of light coupling into the eyebox, ensuring a full color functioning display with improved uniformity and reduced banding, allowing for a smaller input pupil size while accommodating larger fields of view and color systems. The micro-prism array structure implements two reflections and refraction

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS10281655B2Field inversion waveguide using micro-prism array

Publication Date: 2019.05.07 QIOPTIQ LTD

AI summary

A field inverting optical waveguide is disclosed. The waveguide is configured to convey electromagnetic radiation from an ingress end to an egress end along an optical path. The waveguide includes an optically flat input surface disposed at the waveguide ingress end, and an exit surface disposed substantially opposite the input surface at the waveguide egress end. The exit surface includes an array of prisms projecting outward from or inward to the exit surface. The input surface and the exit surface are arranged substantially orthogonally to the optical path.