• 专利附录
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    • 专利摘要:
    Calibration system comprising a Helmholtz device defining an internal volume with three pairs of coils, with each pair of coils configured to generate a uniform magnetic field; a mount configured to accept a device with a magnetic sensor, wherein with the device placed in the mount at least a portion of the mount is positioned such that the magnetic sensor is positioned at or near the center of the internal volume; and a computer system configured to communicate with the Helmholtz device and the magnetic sensor; the computer system being configured to: provide instructions to each pair of coils to generate a magnetic field; receive signals from the magnetic sensor; measuring, depending on said signals, one or more characteristics of the magnetic sensor; and by means of a calibration algorithm, determine one or more calibration correction factors for the magnetic sensor. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2720281A2
    申请号:ES201930033
    申请日:2019-01-18
    公开日:2019-07-19
    发明作者:Mark Robert Schneider；Charles Robertson
    申请人:Ascension Technology Corp；
    IPC主号:
    专利说明:

    [0001]
    [0002] CALIBRATION OF A MAGNETIC SENSOR
    [0003]
    [0004] Priority Claim
    [0005] This application claims the priority according to USC §119 (e) of United States patent application serial number 62 / 619,232, filed on January 19, 2018, the complete content of which is incorporated herein by reference.
    [0006] Technical field
    [0007] This disclosure refers to the calibration of a magnetic sensor.
    [0008] Background
    [0009] Electromagnetic Tracking (EMT) systems in general, and Augmented Reality (AR) and Virtual Reality (VR) systems in particular, can determine the location of devices in various contexts (for example, medical devices, etc.). Such systems use a magnetic transmitter near a magnetic sensor so that the sensor and the transmitter can be spatially located in relation to each other. Incorrect calibration of the transmitter with respect to the sensor (or vice versa) can cause the EMT system to report the incorrect positions of the sensor or transmitter.
    [0010] Summary
    [0011] The calibration of a magnetic sensor can be performed by placing the sensor in a Helmholtz device (for example, a Helmholtz coil) that is configured to generate one or more known magnetic fields (for example, well-controlled and well-defined magnetic fields). In this way, the Helmholtz device acts as a virtual transmitter. The sensor, which can be incorporated into a device such as a head-mounted display (HMD), can be placed in the Helmholtz device (for example, near a center of a volume of the Helmholtz device), for example, a location in the that the magnetic fields generated are known or expected to be known. In some implementations, Helmholtz devices can generate the magnetic fields at a relatively low frequency (for example, 90 Hz) during calibration to minimize or eliminate interference in the generated magnetic fields that could otherwise be caused by materials from the HMD in which the built-in sensor is located.
    [0012] The generated magnetic fields are received by the sensor and converted into one or more electrical signals indicative of one or more sensor characteristics (for example, sensor characterization data).
    [0013] The computer system can determine one or more calibration correction factors using a calibration algorithm. Calibration correction factors can be used to correct (for example, calibrate) the sensor so that future readings obtained by the sensor result in precise position and orientation determinations (for example, with respect to a coordinate system of the Helmholtz device and with respect to a transmitter used in an AR, VR and / or EMT system).
    [0014] In general, in one aspect, a calibration system includes a Helmholtz device that includes three pairs of coils that define an internal volume. Each of the three pairs of coils is configured to generate a magnetic field that is uniform throughout the interior volume. The calibration system also includes a mounting surface (for example, a mount) configured to accept a device that includes a magnetic sensor. At least a part of the mount is positioned within the internal volume, so that the magnetic sensor is placed at or near a center of the internal volume when the device is placed on the mount. The calibration system also includes a computer system configured to communicate with the Helmholtz device and the magnetic sensor. The computer system is configured to provide instructions to make each of the three pairs of coils generate a magnetic field, receive signals from the magnetic sensor that are based on the characteristics of the magnetic fields received on the magnetic sensor, measure, based on the signals received from the magnetic sensor, one or more characteristics of the magnetic sensor, and determining, by means of a calibration algorithm, one or more calibration correction factors for the magnetic sensor based on one or more characteristics of the magnetic sensor and the instructions provided . The implementations may include one or more of the following features.
    [0015] In some implementations, the computer system is configured to create a calibration file that includes the calibration correction factors and apply the calibration file to the magnetic sensor.
    [0016] In some implementations, the device is a head-mounted screen, and the mount is configured to keep the head-mounted screen and the magnetic sensor in a fixed position and orientation with respect to the Helmholtz device.
    [0017] In some implementations, the device is configured to communicate with one or both of the computer system or the Helmholtz device.
    [0018] In some implementations, the device is configured for use in one of the two Augmented Reality (AR) systems or in a Virtual Reality (VR) system.
    [0019] In some implementations, each of the three pairs of coils is configured to generate the magnetic field at a frequency of less than 100 EMT Hz system.
    [0020] In some implementations, each of the three pairs of coils is configured to generate the magnetic field at a frequency of 90 Hz.
    [0021] In some implementations, the magnetic sensor is configured to receive magnetic fields with frequencies greater than 30 KHz when used in an AR system or in a VR system
    [0022] In some implementations, the mount is configured to accept a calibrated magnetic sensor. The computer system is configured to provide instructions to make each of the three pairs of coils generate a second magnetic field that is uniform throughout the internal volume, receive signals from the calibrated magnetic sensor that are based on the characteristics of the second magnetic fields received on the calibrated magnetic sensor, measure, based on the signals received from the calibrated magnetic sensor, one or more characteristics of the calibrated magnetic sensor, and determine, using a calibration algorithm, one or more calibration correction factors for one or more of the three pairs of coils based on one or more characteristics of the calibrated magnetic sensor. In some implementations, the computer system is configured to create one or more calibration files that include calibration correction factors, and apply one or more calibration files to one or more of the three pairs of coils.
    [0023] In some implementations, the instructions to make each of the three pairs of coils generate the magnetic field are adjusted based on one or more calibration correction factors for one or more of the three pairs of coils.
    [0024] In general, in another aspect, a method includes providing, by means of a computer system, instructions to make current flow through each of the three pairs of coils that define an internal volume. The current causes each of the three pairs of coils to generate a magnetic field that is uniform throughout the interior volume. The method also includes receiving, from a magnetic sensor incorporated into a device that is placed within the internal volume, signals that are based on the characteristics of the magnetic fields received on the magnetic sensor. The method also includes the measurement, based on the signals received from the magnetic sensor, one or more characteristics of the magnetic sensor. The method also includes determining, using a calibration algorithm, one or more calibration correction factors for the magnetic sensor based on one or more characteristics of the magnetic sensor and the instructions provided.
