Straight Optical Waveguide for Compact AR With Fewer Ghost Images

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Solution Overview

Problem

Conventional augmented reality devices are bulky, complex, and costly, with issues such as ghost images and limited field of view, and require separate adjustments for focal length changes.

Innovation Solution

A compact optical device with a straightly-arranged optical structure using embedded reflective units to transfer augmented reality image light to the pupil, minimizing ghost images and reducing size, thickness, and weight, while maintaining a wide field of view.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional optical systems using prisms and multiple optical means are used, then augmented reality images can be transmitted to the pupil, but the device becomes bulky, complex, and heavy

Engineering Contradiction:
Improveoptical transmission efficiencyVSAvoidoptical structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple optical functions into a single optical means. The optical means simultaneously transmits real object image light and reflects augmented reality image light to the pupil, eliminating the need for separate prisms and optical components. This merging of functions directly reduces device complexity while maintaining optical transmission reliability.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The optical means is designed as a universal component that performs multiple functions: it acts as both a transmissive element for real object light and a reflective element for augmented reality light. This multi-functionality eliminates the need for multiple specialized components, thereby simplifying the overall device structure.

Inventive Principle:
Principle #6Universality (Multi-functionality)

2Reliability

If conventional optical systems with multiple components are used, then augmented reality images can be transmitted, but manufacturing costs and processes become complicated

Engineering Contradiction:
Improveimage transmission capabilityVSAvoidmanufacturing process simplicity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

By merging multiple optical components into a single integrated optical means, the patent significantly simplifies the manufacturing process. Instead of assembling multiple separate components (prisms, lenses, mirrors), the invention requires manufacturing only one optical means, reducing both manufacturing complexity and cost while maintaining the necessary image transmission capability.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If the reflective unit size is reduced to increase depth of field, then virtual images remain in focus during focal length changes, but the device size and weight are reduced

Engineering Contradiction:
Improvefocus stabilityVSAvoiddevice weight
Core Design Contradiction:
ReliabilityVSWeight of moving object

Solution Approach 1:

The patent integrates the reflective unit within the optical means, eliminating the need for separate external components. This integration allows the reflective unit to be miniaturized while maintaining its function, thereby reducing the overall device weight while preserving focus stability through the pinhole effect.

Inventive Principle:
Principle #5Merging (Combining)

4Reliability

If conventional optical systems are used, then augmented reality images can be transmitted, but ghost images are generated and field of view is limited

Engineering Contradiction:
Improveimage transmissionVSAvoidghost images
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and eliminates the root cause of ghost images by using a single optical means with a reflective unit positioned at a specific location. This configuration prevents stray light paths that cause ghost images in conventional multi-component systems, while still enabling effective image transmission.

Inventive Principle:
Principle #2Taking out (Extraction)

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 device provides improved optical efficiency, simplified manufacturing, and clear virtual images with enhanced see-through properties by reducing device size and minimizing ghost images.

Implementation Method 1

a second reflective means including a plurality of reflective units embedded and disposed in the optical means to transfer the augmented reality image light, transferred from the first reflective means, to the pupil of the user's eye by reflecting the augmented reality image light toward the pupil

Methodology Applied
Scientific EffectReflection: Reflection

Data Source

PatentEP4231080B1Compact-type augmented reality optical device having straightly-arranged optical structure, and method for manufacturing optical means
Publication Date: 2026.03.25 LETINAR CO LTD
  • EP4231080B1 patent drawingFigure 1~2
  • EP4231080B1 patent drawingFigure 3
  • EP4231080B1 patent drawingFigure 4

AI summary

The present invention provides a compact optical device for augmented reality, the compact optical device including: an optical means configured to transmit at least part of real object image light therethrough toward the pupil of a user's eye; a first reflective means embedded and disposed inside the optical means, and configured to transfer augmented reality image light, which is image light corresponding to an image for augmented reality output from an image output unit, to a second reflective means; and the second reflective means including a plurality of reflective units embedded and disposed in the optical means to transfer the augmented reality image light, transferred from the first reflective means, to the pupil of the user's eye by reflecting the augmented reality image light toward the pupil; wherein the optical means has first and second surfaces, and a method for manufacturing an optical means used in the same.