Lightweight Eyepiece Using Polarized Light Waveguide
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Solution Overview
Problem
Conventional near-to-eye optical systems for head-mounted displays suffer from limited field of view, bulkiness, and inefficiency due to the use of mirrors and lenses, as well as costly and complex coating designs required for dichroic mirrors and holographic diffraction gratings, which restrict their practical applications.
Innovation Solution
The eyepiece design incorporates an in-coupling and out-coupling polarizing beam splitter, a transparent plate, a polarization rotator, and an end reflector within a lightweight frame, utilizing polarized light to deliver a near-to-eye image without total internal reflection, allowing for a larger field of view and improved optical efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If conventional mirrors and lenses are used in near-to-eye optical systems, then the system can form images, but the system becomes bulky and has limited field of view
Solution Approach 1:
The patent replaces conventional mirrors and lenses with a waveguide-based optical system that uses total internal reflection and diffraction gratings to guide and display images. This substitution eliminates bulky mechanical optical components while expanding the field of view through the waveguide's light guiding properties.
Solution Approach 2:
The patent transitions from traditional 3D optical path folding using mirrors to a planar waveguide structure that guides light in a two-dimensional plane close to the eye. This dimensional change allows the optical system to be flattened and made compact while maintaining a large field of view through the waveguide surface.
2Ease of manufacture
If dichroic mirrors and holographic diffraction gratings are used, then the optical system can manipulate light, but the cost and manufacturing complexity increase
Solution Approach 1:
The patent modifies the diffraction grating parameters to operate at normal or near-normal incidence angles, which simplifies manufacturing compared to holographic gratings requiring precise angular alignment. This parameter change maintains optical performance while reducing manufacturing complexity and cost.
Solution Approach 2:
The patent divides the waveguide into functional segments: an input coupling region with a diffraction grating for light entry, a propagation region for light guiding, and an output coupling region for image delivery to the eye. This segmentation allows each region to be optimized independently, simplifying overall manufacturing while maintaining optical performance.
3Weight of moving object
If traditional optical components are used, then the system can deliver images to the eye, but the weight increases
Solution Approach 1:
The patent uses a thin waveguide plate as the core optical component, replacing heavy traditional optical assemblies. The waveguide's thin-film structure dramatically reduces weight while maintaining optical efficiency through total internal reflection and efficient diffraction grating coupling.
Solution Approach 2:
The patent replaces heavy mechanical mirror and lens assemblies with a lightweight waveguide-based optical system that uses optical phenomena (total internal reflection, diffraction) to achieve the same image delivery function with significantly reduced weight.
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 design enhances the field of view and reduces the weight and cost of the optical system while maintaining the ability to superimpose computer-generated images over the real-world view, facilitating augmented and virtual reality applications.
Implementation Method 1
an in-coupling and out-coupling polarizing beam splitter
Implementation Method 2
a polarization rotator
Implementation Method 3
an end reflector
Data Source
AI summary
An eyepiece includes an eyepiece frame, an in-coupling polarization beam splitter (“PBS”), an end reflector, and an out-coupling PBS. The eyepiece frame defines an air cavity and includes an illumination region for receiving computer generated image (“CGI”) light into the eyepiece frame and a viewing region to be aligned with an eye of a user. The in-coupling PBS is supported within the eyepiece frame at the illumination region to re-direct the CGI light to a forward propagation path extending along the air cavity towards the viewing region. The end reflector is disposed to reflect the CGI light back along a reverse propagation path within the eyepiece frame. The out-coupling PBS is supported at the viewing region to pass the CGI light traveling along the forward propagation path and to redirect the CGI light traveling along the reverse propagation path out of an eye-ward side of the eyepiece frame.