    [0025] The implementations may include one or more of the following features.
    [0026] In some implementations, the method also includes the creation of a calibration file that includes the calibration correction factors and the application of the calibration file to the magnetic sensor.
    [0027] In some implementations, the device is a head-mounted screen, and a mount is configured to hold the head-mounted screen and the magnetic sensor in a fixed position and orientation relative to the three pairs of coils.
    [0028] In some implementations, one or more of the magnetic sensor, the device or the three pairs of coils are configured to communicate with the computer system.
    [0029] In some implementations, the device is configured for use in one of the two Augmented Reality (AR) systems or in a Virtual Reality (VR) system.
    [0030] In some implementations, each of the three pairs of coils is configured to generate the magnetic field at a frequency of less than 100 Hz.
    [0031] In some implementations, each of the three pairs of coils is configured to generate the magnetic field at a frequency of 90 Hz.
    [0032] In some implementations, the magnetic sensor is configured to receive magnetic fields with frequencies greater than 30 KHz when used in an AR system or in a VR system
    [0033] In some implementations, the method includes providing, by means of a computer system, instructions to make the second current flow through each of the three pairs of coils. The second current causes each of the three pairs of coils to generate a second magnetic field that is uniform throughout the interior volume. The method also includes receiving, from a calibrated magnetic sensor that is placed within the internal volume, signals that are based on the characteristics of the second magnetic fields received on the calibrated magnetic sensor. The method also includes measurement, based on the signals received from the calibrated magnetic sensor, one or more characteristics of the calibrated magnetic sensor. The method also includes determining, using a calibration algorithm, one or more calibration correction factors for one or more of the three pairs of coils based on one or more characteristics of the calibrated magnetic sensor.
    [0034] In some implementations, the method also includes the creation of one or more calibration files that include the calibration correction factors, and the application of one or more calibration files to one or more of the three pairs of coils.
    [0035] In some implementations, the instructions to make each of the three pairs of coils generate the magnetic field are adjusted based on one or more calibration correction factors for one or more of the three pairs of coils.
    [0036] The advantages of the system described here include the use of a dedicated calibration device to calibrate multiple sensors (for example, multiple devices under test (DUT)) quickly and accurately. The Helmholtz device does not require moving parts (for example, moving a transmitter to multiple different locations). Rather, the Helmholtz device acts as a virtual transmitter that generates one or more magnetic fields that cause the sensor to provide particular characterization data. The Helmholtz device simplifies the calibration procedure and accelerates calibration and testing. He eliminates the need for a three-axis translation system (for example, one that includes a gantry).
    [0037] In addition, the sensor can be calibrated while it is built into a device (for example, an HMD), thus eliminating the need to remove the sensor from the HMD before calibration. The resulting calibration may have improved accuracy due to the calibration performed on the device (for example, the HMD) in which the sensor is finally used (for example, when it is implemented in an AR, VR and / or EMT system ). In some implementations, the paired coils of the Helmholtz device are configured to generate magnetic fields at a relatively low frequency (for example, 90 Hz) to minimize interference that could otherwise be caused by HMD materials. For example, the HMD in which the sensor is incorporated may include one or more materials (e.g., metallic materials) that can cause eddy currents to occur in response to magnetic fields that have relatively high frequencies (e.g., 34 KHz ). These eddy currents can cause the generated magnetic fields to distort, so that the sensor receives distorted magnetic fields. However, magnetic fields generated at a relatively low frequency of approximately 90 Hz can reduce or eliminate the occurrence of eddy currents, which allows the sensor to receive the expected magnetic fields (for example, true) generated by the Helmholtz device.
    [0038] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects and advantages will be apparent from the description and drawings, and from the claims.
    [0039] Description of the drawings
    [0040] FIG. 1 is a schematic diagram of an example of an electromagnetic tracking system (EMT).
    [0041] FIG. 2 shows an example of a calibration system that includes a Helmholtz device to help calibrate a sensor for use in the EMT system of FIG. 1. FIG. 3 shows the calibration system and the Helmholtz device of FIG. 2 running in autocalibration mode.
    [0042] FIG. 4 shows an example of a computing device and a mobile computing device that can be used to implement the techniques described in this document.
    [0043] Similar reference symbols in the various drawings indicate similar elements.
    [0044] Detailed description
    [0045] An Electromagnetic Tracking (EMT) system can be used in games and / or surgical configurations to track devices (for example, game controllers, head-mounted screens, medical equipment, robotic arms, etc.), thus allowing their respective positions and three-dimensional orientations to be known by a user of the system. The Augmented Reality (AR) and Virtual Reality (VR) systems also use the EMT systems to track the head, hands and body, for example, to synchronize the user's movement with the AR / VR content. Such systems use a magnetic transmitter near a magnetic sensor to determine the position and / or orientation of the sensor with respect to the transmitter. The transmitters and sensors used in such systems are calibrated to ensure that the transmitters and sensors can provide accurate position and orientation information to the user. If the sensor or transmitter is not calibrated or is incorrectly calibrated, the accuracy may decrease considerably.
    [0046] The calibration of a magnetic sensor can be performed using a calibration system that includes a Helmholtz device (for example, a Helmholtz coil). The sensor can be placed in the Helmholtz device, which is configured to generate one or more uniform magnetic fields (well-controlled and well-defined magnetic fields). In this way, the Helmholtz device acts as a virtual transmitter. For example, a mounting surface (for example, a mount) positioned on the Helmholtz device is configured to receive a device (for example, a head-mounted display (HMD)) that includes the sensor. The device and the sensor are located in a particular location (for example, a central location) of the Helmholtz device in which the magnetic fields are uniform. A computer system in communication with the Helmholtz device can provide instructions to make the Helmholtz device generate one or more magnetic fields (for example, well-controlled and well-defined magnetic fields). For example, particular instructions may cause the Helmholtz device to generate one or more magnetic fields that are expected to have particular characteristics. In this way, the characteristics of the magnetic fields generated for the location where the device and the sensor are placed are known (for example, assuming that the Helmholtz device is calibrated). In some implementations, the Helmholtz device can be calibrated before sensor calibration, as described in more detail below.
    [0047] The sensor receives (for example, detects) the generated magnetic fields and converts the magnetic fields into one or more electrical signals indicative of one or more characteristics of the sensor (for example, sensor characterization data). In some examples, the sensor characterization data may be indicative of the position and orientation of the sensor with respect to the Helmholtz device.
