Orthogonal Geometric Phase Lens Alignment for AR HMD Dispersion
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Solution Overview
Problem
Augmented reality (AR) head-mounted displays (HMDs) using geometric phase lenses (GPLs) face significant color dispersion issues due to their design wavelength limitations, leading to reduced see-through quality and user discomfort from vergence-accommodation conflicts.
Innovation Solution
Incorporating a compensation assembly with GPLs orthogonally aligned to the focusing assembly's GPLs, which includes multilayer or switchable GPL stacks to correct axial chromatic aberration and provide multi-focal capabilities, ensuring that light from the local area is unaltered and presented at appropriate focal distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If geometric phase lenses (GPLs) are used as focusing optics in AR headset, then focusing power is achieved, but color dispersion increases making the AR headset unusable
Solution Approach 1:
The patent divides the optical system into two separate assemblies: a focusing assembly containing GPLs with a first axis of orientation, and a compensation assembly containing GPLs with a second axis of orientation orthogonal to the first. This segmentation allows each assembly to perform its specific function while minimizing color dispersion. The focusing assembly provides the necessary focusing power, while the compensation assembly specifically addresses color dispersion by having its GPLs oriented orthogonally, which causes them to affect different polarization components of light and thereby cancel out the color dispersion effects.
Solution Approach 2:
The compensation assembly acts as an intermediary element between the focusing assembly and the user's eye. It mediates the optical path by compensating for the color dispersion introduced by the focusing assembly. The compensation assembly's GPLs, oriented orthogonally to those in the focusing assembly, serve as a mediating optical element that corrects the polarization state and eliminates color dispersion without significantly affecting the focusing power.
2Power
If GPLs with spatially varying optic-axis are used, then focusing power is produced, but light leakage occurs for wavelengths not having the designed wavelength
Solution Approach 1:
The optical system is segmented into focusing and compensation functions performed by separately oriented GPL assemblies. The focusing assembly's GPLs are designed for specific wavelengths and provide focusing power, while the compensation assembly's orthogonally oriented GPLs address the light leakage issue by compensating for wavelength-dependent polarization effects, thereby reducing leakage across a broader wavelength range.
3Ease of operation
If focusing assembly presents image at focal distance, then vergence-accommodation conflict occurs, but see-through quality is degraded by color dispersion
Solution Approach 1:
By separating the optical functions into two independently oriented assemblies, the patent enables the focusing assembly to address vergence-accommodation comfort while the compensation assembly specifically targets color dispersion reduction. The orthogonal orientation ensures that the compensation assembly's effect on color dispersion does not significantly interfere with the focusing assembly's ability to present images at appropriate focal distances.
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 configuration effectively eliminates color dispersion and axial chromatic aberration, enhancing the see-through quality and reducing user fatigue by ensuring that virtual and real-world images are presented at comfortable focal distances, thereby improving the overall AR HMD experience.
Implementation Method 1
A GPL is an optical half-wave plate (HWP) with spatially varying optic-axis
Implementation Method 2
The GPL has different retardances for light with different wavelengths
Implementation Method 3
Each GPL of the compensation element has an axis of orientation orthogonal to the axis of orientation of a GPL of the focusing assembly. The orthogonal alignment compensates the focusing power of the focusing assembly and eliminates color dispersion.
Implementation Method 4
The orthogonal alignment can be applied to a multilayer GPL, where each layer is configured to have half-wave retardance for a particular wavelength but one-wave retardance for other wavelengths
Data Source
AI summary
A HMD includes a display block. The display block combines light from a local area with image light to form an augmented scene. The display block also provides the augmented scene to an eyebox corresponding a location of a user's eye. The display block includes a waveguide display, a focusing assembly and a compensation assembly. The waveguide display emits the image light. The focusing assembly includes a focusing geometric phase lens and presents the augmented scene at a focal distance. The compensation assembly includes a compensation geometric phase lens that has an axis of orientation orthogonal to an axis of orientation of the focusing geometric phase lens. The compensation assembly compensates the optical power of the focusing assembly.