Hybrid Head Tracking System Sensor Fusion
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Solution Overview
Problem
Existing head tracking systems face issues with unavailable data or elevated errors, particularly when relying on inertial measurements alone, leading to potential hazards due to accumulating errors, and when optical measurements are unavailable.
Innovation Solution
A hybrid head tracking system that combines optical and inertial sensors to determine head position and orientation, using a processor to validate tracking states and compare measurements to ensure safe operation, and employs multiple inertial sensors for redundancy and error mitigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inertial measurements are used alone for head tracking, then the system can operate without optical references, but errors accumulate over time leading to degraded tracking accuracy
Solution Approach 1:
The patent combines inertial measurements from IMUs with optical measurements from tracking systems into a unified head tracking solution. The system integrates data from both sensor types, using optical measurements when available for high accuracy and inertial measurements as a supplement or fallback, thereby resolving the contradiction between operational independence and tracking accuracy
Solution Approach 2:
The system continuously monitors the validity and quality of both optical and inertial measurements, using feedback mechanisms to determine when to rely on one sensor type over the other. When optical tracking is unavailable or degraded, the system transitions to inertial-only mode with appropriate error compensation, maintaining accuracy while preserving operational independence
2Measurement precision
If optical measurements are used for head tracking, then high accuracy can be achieved, but the system becomes unavailable when no optical solution can be realised
Solution Approach 1:
The system prepares for optical tracking failures by having inertial sensors ready to take over. The inertial measurement units continuously track head orientation and position, providing a cushion against complete system failure when optical tracking becomes unavailable due to environmental factors or occlusions
Solution Approach 2:
The system dynamically switches between optical and inertial tracking modes based on real-time conditions. When optical measurements are valid and reliable, the system uses them for high accuracy; when they become unavailable, the system transitions to inertial measurements, ensuring continuous operation and maintaining reliability while preserving the ability to achieve high accuracy when conditions permit
3Reliability
If multiple inertial sensors are used for redundancy, then system reliability improves, but device complexity increases
Solution Approach 1:
The system segments the sensing function by using multiple independent inertial measurement units, each capable of providing complete head tracking data. This segmentation provides redundancy without requiring a single complex sensor system, as each IMU is a relatively simple standalone unit that can operate independently or in conjunction with others
Data Source
AI summary
A head tracking system HTS, configured to determine a head position and a head orientation of a user to which display images are configured to align with the outside world scene and are configured to be presented, the HTS comprising: one or more optical sensors generating an optical measurement; and a number of inertial sensors generating an inertial measurement; a processor configured to determine the head position and the head orientation from one or both of the one or more optical sensors and the number of inertial sensors and configured to: determine an optical tracking state from the optical measurement and an inertial tracking state from the inertial measurement; when both the optical tracking state and the inertial tracking state are valid, flagging/asserting HTS operation as normal; when both the optical tracking state and the inertial tracking state are invalid, flagging/asserting HTS failure; when the optical tracking state and the inertial tracking state are valid comparing the optical measurement and the inertial measurement to determine if the HTS can operate safely based on a predetermined tracking performance required by the system.