    [0048] According to the characteristics of the magnetic sensor and the instructions provided to make the Helmholtz device generate one or more magnetic fields, the system The computer can determine one or more calibration correction factors according to a calibration algorithm. Calibration correction factors can be used to calibrate the sensor so that future readings obtained by the sensor result in accurate P&O data determined by the computer system, and accurate P&O data determined by an AR, VR and / or EMT system in which the sensor is included.
    [0049] FIG. 1 shows an example of an EMT system 100 EMT system that can be used as part of a VR / AR system. The EMT system 100 includes at least one head-mounted display (HMD) 102 that includes a magnetic sensor 112 and a controller 104 that includes a magnetic transmitter 114. The HMD 102 and the controller 104 are configured to track the position (for example, in x, y, and z) and orientation (for example, in azimuth, altitude and displacement) in the three-dimensional space relative to each other. For example, the HMD 102 is configured to track the HMD sensor 112 in relation to a reference frame defined by the transmitter 114 of the controller 104. In some implementations, the transmitter 114 of the controller 104 is configured to track the sensor 112 of the HMD 102 in relation to a reference frame defined by the position and orientation of the transmitter 114, and / or the sensor 112 of the HMD 102 is configured to track the transmitter 114 of the controller 104 in relation to a reference frame defined by the position and orientation of the sensor 112. The particular sensor 112 and the transmitter 114 employed by the EMT system 100 can be determined by the type of procedure, the measurement performance requirements, etc.
    [0050] The position and orientation of the HMD 102 and the controller 104 can be traced to each other within a tracking volume 106. While the tracking volume 106 is illustrated as a defined space, it should be understood that the tracking volume 106 can be any space three-dimensional, including dimensionless three-dimensional spaces (for example, large interior and / or exterior areas, etc.).
    [0051] In some implementations, the transmitter 114 includes three orthogonally wound magnetic coils, referred to herein as the x, y, and z coils. The electric currents that travel through the three coils cause the coils to produce three magnetic fields (for example, orthogonal sinusoidal magnetic fields) at three frequencies (for example, three different frequencies). The three frequencies can be three closely spaced frequencies, for example, 34 KHz, 34.25 KHz and 34.5 KHz, although other frequencies can also be used alternately. In some implementations, the coils can produce magnetic fields at the same frequency (for example, 34 KHz). Sensor 112 also includes three coiled magnetic coils (for example, orthogonally coiled), referred to herein as coils x, y and z. Voltages are induced in the sensor coils 112 in response to the magnetic fields detected by induction magnetic Each coil of the sensor 112 generates an electrical signal for each of the magnetic fields generated by the coils of the transmitter 114; for example, the coil x of the sensor 112 generates a first electrical signal in response to the generated magnetic field (and, for example, detected by / received from) the coil x of the transmitter 114, a second electrical signal in response to the magnetic field generated by (and, for example, detected by / received from) the coil and the transmitter 114, and a third electrical signal in response to the magnetic field generated by (and, for example, detected by / received from) the coil z of the transmitter 114. The coils yyz of the sensor 112 similarly generate electrical signals for each of the magnetic fields generated by the coils of the transmitter 114.
    [0052] In the illustrated example, the sensor 112 is incorporated in the EMT system 100, and as such, the data of the sensor 112 is indicative of the position and orientation of the sensor 112 with respect to the transmitter 114, or vice versa. The data of the sensor 112 can be represented as a data matrix (for example, a 3x3 matrix), which can be resolved at the position and orientation of the sensor 112 with respect to the transmitter 114, or vice versa. In this way, the position and orientation of the sensor 112 and the transmitter 114 are measured. In particular, the electronic components incorporated in the HMD 102 are configured to determine the position and orientation of the controller 104 in relation to the HMD 102 based on the characteristics of the magnetic fields generated by the transmitter 114 and the various electrical signals generated by the sensor 112. As described below, a separate computer system (for example, the computer system 212 of Figures 2 and 3) can be configured to determine the position and orientation of a sensor and / or a transmitter.
    [0053] If the transmitter 114 and / or the sensor 112 are not accurately calibrated, the determined position and orientation (for example, measurements) of the transmitter 114 and / or the sensor 112 may not reflect the true position and orientation (for example, real). As such, before the sensor 112 (for example, incorporated in the HMD 102) is used in the EMT system 100, the sensor 112 must be calibrated.
    [0054] Calibrate the sensor
    [0055] FIG. 2 shows an example of a calibration system 200 that includes a Helmholtz device 202 (for example, a Helmholtz coil) for calibrating a sensor (for example, the sensor 112 of Figure 1). The Helmholtz device 202 can be used to calibrate the sensor 112 while the sensor 112 is incorporated (for example, housed in) the HMD 102. The Helmholtz device 202 can be configured to calibrate a plurality of devices under test (eg, DUT). That is, the Helmholtz 202 device can calibrate a first DUT in the form of a first sensor incorporated in a first HMD, a second DUT in the form of a second sensor incorporated in a second HMD, etc. Such DUT calibration Multiple can guarantee that all sensors 112 and HMD 102 in several EMT 100 systems have common calibration characteristics.
    [0056] The 202 Helmholtz device includes three sets of paired coils 220A, 220B, 230A, 230B, 240A, 240B, which can be organized and grouped together to create uniform magnetic fields along a coordinate system defined by the 202 Helmholtz device (e.g., the x, y and z axes). The uniformity of the magnetic fields depends on the size, shape and geometry of the paired coils, and larger coils usually provide larger central regions of uniformity. Said device 202 Helmholtz is advantageously used in the calibration of the sensor 112 because the magnetic fields in the entire internal volume of the device 202 Helmholtz (for example, where the sensor 112 and the HMD 102 are placed) are uniform, well known and well known. defined. The magnetic fields along the internal volume of the 202 Helmholtz device (for example, limited and defined by paired coils 220, 230, 240) remain constant, since the magnetic fields form the basis for sensor 112 calibration. 200 calibration system Includes a mounting surface. In particular, in the illustrated example, the calibration system 200 includes a support 206, at least a portion of which resides within the internal volume of the Helmholtz device 202 defined by the paired coils 220, 230, 240. Mount 206 is configured to accept a device for calibration. For example, the HMD 102 which includes the sensor 112 of FIG. 1 can be placed in mount 206 for calibration. In some implementations, the mount 206 is positioned such that the sensor 112 is placed at or near the center of the volume of the Helmholtz device 202 when the HMD 102 is placed in the mount 206. In some implementations, the mount 206 includes one or more mechanisms (eg, pins or pins) configured to interact with the corresponding openings of the HMD 102 to help keep the HMD 102 in position at mount 206 during calibration. In some implementations, mount 206 may alternatively or additionally include additional fasteners, such as a harness, to help hold the HMD 102 in place. The calibration system 200 also includes a communications interface 210 that allows the Helmholtz device 202 to interact with a computer device, such as a computer system 212. That is, the communication interface 210 facilitates communication between the Helmholtz device 202 and the computer system 212. In some implementations, the computer system 212 is part of the calibration system 200. While the computer system 212 is illustrated as being connected to the 202 Helmholtz device via a cable connection, in some implementations, the 202 Helmholtz device may include wireless communication capabilities such as the 202 Helmholtz device can communicate wirelessly with the 212 system IT The paired 220, 230, 240 coils they are connected to the communication interface 210, so that the computer system 212 can communicate with paired coils 220, 230, 240 (eg, provide signals and / or instructions to paired coils 220, 230, 240).
