Waveguide Display Air Cushion for Impact Protection
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Solution Overview
Problem
External forces such as impacts or drop events can cause optical components in electronic device displays to become misaligned or damaged, leading to performance issues.
Innovation Solution
The electronic device includes a display with a projector and a waveguide, where the optics are mounted to the waveguide using a ring of adhesive that laterally surrounds an air cavity. A surface relief grating is mounted to the waveguide within the air cavity, and air flow channels are configured to constrain air flow out of the air cavity during external forces, forming an air cushion for optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optics are mounted directly to the waveguide without an air cavity, then the structural complexity is reduced and manufacturing is simplified, but the optical components become vulnerable to damage from external forces such as impacts or drops
Solution Approach 1:
An air cavity is introduced between the optics and waveguide before assembly, surrounded by a ring of adhesive. This air cavity acts as a cushion that absorbs and distributes external forces (impacts, drops) before they reach the optical components, protecting them from damage while maintaining a relatively simple overall structure.
2Reliability
If the air cavity is completely sealed, then the optical components are protected from environmental contaminants, but air pressure changes in the surrounding environment cannot equalize with the interior of the air cavity
Solution Approach 1:
The ring of adhesive surrounding the air cavity is designed with selective permeability or localized channels that allow air molecules to pass through at controlled rates. This creates different local properties: the adhesive ring permits slow air diffusion for pressure equalization while still providing barrier protection against larger contaminants, thus achieving both protection and pressure equilibrium.
3Reliability
If air flow channels are made highly restrictive to maintain air cushion during impacts, then protection during short-duration external forces is improved, but air pressure equalization during long-duration ambient pressure changes is hindered
Solution Approach 1:
The air flow channels in the ring of adhesive are designed with dynamic characteristics that adapt to different time scales. During short-duration impacts, the channels restrict rapid air outflow to maintain the air cushion. During long-duration ambient pressure changes, the same channels allow gradual air diffusion to equalize pressure. The adhesive material's viscoelastic properties or the channel geometry enables this time-dependent flow behavior.
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 helps maintain the volume and integrity of the air cavity during external forces, preventing damage to optical components and ensuring display performance.
Implementation Method 1
a waveguide that propagates the image light via total internal reflection
Implementation Method 2
The surface relief grating may diffract the image light out of the waveguide and towards an eye box
Data Source
AI summary
An electronic device may include a display having a waveguide that propagates image light and having optics such as a tint layer or bias lens mounted to the waveguide by a ring of adhesive. The ring may laterally surround an air cavity between the optics and the waveguide. A surface relief grating may be mounted to the waveguide within the air cavity. One or more air flow channels may be provided in the ring of adhesive and/or the optics to constrain air flow out of the air cavity on the time scale of a drop or impact event. This may configure the air cavity to maintain its volume during the event, effectively forming an air cushion for components in the air cavity. The air flow channels may pass air between the air cavity and the environment on the time scale of environmental ambient pressure changes.