阅读说明：本技术 用于增强显示系统中电磁跟踪的定向发射器/传感器 (Directional emitter/sensor for enhanced electromagnetic tracking in display systems ) 是由 R·B·陈 于 2019-09-05 设计创作，主要内容包括：一种电磁跟踪系统包括手持控制器,该手持控制器包括被配置为产生由电磁场图案表征的电磁场的电磁发射器；以及邻近电磁发射器定位并被配置为形成修改的电磁场图案的第一电磁反射器。该电磁跟踪系统还包括头戴式增强现实显示器,该头戴式增强现实显示器包括被配置为感测电磁场图案的电磁传感器；以及邻近被配置为最佳地感测感兴趣区域中的电磁场图案的电磁传感器的第二电磁反射器。(An electromagnetic tracking system includes a handheld controller including an electromagnetic transmitter configured to generate an electromagnetic field characterized by an electromagnetic field pattern; and a first electromagnetic reflector positioned adjacent to the electromagnetic emitter and configured to form a modified electromagnetic field pattern. The electromagnetic tracking system also includes a head mounted augmented reality display including an electromagnetic sensor configured to sense an electromagnetic field pattern; and a second electromagnetic reflector adjacent the electromagnetic sensor configured to optimally sense the electromagnetic field pattern in the region of interest.)

1. An electromagnetic tracking system, comprising:

a handheld controller, comprising:

an electromagnetic transmitter configured to generate an electromagnetic field characterized by an electromagnetic field pattern; and

a first electromagnetic reflector positioned adjacent to the electromagnetic emitter and configured to form a modified electromagnetic field pattern;

a head-mounted augmented reality display, comprising:

an electromagnetic sensor configured to sense the modified electromagnetic field pattern; and

a second electromagnetic reflector proximate to the electromagnetic sensor configured to sense the modified electromagnetic field pattern in a region of interest.

2. The electromagnetic tracking system of claim 1, further comprising a controller operable to:

controlling the timing of the electromagnetic emission and sensing; and

digitally calculating the position and orientation of the electromagnetic transmitter and the electromagnetic sensor based on the modified electromagnetic field pattern.

3. The electromagnetic tracking system of claim 2, further comprising an auxiliary unit comprising the controller.

4. The electromagnetic tracking system of claim 3, wherein the auxiliary unit comprises a belt pack.

5. The electromagnetic tracking system of claim 3, wherein the controller is distributed among the handheld controller, the head mounted augmented reality display, and the auxiliary unit.

6. An electromagnetic tracking system according to claim 1, wherein the electromagnetic field pattern is characterized by an initial full width at half maximum and the modified electromagnetic field pattern is characterized by a modified full width at half maximum that is less than the initial full width at half maximum.

7. The electromagnetic tracking system of claim 6, wherein the modified electromagnetic field pattern is characterized by a field strength at the center of the lobe that is higher than the electromagnetic field pattern.

8. The electromagnetic tracking system of claim 1, wherein the electromagnetic emitter and the electromagnetic sensor comprise parallel plates aligned with an x-axis, the electromagnetic field extends along a negative z-axis and a positive z-axis, and the modified electromagnetic field pattern extends only along the positive z-axis.

9. The electromagnetic tracking system of claim 1, wherein at least one of the first electromagnetic reflector or the second electromagnetic reflector comprises two or more reflective plates.

10. The electromagnetic tracking system of claim 9, wherein the two or more reflective sheets are joined at an apex.

11. The electromagnetic tracking system of claim 9, wherein the two or more reflective plates include three reflective plates defining angular vertices of a cube.

12. The electromagnetic tracking system of claim 1, wherein at least one of the first electromagnetic reflector or the second electromagnetic reflector comprises a single reflector element.

13. A method of operating an electromagnetic tracking system, the method comprising:

generating an electromagnetic field using an electromagnetic transmitter;

reflecting the electromagnetic field using a first electromagnetic reflector to form a modified electromagnetic field pattern;

reflecting a portion of the modified electromagnetic field pattern using a second electromagnetic reflector; and

sensing the reflected portion of the modified electromagnetic field pattern using an electromagnetic sensor adjacent to the second electromagnetic reflector.

