EM Head Tracking With Multi-Frequency Noise Cancellation
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Solution Overview
Problem
Current localization systems in augmented reality (AR) and virtual reality (VR) devices face challenges in achieving high accuracy and low latency, which are essential for providing a realistic and immersive experience.
Innovation Solution
The use of an electromagnetic (EM) tracking system, which includes an EM field emitter and sensor, allows for precise tracking of head pose and body gestures by analyzing the EM field sensed by the sensor. This system employs time division multiplexing (TDM) and dynamic frequency tuning to operate at multiple frequencies, and incorporates noise cancellation to reduce interference from audio speakers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic tracking system operates at multiple frequencies using TDM, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The electromagnetic tracking system segments the tracking function across multiple frequencies, with each frequency carrying specific positional or orientational information. The TDM circuit divides the operation into time slots for different frequencies, allowing precise localization through frequency-separated measurements while managing system complexity through structured segmentation.
Solution Approach 2:
The system dynamically switches between multiple frequencies using time division multiplexing, adapting the operating frequency based on tracking requirements. This dynamic frequency switching enables the system to optimize measurement precision for different spatial conditions while maintaining manageable complexity through controlled temporal separation of frequency operations.
2Volume of moving object
If voltage gain control is implemented in the transmitter, then sensor size is reduced, but manufacturing precision requirements increase
Solution Approach 1:
Instead of implementing voltage gain control in the sensor (receiver), the system inverts the control function to the transmitter. This allows the larger transmitter to handle the complex voltage regulation and gain control, enabling the sensor to be miniaturized without compromising measurement capability, as the precision control is performed at the source rather than at the small sensor.
3Reliability
If noise cancellation is implemented in the sensor, then reliability is improved, but device complexity increases
Solution Approach 1:
The system introduces noise cancellation as an intermediary function within the sensor, where reference signals from the transmitter are used to identify and subtract electromagnetic interference from audio speakers. This mediator approach improves tracking reliability by actively compensating for environmental noise while adding only minimal complexity through the use of available reference signals and subtraction algorithms.
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
The EM tracking system achieves high precision localization with minimal latency, enabling accurate rendering of virtual content in AR systems and improving user interaction with virtual objects.
Implementation Method 1
an EM emitter and the head-mounted AR device can include an EM sensor. In some implementations, the EM emitter generates an EM field that can be sensed by the EM sensor
Implementation Method 2
The EM emitter and sensor may utilize time division multiplexing (TDM) or dynamic frequency tuning that allows the tracking system to operate at multiple frequencies
Implementation Method 3
An embodiment of an electromagnetic (EM) tracking system comprises an EM field emitter comprising an automatic gain control (AGC) circuit and a transmitter coil; and an EM sensor without an AGC circuit
Implementation Method 4
The EM sensor can implement noise cancellation to reduce the level of EM interference generated by nearby audio speakers
Data Source
AI summary
Head-mounted augmented reality (AR) devices can track pose of a wearer's head to provide a three-dimensional virtual representation of objects in the wearer's environment. An electromagnetic (EM) tracking system can track head or body pose. A handheld user input device can include an EM emitter that generates an EM field, and the head-mounted AR device can include an EM sensor that senses the EM field. EM information from the sensor can be analyzed to determine location and/or orientation of the sensor and thereby the wearer's pose. The EM emitter and sensor may utilize time division multiplexing (TDM) or dynamic frequency tuning to operate at multiple frequencies. Voltage gain control may be implemented in the transmitter, rather than the sensor, allowing smaller and lighter weight sensor designs. The EM sensor can implement noise cancellation to reduce the level of EM interference generated by nearby audio speakers.