Switchable Waveplate Optical Assembly for Dynamic Focal Length
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current optical assemblies for head-mounted displays (HMDs) face challenges in providing a high-resolution image with a wide field of view, as existing technologies struggle to dynamically adjust the effective focal length and field of view to match user needs in various contexts, such as Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR).
Innovation Solution
The implementation of an optical assembly with switchable waveplates that allow for electronically selectable effective focal lengths and fields of view, utilizing a combination of switchable waveplates and reflective polarizers to direct display light, enabling users to select between different focal lengths and fields of view, with images being interlaced at a high frame rate to present a combined image with higher resolution in the center and lower resolution at the edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed focal length is used in the optical assembly, then the device structure is simple, but the field of view cannot be dynamically adjusted to match user needs in different contexts
Solution Approach 1:
The patent applies the dynamics principle by implementing switchable waveplates that can dynamically change the effective focal length of the optical assembly. The waveplates are controlled by a processor to switch between different focal lengths based on detected eye position, enabling the field of view to be dynamically adjusted without requiring multiple fixed optical assemblies. This resolves the contradiction by making the optical properties changeable rather than fixed.
Solution Approach 2:
The patent applies parameter changes by modifying the effective focal length parameter of the optical assembly through the use of switchable waveplates. By changing the optical parameter (focal length) in response to eye position detection, the system can adapt the field of view for different viewing contexts without physically reconfiguring the entire optical assembly, thus maintaining structural simplicity while achieving adaptability.
2Area of stationary object
If a wide field of view is provided, then more of the scene is visible, but the resolution in the central viewing area decreases
Solution Approach 1:
The patent applies local quality by providing different resolution qualities in different regions of the field of view. The system detects eye position and dynamically adjusts the effective focal length to concentrate optical resources on the central viewing area where the user is looking, while maintaining a wider overall field of view. This creates a non-uniform quality distribution with higher resolution in the foveal region and lower resolution in peripheral regions, matching human visual perception characteristics.
Solution Approach 2:
The system dynamically adjusts the effective focal length based on real-time eye position detection, allowing the high-resolution central area to track the user's gaze while maintaining a wide overall field of view. This dynamic adjustment ensures that the region of interest always receives maximum optical quality without sacrificing the benefits of a wide field of view.
3Measurement precision
If a high-resolution image is focused on the central area, then the central viewing quality improves, but the overall field of view decreases
Solution Approach 1:
The patent resolves this contradiction by making the effective focal length dynamic rather than fixed. The system can switch between different focal length states to provide either a narrow high-resolution view when the user is focused on a specific point, or a wider field of view when peripheral vision is needed. This dynamic switching capability allows the system to provide both high central resolution and wide field of view at different times, depending on user needs.
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 allows for a higher resolution image to be presented to the user while maintaining a larger field of view, improving user experience by focusing on the central area where users typically gaze, and enhancing presence through dynamic adjustment of the optical assembly's focal lengths and fields of view.
Implementation Method 1
Each switchable waveplate may be configured to provide a first retardance value (e.g., 0λ or λ/2) and a second retardance value (e.g., λ/4 or λ/4+ε).
Implementation Method 2
At least one reflective polarizer is included in the optical assembly. Selecting a retardance value of the switchable waveplate results in selecting a polarization orientation of display light that is either reflected or passed by the reflective polarizer.
Data Source
AI summary
An optical assembly includes at least one switchable waveplate and a reflective polarizer layer. The reflective polarizer layer is configured to pass a first polarization orientation of display light and reflect a second polarization orientation orthogonal to the first polarization orientation. The optical assembly provides a first effective focal length when the switchable waveplate is switched to a first retardance value and the optical assembly provides a second effective focal length when the switchable waveplate is switched to a second retardance value.