14. The method of claim 13, wherein the electromagnetic emitter is disposed in a handheld controller and the electromagnetic sensor is disposed in a head mounted augmented reality display.

15. The method of claim 13, wherein the first electromagnetic reflector is positioned adjacent to the electromagnetic emitter.

16. The method of claim 13, further comprising:

controlling a timing of generating an electromagnetic field and sensing the reflected portion of the modified electromagnetic field pattern; and

digitally calculating the position and orientation of the electromagnetic transmitter and the electromagnetic sensor based on the modified electromagnetic field pattern.

17. The method of claim 13, wherein at least one of the first or second electromagnetic reflectors comprises two or more reflective plates.

18. The method of claim 17, wherein the two or more reflective sheets are joined at an apex.

19. The method of claim 17, wherein the two or more reflective plates comprise three reflective plates defining angular vertices of a cube.

20. The method of claim 13, wherein at least one of the first or second electromagnetic reflectors comprises a single reflector element.

Background

Modern computing and display technologies have facilitated the development of systems for so-called "virtual reality" (VR) or "augmented reality" (AR) experiences, in which a digitally-rendered image, or a portion thereof, is presented to a user in a manner that looks, or can be perceived as, real. VR scenes generally involve the rendering of digital or virtual image information that is opaque to other actual real-world visual inputs, and AR scenes typically involve the rendering of digital or virtual image information as an enhancement to the visualization of the actual real-world surrounding the user.

Despite the advances made in these display technologies, there remains a need in the art for improved methods and systems related to augmented reality systems, and in particular display systems.

Disclosure of Invention

The present disclosure relates to virtual reality and/or augmented reality imaging and visualization systems. The present disclosure relates generally to methods and systems related to electromagnetic tracking in virtual reality and/or augmented reality systems. More specifically, embodiments of the present disclosure provide methods and systems for directing energy transmitted by a transmitter (also referred to as a transmitter) and/or received by a sensor (also referred to as a receiver) to improve performance of a positioning process. In some embodiments, a shaped Electromagnetic (EM) reflector is used to modify the transmit pattern generated using the EM transmitter/receive pattern received by the EM sensor. In some embodiments, unformed EM modes are easily deformed, which may affect their ability to accurately determine position and orientation. In some embodiments, the shaped EM field may minimize distortion and may increase field strength. Thus, the field strength in the vicinity of the electromagnetic sensor is increased. Similarly, the receiving capability of the electromagnetic sensor in the direction of the electromagnetic transmitter is improved. These modifications may improve positioning information, increase power consumption efficiency, reduce EM distortion, and reduce the size of the electromagnetic transmitter and/or electromagnetic sensor. The present disclosure is applicable to a variety of applications in computer vision and image display systems.

According to an embodiment of the present invention, an electromagnetic tracking system is provided. The electromagnetic tracking system includes a handheld controller comprising: an electromagnetic transmitter configured to generate an electromagnetic field characterized by an electromagnetic field pattern; and a first electromagnetic reflector positioned adjacent to the electromagnetic emitter and configured to form a modified electromagnetic field pattern. The electromagnetic tracking system also includes a head-mounted augmented reality display comprising: an electromagnetic sensor configured to sense the modified electromagnetic field; and a second electromagnetic reflector adjacent to the electromagnetic sensor configured to optimally sense the modified electromagnetic field pattern in a region of interest.

According to a particular embodiment of the present invention, a method of operating an electromagnetic tracking system is provided. The method comprises generating an electromagnetic field using an electromagnetic transmitter; and reflecting the electromagnetic field using a first electromagnetic reflector to form a modified electromagnetic field pattern. The method further comprises reflecting a portion of the modified electromagnetic field pattern using a second electromagnetic reflector; and sensing the reflected portion of the modified electromagnetic field pattern using an electromagnetic sensor adjacent to the second electromagnetic reflector.

