Apple Inc.

Omnivision Technologies, Inc.

Tufts University

Jian Guo

Savas Gider

John Greer Elias

Tiejun Dai

Guangwu Duan

Manoj K Bhattacharyya

Rui Wang

Henry Hung Yang

Peter George Hartwell

Chaitanya Mudivarthi

Sameer Sonkusale

Harish Venkataraman

Sean M Gordoni

Hong Pan

Christopher E Balcells

A hybrid Hall/MR magnetometer with self-calibration includes a circuit coupled to a magnetometer and configured to determine whether the magnetometer is to operate in a sensing operation mode or a self-calibration operation mode. The magnetometer comprises a Hall sensor and MR sensor coupled to the circuit. In accordance with determining a sensing operation mode, the Hall sensor is turned off and the MR sensor is turned on; and an external magnetic field is measured using the MR sensor. The magnetic field measurement is calibrated using a MR sensor bias error determined in a self-calibration operation mode of the sensor.

Hybrid Hall-effect/Magnetoresistance (MR) magnetometer with self-calibration

Disclosed is a compact, multi-user magnetic tracking system. In an embodiment, a compactness is achieved by using a single coil and inertial sensors at the transmitter and magnetometers and inertial sensors at the receiver for sensing the magnetic field generated by the single coil and for determining a position and attitude of the receiver relative to the transmitter. The transmitter and receiver each include a wireless transceiver for exchanging clock synchronization data and sending transmitter attitude data to the receiver. In another embodiment, frequency or time division multiplexing is used to differentiate between multiple users of the multi-user magnetic tracking system.

Compact, multi-user, multi-level, multi-target magnetic tracking system

Systems, methods, apparatuses and non-transitory, computer-readable mediums are disclosed for short-range position tracking using a stationary magnetic field gradient. In an embodiment, a method comprises: obtaining, by a sensing array of a device worn or held by a user in an environment, a measurement of a stationary magnetic field generated by a magnetic source in the environment, the stationary magnetic field being independent of an ambient magnetic field in the environment; determining based on the measurement, a change in the magnetic field over time; determining based on the measurement, a change in the magnetic field over distance; obtaining, by the processor, a rotation angle of the device; determining a velocity of the device based on the change in the magnetic field over time, the change in the magnetic field over distance and the rotation angle of the device; and integrating the velocity to obtain a position of the device.

Short-range position tracking using stationary magnetic field gradient

Disclosed is a compact 3-axis coil design for a magnetic tracking system. In an embodiment, compactness is achieved by using a 3-axis coil in the transmitter that includes a scaffold design with a side surface having a curved groove for guiding one or more windings of a z-axis coil, such that the physical geometry is not increased.

Compact 3-axis coil design for magnetic tracking

A configurable AC/DC readout architecture that can be operated in an AC measurement mode or a DC measurement mode is disclosed. The configurable AC/DC architecture can utilize shared circuitry such as amplifiers and analog-to-digital converters (ADCs). The configurable AC/DC readout can be used other sensor configurations where both AC and DC measurement signals can captured and require readout and conversion to digital signals. The configurable AC/DC readout architecture can include a filter configured to filter out a DC signal component in the AC measurement mode. The configurable AC/DC readout architecture can include a bypass witch to bypass the filter in the DC measurement mode. A programmable gain amplifier can adjust the signal amplitude of DC or AC signals to allow use of a shared analog-to-digital converter.

Configurable AC/DC sensor readout architecture

Magnetic sensing technology can be used to detect changes, or disturbances (e.g., changes in magnetic field strength), in magnetic fields and can be used to measure the precise location/positioning of an electronic device in proximity to a magnetic source. In order to avoid interference by earth's static magnetic field, a modulated magnetic field can be used for magnetic based proximity sensing. Received modulated magnetic field signals can be demodulated to determine a received magnetic field strength. A drive current of a magnetic transmitter coil can be varied to maintain the detected magnetic field strength at a target value or within a desirable range. The drive current can also be varied to remain below a burnout current level that can cause damage to the transmitter coil.

Dynamic current control of a transmitter for magnetic proximity sensing

Systems, methods and non-transitory, computer-readable mediums are disclosed for a magnetic field sensor array with electromagnetic interference cancellation. In an embodiment, a circuit comprises: a first circuit configured for obtaining an output signal from a magnetic field sensor array in an electronic system, the output signal representing a magnetic field present in the electronic system, the magnetic field including electromagnetic interference (EMI) generated by one or more magnetic aggressors of the electronic system; and a second circuit configured to apply one or more magnetic field gradient heat maps to the output signal.

Magnetic field sensor array with electromagnetic interference cancellation

Magnetic sensing technology can be used to detect changes, or disturbances (e.g., changes in magnetic field strength), in magnetic fields and can be used to measure the precise location/positioning of an electronic device in proximity to a magnetic source. In order to avoid interference by earth's static magnetic field, a modulated magnetic field can be used for magnetic based proximity sensing. Received modulated magnetic field signals can be demodulated to determine proximity of the sensor to the source of the modulated magnetic field. Devices such as gloves or devices with fingertip nodes based on receiving modulated magnetic fields can be used to detect user hand position.

