Calibrating a magnetic transmitter
Inventors
Schneider, Mark Robert • Robertson, Charles • Durfee, Joseph Bruce
Assignees
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Publication Number
US-11604057-B2
Publication Date
2023-03-14
Expiration Date
Abstract
A calibration device comprising: a plurality of magnetic sensors positioned at the calibration device, the plurality of magnetic sensors defining a space; a controller configured to be positioned in the space defined by the plurality of magnetic sensors, wherein the controller includes a magnetic transmitter; and one or more processors configured to: cause the magnetic transmitter to generate magnetic fields; receive signals from the plurality of magnetic sensors that are based on characteristics of the magnetic fields received at the plurality of magnetic sensors; calculate, based on the signals received from the plurality of magnetic sensors, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the magnetic transmitter; and determine whether the calculated positions and orientations of the plurality of magnetic sensors are within one or more threshold limits of known positions and orientations of the plurality of magnetic sensors.
Core Innovation
The invention relates to calibrating a magnetic transmitter using a dedicated calibration device that includes a plurality of sensors positioned at the calibration device, thereby defining a space. A reference controller is positioned in the space and includes a first transmitter, while a controller is positioned in the space and includes a second transmitter. The first transmitter generates a first plurality of electromagnetic fields, and the plurality of sensors sense electromagnetic-field characteristics to enable position-and-orientation calculations relative to the first transmitter.
The calculated positions and orientations are compared to known positions and orientations of the plurality of sensors, and one or more first calibration correction factors are determined based on the comparing. The calibration device further causes the second transmitter of the controller to generate a second plurality of electromagnetic fields, and the plurality of sensors sense characteristics of the second plurality of electromagnetic fields to calculate positions and orientations relative to the second transmitter.
The calculated positions and orientations for the second transmitter are compared to known positions and orientations, and one or more second calibration correction factors for the second transmitter are determined based on the comparing. The described calibration device workflow supports calibrating both a transmitter of a controller under test and the calibration device itself, using a reference calibrated transmitter, while using known positions for comparison and one or more threshold limits to decide whether results meet threshold limits.
Calibration correction factors may be stored or created as a calibration file and then applied to one or more sensors and/or applied to or flashed to one or more transmitters, including calibration algorithm support features such as multiplexed sensor readout via a multiplexing switch.
Claims Coverage
One independent claim is identified. The claim covers a two-transmitter calibration arrangement, electromagnetic-field-based position-and-orientation calculation using a plurality of sensors at known positions, comparison to known positions and orientations, and determination of calibration correction factors for both sensor-related correction factors and transmitter-related correction factors.
Dual-transmitter calibration with reference and controller under test
A reference controller including a first transmitter and a controller including a second transmitter are positioned within a space defined by a plurality of sensors, and the system calibrates the sensors relative to the first transmitter and calibrates the second transmitter relative to the sensor measurements.
Electromagnetic-field sensing to calculate sensor positions and orientations relative to each transmitter
Based on characteristics of a first plurality of electromagnetic fields sensed by the plurality of sensors, positions and orientations of the plurality of sensors are calculated relative to the first transmitter, and based on characteristics of a second plurality of electromagnetic fields sensed by the plurality of sensors, positions and orientations are calculated relative to the second transmitter.
Comparison to known sensor positions and orientations and determination of calibration correction factors
The calculated positions and orientations of the plurality of sensors relative to the first transmitter and the second transmitter are compared to known positions and orientations, and one or more first calibration correction factors and one or more second calibration correction factors are determined.
Magnetic-field embodiment using magnetic sensors and magnetic transmitters
The electromagnetic fields are magnetic fields, using magnetic sensors as the plurality of sensors and magnetic transmitters as the transmitters.
Calibration-file creation and application of calibration correction factors
Calibration files contain calibration correction factors and are applied to one or more of a plurality of sensors.
Multiplexed sequential sensor signal acquisition via multiplexing switch
A multiplexing switch is used to receive sensor signals sequentially from a plurality of sensors.
Threshold-limit handling for calibration correction-factor determination
One or more threshold limits are set to zero so that second calibration correction factors for a second transmitter are determined without regard to differences between measured and known sensor positions and orientations.
Controller usability in augmented reality and virtual reality systems
The controller is usable in either an Augmented Reality system or a Virtual Reality system.
The claim coverage centers on electromagnetic-field sensing to calculate positions and orientations of sensors relative to a reference transmitter and a transmitter under test, comparison to known positions and orientations, and determination of calibration correction factors. The referenced refinements further specify magnetic-field implementation, calibration-file handling, multiplexed sequential acquisition, threshold-limit behavior, and AR/VR controller usability.
Stated Advantages
Faster calibration without moving sensor parts.
Accurate calibration.
Documented Applications
Calibration of a magnetic transmitter in an electromagnetic tracking system/tracking volume context.
Use with Augmented Reality systems and Virtual Reality systems.
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