Many advantages over conventional techniques are obtained by the present disclosure. For example, embodiments of the present disclosure provide methods and systems for increasing the strength of an electromagnetic field in a predetermined manner. Thus, the system can achieve desired functions while reducing transmission power, reducing component size, reducing or avoiding EM distortion, and the like. These and other embodiments of the present disclosure, as well as many of its advantages and features, are described in more detail in conjunction with the following text and accompanying drawings.

Drawings

Fig. 1 schematically illustrates a system diagram of an Electromagnetic (EM) tracking system, in accordance with some embodiments.

FIG. 2 is a flow chart describing the operation of an electromagnetic tracking system according to some embodiments.

Fig. 3 schematically illustrates an electromagnetic tracking system in combination with an Augmented Reality (AR) system, in accordance with some embodiments.

FIG. 4 is a flow diagram that describes functionality of an electromagnetic tracking system in the context of an AR device, in accordance with some embodiments.

Fig. 5 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines according to some embodiments.

FIG. 6 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a double-sided reflector according to some embodiments.

FIG. 7 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a segmented reflector according to some embodiments.

FIG. 8 is a plan view of an electromagnetic emitter incorporating a trihedral reflector and corresponding electromagnetic field lines, according to some embodiments

Fig. 9 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a hemispherical reflector according to some embodiments.

FIG. 10A is a perspective view illustrating integration of an electromagnetic transmitter incorporating a trihedral reflector with a handheld controller according to some embodiments.

Figure 10B is a perspective view illustrating integration of an electromagnetic sensor incorporating a trihedral reflector with a headset according to some embodiments.

Fig. 10C is a perspective view showing an expanded view of the sensor housing shown in fig. 10B.

FIG. 11 is a simplified flow diagram illustrating a method of operating an electromagnetic tracking system incorporating an integrated reflector according to an embodiment of the present invention.

Detailed Description

In an Augmented Reality (AR) system, the AR system may be designed to interact with a user. As an example, a user may be provided with a handheld controller, also known as totem (totem), with which the user may interact with the AR system. Therefore, it would be useful to have the ability to determine the position and orientation (e.g., 6 degree of freedom (DOF) pose) of the totem relative to other elements of the AR system, including the head-mounted display system worn by the user, also referred to as the headset or AR headset.

One approach to achieving high precision positioning may involve the use of an electromagnetic field (EM), such as an EM transmitted by an EM transmitter coupled with an EM sensor strategically placed on a user's AR headset, belt pack, and/or other auxiliary device (e.g., totem, haptic device, game tool, etc.). Electromagnetic tracking systems typically include at least one electromagnetic field emitter (generally referred to as a "transmitter") and at least one electromagnetic field sensor (generally referred to as a "sensor"). The transmitter generates an electromagnetic field having a known spatial (and/or temporal) distribution in the environment of the user of the AR headset. The sensor measures an electromagnetic field generated at the location of the sensor. Based on these measurements and knowledge of the distribution of the generated electromagnetic field, the attitude (e.g., position and/or orientation) of the sensor relative to the emitter may be determined. Thus, the pose of the object to which the sensor and/or emitter is attached may be determined. That is, the relative positions of the sensor and emitter may be determined.

Referring now to FIG. 1, an example system diagram of an electromagnetic tracking system is shown. In some embodiments, the electromagnetic tracking system includes one or more electromagnetic field transmitters 102 (generally referred to as "transmitters 102") configured to transmit a known electromagnetic field. As shown in fig. 1, the transmitter 102 may be coupled to a power source 110 (e.g., a current, a battery, etc.) that provides power to the transmitter 102.

In some embodiments, transmitter 102 includes several coils that generate electromagnetic fields (e.g., at least three coils positioned perpendicular to each other to generate fields in X, Y and the Z direction). The electromagnetic field is used to establish a coordinate space (e.g., an X-Y-Z Cartesian coordinate space). This allows the system to map the position (e.g., (X, Y, Z) position) of the electromagnetic sensors 104a, 104b relative to a known electromagnetic field and determine the position and/or orientation of the electromagnetic sensors 104a, 104 b. In some embodiments, electromagnetic sensors 104a, 104b (generally referred to as "sensors" 104) may be attached to one or more real objects. The sensor 104 may include a coil in which a current is induced by an electromagnetic field (e.g., an electromagnetic field emitted by the transmitter 102). The sensor 104 may include coils or loops (e.g., at least three coils positioned perpendicular to each other) coupled together in a small structure such as a cube or other container that, by positioning/orientation, capture the incoming electromagnetic flux from an electromagnetic field (e.g., the electromagnetic field emitted by the transmitter 102), and by comparing the currents induced via the coils, and knowing the positioning and orientation of the coils relative to each other, the relative position and orientation of the sensor 104 with respect to the transmitter 102 may be calculated.

