Conical Optical Combiner for AR Interference Reduction

Solution Overview

Problem

Optical devices, particularly head-worn devices, face challenges in combining real-world observation with displayed images due to differences in sources and variable environmental conditions, leading to interference and distortion in augmented reality applications.

Innovation Solution

An optical system comprising a display device with associated optics, a conical optical combiner with a beam splitter, a see-through distortion corrector, and a shutter, which minimizes interference by delivering display rays to a pupil plane parallel to the small base while allowing real-world scene rays to pass through, with coatings and polarizing elements to enhance contrast and correct distortions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a conventional beam splitter is used to combine display images with real-world view, then the display images can be overlaid on the real-world scene, but interference and distortion occur due to variable environmental conditions and different light sources

Engineering Contradiction:

Improvecombining capability of display and real-world viewVSAvoidinterference and distortion

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The optical combiner uses different surface coatings on different regions: the first surface (display side) has a reflective coating to direct display rays, while the second surface (real-world view side) has an anti-reflective coating to minimize interference. This local differentiation of optical properties resolves the contradiction by optimizing each surface for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The optical combiner employs curved surfaces rather than flat planes, with the first surface having a specific radius of curvature to focus display rays onto the pupil plane, and the second surface curved to match the user's pupillary distance. This curvature optimization minimizes optical distortion and interference across different viewing angles and environmental conditions.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Adaptability or versatility

If the optical combiner is made transparent to allow real-world scene rays to pass through, then see-through capability is achieved, but display image contrast and visibility are reduced

Engineering Contradiction:

Improvesee-through capabilityVSAvoiddisplay image contrast

Core Design Contradiction:

Adaptability or versatilityVSIllumination intensity

Solution Approach 1:

The optical combiner uses different surface coatings on different regions: the first surface (display side) has a reflective coating to direct display rays, while the second surface (real-world view side) has an anti-reflective coating to minimize interference. This local differentiation of optical properties resolves the contradiction by optimizing each surface for its specific function.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The optical combiner pre-focuses display rays onto the user's pupil plane using curved surfaces with specific radii of curvature matched to the user's pupillary distance. This preliminary optical adjustment ensures that display images maintain high contrast and visibility even when the combiner is transparent to real-world rays.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If the optical combiner is designed to deliver display rays to a pupil plane, then clear display images are achieved, but the device complexity increases with multiple coatings and curved surfaces

Engineering Contradiction:

Improveimage clarity and focus precisionVSAvoidnumber of coatings and curved surfaces

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The optical combiner merges multiple functions into a single component: it acts as both a beam splitter and a distortion corrector, combines display ray direction and real-world ray transmission, and integrates focus adjustment for different pupillary distances. This consolidation achieves clear, focused images while reducing the number of separate optical elements and simplifying the overall device structure.

Inventive Principle:

Principle #5Merging (Combining)

4Object-affected harmful factors

If the optical combiner uses a conical shape with curved surfaces to minimize interference, then optical performance is improved, but manufacturing difficulty increases

Engineering Contradiction:

Improveoptical interference minimizationVSAvoidmanufacturing of curved surfaces and coatings

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The optical combiner employs curved surfaces rather than flat planes, with the first surface having a specific radius of curvature to focus display rays onto the pupil plane, and the second surface curved to match the user's pupillary distance. This curvature optimization minimizes optical distortion and interference across different viewing angles and environmental conditions.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The optical combiner uses different surface coatings on different regions: the first surface (display side) has a reflective coating to direct display rays, while the second surface (real-world view side) has an anti-reflective coating to minimize interference. This local differentiation of optical properties resolves the contradiction by optimizing each surface for its specific function.

Inventive Principle:

Principle #3Local quality

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 system provides a clear, interference-minimized see-through view of the real world and display images with improved contrast, enabling effective combination of real-world and virtual content, and allows for diopter and display distance adjustments for user comfort.

Implementation Method 1

an optical combiner comprising a beam splitter

Methodology Applied

Scientific EffectPartial reflection: Reflection

Implementation Method 2

the small base and the flat side of the see-through distortion corrector are coated with anti-reflective coatings

Methodology Applied

Scientific EffectAnti-reflection: Anti-Reflective Coating

Implementation Method 3

the curved side, which is part of a truncated cone, is coated with an absorptive coating

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 4

the large base is coated with a partly reflective coating

Methodology Applied

Scientific EffectPartial reflection: Reflection

Data Source

PatentEP3714315B1A conical optical combiner

Publication Date: 2022.04.06 ELBIT SYSTEMS LTD

Figure 1A~1D
Figure 1E~1F
Figure 2A~2B

AI summary

Optical systems and methods are provided, which combine see-through view of the real world and display source images using a conical optical combiner cut to have flat surfaces normal to the viewer line of sight. The conical shape minimizes interferences in the view of the real world as the edges of the optical combiner are tangent to the viewer vision field of view and the inner part of the optical combiner is semitransparent. Additionally, the optical system comprises a beam splitter, a shutter(s) for attenuating or blocking the see-through path and may employ polarizing element to improve the contrast between the scene observation and the projected display and thus enabling selective viewing of either. The system may also be configured to enable diopter adjustment and virtual display distance adjustments.