    [0057] The HMD 102 and the sensor 112 are placed in the mount 206 such that the sensor 112 is in a fixed position and orientation within the uniform fields of the Helmholtz 202 device. The computer system 212 is configured to provide instructions for causing the Helmholtz device 202 to generate one or more magnetic fields (for example, well-controlled and well-defined uniform magnetic fields). For example, computer system 212 may provide instructions that include electrical parameters (eg, current parameters, voltage parameters, etc.) that cause paired coils 220, 230, 240 to generate magnetic fields.
    [0058] In some implementations, instead of and / or in addition to the computer system 212 being provided as a separate component of the calibration system 200, the Helmholtz device 202 may include one or more computer components such that the Helmholtz device 202 itself includes and / or act as a computer system. For example, Helmholtz device 202 may include computer components that cause Helmholtz device 202 to perform various functions as described in this document with respect to computer system 212 (for example, generating magnetic fields, etc.).
    [0059] Before calibrating the sensor 112, the 202 Helmholtz device can undergo its own calibration to ensure that the paired coils 220, 230, 240 are calibrated. For example, the 202 Helmholtz device can be calibrated to ensure that the instructions provided to the 202 Helmholtz device cause the paired coils 220, 230, 240 to generate the magnetic fields, in fact, they result in the paired coils 220, 230, 240 generate magnetic fields that have expected characteristics. Said calibration of the 202 Helmholtz device is described in more detail below.
    [0060] A first DUT is placed in mount 206 (for example, after calibrating Helmholtz device 202 or after confirming that Helmholtz device 202 is calibrated). In particular, the HMD 102 that includes the sensor 112 is placed in the mount 206. In some implementations, the mount 206 may include electrical contacts that are configured to form electrical connections with electrical contacts of the HMD 102, so that the Helmholtz 202 device and the HMD 102 (for example, and the sensor 112) can interact and exchange information. In some implementations, the HMD 102 can be electrically connected to the Helmholtz device 202 and / or connected to the computer system 212 (for example, by a universal serial bus (USB) cable. In some implementations, the HMD 102 can be configured to exchange information with the 202 Helmholtz device and / or the computer system 212 via a wireless connection.
    [0061] With the HMD 102 placed in mount 206, the computer system 212 can cause paired coils 220, 230, 240 to generate one or more uniform magnetic fields. In particular, computer system 212 provides instructions to make current flow through a first pair of coils 220 (e.g., coils x) to generate a magnetic field x, current flows through a second pair of coils 230 (for example, coils y) to cause a magnetic field to be generated, and the current to flow through a third pair of coils 240 (for example, coils z) to cause a magnetic field z to be generated, causing so Helmholtz device 202 produces three orthogonal magnetic fields. These can be sinusoidal, pulse DC or some other excitation. The x, y, and z fields can be generated at particular frequencies (for example, the same frequency, different frequencies, etc.) or multiplexed in time.
    [0062] The magnetic fields generated by the Helmholtz 202 device are received in the sensor 112 and induce voltages in the coils x, y and z of the sensor 112. The voltages are induced in the coils of the sensor 112 in response to the magnetic fields detected by magnetic induction. Each coil of the sensor 112 generates an electrical signal for each of the magnetic fields generated by the 202 Helmholtz device. For example, the coil x of the sensor 112 generates a first electrical signal in response to the magnetic field received from the coils x 220, a second electrical signal in response to the magnetic field received from the coils and 230, and a third electrical signal in response to the magnetic field received from coils z 240. Coils yyz of sensor 112 generate similar electrical signals for each of the magnetic fields received from each of coils x 220, and 230 yz 240.
    [0063] One or more characteristics of the magnetic sensor (for example, sensor characterization data) are measured based on the signals received from the sensor 112. In some implementations, the sensor data 112 may be represented as an array of characterization data (by example, a 3x3 matrix).
    [0064] One or more calibration correction factors for the sensor 112 are determined based on one or more characteristics of the sensor 112 and the instructions provided to cause the Helmholtz device 202 to generate the magnetic fields. Calibration correction factors can be applied to sensor 112 to correct inaccuracies and / or minimize errors due to variations from unit to DUT unit (for example, between various sensors incorporated through various systems). Calibration correction factors are determined using a calibration algorithm. In some implementations (for example, implementations in which the 202 Helmholtz device does not is calibrated), the calibration correction factors for the sensor 112 are determined based on the calibration correction factors for the Helmholtz device 202, as described in more detail below with respect to FIG. 3. In some implementations, the calibration correction factors may be stored in the sensor 112, stored in the electronics of the HMD 102, or stored in another part of the EMT system 100 in which the sensor 112 is finally incorporated. In some implementations, Calibration correction factors can be stored in network storage (for example, on a server, such as a cloud server) for later use to calibrate the DUT. In some implementations, calibration of sensor 112 may take approximately one minute or less.
    [0065] In some implementations, it can be determined that sensor 112 does not require calibration. As such, calibration correction factors can be determined as zero. In other words, the EMT system 100 can determine that sensor 112 provides relatively accurate data and that sensor 112 calibration is not required, and this can be indicated by calibration correction factors with a given zero value. If calibration of sensor 112 is not required, sensor 112 may be left as is (for example, no calibration correction factors are applied to sensor 112, or calibration correction factors that have a value of zero apply to the sensor 112, thus resulting in no change in the way the sensor 112 generates and provides data). As described above, the sensor 112 is calibrated while the sensor 112 is incorporated (for example, into) an HMD 102 housing. In some implementations, the HMD 102 housing materials may cause distortions in the magnetic fields generated by the 202 Helmholtz device. For example, the eddy current produced in metallic materials of HMD 102 may cause the magnetic fields to distort at or near HMD 102. As a result, the magnetic fields that are received in the sensor 112 are different from the magnetic fields that are expect to receive at sensor 112 (for example, according to the instructions provided by computer system 212). Because the magnetic fields actually received by the sensor 112 may be different from those expected, the electrical signals indicative of the characteristics of the sensor 112 are based on the distorted magnetic fields, and the calibration data calculated by the system 212 Computer may be inaccurate. This can cause inaccurate P&O data to be calculated.