One or more parameters related to characteristics of the coils and inertial measurement unit ("IMU") components operatively coupled to the sensor 104 may be measured to detect the position and/or orientation of the sensor 104 (and the object to which it is attached) relative to a coordinate system to which the transmitter 102 is coupled. In some embodiments, multiple sensors 104 may be used relative to the transmitter 102 to detect the position and orientation of each sensor 104 within the coordinate space. The electromagnetic tracking system may provide positions in three directions (e.g., X, Y and the Z direction), and may also provide two or three orientation angles. In some embodiments, measurements of the IMU may be compared to measurements of the coils to determine the position and orientation of the sensor 104. In some embodiments, Electromagnetic (EM) data and IMU data, as well as various other data sources, such as cameras, depth sensors, and other sensors, may be combined to determine position and orientation. This information may be sent (e.g., via wireless communication, bluetooth, etc.) to the controller 106. In some embodiments, the gestures (or positions and orientations) may be reported at a relatively high refresh rate in conventional systems. Conventionally, an electromagnetic field emitter is coupled to a relatively stable and large object, such as a table, operating table, wall, or ceiling, and one or more sensors are coupled to a smaller object, such as a medical device, handheld game component, or the like. Alternatively, as described below with reference to FIG. 3, various features of an electromagnetic tracking system may be used to create such a configuration: wherein changes or variations in position and/or orientation between two objects moving in space can be tracked relative to a more stable global coordinate system; in other words, fig. 3 shows such a configuration: wherein changes to the electromagnetic tracking system can be utilized to track delta (changes) in position and orientation between the head-mounted component and the hand-held component while otherwise determining the pose of the head relative to a global coordinate system (e.g., the user's local room environment), such as by means of instant positioning and mapping ("SLAM") techniques using an outward facing capture camera that may be coupled to the system's head-mounted component.

Controller 106 may control transmitter 102 and may also capture data from sensor 104. It should be understood that the various components of the system may be coupled to each other by any electromechanical or wireless/bluetooth means. The controller 106 may also include data regarding a known electromagnetic field and coordinate space relative to the electromagnetic field. This information is then used to detect the position and orientation of the sensor 104 relative to a coordinate space corresponding to the known electromagnetic field.

One advantage of electromagnetic tracking systems is that they produce high resolution and highly repeatable tracking results with minimal delay. In addition, the electromagnetic tracking system does not have to rely on an optical tracker and can easily track sensors/objects that are not in the line of sight of the user.

It should be appreciated that the strength v of the electromagnetic field decreases as a cubic function of the distance r from the coil transmitter (e.g., transmitter 102). Thus, an algorithm based on the distance from the transmitter 102 may be used. Controller 106 may be configured with such algorithms to determine the position and orientation of sensor 104 at different distances from emitter 102. Given that the strength of the electromagnetic field drops rapidly as the sensor 104 moves away from the transmitter 102, the best results in terms of accuracy, efficiency, and low latency can be obtained at closer distances. In a typical electromagnetic tracking system, the transmitter is powered by an electric current (e.g., a plug-in power supply) and the sensor is located within a 20 foot radius of the transmitter. In many applications, including AR applications, it is more desirable to have a shorter radius between the sensor and the emitter.

