Google Patent | Magnetometer-based gesture sensing with a wearable device

Patent: Magnetometer-based gesture sensing with a wearable device

Publication Number: 10146323

Publication Date: 2018-12-04

Applicants: Google LLC

Abstract

A wearable computing device such as a head-mounted display (HMD) may be equipped with a magnetometer for detecting presence and motion of a hand-wearable magnet (HWM). The HMD may analyze magnetic field measurements of the magnetometer to determine when the HWM moves within a threshold distance of the magnetometer, and may thereafter determine one or more patterns of motion of the HWM based the magnetic field measurements. The HMD may operate in a background detection state in order to determine a background magnetic field strength and to monitor for magnetic disturbances from the HWM. Upon occurrence of a trigger event corresponding to magnetic disturbance above a threshold level, the HMD may transition to operating in a gesture detection state in which it analyzes magnetometer measurements for correspondence with known gestures. Upon recognizing a known gesture, the HMD may carry out one or more actions based on the recognized known gesture.

BACKGROUND 

Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.

Various technologies can be utilized to provide users with electronic access to data and services in communication networks, as well as to support communication between users. For example, devices such as computers, telephones, and personal digital assistants (PDAs) can be used to exchange information over communication networks including the Internet. Communication networks may in turn provide communication paths and links to servers, which can host applications, content, and services that may be accessed or utilized by users via communication devices. The content can include text, video data, audio data and/or other types of data.

SUMMARY 

In one aspect, an example embodiment presented herein provides, in a wearable head-mounted display (HMD) having a processor and a magnetometer device with three orthogonal measurement axes, a computer-implemented method comprising: operating in a background detection state; while operating in the background detection state, carrying out functions of the background state including, measuring three orthogonal components of a background magnetic field with the magnetometer device, and determining a field magnitude of the background magnetic field from the three measured orthogonal components, determining an occurrence of a trigger from a hand-wearable magnet (HWM) at a time T.sub.start upon detecting a perturbation by the HWM of the determined field magnitude at least as large as a perturbation threshold, and upon determining the occurrence of the trigger, transitioning to operating in a gesture detection state; and while operating in the gesture detection state, carrying out functions of the gesture detection state including, tracking motion of the HWM by determining time derivatives of magnetic field strength measured by the magnetometer device along each of the three orthogonal measurement axes, making a comparison of the determined time derivatives with one or more sets of pre-determined time derivatives of magnetic field strength, each of the one or more sets being stored at the wearable HMD and each being associated with a respective known gesture, upon matching the determined time derivatives with a particular set of the one or more sets based on the comparison, identifying the respective known gesture associated with the particular set, and transitioning to operating in the background detection state upon both of, measuring the magnitude perturbation by the HWM of the determined field magnitude to be less than the perturbation threshold, and determining an expiration of a time interval W that begins at T.sub.start.

In another aspect, an example embodiment presented herein provides a wearable head-mount display (HMD) comprising: a processor; memory; a magnetometer device with three orthogonal measurement axes; means for operating in a background detection state, wherein operating in the background detection state comprises carrying out functions of the background state including, measuring three orthogonal components of a background magnetic field with the magnetometer device, and determining a field magnitude of the background magnetic field from the three measured orthogonal components, determining an occurrence of a trigger from a hand-wearable magnet (HWM) at a time T.sub.start upon detecting a perturbation by the HWM of the determined field magnitude at least as large as a perturbation threshold, and upon determining the occurrence of the trigger, transitioning to operating in a gesture detection state; and means for operating in the gesture detection state, wherein operating in the gesture detection state comprises carrying out functions of the gesture detection state including, tracking motion of the HWM by determining time derivatives of magnetic field strength measured by the magnetometer device along each of the three orthogonal measurement axes, making a comparison of the determined time derivatives with one or more sets of pre-determined time derivatives of magnetic field strength, wherein each of the one or more sets is stored at the wearable HMD and each is associated with a respective known gesture, upon matching the determined time derivatives with a particular set of the one or more sets based on the comparison, identifying the respective known gesture associated with the particular set, and transitioning to operating in the background detection state upon both of, measuring the magnitude perturbation by the HWM of the determined field magnitude to be less than the perturbation threshold, and determining an expiration of a time interval W that begins at T.sub.start.

In still another aspect, an example embodiment presented herein provides a nontransitory computer-readable medium having instructions stored thereon that, upon execution by one or more processors of a wearable head-mounted display (HMD), cause the wearable HMD to carry out operations comprising: operating in a background detection state; while operating in the background detection state, carrying out functions of the background state including, measuring three orthogonal components of a background magnetic field using three orthogonal measurement axes of magnetometer device of the wearable HMD, and determining a field magnitude of the background magnetic field from the three measured orthogonal components, determining an occurrence of a trigger from a hand-wearable magnet (HWM) at a time T.sub.start upon detecting a perturbation by the HWM of the determined field magnitude at least as large as a perturbation threshold, and upon determining the occurrence of the trigger, transitioning to operating in a gesture detection state; and while operating in the gesture detection state, carrying out functions of the gesture detection state including, tracking motion of the HWM by determining time derivatives of magnetic field strength measured by the magnetometer device along each of the three orthogonal measurement axes, making a comparison of the determined time derivatives with one or more sets of pre-determined time derivatives of magnetic field strength, wherein each of the one or more sets is configured to be stored at the wearable HMD and each is associated with a respective known gesture, upon matching the determined time derivatives with a particular set of the one or more sets based on the comparison, identifying the respective known gesture associated with the particular set, and transitioning to operating in the background detection state upon both of, measuring the magnitude perturbation by the HWM of the determined field magnitude to be less than the perturbation threshold, and determining an expiration of a time interval W that begins at T.sub.start.

These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings. Further, it should be understood that this summary and other descriptions and figures provided herein are intended to illustrative embodiments by way of example only and, as such, that numerous variations are possible. For instance, structural elements and process steps can be rearranged, combined, distributed, eliminated, or otherwise changed, while remaining within the scope of the embodiments as claimed.

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