Waveguide Angular Filters for See-Through Display Flare Mitigation
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Solution Overview
Problem
Designing optical systems for devices like virtual and augmented reality headsets is challenging due to the potential for unsightly and bulky components that do not exhibit desired optical performance, particularly in mitigating distracting flares caused by high-angle ambient light.
Innovation Solution
An optical combiner with a waveguide structure incorporating an angular filter that includes angled absorbers or diffractive gratings to block flare-inducing light while allowing real-world light within the field of view, using substrates and grating media to redirect and expand image light effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional optical systems are used without angular filters, then the structure is simpler and components are fewer, but distracting flares are produced by high-angle ambient light
Solution Approach 1:
An angular filter is introduced as an intermediary component between the waveguide and the environment. This filter selectively blocks high-angle ambient light that would otherwise cause distracting flares, while allowing low-angle light within the field of view to pass through. The angular filter acts as a mediator that resolves the contradiction by filtering harmful light angles without blocking useful light.
Solution Approach 2:
The angular filter is positioned specifically at regions where flares would be generated, such as near the eye box or at the waveguide input. This localized placement ensures that flare mitigation occurs precisely where needed, rather than requiring the entire optical system to be modified. The filter applies selective quality control to specific spatial zones.
2Reliability
If angular filters are added to block flare-inducing light, then optical performance is improved, but the device becomes bulkier and more complex
Solution Approach 1:
The angular filter is implemented as a thin film or coating on the waveguide surface, rather than a bulky mechanical component. This thin-film approach provides effective angular filtering while adding minimal volume and weight to the device. The filter can be deposited directly onto the waveguide substrate, creating a compact integrated structure.
Solution Approach 2:
The angular filter is merged with the waveguide structure itself, forming an integrated component rather than a separate additive element. The filter substrate is coupled to the waveguide, creating a unified optical element that performs both light guidance and angular filtering functions. This merging reduces overall device volume compared to using separate filter components.
3Adaptability or versatility
If the field of view is made wider, then more real-world light is captured, but more high-angle light enters and causes flares
Solution Approach 1:
The angular filter serves as a mediator that decouples the relationship between field of view width and flare generation. By filtering based on light angle rather than blocking the entire periphery, the angular filter allows the field of view to be widened while preventing high-angle light from causing flares. This enables independent optimization of field of view and flare control.
Solution Approach 2:
The angular filter changes the angular parameter distribution of incoming light by blocking high-angle components while transmitting low-angle components. This parameter filtering allows the system to accept a wider range of light directions (wider field of view) while maintaining control over the harmful high-angle light that causes flares.
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 solution effectively minimizes distracting flares while maintaining a wide field of view and optimizing optical performance, ensuring clear and seamless image presentation.
Implementation Method 1
The angular filter may include angled absorbers in a 'venetian blinds' configuration
Implementation Method 2
The angular filter may include diffractive grating structures in the filter substrate
Implementation Method 3
a waveguide having a grating medium interposed between first and second waveguide substrates
Implementation Method 4
a cross coupler on the waveguide and configured to diffract the display light towards the output coupler
Data Source
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AI summary
An electronic device may include a display with an optical combiner. The combiner may include a waveguide and a cross coupler on the waveguide. The combiner may redirect light from a display module to an eye box while passing world light to the eye box within a field of view. The cross coupler may include surface relief gratings or other broadband gratings. The combiner may include an angular filter that at least partially overlaps the cross coupler. The cross coupler may include surface relief grating structures or other broadband gratings. The angular filter may include angled absorbers or diffractive gratings. The angular filter may prevent world light that would otherwise produce distracting flares at the eye box (e.g., world light incident on the waveguide outside the field of view such as high-incident angle light from an overhead light source) from passing to the cross coupler.