    [0066] In some implementations, the potential distortions in the generated magnetic fields can be minimized or eliminated by controlling the frequencies at which the paired coils 220, 230, 240 generate the magnetic fields. The excitations of the components of the eddy current in HMD 102 can be minimized by reducing the frequency of magnetic fields. For example, computer system 212 may cause paired coils 220, 230, 240 to operate at a particular frequency, such as a relatively low frequency. In some implementations, paired coils 220, 230, 240 may operate at a frequency less than 100 Hz (for example, 90 Hz), although other frequencies may alternatively be used depending on the circumstances. Measurements at these lower frequencies can be adjusted to provide sensor characteristics at higher operating frequencies. In other words, the one or more measured characteristics of the sensor 112 can be adjusted depending on the operating frequency that will be used in a system in which the sensor 112 will subsequently be incorporated. In some implementations, the particular frequency at which paired coils 220, 230, 240 are executed is based on the particular characteristics of the HMD 102. As described above, the transmitter 114 of the 100 EMT system can be configured to operate at frequencies in the Order of about 30 KHz or more (for example, 34 KHz). Therefore, the frequency at which the sensor 112 is calibrated (for example, 90 Hz) may be different from the frequency of the magnetic fields (for example, 34 KHz) received by the sensor 112 in a use case (for example, a real implementation system 100 EMT). That is, the frequency at which sensor 112 is calibrated may be different from the frequency at which sensor 112 operates in an EMT, AR and / or VR system implementation.
    [0067] Helmholtz device calibration
    [0068] As described above, the Helmholtz device 202 may undergo a calibration process such that the fields generated by the paired coils 220, 230, 240 are known in amplitude and geometry. Then one or more calibration correction factors (for example, the Helmholtz calibration correction factors, generally referred to as Helmholtz calibration data) can be used to algorithmically mimic an ideal (for example, perfect) Helmholtz device. In this way, the calibration correction factors can be used to adjust the instructions provided by the computer system 212 to ensure that the magnetic fields generated by the paired coils 220, 230, 240 have the expected characteristics. A sensor that is known to be calibrated using other means (for example, known to produce accurate results / characterization data when used with this calibration) can be used to perform such calibration of the 202 Helmholtz device.
    [0069] FIG. 3 shows an example of the 202 Helmholtz device of FIG. 2 running in autocalibration mode. In this example, the HMD 102 has been replaced with a reference device, such as a reference sensor 312 (for example, a calibrated sensor) that is known to produce accurate results when used with its calibration. In other words, it is known that the calibrated reference sensor 312 generates electrical signals in response to the detection of the generated magnetic fields that result in the computer system 212 providing accurate characterization data, provided that the coils 220, 230, 240 are calibrated paired.
    [0070] The reference sensor 312 is placed in the mount 206 so that the reference sensor 312 assumes a fixed position at or near the center of the volume of the Helmholtz device 202. In some implementations, the reference sensor 312 is electrically connected to the Helmholtz device 202 through one or more electrical contacts in the mount 206 or through a separate wired electrical connection. In some implementations, the reference sensor 312 is connected to the computer system 212 via a wireless or wired connection (for example, through a USB cable). In some implementations, the reference sensor 312 may be configured to exchange information with the Helmholtz device 202 and / or the computer system 212 via a wireless connection.
    [0071] With the reference sensor 312 placed in mount 206, the computer system 212 can cause paired coils 220, 230, 240 to generate one or more uniform magnetic fields. In particular, the computer system 212 provides instructions to make current flow through each of the paired coils 220, 230, 240, which makes the paired coils 220, 230, 240 produce three orthogonal sinusoidal magnetic fields at frequencies private individuals The magnetic fields generated by the paired coils 220, 230, 240 are received in the reference sensor 312 and cause voltages to be induced in the coils of the reference sensor 312.
    [0072] One or more characteristics of the reference sensor 312 (for example, characterization data of the reference sensor) are measured according to the signals received from the reference sensor 312. In some implementations, the reference sensor 312 data may be represented as an array of characterization data (for example, a 3x3 matrix). Because it is known that the reference sensor 312 is calibrated (for example, by other means), it is known that the characterization data of the reference sensor represents the ideal characteristics of a sensor, assuming that a calibrated Helmholtz device is provided. Therefore, any inaccuracy in the characterization data of the reference sensor can be attributed to inaccuracies in the 202 Helmholtz device. Therefore, the characterization data of the reference sensor can be used to determine the calibration data for the 202 Helmholtz device.
    [0073] One or more calibration correction factors for the Helmholtz device 202 are determined according to the one or more characteristics of the reference sensor 312 and according to a calibration algorithm. The calibration correction factors for the Helmholtz 202 device are sometimes referred to as Helmholtz calibration data. In some implementations, Helmholtz calibration data is represented as a data matrix (for example, a 3x3 matrix). The Helmholtz calibration data can be used to adjust the instructions provided by the computer system 212 to cause the transmitter coils to generate the magnetic fields. As such, the magnetic fields generated during the calibration of the sensor 112 have known characteristics (for example, known amplitude and geometry). In this way, the sensor 112 is calibrated by means of a calibrated 202 Helmholtz device that is confirmed to generate uniform, well-controlled and well-defined magnetic fields. In other words, the Helmholtz calibration data is used to adjust the Helmholtz device 202 in an ideal (eg, perfect) Helmholtz device. In some implementations, the 202 Helmholtz device can be calibrated according to the techniques described in this document before calibrating the DUTs.
    [0074] The calibration correction factors for the Helmholtz device 202 can be determined for one or more of the paired coils 220, 230, 240. In some implementations, each of the paired coils 220, 230, 240 of the 202 Helmholtz device can be independently calibrated. For example, zero, one, two or three of the pairs of coils 220, 230, 240 can be calibrated. In some implementations, only one of each pair of coils can be determined to require calibration.
    [0075] In some examples, the one or more calibration correction factors for the 202 Helmholtz device can be applied to paired coils 220, 230, 240 to correct inaccuracies and / or minimize errors that might otherwise occur during the future calibration of a sensor. 112 DUT In some implementations, calibration correction factors may be stored in the electronics of the 202 Helmholtz device. In some implementations, calibration correction factors may be stored in network storage (for example, on a server, such as a cloud server) for later use to calibrate one or more of the paired coils 220, 230, 240. In some implementations, the calibration of the Helmholtz device 202 (for example, the calibration of one or more of the paired coils 220, 230, 240) may take approximately one minute or less.
