Multi-pass Optical Relay for Compact WHUD Scanners
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Solution Overview
Problem
Wearable heads-up displays (WHUDs) face challenges due to the large size of optical scanners configured to scan light in two or more directions, which increases the form factor and can introduce pupil walk, affecting user experience and the appeal of the device.
Innovation Solution
The implementation of an optical scanner with a multi-pass optical relay, featuring two 1D scan mirrors and a polarizing beam splitter, helps reduce the size of the optical scanner while minimizing pupil walk by efficiently relaying light between the scan mirrors and the waveguide incoupler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If optical scanners are configured to scan received light in two or more directions, then the scanning capability is improved, but the size of the optical scanner increases
Solution Approach 1:
The optical scanner is divided into multiple specialized components: a first scan mirror for scanning in a first direction, a second scan mirror for scanning in a second direction, and a multi-pass optical relay system. This segmentation allows each component to be optimized for its specific function while working together to achieve two-directional scanning with reduced overall size compared to a single large scanner.
Solution Approach 2:
The patent introduces a multi-pass optical relay that folds the optical path through multiple reflections and passes. By utilizing multiple dimensions of the optical path (multiple passes through the same physical space), the system achieves two-directional scanning capability without requiring a proportionally larger physical footprint, thus reducing the volume of the optical scanner.
2Adaptability or versatility
If optical scanners are configured to scan received light in two or more directions, then the scanning capability is improved, but pupil walk is introduced
Solution Approach 1:
The multi-pass optical relay acts as an intermediary between the two scan mirrors and the waveguide. It carefully manages the optical path to ensure that light scanned in both directions is relayed to the correct location on the waveguide, minimizing pupil walk by maintaining precise optical alignment throughout the multi-pass journey.
Solution Approach 2:
The optical relay system is designed with specific optical elements positioned at precise locations to correct and minimize pupil walk at each stage of the optical path. By optimizing the local quality of light transmission and reflection at each pass, the system maintains high precision in the final image delivery to the user's eye.
3Volume of moving object
If the size of the optical scanner is reduced, then the form factor of WHUD is improved, but the complexity of the optical relay system increases
Solution Approach 1:
The multi-pass optical relay system performs multiple functions within a single integrated structure: it relays light from the first scan mirror to the second scan mirror, relays light from the second scan mirror to the waveguide, and simultaneously works to minimize pupil walk. This multi-functionality reduces the need for separate dedicated components, thereby reducing overall size while managing complexity.
Solution Approach 2:
The patent merges the functions of multiple optical relays into a single multi-pass optical relay system. By combining the light relay functions and pupil walk correction into one integrated system rather than separate components, the overall size of the optical scanner is reduced while the complexity is managed through unified design.
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 effectively reduces the size of the optical scanner, enhancing the form factor and fashion appeal of WHUDs, while also minimizing pupil walk, thereby improving user experience and the overall design of wearable displays.
Implementation Method 1
a polarizing beam splitter configured to reflect light having a first predetermined polarization toward the multi-pass optical relay and configured to transmit light having a second predetermined polarization toward the incoupler of the waveguide
Implementation Method 2
a quarter-wave plate configured to polarize the light scanned in the first and second directions such that the light scanned in the first and second directions has a second predetermined polarization
Implementation Method 3
The multi-pass optical relay can include a fold mirror configured to reflect light from a first lens of the multi-pass optical relay to a second lens of the multi-pass optical relay
Data Source
AI summary
A WHUD includes an optical scanner having two scan mirrors and a multi-pass optical relay. The first scan mirror receives light emitted from an optical engine representative of one or more images. The first scan mirror oscillates in a first direction such that the received light is scanned in a first direction and provides the light scanned in the first direction to a multi-pass optical relay. The multi-pass optical relay then relays the light to a second scan mirror. The second scan mirror is configured to oscillate in a second direction such that the relayed light is scanned in both the first and second directions. The second scan mirror then provides the light scanned in the first and second directions back to the multi-pass optical relay which relays the light scanned in the first and second directions to an incoupler of a waveguide.