Magnetic sensor based proximity sensing

Disclosed is a magnetometer architecture that uses a separate shield to minimize cross-axis sensitivity with low impact on main axis sensitivity. In an embodiment, a magnetometer with cross-axis shielding comprises: a ring shield; a magnetic yoke disposed within the ring shield; and one or more magnetic field sensors disposed between the ring shield and the magnetic yoke, the magnetic field sensors positioned relative to the ring shield and the magnetic yoke such that flux induced by a magnetic field is absorbed in a cross-axis direction of the magnetometer.

Cross-axis shield for out-of-plane magnetometer

Systems, methods, apparatuses and non-transitory computer-readable mediums are disclosed for a self-calibrating system architecture for magnetic distortion compensation. In an embodiment, an electronic system comprises: a magnetometer; a plurality of spaced-apart calibration coils proximate to the magnetometer; first circuitry configured to excite the calibration coils during a calibration phase of the electronic system; second circuitry configured to measure a first magnetic field vector in a vicinity of the magnetometer that is generated by the excited calibration coils; third circuitry configured to: generate sensitivity values based on the first magnetic field vector measurement and a baseline magnetic field vector; and a storage device configured for storing the sensitivity values.

Self-calibrating system architecture for magnetic distortion compensation

An electronic device is disclosed. In some examples, a crown comprising a housing can be operatively coupled to a body of the electronic device, and configured to rotate in a first direction with respect to the body of the electronic device in response to a mechanical input provided by the user. A rotating member can be disposed at least partially inside the crown housing and configured to rotate in the first direction in response to the mechanical input. A first magnetic sensing cell can be attached to the rotating member at a first location of the rotating member and can be electrically connected to an electronic circuit. A magnet can be configured to remain stationary with respect to the body of the electronic device. The electronic circuit can be configured to generate a first signal corresponding to a rotational position of the crown with respect to the body of the electronic device.

Magnetic sensor array for crown rotation

A high dynamic range magnetometer architecture and method are disclosed. In an embodiment, a magnetometer sensor comprises: a variable magnetic gain stage including a plurality of selectable signal gain paths, each signal gain path including a magnetic sensor and a magnetic flux concentrator, and for each signal gain path the magnetic flux concentrator being positioned a different distance from the magnetic flux concentrator to provide a different magnetic gain for the signal gain path; a variable magnetic sensing stage coupled to the variable magnetic gain stage, the variable magnetic sensing stage operable to provide variable magnetic sensing to each signal gain path; and a gain control stage coupled to the variable magnetic sensing stage, the gain control stage operable to select one of the signal gain paths and to provide signal conditioning to the selected signal gain path.

High dynamic range magnetometer architecture

An array of resistive sensor circuits may be used to gather sensor data. Each resistive sensor circuit may have a resistive sensor and an associated switch. Row decoder circuitry may supply rows of the sensor circuits with control signals on row lines. Capacitors associated with respective columns of the array may be provided with an initialization voltage. The control signals on the row lines may be used to turn on the switches in a selected row of the resistive sensor circuits and thereby discharge the capacitors through the resistive sensors of that row. Comparators may have first inputs coupled to the capacitors and second inputs that receive a reference voltage. A column readout circuit may have memory and processing circuitry that receives count values from a counter and that stores the count values in response to toggling output signals from the comparators.

Electronic device with resistive sensor array

Systems, methods, and computer-readable media for calibrating the offset of a magnetometer assembly with reduced power are provided. In one embodiment, a method for operating an assembly may include determining a difference between a current signal measurement output component of a first magnetometer sensor and a previous signal measurement output component of the first magnetometer sensor, comparing the determined difference with a current threshold value, and generating an assembly output based on the comparing, where, when the determined difference is greater than the current threshold value, the generating may include providing a first assembly output using a current offset output component of a second magnetometer sensor, and, when the determined difference is less than the current threshold value, the generating may include providing a second assembly output using a previous offset output component of the second magnetometer sensor.

Low-power magnetometer assemblies with high offset stability

A compensation coil placed at least partially underneath a magnetic field sensor package in an electronic system provides attenuation of electromagnetic interference (EMI). In an embodiment, the compensation coil attenuates EMI in a frequency band which overlaps with an operating frequency band of the magnetic field sensor. This allows the magnetic field sensor to make accurate magnetic field measurements in the presence of system level alternating current (AC) EMI. In an embodiment, a system comprises: a magnetic field sensor; a compensation coil placed at least partially underneath the magnetic field sensor; and a reverse current generator coupled to the compensation coil and to a power supply that is coupled to an electromagnetic interference (EMI) source, the reverse current generator operable to generate a reverse current in the compensation coil to generate a counter magnetic field for compensating the EMI.

Growing community of inventors

Milpitas, CA, United States of America

Jian Guo