Referring now to FIG. 2, an example flow diagram describing the operation of an electromagnetic tracking system in accordance with some embodiments is briefly described. At 202, a known electromagnetic field is emitted. In some embodiments, the electromagnetic field emitter may generate an electromagnetic field. For example, each coil of the electromagnetic field transmitter may generate an electromagnetic field in one direction (e.g., X, Y or Z). The electromagnetic field may be generated in an arbitrary waveform. In some embodiments, the electromagnetic field components along each axis may oscillate at a slightly different frequency than other electromagnetic field components along other directions. At 204, a coordinate space corresponding to the electromagnetic field may be selectively determined. For example, the controller may automatically determine a coordinate space surrounding the emitter and/or sensor based on the electromagnetic field. In some embodiments, the coordinate space is not determined at this stage of the method. At 206, a characteristic of the coil at a sensor (which may be attached to a known object) may be detected. For example, the current induced at the coil may be calculated. In some embodiments, the rotation of the coil or any other quantifiable characteristic may be tracked and measured. At 208, the characteristic may be used to detect a position or orientation of the sensor and/or a known object (e.g., an AR headset including the sensor) relative to the transmitter, or vice versa. For example, the controller 106 may query a mapping table that associates characteristics of the coil at the sensor with various positions or orientations. Based on these calculations, the position in the coordinate space and the orientation of the sensor and/or transmitter may be determined.

In the context of AR systems, it may be desirable to modify one or more components of an electromagnetic tracking system to facilitate accurate tracking of moving components (e.g., emitters and sensors). As described above, in many AR applications, it may be desirable to track the head pose and orientation of a user. Accurately determining the head pose and orientation of the user may cause the AR system to display appropriate/relevant virtual content to the user. For example, a virtual scene may include a virtual monster hidden behind a real building. Depending on the pose and orientation of the user's head relative to the building, the view of the virtual monster may need to be modified in order to provide a realistic AR experience. Alternatively, the location and/or orientation of the totem, haptic device, or some other means of interacting with the virtual content may be important to the user's interaction with the AR system. For example, in many gaming applications, the AR system may detect the position and orientation of a real object relative to virtual content. Alternatively, when the virtual interface is displayed, the position of the totem, the user's hand, the haptic device, or any other real object configured to interact with the AR system, relative to the displayed virtual interface is known to facilitate the system's understanding of commands, interactions, and the like. Some localization methods, including optical tracking, and others, may suffer from high latency, low resolution issues, which make rendering virtual content extremely challenging in many AR applications.

In some embodiments, the electromagnetic tracking system discussed with respect to fig. 1 and 2 may adapt the AR system to detect the position and orientation of one or more objects relative to the emitted electromagnetic field. Typical electromagnetic tracking systems typically have large, bulky electromagnetic emitters (e.g., 102 in fig. 1), which is problematic for, for example, head-mounted AR devices with totems. However, in the context of AR systems, a known electromagnetic field may be transmitted using a smaller electromagnetic transmitter (e.g., in the millimeter range).

Referring now to FIG. 3, an electromagnetic tracking system may be incorporated into the AR system as shown, with an electromagnetic field transmitter 302 (generally referred to as "transmitter 302") incorporated as part of a handheld controller 306 (generally referred to as "controller 306"). The controller 306 may move independently with respect to the AR headset 301 (or harness wrap 370). For example, the controller 306 may be held in a hand of the user, or the controller 306 may be mounted on a hand or arm of the user (e.g., as a ring or bracelet or as part of a glove worn by the user). In some embodiments, the controller 306 may be a totem, for example, for use in a gaming scenario (e.g., a multiple degree of freedom controller), or to provide a rich user experience in an AR environment, or to allow a user to interact with an AR system. In some embodiments, the controller 306 may be a haptic device. In some embodiments, transmitter 302 may be incorporated as part of a bundle pack 370. The controller 306 may include a battery 310 or other power source to power the transmitter 302. It should be appreciated that the transmitter 302 may also include or be coupled to an IMU 350 component configured to facilitate determining a position and/or orientation of the transmitter 302 relative to other components. This is particularly advantageous where both the transmitter 302 and the electromagnetic field sensor 304 (generally referred to as "sensor 304") are mobile. Placing the transmitter 302 in the controller 306 instead of the belt pack 370 as shown in the embodiment of fig. 3 helps to ensure that the transmitter 302 does not contend for resources at the belt pack 370, but rather uses its own battery source on the controller 306. In some embodiments, the transmitter 302 may be disposed on the AR headset 301, while the sensor 304 may be disposed on the controller 306 or the harness wrap 370. Thus, embodiments of the invention provide embodiments in which the controller 306 is implemented as a handheld unit, while in other embodiments the controller is implemented in the AR headset 301, but in further embodiments the controller is implemented in an auxiliary unit (e.g., a belt pack 307). Further, in addition to embodiments in which the controller 306 is implemented in a single device, the functionality of the controller and accompanying physical components may also be distributed across multiple devices, such as the controller 306, the AR headset 301, and/or an auxiliary unit (e.g., the belt pack 307).

