Calibrating a magnetic transmitter
Inventors
Schneider, Mark Robert • Robertson, Charles • Durfee, Joseph Bruce
Assignees
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Publication Number
US-10883812-B2
Publication Date
2021-01-05
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 provides a calibration device with a plurality of magnetic sensors positioned at the calibration device, where the plurality of magnetic sensors define a space. A controller is configured to be positioned in the space defined by the plurality of magnetic sensors and the controller includes a first magnetic transmitter. The controller causes the first magnetic transmitter to generate a plurality of magnetic fields and the plurality of magnetic sensors output signals based on characteristics of the plurality of magnetic fields received at the plurality of magnetic sensors.
The system calculates, based on the signals, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the controller and the first magnetic transmitter. The invention determines 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, and compares calculated positions and orientations to the known positions and orientations.
The invention further causes a second magnetic transmitter of a reference controller to generate a second plurality of magnetic fields and receives second signals from the plurality of magnetic sensors based on characteristics of the second plurality of magnetic fields. Based on the second signals, the system calculates positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the second magnetic transmitter, and based on the comparing determines one or more calibration correction factors for one or more of the plurality of magnetic sensors.
Claims Coverage
The partial claims provided include two independent claims. Across these independent claims, the inventive content is centered on calibration of magnetic sensors and calibration correction factors by generating magnetic fields with a controller magnetic transmitter, calculating sensor positions and orientations from sensor signals, comparing the calculated positions and orientations to known positions and orientations with threshold limits, and using a reference controller/transmitter for comparative calculation.
Calibration device with sensor-defined space and controller magnetic transmitter
A calibration device comprising a plurality of magnetic sensors positioned at the calibration device that define a space, and a controller configured to be positioned in the space and including a first magnetic transmitter.
Measure sensor position and orientation from magnetic fields and signals
Processors cause the first magnetic transmitter to generate a plurality of magnetic fields; receive signals from the plurality of magnetic sensors based on characteristics of the plurality of magnetic fields received at the plurality of magnetic sensors; and calculate, based on the signals, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the controller and the first magnetic transmitter.
Threshold-limit check against known positions and orientations
Processors 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.
Reference controller magnetic fields for comparative calculation
Processors cause a second magnetic transmitter of a reference controller to generate a second plurality of magnetic fields; receive second signals from the plurality of magnetic sensors based on characteristics of the second plurality of magnetic fields received at the plurality of magnetic sensors; and calculate, based on the second signals, positions and orientations of the plurality of magnetic sensors relative to a position and orientation of the second magnetic transmitter.
Calibration correction factors based on comparing to known positions and orientations
Processors compare the calculated positions and orientations of the plurality of magnetic sensors to the known positions and orientations of the plurality of magnetic sensors and, based on the comparing, determine one or more calibration correction factors for one or more of the plurality of magnetic sensors.
System integrating controller, calibration device housing and mount
A system comprising a controller including a first magnetic transmitter, a calibration device comprising a housing, a plurality of magnetic sensors positioned at the housing, and a mount positioned inside the housing configured to accept the controller, and a computer system in communication with the calibration device.
Computer-system execution of calculation, threshold determination, comparison and correction factors
The computer system causes the first magnetic transmitter to generate a plurality of magnetic fields; receives signals from the plurality of magnetic sensors based on characteristics of the plurality of magnetic fields; calculates positions and orientations relative to a position and orientation of the controller and the first magnetic transmitter; determines whether the calculated positions and orientations are within one or more threshold limits of known positions and orientations; causes a second magnetic transmitter of a reference controller to generate a second plurality of magnetic fields; receives second signals; calculates positions and orientations relative to a position and orientation of the second magnetic transmitter; compares the calculated positions and orientations to the known positions and orientations; and based on the comparing determines one or more calibration correction factors.
Mount-fixed controller and transmitter configuration inside sensor housing
The system includes a mount configured to keep the controller and magnetic transmitter fixed in a set position and orientation relative to the plurality of sensors.
Ar/vr controller context for the controller
The system specifies that its controller is configured to be used in either an Augmented Reality (AR) system or a Virtual Reality (VR) system.
Multiplexed serial acquisition of sensor signals
The system includes a multiplexing switch that enables a computer system to receive signals from multiple magnetic sensors in series.
Across the independent claims, the core claim coverage is calibration of magnetic sensors and determination of calibration correction factors by generating magnetic fields with a controller magnetic transmitter, calculating sensor positions and orientations from sensor signals, evaluating the calculated results against known positions and orientations with threshold limits, and performing comparative calculation using a reference controller/transmitter.
Stated Advantages
Not explicitly described in patent.
Documented Applications
Target use in AR/VR/EMT systems, including an example electromagnetic tracking (EMT) architecture and use with an HMD head-mounted display and gaming controllers.
Calibration of an electromagnetic tracking magnetic transmitter using dedicated calibration for multiple DUT transmitters and optional self-calibration of the calibration device using a reference controller/transmitter.
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