LED Emitter Timing Alignment for AR Tracking
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Solution Overview
Problem
Artificial reality systems face challenges in efficiently tracking peripheral devices due to synchronization issues between internal clocks and limited direct communication, leading to increased power consumption and computational resource expenditure.
Innovation Solution
The system employs image capture devices to capture small exposure periods of image data, synchronizing emitter pulsing on peripheral devices with image capture exposure windows, using timestamp information and visual search techniques to refine alignment and reduce resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system continuously captures image data and processes emitter detection without synchronization, then tracking accuracy is maintained, but power consumption and computational resource expenditure increase significantly
Solution Approach 1:
The system implements periodic emitter pulsing at specific frequencies that align with image capture exposure windows. Emitters pulse only during designated time intervals rather than continuously, and image capture occurs only during synchronized exposure windows. This periodic action maintains tracking reliability while dramatically reducing power consumption and computational resource usage by eliminating continuous operation.
2Loss of time
If the system uses small exposure windows for image capture to reduce processing time, then power consumption decreases, but the difficulty of detecting and measuring active emitters increases
Solution Approach 1:
The system performs preliminary synchronization by calculating and establishing the temporal relationship between emitter pulsing intervals and image capture exposure windows before actual tracking begins. The waveform controller pre-configures emitter pulsing timing based on anticipated exposure window locations. This preliminary action ensures that when the small exposure windows occur, emitters are guaranteed to be active during those intervals, making detection straightforward despite the brief duration.
3Device complexity
If the system relies solely on timestamp information from wireless communication for synchronization, then device complexity is reduced, but measurement precision of timing alignment is insufficient
Solution Approach 1:
The system uses timestamp information exchanged via wireless communication as an intermediary to establish initial synchronization between the peripheral device and HMD. These timestamps provide a coarse timing reference that guides the waveform controller in configuring emitter pulsing intervals. This intermediary approach enables synchronization without requiring complex direct communication protocols, while still achieving sufficient timing alignment precision for the application.
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 approach reduces power consumption and computational resources while maintaining accurate tracking of peripheral devices, even with loosely synchronized clocks and limited direct communication protocols.
Implementation Method 1
the peripheral devices may be keyboards, mice, controllers, and/or other devices that periodically pulse a constellation of emitters (e.g., infrared LEDs) located at predetermined positions on the peripheral device
Data Source
AI summary
An artificial reality system is described that includes a head mounted display (HMD) configured to output artificial reality content and image capture devices configured to capture image data of a peripheral device positioned within a physical environment, where the image data comprises a plurality of successive image frames and the image capture devices capture each image frame during an exposure window of a respective frame period. The artificial reality system further includes a waveform controller configured to program a pulse waveform for a plurality of emitters on a peripheral device, wherein the pulse waveform specifies a pattern by which the plurality of emitters emit light and a pulse emitter synchronizer configured to synchronize the emission of light by the plurality of emitters according to the pulse waveform with the exposure window over the successive image frames from the image capture devices.