Focus-Tunable Display Optics for Vergence-Accommodation Conflict
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Solution Overview
Problem
Conventional VR/AR displays cause discomfort and distorted 3D perception due to the vergence-accommodation conflict (VAC) by incorrectly aligning the focus of the eye with the displayed images, leading to a mismatch between vergence and accommodation cues.
Innovation Solution
A display system that generates a dense collection of focal planes by driving a focus-tunable lens to sweep a range of focal lengths at high frequency and tracks the focal length in real-time, enabling the display of 1600 focal planes per second, using a control system to synchronize image frames with corresponding focal planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a focus-tunable lens is used to generate multiple focal planes, then the vergence-accommodation conflict is resolved and spatial resolution is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs a focus-tunable lens that dynamically adjusts its focal length in real-time to generate multiple focal planes. The lens is driven by a control signal that causes it to sweep through a range of focal lengths at high frequency, enabling the display system to render content at different depths without requiring multiple static lenses or complex mechanical moving parts.
Solution Approach 2:
The patent changes the focal length parameter of the optical element dynamically by applying varying control signals. The focus-tunable lens responds to electrical signals by altering its optical power, allowing the system to generate a dense collection of focal planes (1600 per second) by modulating the focal length parameter rather than physically reconfiguring the optical path.
2Measurement precision
If the focus-tunable lens settles onto each focal length sequentially, then precise focus is achieved, but the frame rate and productivity are limited to 200 focal planes per second
Solution Approach 1:
The patent employs periodic sweeping action where the focus-tunable lens is driven to continuously sweep through its entire range of focal lengths at high frequency rather than settling sequentially. This periodic back-and-forth motion enables the system to generate 1600 focal planes per second by displaying each focal plane for a brief duration during the sweep, maintaining both precision and high frame rate.
Solution Approach 2:
The patent maintains continuous useful action by keeping the focus-tunable lens in constant motion through its focal range rather than pausing at each focal length. The lens continuously sweeps through all focal planes, and the display system synchronizes content presentation with the lens position, ensuring that every moment of lens operation contributes to displaying a valid focal plane.
3Reliability
If the focus-tunable lens is driven with simple step edge excitations, then the lens settles reliably, but the response speed is limited and the cut-off frequency is not充分利用
Solution Approach 1:
The patent transitions from static step-edge excitations to dynamic periodic excitations. The lens is driven with continuous sweeping motions that exploit its full frequency response capability, allowing the system to operate at frequencies well below the 1000 Hz cut-off and achieve stable, repeatable focal plane generation at 1600 sweeps per second.
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 system effectively resolves the vergence-accommodation conflict by providing precise focus cues, achieving high spatial resolution and realistic virtual worlds with minimal blur and artifacts, supporting 40 focal planes per frame at 40 frames per second.
Implementation Method 1
an optical element having a focal length on an optical axis of the optical element that varies in response to a control signal
Implementation Method 2
a display module configured to provide a variable light field along an optical path of the display system
Implementation Method 3
the control system being programmed to generate the control signal to cause the optical element to cycle through a series of focal lengths at a frequency
Data Source
AI summary
A display system includes an optical element positioned in the optical path to receive light from the display module and direct the light into a field of view to display a scene. The optical element has a focal length on an optical axis of the optical element that varies in response to a control signal. A control system is programmed to generate the control signal to cause the optical element to cycle through a series of focal lengths at a frequency. Each focal length of the series corresponds to a focal plane of a series of focal planes. The control system is programmed to vary the light field from the display module to display the scene as a sequence of different image frames, the different image frames being synchronized so that each of the different image frames is presented at a corresponding one of the series of focal planes.