AR Optical Waveguide Using Total Internal Reflection for Stable Focus
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Solution Overview
Problem
Conventional augmented reality devices are bulky, heavy, and costly due to complex manufacturing processes, and require separate adjustments for focal length changes, often leading to out-of-focus virtual images.
Innovation Solution
A compact optical device using total internal reflection within an optical means, incorporating an auxiliary reflective unit as a collimator to transfer augmented reality image light via internal reflection, minimizing device size, weight, and ghost images, while maintaining focus through a pinhole effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical systems with separate collimators and reflective units are used, then augmented reality image quality can be maintained, but device size, weight, and volume increase significantly
Solution Approach 1:
The patent combines the collimator and reflective unit into a single integrated optical component. The collimator portion parallelizes light from the image output unit, while the reflective unit portion reflects this collimated light toward the user's eye. This merging eliminates the need for separate optical components and their individual mounting structures, thereby reducing device volume while maintaining augmented reality image quality.
Solution Approach 2:
The integrated optical means performs multiple functions simultaneously: it acts as both a collimator to parallelize light and a reflective unit to redirect light toward the pupil. This multi-functionality reduces the number of components needed in the optical system, contributing to compact device design without compromising image quality.
2Reliability
If conventional optical systems with multiple separate components are used, then optical functionality can be achieved, but manufacturing complexity and cost increase
Solution Approach 1:
By integrating the collimator and reflective unit into a single optical means, the patent reduces the number of manufacturing steps, assembly operations, and quality control checkpoints. This single-component approach simplifies the manufacturing process and reduces overall system complexity while maintaining reliable optical functionality.
3Manufacturing precision
If variable focal length mechanisms are added to maintain focus during focal length changes, then virtual image focus can be maintained, but device complexity and weight increase
Solution Approach 1:
The patent employs a pinhole effect achieved through a small aperture in the optical means that automatically maintains focus on virtual images regardless of changes in the user's focal length for viewing the real world. This self-adjusting mechanism eliminates the need for separate variable focal length mechanisms, processors, or software controls, thereby maintaining virtual image focus without increasing device complexity.
4Volume of moving object
If total internal reflection is used to reduce device size, then device compactness is improved, but ghost images may be generated
Solution Approach 1:
The patent acknowledges that total internal reflection may generate ghost images as a harmful effect, but converts this challenge into a benefit by strategically utilizing the reflection properties. The optical means is designed to use total internal reflection for the primary optical path while incorporating a reflective coating on the outer surface to manage and redirect potential ghost image light, thereby minimizing their impact while maintaining the compactness advantages of total internal reflection.
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 achieves reduced size, weight, and cost, with consistent focus regardless of focal length changes, and minimizes ghost images by utilizing internal reflection and a ghost image light absorption unit.
Implementation Method 1
augmented reality image light is transferred to a reflective unit by using total internal reflection on the inner surface of the optical means
Implementation Method 2
is reflected by the first reflective unit and output toward the first surface of the optical unit
Implementation Method 3
is reflected by total internal reflection on the first surface of the optical means and transferred to the second reflective unit
Data Source
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 an eye of a user; a first reflective unit disposed inside the optical unit 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 unit; and the second reflective unit disposed inside the optical means and configured to transfer the augmented reality image light transferred from the first reflective unit toward the pupil of the eye of the user by reflecting it, thereby proving an image for augmented reality to the user.