Scanning Mirror Input Coupler for Wide Field of View Waveguides
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Solution Overview
Problem
Designing virtual and augmented reality headsets with near-eye displays that provide a large field of view without increasing the size or power consumption of the display module is challenging, as existing solutions often result in unsightly, bulky components with suboptimal optical performance.
Innovation Solution
The use of a scanning mirror or liquid crystal steering element in conjunction with a prism and waveguide optical system, which redirects and expands the field of view by rotating over various orientations to fill the eye box with image light, allowing for a larger effective field of view without increasing the display module's size or power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display module size is increased to provide a larger field of view, then the field of view is improved, but the device becomes bulky and unsightly
Solution Approach 1:
The patent introduces a scanning mirror that adds a temporal dimension to the optical path. Instead of providing all field of view angles simultaneously through a large display module, the system scans through different angles over time, effectively trading spatial dimension for temporal dimension to achieve large field of view with compact display hardware.
Solution Approach 2:
The scanning mirror dynamically changes its orientation angle to direct light from the compact display module to different portions of the eye box. This dynamic angular adjustment allows a single compact display to serve multiple field of view positions sequentially, resolving the contradiction between display size and field of view.
2Adaptability or versatility
If the display module power consumption is increased to provide a larger field of view, then the field of view is improved, but the energy efficiency deteriorates
Solution Approach 1:
The scanning mirror dynamically directs light to different eye box portions sequentially, allowing the display module to operate at lower power while still providing comprehensive field of view coverage over time. The dynamic scanning approach reduces the instantaneous light output requirement compared to illuminating the entire field of view simultaneously.
Solution Approach 2:
The system employs periodic scanning motion of the mirror to cycle through different field of view portions. This periodic action allows the display module to refresh the entire field of view content over multiple scan cycles at reduced power consumption, rather than maintaining continuous high-level illumination across all angles simultaneously.
3Adaptability or versatility
If a scanning mirror is added to expand the field of view, then the field of view is improved, but the device complexity increases
Solution Approach 1:
The scanning mirror serves multiple functions: it expands the effective field of view, enables gaze tracking capability, and allows a single compact display to replace multiple larger displays. This multi-functionality justifies the added component by providing several capabilities from a single element.
Solution Approach 2:
The scanning mirror acts as an intermediary between the compact display module and the eye box, mediating the light path to achieve field of view expansion. This intermediary approach allows the display and eye box to remain compact while the mirror handles the complexity of angular redirection, isolating the complexity to a single controllable component.
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 enables a wider field of view for the user while maintaining compact and energy-efficient display module design, effectively addressing the limitations of existing technologies by dynamically adjusting the orientation of the input coupler to direct image light to specific portions of the eye box.
Implementation Method 1
The scanning mirror may reflect the image light into the waveguide through the prism while being rotated over a set of orientations
Implementation Method 2
The input coupler may redirect light from the display module so that the light propagates in the waveguide towards the output coupler
Implementation Method 3
The output coupler may include diffractive grating structures such as volume holograms in the waveguide
Implementation Method 4
The prism may have a tilted surface oriented at a non-parallel angle with respect to a lateral surface of the waveguide
Data Source
AI summary
An electronic device may include a display module that generates light and an optical system that redirects the light towards an eye box. The system may include an input coupler that couples the light into the waveguide. The input coupler may include a prism on the waveguide and a scanning mirror. The scanning mirror may receive the light through the waveguide and the prism and may reflect the light into the waveguide through the prism while being rotated over a set of orientations. The scanning mirror may fill a relatively large field of view eye box with a corresponding image frame despite the limited field of view of the image light produced by the display module. The orientation of the scanning mirror may be adjusted based on gaze tracking data.