Time-Multiplexed Virtual-Depth Display With Polarization-Selective Lenses
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Solution Overview
Problem
Existing augmented reality (AR) systems face challenges in presenting virtual content at various depths without distorting the perception of the real world, leading to diminished user experience due to optical power applied to both virtual and real-world light.
Innovation Solution
The use of adaptive lens assemblies, including a polarization-selective lens stack comprising a birefringent lens and an isotropic lens, along with shutter elements, allows for the application of optical power to virtual image light while minimizing distortion of real-world light, enabling clear presentation of both virtual and real-world content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical power is applied to virtual image light to present content at various depths, then virtual content display capability is improved, but real-world light is distorted
Solution Approach 1:
The patent employs time-multiplexed operation where the adaptive lens assembly alternates between applying optical power for virtual content and not applying optical power for real-world viewing. This periodic switching allows the same optical component to serve dual purposes without causing distortion to real-world light, as the optical power is only applied during time slots dedicated to virtual content display.
Solution Approach 2:
The adaptive lens assembly dynamically adjusts its optical power based on the content being displayed. By making the optical power variable and controllable, the system can optimize for virtual content depth presentation when needed while maintaining natural real-world light transmission when the adaptive lens is in its neutral state, thus resolving the contradiction between virtual content capability and real-world light fidelity.
2Power
If conventional adaptive lens assemblies are used, then optical power can be applied, but device size and weight increase
Solution Approach 1:
The patent utilizes liquid crystal materials that can change their optical properties (refractive index) in response to electrical field changes. By changing the physical state or optical parameters of the liquid crystal molecules through voltage application, the adaptive lens assembly can achieve variable optical power without requiring large mechanical adjustments or bulky components, thus maintaining compact size and reduced weight.
Solution Approach 2:
The invention replaces traditional mechanical lens adjustment mechanisms with an electrically controlled liquid crystal-based adaptive lens. This substitution eliminates the need for moving parts, large focal length adjustments, or complex mechanical assemblies, resulting in a much more compact and lightweight design while maintaining the ability to apply variable optical power.
3Adaptability or versatility
If adaptive lens assemblies are included, then optical functionality is improved, but device complexity increases
Solution Approach 1:
The adaptive lens assembly serves multiple functions within a single component: it can present virtual content at various depths, maintain natural real-world light transmission when not activated, and potentially adjust for different viewing conditions. This multi-functionality reduces the need for separate optical components for each function, thereby simplifying the overall device structure despite the advanced capabilities provided.
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 approach provides compact, lightweight, and efficient AR devices with high bandwidth, reduced chromatic aberrations, and increased switching speeds, offering improved user experience by maintaining the clarity of real-world objects and presenting virtual content at desired depths.
Implementation Method 1
the birefringent lens has an optic axis extending in a lateral direction perpendicular to a direction of light propagation, and is configured to exert a first optical power to linearly polarized light having a polarization direction parallel to the optic axis, and to exert a second optical power to linearly polarized light having a polarization direction perpendicular to the optic axis
Implementation Method 2
the isotropic lens is configured to exert to light passing through it a third optical power opposite in sign as the second optical power
Implementation Method 3
the switchable waveplate is configured to rotate a polarization direction of linearly polarized light passing through it by 90 degrees upon electrical activation
Data Source
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Figure 3A~3B
AI summary
Techniques for operating an optical system are disclosed. World light may be linearly polarized along a first axis. When the optical system is operating in accordance with a first state, a polarization of the world light may be rotated by 90 degrees, the world light may be linearly polarized along a second axis perpendicular to the first axis, and zero net optical power may be applied to the world light. When the optical system is operating in accordance with a second state, virtual image light may be projected onto an eyepiece of the optical system, the world light and the virtual image light may be linearly polarized along the second axis, a polarization of the virtual image light may be rotated by 90 degrees, and non-zero net optical power may be applied to the virtual image light.