AR Optical Waveguide Layout for Ghost Image Prevention
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Solution Overview
Problem
Existing optical devices for augmented reality suffer from the generation of unintended ghost images due to the disposition of the first optical element inside the optical means.
Innovation Solution
The optical device adjusts the distance and inclination angle between the image output unit and the optical means by forming the third surface of the optical means at an inclination angle and spacing the image output unit apart to satisfy the equation Lg≥Ld21-n2sin2θinn2sin2θin, where Ld is the length of the image output unit, θin is the inclination angle, and n is the refractive index of the optical means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the first optical element is disposed inside the optical means, then the device achieves compact integration and reduced size, but unintended ghost images are generated due to stray light paths
Solution Approach 1:
The patent extracts the problematic first optical element from the interior of the optical means and repositions it to the exterior. This separation removes the source of ghost image generation while preserving the compact design benefits, as the first optical element can be integrated into the display assembly rather than being embedded within the optical means structure.
Solution Approach 2:
The patent introduces a window as an intermediary component between the first optical element and the optical means. This window serves as a mediator that allows light to pass through while blocking unwanted stray light paths that cause ghost images, enabling the first optical element to be positioned externally without compromising the compact integration.
2Device complexity
If the first optical element is disposed inside the optical means, then the optical path is simplified and integration is improved, but stray light paths cause unintended ghost images
Solution Approach 1:
The first optical element is extracted from the interior positioning and repositioned to the exterior of the optical means. This extraction eliminates the complex internal light paths that generate ghost images while maintaining overall optical path simplicity through a more straightforward external configuration.
Solution Approach 2:
A window is introduced as an intermediary component between the first optical element and the optical means. This window simplifies the optical path by providing a clean light transmission interface while blocking stray light paths that would otherwise create ghost images, achieving both simplicity and image 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
This configuration minimizes ghost images by preventing stray light paths that cause ghost images, ensuring clear virtual image focus regardless of focal length changes.
Implementation Method 1
the third surface is formed to have an inclination angle θin with respect to the normal line in the forward direction from the pupil
Implementation Method 2
an optical means 20 that transmits real object image light, output from a real object in the real world, therethrough toward a pupil 50 of a user
Implementation Method 3
a first optical element 30 that transfers the virtual image light, output and transferred from the image output unit 10, to the second optical elements 40
Data Source
AI summary
Provided is an optical device for augmented reality having a ghost image prevention function. The optical device includes: an image output unit to output virtual image light; an optical unit configured such that the virtual image light propagates through an inside thereof and real object image light is transmitted therethrough toward a pupil; a first optical element inside the optical unit to transfer the virtual image light to a plurality of second optical elements; and the second optical elements disposed inside the optical unit, and configured to provide a virtual image to the user by transferring the virtual image light toward the user's pupil. The optical unit has a first, a second, and a third surfaces. The third surface has an inclination angle to a normal line in a forward direction from the user's pupil and the image output unit is spaced apart from the third surface.