Waveguide Display with Astigmatic Optics and Aberration Compensation
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Solution Overview
Problem
Existing near-eye display systems using waveguide technology suffer from image aberrations introduced by cylindrical mirrors, leading to poor image quality and complications in design such as incomplete waveguide aperture filling and increased optical path differences.
Innovation Solution
The implementation of a waveguide system with a reflective optical arrangement featuring a cylindrical mirror integrated with the substrate, accompanied by additional components like astigmatic optical elements and etendue expanders to compensate for image aberrations and enhance image expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a cylindrical mirror is used for pupil expansion in the waveguide plane, then the field of view is increased, but image aberration is introduced
Solution Approach 1:
An etendue expander is introduced as an intermediary optical element between the image source and the cylindrical mirror. This etendue expander prepares the light beam by expanding its etendue (product of area and solid angle) before it enters the cylindrical mirror, thereby reducing the aberration caused by the mirror while preserving the field of view expansion benefit.
Solution Approach 2:
The patent changes the optical parameters of the light beam by using an etendue expander to modify the beam's angular distribution and spatial profile. This parameter change ensures that when the light reflects off the cylindrical mirror, the aberration is minimized while the field of view remains expanded.
2Volume of moving object
If a cylindrical mirror is used for image expansion, then the numerical aperture is increased, but waveguide aperture filling becomes incomplete
Solution Approach 1:
The etendue expander serves as a mediator that conditions the light beam to properly fill the waveguide aperture. By expanding the etendue of the incoming beam, it ensures that the light distribution matches the waveguide aperture dimensions, achieving complete filling while maintaining high numerical aperture.
3Measurement precision
If a cylindrical mirror is used for pupil expansion, then the image resolution is improved, but the optical path difference increases
Solution Approach 1:
The etendue expander is positioned and designed to compensate for the optical path differences introduced by the cylindrical mirror. It acts as a corrective intermediary that equalizes the optical paths of different rays, thereby maintaining high image resolution while managing the optical path difference.
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 achieves high image resolution with a compact projection optics design, eliminating image aberrations and ensuring complete waveguide aperture filling, thereby improving image quality and system efficiency.
Implementation Method 1
The light propagates along the waveguide via total internal reflection (TIR) and is gradually coupled-out via one or more light extraction elements
Implementation Method 2
a reflective optical arrangement having cylindrical optical power ('cylindrical mirror') at the waveguide end... for reflecting at least part of the image illumination so as to propagate in a second in-plane direction
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
A display for providing an image to an eye of an observer is disclosed. An image generator provides image illumination corresponding to the image to a substrate having mutually-parallel major external surfaces for propagation within the substrate. An intermediate optical arrangement including at least one astigmatic optical element directs the image illumination from the image generator so as to propagate within the substrate in a first in-plane direction by internal reflection. A reflective optical arrangement having cylindrical optical power reflects the image illumination so as to propagate in a second in-plane direction by internal reflection. A coupling-out arrangement couples out the collimated image illumination towards an eye of an observer. The intermediate optical arrangement includes an element deployed to generate a corrective optical aberration that at least partially cancels out with a characteristic aberration introduced by the reflective optical arrangement.