    [0076] Once the 202 Helmholtz device (for example, paired coils 220, 230, 240) has been calibrated, the 202 Helmholtz device can be used to calibrate several 112 DUT sensors.
    [0077] Operating the calibration device
    [0078] If the Helmholtz 202 device is used to calibrate a DUT or calibrates itself, a user of the 202 Helmholtz device and the computer system 212 can perform the calibration procedure by interacting with the computer system 212. In some implementations, the Computer system 212 is configured to provide instructions for the user through a graphical user interface (GUI). For example, the computer system 212 may be a portable computer that is configured to execute a program used to calibrate a DUT or calibrate the Helmholtz 202 device. The program can cause a laptop screen to display instructions to help the user carry out the particular calibration procedure. For example, the instructions may include textual, visual and / or audible instructions that instruct the user to place the HMD 102 or the reference sensor 312 on the mount 206, electrically connect the HMD 102 or the reference sensor 312 to the mount 206 or the computer system 212 (for example, if required to form a cable connection), connect the computer system 212 to the Helmholtz device 202 (for example, if necessary to form a cable connection), etc.
    [0079] In some implementations, the program operating in the computer system 212 may include one or more user selectable values and / or user input fields to allow the user to define one or more characteristics of the calibration procedure. For example, the program may allow the user to specify particular frequencies at which paired coils 220, 230, 240 operate to generate respective magnetic fields. In some implementations, the program may allow the user to store, retrieve and / or apply calibration correction values to sensor 112 (for example, during sensor 112 calibration) and / or to one or more of coils 220, 230, 240 paired (for example, during the calibration of the Helmholtz device 202). In some implementations, the program is configured to provide an indication that the sensor 112 requires calibration, an indication that the sensor 112 does not require calibration, an indication that the Helmholtz device 202 requires calibration and / or an indication that the sensor Helmholtz device 202 does not require calibration (for example, an approval / failure result). For examples where a calibration is required, the program may provide a user interface element that may allow the user to initiate a calibration procedure when interacting with the user interface element.
    [0080] In some implementations, the 202 Helmholtz device and the computer system 212 may be configured to perform calibrations on different types (eg, different models) of sensors and / or HMD. In some implementations, the program may accept an input indicative of the sensor model and / or HMD to calibrate. The particular parameters stored in the computer system 212 may be implemented during calibration based on the model of the sensor and / or HMD in use. For example, a first sensor model may require that particular quantities of currents pass through the paired coils 220, 230, 240 of the 202 Helmholtz device and / or certain frequencies for magnetic fields to be generated by paired coils 220, 230, 240 and a second sensor model may require that different magnitudes of currents pass through paired coils 220, 230, 240 of the 202 Helmholtz device and / or different frequencies so that the magnetic fields are generated by paired coils 220, 230, 240.
    [0081] In some implementations, the calibration correction factors for a particular 112 DUT sensor or for one or more of the paired coils 220, 230, 240 may be included as part of a calibration file created by the program operating in the computer system 212 . For example, once the one or more calibration correction factors are determined, a calibration file can be created that can be used to update a particular 112 DUT sensor or one or more of the paired coils 220, 230, 240 . In some implementations, the calibration file may be "projected" to the 112 DUT sensor or the paired coil 220, 230, 240. In some implementations, a firmware of the 112 DUT sensor and / or the paired coil 220, 230, 240 can be update based on calibration file.
    [0082] As described above, the device 202 Helmholtz of Figs. 2 and 3 can be operated using software executed by a computing device (for example, the computer system 212 of Figures 2 and 3). In some implementations, the software is included in a computer-readable medium for execution in the computer system 212. FIG. 4 shows an example of a computing device 400 and an example of a mobile computing device 450, which can be used to implement the techniques described in this document. For example, the calibration of the sensor 112 and / or the calibration of the paired coils 220, 230, 240 of the Helmholtz 202 device can be executed and controlled by the computing device 400 and / or the mobile computing device 450. The computing device 400 is intended to represent various forms of digital computers, including, for example, laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes and other appropriate computers. The computing device 450 is intended to represent various forms of mobile devices, including, for example, personal digital assistants, cell phones, smartphones and other similar computing devices. The components shown here, their connections and relationships, and their functions, are intended as examples only, and are not intended to limit the implementations of the techniques described and / or claimed in this document.
    [0083] The computing device 400 includes the processor 402, the memory 404, the storage device 406, the high-speed interface 408 that connects to the memory 404 and the high-speed expansion ports 410, and the low-speed interface 412 that connects to low speed bus 414 and storage device 406. Each of the components 402, 404, 406, 408, 410 and 412, are interconnected using various buses, and can be mounted on a common motherboard or in other ways, as appropriate. The processor 402 can process instructions for execution within the computing device 400, including the instructions stored in the memory 404 or in the storage device 406, to display graphic data for a GUI on an external input / output device, including, by For example, the screen 416 coupled to the high speed interface 408. In some implementations, multiple processors and / or multiple buses may be used, as appropriate, along with multiple memories and types of memory. In addition, multiple computing devices 400 can be connected, and each device provides parts of the necessary operations (for example, such as a server bank, a group of blade servers, a multiprocessor system, etc.).
    [0084] The 404 memory stores data within the computing device 400. In some implementations, the 404 memory is a unit or units of volatile memory. In some implementation, memory 604 is a unit or units of nonvolatile memory. The 404 may also be another form of computer-readable media, including, for example, a magnetic or optical disk.
    [0085] The storage device 406 is capable of providing mass storage for the computing device 400. In some implementations, the storage device 406 may be or contain a computer-readable medium, which includes, for example, a floppy disk device, a hard disk device, an optical disk device, a tape device, a flash memory or other similar solid-state memory device, or a series of devices, including devices in a storage area network or other configurations. A computer program product can be tangibly incorporated into a data carrier. The software product may also contain instructions that, when executed, perform one or more methods, including, for example, those described above. The data mount is a computer or machine readable medium, which includes, for example, memory 404, storage device 406, memory in processor 402 and the like.