In some embodiments, the sensors 304 may be placed at one or more locations on the AR headset 301 along with other sensing devices such as one or more IMUs or additional electromagnetic flux capture coils 308. For example, as shown in fig. 3, the sensors 304, 308 may be placed on one or both sides of the AR headset 301. Since the sensors 304, 308 may be designed to be relatively small (and in some cases may be less sensitive), multiple sensors 304, 308 may be included to improve efficiency and accuracy. In some embodiments, one or more sensors may also be placed on the harness wrap 370 or any other part of the user's body. The sensors 304, 308 may communicate wirelessly, such as via bluetooth, with a computing device that determines the pose and orientation of the sensors 304, 308 (and the AR headset 301 to which they are attached). In some embodiments, the computing device may reside on the belt pack 370. In some embodiments, the computing device may reside on the AR headset 301 or the controller 306. In some embodiments, the computing device may further include a mapping database 330 (e.g., mapping database, cloud resources, federated (passable) world model, coordinate space, etc.) for detecting gestures to determine coordinates of real and/or virtual objects, and may even be connected to cloud resources and the federated world model. In one embodiment, the controller 306 can control the timing of the electromagnetic emissions of the electromagnetic emitter and the sensing of the electromagnetic sensor to calculate the position and orientation of the electromagnetic emitter and the electromagnetic sensor based on the field from the modified electromagnetic field pattern. In some embodiments, the position and orientation of the electromagnetic emitter relative to the electromagnetic sensor is calculated. In other embodiments, the position and orientation of the electromagnetic sensor relative to the electromagnetic emitter is calculated. In some embodiments, the position and orientation of the electromagnetic emitter and the electromagnetic sensor are calculated simultaneously.

As mentioned above, some electromagnetic emitters may be too large for AR devices. Thus, the transmitter can be designed to be more compact using smaller components (e.g., coils) than conventional systems. However, considering that the electromagnetic field strength decreases as a cubic function of distance from the transmitter, a shorter radius (e.g., about 3 to 3.5 feet) between the sensor 304 and the transmitter 302 than the conventional system detailed in FIG. 1 may be used to reduce power consumption.

In some embodiments, this aspect may be used to extend the life of the battery 310 that powers the controller 306 and the transmitter 302 in one or more embodiments. In some embodiments, this aspect may be used to reduce the size of the coil that generates the electromagnetic field at the transmitter 302. However, to obtain the same electromagnetic field strength, the power may need to be increased. This allows the use of a compact transmitter 302 that fits compactly on the controller 306.

Some other modifications may be made when using the electromagnetic tracking system for an AR device. Although this rate of posture reporting is quite excellent, AR systems may require a more efficient rate of posture reporting. To this end, IMU-based pose tracking may be (additionally or alternatively) used. Advantageously, the IMU remains as stable as possible to improve the efficiency of the pose detection process. The IMU may be designed to be stable for up to 50-100 milliseconds. It should be appreciated that some embodiments may utilize an external pose estimation module capable of reporting pose updates at a rate of 10 to 20Hz (e.g., the IMU may drift over time). By keeping the IMU stable at a reasonable rate, the pose update rate can be significantly reduced to 10 to 20Hz (compared to the higher frequencies in conventional systems).

