Pancake Lens Assembly Optical Phase Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Near-eye displays for virtual and augmented reality systems often cause visual fatigue, eyestrain, and vergence-accommodation conflict due to limited adjustable optical phase and improper eye alignment.
Innovation Solution
An optical system incorporating a pancake lens assembly with a lens unit comprising a partially reflective mirror, a reflective polarizer, and a quarter waveplate, along with a liquid crystal device where the long axes of liquid crystal molecules are oriented parallel to the X-Z plane, allowing for enhanced optical phase modulation and adjustable focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the distance between the near-eye display and the user's eye is kept at a limited range (15mm to 50mm), then the field of view is improved, but users wearing eyeglasses cannot maintain this distance
Solution Approach 1:
The patent introduces a folded light path configuration where light travels through multiple segments (first path segment, second path segment, third path segment) at different spatial dimensions. This allows the optical system to achieve the required optical path length for improved field of view while maintaining a compact physical distance from the eye, thereby accommodating users with eyeglasses.
Solution Approach 2:
The patent employs a partially reflective mirror as an intermediary element to split and redirect light paths. This mediator enables the light to traverse multiple segments through different spatial dimensions, allowing the system to achieve extended optical path length without increasing the physical distance from the eye, thus resolving the conflict between field of view and eye alignment for eyeglass wearers.
2Volume of moving object
If a folded light path is formed to reduce total volume, then the device size is reduced, but the optical phase modulation capability is limited
Solution Approach 1:
The patent configures the light path to continue through multiple segments without interruption, with each segment contributing to the overall optical phase modulation. The light traverses the first path segment, reflects at the partially reflective mirror, continues through the second path segment, and finishes through the third path segment, ensuring continuous useful action that accumulates optical phase modulation while maintaining a compact folded structure.
Solution Approach 2:
By arranging the light path segments in different spatial dimensions and orientations, the patent achieves extended optical interaction length within a compact physical volume. The folded configuration allows the light to traverse multiple segments that project in different directions, thereby increasing optical phase modulation capability without proportionally increasing the device volume.
3Adaptability or versatility
If the liquid crystal device is positioned to modulate light phase, then optical phase adjustment is achieved, but the vergence-accommodation conflict is not resolved
Solution Approach 1:
The patent employs a partially reflective mirror that provides optical feedback by reflecting light back through the path segments. This feedback mechanism enables the light to traverse the optical path multiple times, accumulating sufficient phase modulation to adjust the focal plane and accommodate different viewing distances, thereby resolving the vergence-accommodation conflict while maintaining optical phase control.
Solution Approach 2:
The continuous light path configuration ensures that the light interacts with the optical elements (including the liquid crystal device) multiple times as it traverses the folded path segments. This continuous interaction accumulates optical phase modulation over an extended effective path length, enabling sufficient phase adjustment to resolve vergence-accommodation conflict without requiring additional optical components.
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 optical system reduces the total volume of the display, increases the adjustable optical phase, mitigates vergence-accommodation conflict, and provides vision correction, enhancing user experience by reducing visual fatigue and improving field of view.
Implementation Method 1
The liquid crystal device has liquid crystal molecules. Long axes of the liquid crystal molecules are orientated parallel to an X-Z plane defined by the X and Z directions
Implementation Method 2
by arranging the long axes of the liquid crystal molecules in parallel to the X-Z plane, the light passing through the pancake lens assembly can be adjusted by the liquid crystal device two times, which is beneficial for solving the problem of limited adjustable optical phase
Implementation Method 3
an X-polarized light polarized in an X direction orthogonal to the Z direction travels on two of the three path segments, and a Y-polarized light polarized in a Y direction orthogonal to both the X and Z directions travels on a remaining one of the three path segments
Implementation Method 4
The lens unit includes a partially reflective mirror, a reflective polarizer, and a quarter waveplate disposed between the partially reflective mirror and the reflective polarizer
Data Source
AI summary
An optical system includes a pancake lens assembly which has a lens unit and a liquid crystal device. The lens unit includes a partially reflective mirror, a reflective polarizer, and a quarter waveplate disposed between the partially reflective mirror and the reflective polarizer. The liquid crystal device is disposed between the quarter waveplate and the reflective polarizer. When a light is introduced into the pancake lens assembly in a Z direction, an X-polarized light passes through the liquid crystal device two times and a Y-polarized light passes through the liquid crystal device one time.