    [0086] The high speed controller 408 manages the intensive bandwidth operations for the computing device 400, while the low speed controller 412 manages the intensive operations of lower bandwidth. Such assignment of functions is only an example. In some implementations, the high-speed controller 408 is coupled to the memory 404, the screen 416 (for example, through a graphics processor or accelerator), and the high-speed expansion ports 410, which can accept various cards expansion (not shown). In some implementations, the 412 controller of Low speed is coupled to storage device 406 and low speed expansion port 414. The low-speed expansion port, which can include several communication ports (for example, USB, Bluetooth®, Ethernet, wireless Ethernet), can be attached to one or more input / output devices, including, for example, a keyboard , a pointing device, a scanner or a network device that includes, for example, a switch or router (for example, through a network adapter). The computing device 400 can be implemented in several different ways, as shown in FIG. 4. For example, the computing device 400 may be implemented as a standard server 420, or several times in a group of such servers. The computing device 400 can also be implemented as part of the rack server system 424. In addition, or as an alternative, the computing device 400 may be implemented in a personal computer (for example, a laptop 422). In some examples, the components of the computing device 400 may be combined with other components in a mobile device (for example, the mobile computing device 450). Each of these devices may contain one or more of the 400, 450, computing devices and a complete system may consist of multiple 400, 450 computing devices that communicate with each other.
    [0087] The computer device 450 includes the processor 452, the memory 464 and an input / output device that includes, for example, the screen 454, the communication interface 466 and the transceiver 468, among other components. The device 450 may also be provided with a storage device, which includes, for example, a microdrive or other device, to provide additional storage. Components 450, 452, 464, 454, 466 and 468 can be interconnected using several buses, and several of the components can be mounted on a common motherboard or in other ways, as appropriate.
    [0088] The processor 452 can execute instructions within the computing device 450, including the instructions stored in memory 464. The processor 452 can be implemented as a set of chip chips that include independent and multiple analog and digital processors. The processor 452 can provide, for example, the coordination of the other components of the device 450, including, for example, the control of the user interfaces, the applications executed by the device 450 and the wireless communication by the device 450.
    [0089] The processor 452 can communicate with a user through the control interface 458 and the screen interface 456 coupled to the screen 454. The screen 454 can be, for example, a TFT LCD screen (liquid crystal display with film transistor fine) or an OLED (organic light emitting diode), or other suitable display technology. The screen interface 456 may comprise appropriate circuits to activate the screen 454 to present graphic data and other data to a user. The control interface 458 can receive commands from a user and convert them to be sent to the processor 452. In addition, the external interface 462 can communicate with the processor 442, in order to allow communication of the device 450 with other devices in the nearby area. The external interface 462 may provide, for example, cable communication in some implementations or wireless communication in some implementations. Multiple interfaces can also be used. Memory 464 stores data within computer device 450. Memory 464 can be implemented as one or more computer-readable media or media, a volatile memory unit or units or a non-volatile memory unit or units. The expansion memory 474 can also be provided and connected to the device 450 via the expansion interface 472, which may include, for example, a SIMM card interface (single line memory module). Said expansion memory 474 may provide additional storage space for the device 450, and / or may store applications or other data for the device 450. Specifically, the expansion memory 474 may also include instructions for carrying out or complementing the processes described. above and may include secure data. Thus, for example, expansion memory 474 can be provided as a security module for device 450 and can be programmed with instructions that allow the safe use of device 450. In addition, secure applications can be provided through SIMM cards , together with additional data, which include, for example, placing identification data on the SIMM card in a non-hackable manner.
    [0090] Memory 464 may include, for example, flash memory and / or NVRAM memory, as explained below. In some implementations, a computer program product is tangibly incorporated into a data carrier. The product of the computer program contains instructions that, when executed, perform one or more methods, including, for example, those described above with respect to the calibration of sensor 112 and / or the calibration of paired coils 220, 230, 240 of the 202 Helmholtz device. The data carrier is a computer or machine readable medium, which includes, for example, memory 464, expansion memory 474 and / or memory in processor 452, which can be received, for example, through transceiver 468 or the external 462 interface.
    [0091] The device 450 can communicate wirelessly through the communication interface 466, which may include digital signal processing circuits when necessary. Communication interface 466 can provide communications under various modes or protocols, including, for example, GSM, SMS, EMS or MMS, CDMA, TDMA, PDC, WCDMA, CDMA2000 or GPRS voice calls, among others. Such communication may occur, for example, through a radio frequency transceiver 468. In addition, you can occur in a short-range communication, which includes, for example, the use of a Bluetooth®, WiFi or other type of transceiver (not shown). In addition, the GPS receiver module 470 (Global Positioning System) can provide additional wireless data related to navigation and location to the device 450, which can be used as appropriate by the applications running on the device 450.
    [0092] The device 450 can also communicate audibly using the audio codec 460, which can receive spoken data from a user and convert it into usable digital data. The audio codec 460 can also generate an audible sound for a user, including, for example, through a loudspeaker, for example, in a headset of the device 450. Said sound may include sound of telephone voice calls, recorded sound ( for example, voice messages, music files, and the like) and also the sound generated by the applications operating on the device 450.
    [0093] The computing device 450 can be implemented in several different ways, as shown in FIG. 4. For example, the computer device 450 may be implemented as a cell phone 480. The computer device 450 may also be implemented as part of the smartphone 482, personal digital assistant or other similar mobile device. Various implementations of the systems and techniques described here can be performed on digital electronic circuits, integrated circuits, specially designed ASICs (application-specific integrated circuits), computer hardware, firmware, software and / or combinations thereof. These various implementations may include one or more executable and / or interpretable computer programs in a programmable system. This includes at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device and at least one device. departure.
    [0094] These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level and / or object-oriented procedure programming language, and / or assembly / machine language. As used herein, the terms "machine readable medium" and "computer readable medium" refer to a product, apparatus and / or computer program device (e.g., magnetic disks, optical disks, memory, programmable logic devices (PLD) used to provide machine instructions and / or data to a programmable processor, including a machine-readable medium that receives instructions from the machine.
    [0095] To provide interaction with a user, the systems and techniques described in this document can be implemented on a computer that has a device for display (for example, a CRT (cathode ray tube) or LCD (liquid crystal display) monitor to present data to the user, and a keyboard and pointing device (for example, a mouse or trackball) by which the user can provide information to the computer Other types of devices can also be used to provide interaction with a user For example, the feedback provided to the user can be a form of sensory feedback (eg, visual feedback, auditory feedback or tactile feedback). User input can be received in one form, including acoustic, voice or touch input.
    [0096] The systems and techniques described here can be implemented in a computer system that includes a backend component (for example, such as a data server), or that includes a middleware component (for example, an application server), or that includes a frontend component (for example, a client computer that has a user interface or a web browser through which a user can interact with an implementation of the systems and techniques described here), or a combination of said backend components, middleware or frontend. System components can be interconnected by a means or means of communicating digital data (for example, a communication network). Examples of communication networks include a local area network (LAN), a wide area network (WAN) and the Internet.
