Monovision Display Optical Stacks to Reduce Vergence-Accommodation Conflict
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Solution Overview
Problem
Conventional augmented reality (AR) systems cause visual discomfort due to vergence accommodation conflict (VAC), leading to issues like visual fatigue, headache, and eyestrain, as they often present virtual content at a single fixed focal plane that mismatches the user's natural vergence and accommodation distances.
Innovation Solution
Implementing a monovision display technique in AR devices, where each eye receives different optical powers through left and right optical stacks with compensating lenses, allowing each eye to accommodate to the sharper image, thereby reducing VAC and enhancing visual comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If virtual content is presented at a single fixed focal plane in conventional AR systems, then the device structure is simple, but vergence accommodation conflict occurs causing visual discomfort
Solution Approach 1:
The optical system is segmented into left and right optical stacks, each with independent accommodating lenses and compensating lenses. This segmentation allows each eye to receive optimized optical power independently, resolving the VAC conflict without requiring a completely complex new system architecture.
Solution Approach 2:
Different optical powers are provided to the left and right eyes based on their specific accommodation needs. The accommodating lenses have different optical powers for each eye, creating local quality differences that allow each eye to focus sharply on virtual content at its optimal focal plane, eliminating visual discomfort.
2Object-affected harmful factors
If different optical powers are provided to each eye through monovision display, then depth of field is extended and visual comfort is improved, but device complexity increases
Solution Approach 1:
The monovision display intentionally introduces asymmetry by providing different optical powers to the left and right accommodating lenses. This asymmetric design is compensated by corresponding asymmetric compensating lenses, ultimately delivering sharp images to both eyes while extending depth of field and improving visual comfort.
Solution Approach 2:
The optical power parameter of the accommodating lenses is changed differently for each eye. The left accommodating lens has a different optical power than the right accommodating lens, allowing each eye to accommodate to different focal planes. This parameter change extends the effective depth of field while maintaining image sharpness.
3Measurement precision
If accommodating lenses with different optical powers are used for left and right eyes, then each eye can focus on sharper images, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces mechanical adjustment mechanisms with optically compensated fixed-power lenses. The compensating lenses are designed to optically compensate for the intentional power differences in the accommodating lenses, eliminating the need for precise mechanical adjustment mechanisms and reducing manufacturing tolerance requirements.
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 monovision display technique extends the depth of field and reduces VAC by allowing each eye to focus on the sharpest image, improving user comfort and perceived sharpness of both virtual and real-world images.
Implementation Method 1
a left accommodating lens disposed between the left eyepiece and the user side of the wearable device; a left compensating lens disposed between the left eyepiece and a world side of the wearable device
Data Source
AI summary
A wearable device includes a left optical stack having a left eyepiece configured to receive left virtual image light, a left accommodating lens, and a left compensating lens. The wearable device also includes a right optical stack having a right eyepiece configured to receive right virtual image light, a right accommodating lens, and a right compensating lens. An optical power of the left accommodating lens is equal in magnitude to an optical power of the left compensating lens, an optical power of the right accommodating lens is equal in magnitude to an optical power of the right compensating lens, and the optical power of the left accommodating lens and the optical power of the right accommodating lens differ by an offset amount.