The AR system may save power if the electromagnetic tracking system may be operated at, for example, a 10% duty cycle (e.g., only ping ground truth every 100 milliseconds). This means that the electromagnetic tracking system wakes up for 10 milliseconds every 100 milliseconds to generate a pose estimate. This may translate directly into power consumption savings, which in turn affects the size, battery life, and cost of the AR device (e.g., the AR headset 301 and/or the controller 306).

In some embodiments, the reduction in duty cycle may be strategically utilized by providing two controllers 306 (not shown) instead of only one controller 306 as shown in fig. 3. For example, the user is playing a game that requires two controllers 306, and the like. Alternatively, in a multi-user game, two users play the game using respective controllers 306. When two controllers 306 (e.g., two symmetrical controllers, one for each hand) are used instead of one, the controllers 306 can operate at offset duty cycles. The same concept may also be applied to a controller 306 used by two different users playing a multiplayer game.

Referring now to FIG. 4, an example flow diagram depicting an electromagnetic tracking system in the context of an AR device is depicted. At 402, a portable (e.g., handheld) controller (e.g., controller 306) emits an electromagnetic field. For example, the transmitter 302 transmits an electromagnetic field. At 404, an electromagnetic sensor (placed on a headset, belt pack, etc.) detects an electromagnetic field. For example, the sensors 304, 308 detect electromagnetic fields. At 406, a pose (e.g., position or orientation) of the AR headset/belt pack is determined based on the characteristics of the coils/IMUs at the sensors. For example, the AR headset 301/band pack 370 determines the pose of the AR headset 301/band pack 370 based on the characteristics of the sensors 304 and/or IMU and coils 308. At 408, the gesture information is transmitted to the computing device. For example, the pose information is communicated to the computing device in the AR headset 301 and/or the harness wrap 370. At 410, the mapping database may be selectively queried to associate real world coordinates (e.g., determined for the headgear/harness) with virtual world coordinates. For example, the mapping database 330 may be queried to associate real world coordinates with virtual world coordinates. At 412, the virtual content may be communicated to the AR headset and displayed to the user (e.g., via a light field display as described herein). For example, the virtual content may be transmitted to the AR headset 301 and displayed to the user. It should be understood that the above-described flow diagrams are for illustration purposes only and should not be construed as limiting.

Potential tracking (e.g., position and orientation of the head, totem, and other controller positions and orientations) may be advantageously accomplished using an electromagnetic tracking system similar to that outlined in fig. 3. This allows the AR system to project virtual content (based at least in part on the determined pose) with greater accuracy and very low latency compared to optical tracking techniques. Furthermore, this allows the AR system to track the user input device (e.g., controller 306) with high accuracy, low power consumption (e.g., of battery 210), low latency, and the like.

Fig. 5 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines according to some embodiments. As shown in fig. 5, electromagnetic wire 520 emitted by electromagnetic emitter 510 (generally referred to as "emitter 510") forms a closed loop that passes through the interior region of emitter 510 along the x-direction, substantially parallel to the line created by emitter 510 connecting the poles. As shown in fig. 5, the electromagnetic field generated by the transmitter 510 extends equally along both the positive and negative z-directions.

As described above with respect to fig. 3, during use, the electromagnetic field created by the transmitter 510 (e.g., transmitter 302 in fig. 3) will be detected at the sensor (e.g., sensor 304 in fig. 3) 304 in order to provide the desired positioning information. Because the transmitted electromagnetic field extends away from the transmitter 510 in both the positive and negative z directions, energy directed in the direction opposite the direction from the transmitter 510 to the sensor is not utilized, thereby reducing system efficiency.

In some embodiments, the graphs in fig. 6-9 may be based on finite element analysis of a time-varying electromagnetic field. In some embodiments, adding reflectors of various shapes and configurations at or near the coils of the emitter and/or sensor may increase the intensity of the electromagnetic wires from the emitter and/or sensor in a region of interest (ROI). The ROI is where motion is most active in an AR or VR system. Although the description is made with respect to a transmitter, a similar reflector may be applied to the sensor to enhance the reception capability of the sensor in the ROI. FIG. 6 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a double-sided reflector according to some embodiments. In FIG. 6, only electromagnetic field lines lying in the x-z plane are shown for clarity, but those skilled in the art will appreciate that there will be a three-dimensional lobe pattern. The design shown in FIG. 6 may be extended to three dimensions, as discussed more fully below with respect to FIG. 8.