    [0097] The computer system may include clients and servers. A client and a server are generally far apart and generally interact through a communication network. The client and server relationship arises by virtue of the computer programs that run on the respective computers and that have a client-server relationship with each other.
    [0098] In some implementations, the components described in this document may be separated, combined or incorporated into a single or combined component. The components shown in the figures are not intended to limit the systems described in this document to the software architectures shown in the figures.
    [0099] Several embodiments have been described. However, it will be understood that several modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, other embodiments are within the scope of the following claims.
    权利要求:
    Claims (22)
    [1]
    1. A calibration system comprising:
    a Helmholtz device comprising three pairs of coils that define an internal volume, in which each of the three pairs of coils is configured to generate a magnetic field that is uniform throughout the interior volume;
    a mount configured to accept a device that includes a magnetic sensor, in which at least a portion of the mount is positioned within the internal volume such that the magnetic sensor is placed at or near a center of the internal volume when the device it is placed on the mount; Y
    a computer system configured to communicate with the Helmholtz device and the magnetic sensor,
    in which the computer system is configured to:
    provide instructions to make each of the three pairs of coils generate a magnetic field;
    receive signals from the magnetic sensor that are based on the characteristics of the magnetic fields received on the magnetic sensor;
    measure, depending on the signals received from the magnetic sensor, one or more characteristics of the magnetic sensor; Y
    determine, using a calibration algorithm, one or more calibration correction factors for the magnetic sensor based on one or more characteristics of the magnetic sensor and the instructions provided.
    [2]
    2. The calibration system of claim 1, wherein the computer system is further configured to:
    create a calibration file that includes calibration correction factors; and apply the calibration file to the magnetic sensor.
    [3]
    3. The calibration system of claim 1, wherein the device is a head-mounted screen, and the mount is configured to hold the head-mounted screen and the magnetic sensor in a fixed position and orientation with respect to the Helmholtz device.
    [4]
    4. The calibration system of claim 1, wherein the device is a head mounted display configured to communicate with one or both of the computer system or the Helmholtz device.
    [5]
    5. The calibration system of claim 1, wherein the device is a head-mounted display configured for use in one of the two Augmented Reality (AR) systems or Virtual Reality (VR) system.
    [6]
    6. The calibration system of claim 1, wherein each of the three pairs of coils is configured to generate the magnetic field at a frequency below 100 Hz.
    [7]
    7. The calibration system of claim 6, wherein each of the three pairs of coils is configured to generate the magnetic field at a frequency of 90 Hz.
    [8]
    8. The calibration system of claim 7, wherein the magnetic sensor is configured to receive magnetic fields that have frequencies greater than 30 KHz when in use in an AR system or a VR system
    [9]
    9. The calibration system of claim 1, wherein the mount is configured to accept a calibrated magnetic sensor, and the computer system is further configured to:
    provide instructions to make each of the three pairs of coils generate a second magnetic field that is uniform throughout the interior volume;
    receive signals from the calibrated magnetic sensor that are based on the characteristics of the second magnetic fields received on the calibrated magnetic sensor;
    measure, based on the signals received from the calibrated magnetic sensor, one or more characteristics of the calibrated magnetic sensor; Y
    determine, using a calibration algorithm, one or more calibration correction factors for one or more of the three pairs of coils based on one or more characteristics of the calibrated magnetic sensor.
    [10]
    10. The calibration system of claim 9, wherein the computer system is further configured to:
    create one or more calibration files that include calibration correction factors; Y
    apply one or more calibration files to one or more of the three pairs of coils.
    [11]
    11. The calibration system of claim 9, wherein the instructions for having each of the three pairs of coils generate the magnetic field are adjusted based on one or more calibration correction factors for one or more of the Three pairs of coils.
    [12]
    12. A method comprising:
    provide, by means of a computer system, instructions to make the current flow through each of the three pairs of coils that define an internal volume, where the current causes each of the three pairs of coils to generate a magnetic field that it is uniform throughout the interior volume;
    receive, from a magnetic sensor incorporated into a device that is positioned within the internal volume, signals that are based on the characteristics of the magnetic fields received on the magnetic sensor;
    measure, based on the signals received from the magnetic sensor, one or more characteristics of the magnetic sensor; Y
    determine, using a calibration algorithm, one or more calibration correction factors for the magnetic sensor based on one or more characteristics of the magnetic sensor and the instructions provided.
    [13]
    13. The method of claim 12, further comprising:
    create a calibration file that includes calibration correction factors; and apply the calibration file to the magnetic sensor.
    [14]
    14. The method of claim 12, wherein the device is a head-mounted screen, and a mount is configured to hold the head-mounted screen and the magnetic sensor in a fixed position and orientation with respect to the three pairs of coils
    [15]
    15. The method of claim 12, wherein one or more of the magnetic sensor, the device or the three pairs of coils are configured to communicate with the computer system.
    [16]
    16. The method of claim 12, wherein the device is a head-mounted display configured for use in one of two Augmented Reality (AR) systems or Virtual Reality (VR) systems.
    [17]
    17. The method of claim 12, wherein each of the three pairs of coils is configured to generate the magnetic field at a frequency of less than 100 Hz.
    [18]
    18. The method of claim 17, wherein each of the three pairs of coils is configured to generate the magnetic field at a frequency of 90 Hz.
    [19]
    19. The method of claim 18, wherein the magnetic sensor is configured to receive magnetic fields that have frequencies of more than 30 KHz when in use in an AR system or a VR system.
    [20]
    20. The method of claim 12, further comprising:
    provide, by means of a computer system, instructions to make the second current flow through each of the three pairs of coils, where the second current causes each of the three pairs of coils to generate a second magnetic field that is uniform throughout the internal volume;
    receive, from a calibrated magnetic sensor that is placed within the internal volume, signals that are based on the characteristics of the second magnetic fields received on the calibrated magnetic sensor;
    measure, based on the signals received from the calibrated magnetic sensor, one or more characteristics of the calibrated magnetic sensor; Y
    determine, using a calibration algorithm, one or more calibration correction factors for one or more of the three pairs of coils based on one or more characteristics of the calibrated magnetic sensor.
    [21]
    21. The method of claim 20, further comprising:
    create one or more calibration files that include calibration correction factors; Y
    apply one or more calibration files to one or more of the three pairs of coils.
    [22]
    22. The method of claim 20, wherein the instructions for having each of the three pairs of coils generate the magnetic field are adjusted based on one or more calibration correction factors for one or more of the three pairs of coils
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    法律状态:
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    2020-10-29| FC2A| Grant refused|Effective date: 20201023 |
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    US201862619232P| true| 2018-01-19|2018-01-19|
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