Varifocal Optical Assembly for Head-Mounted Displays
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Solution Overview
Problem
Head-mounted display devices cause eye fatigue due to the decoupling of vergence and accommodation when displaying three-dimensional images, as the focal distance remains fixed while the fixation point adjusts, leading to discomfort and reduced user satisfaction.
Innovation Solution
A varifocal optical assembly with adjustable optical power is implemented, allowing the perceived distance of displayed images to match the user's eye vergence by configuring multiple optical stages with different states to vary the optical power based on polarization, enabling dynamic adjustment of the focal length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed focal distance is used in the optical assembly, then the device structure is simple, but the vergence-accommodation conflict occurs causing eye fatigue
Solution Approach 1:
The patent implements a dynamic optical assembly where the optical power can be adjusted between multiple discrete states (e.g., first, second, third states with different optical powers). This allows the focal length to be dynamically changed to match different vergence demands, resolving the vergence-accommodation conflict while maintaining manageable device complexity through discrete rather than continuous adjustment
Solution Approach 2:
The patent changes the optical parameter (optical power) of the optical assembly to resolve the contradiction. By providing multiple discrete optical power states, the system can adjust the focal length to match different vergence requirements, improving user comfort without requiring a completely complex continuous adjustment mechanism
2Adaptability or versatility
If multiple optical stages with different states are configured, then the optical power becomes variable to reduce eye fatigue, but the device complexity increases
Solution Approach 1:
The patent divides the optical assembly into multiple discrete optical stages (first optical stage, second optical stage, etc.), where each stage can be independently configured to different states. This segmentation allows the system to achieve variable optical power through combination of discrete stages, making the complexity manageable while providing adaptability
Solution Approach 2:
Each optical stage is designed to be multi-functional, capable of operating in multiple states (first state, second state, third state) with different optical powers. This universality allows the same structural element to serve multiple optical functions, reducing the need for separate components for each optical power level
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 solution reduces eye fatigue and improves user comfort by aligning the perceived distance of displayed images with the user's eye vergence, enhancing overall experience in head-mounted display devices.
Implementation Method 1
In the first state, the respective optical stage has a first respective optical power for light of a first polarization and a second respective optical power, different from the first respective optical power, for light of a second polarization that is orthogonal to the first polarization
Data Source
AI summary
A varifocal optical assembly includes a plurality of optical elements configured to transmit light in successive optical stages. Each respective optical stage of the successive optical stages includes at least one respective optical element of the plurality of optical elements and is configurable to be in one of a first state and a second state. The respective optical stage in the first state has a first respective optical power for light of a first polarization and a second respective optical power for light of a second polarization. The respective optical stage in the second state has a third optical power for light of the first polarization and a fourth optical power for light of the second polarization. The optical power of varifocal optical assembly is adjustable by changing the states of one or more of the successive optical stages.