Referring to fig. 6, two reflective elements have been placed near the emitter 510: a first reflective element 620 and a second reflective element 622, thereby providing an integrated electromagnetic reflector, also referred to as an integrated reflector. The transmitter 510 is oriented such that the electromagnetic field passing through the transmitter coil is aligned with the x-axis. The first reflective element 620 is oriented at a predetermined angle (e.g., 135 deg. angle) with respect to the x-axis and the second reflective element 622 is oriented at a predetermined angle (e.g., 45 deg. angle) with respect to the x-axis. In other words, the first reflective element 620 is aligned with a diagonal having a slope of-1 measured in the x-z plane, and the second reflective element 622 is aligned with a diagonal having a slope of +1 measured in the x-z plane. As shown in fig. 6, the first reflective element 620 and the second reflective element 622 are joined at an apex 630 located at a midpoint of the emitter 510.

The first and second reflective elements 620, 622 are made using a material that has a high electrical conductivity at the operating frequency of the emitter 510 (e.g., 27kHz to 40kHz, such as 35 kHz). In some embodiments, the reflective elements 620, 622 may be formed using highly conductive metal plates (e.g., 2mm thick copper plates). In some embodiments, a substrate coated with a highly conductive material may be employed to take advantage of the mechanical properties of the substrate (e.g., plastic) in combination with the electrical properties of the conductive material coated on the substrate. It will be apparent to those skilled in the art that the materials used to fabricate the first and second reflective elements 620, 622 may be suitably applied to the other reflective elements described herein. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Since the first 620 and second 622 reflective elements reflect the electromagnetic field established along the negative z-direction, the electromagnetic field lines 610 form a single lobe oriented along the positive z-direction. Because of the presence of electromagnetic energy in a single lobe, an electromagnetic field sensor (e.g., sensor 304) positioned along the positive z-axis relative to transmitter 510 will detect a stronger electromagnetic field at a given distance from transmitter 510, thereby improving system performance.

Furthermore, the electromagnetic field lines 610 are characterized by fields of higher intensity over a given lobe width. Referring to fig. 6, the presence of the reflective elements 620 and 622 causes the electromagnetic field lines 610 to compress, thereby generating a field of higher strength. The width of the electromagnetic field lines 610, characterized by half the maximum field strength, is defined as the full width at half maximum (full width half maximum) of the electromagnetic field. As shown in fig. 6, the width is equal to W for electromagnetic field lines 610 having a strength of half the maximum field strength. Thus, the lobe pattern shown in FIG. 6 (which may be referred to as a modified electromagnetic field pattern) has a full width at half maximum of W. This may be compared to the electromagnetic field generated by the emitter in the absence of the first 620 and second 622 reflective elements. In the absence of reflective elements 620 and 622, electromagnetic field lines 610 will extend over a large area and be characterized by a full width at half maximum greater than W, which corresponds to a field of weaker strength in ROI 640, as well as unwanted EM energy in non-ROI regions. Thus, while the conventional electromagnetic field pattern produced by a conventional transmitter is characterized by an initial full width at half maximum, in some embodiments, utilizing a reflective structure such as reflective elements 620 and 622 will produce a modified electromagnetic field pattern characterized by a modified full width at half maximum that is less than the initial full width at half maximum. In other words, the electromagnetic field lines in the ROI 640 have fields of higher strength. Referring to fig. 6, the presence of the reflective elements 620 and 622 will result in the reflection of an electromagnetic field outside of the original electromagnetic field (which was present without the reflective elements 620 and 622). In effect, this produces a modified field pattern having a field strength much higher than the original field without the reflective elements 620 and 622 in the ROI 640. This can be compared to the electromagnetic field generated by the emitter without the reflective elements 620, 622 as shown in fig. 5. In the absence of the reflective elements 620, 622, the electromagnetic field lines 610 will extend over a large area and the field strength in the ROI 640 will be significantly reduced. Thus, the conventional electromagnetic field pattern generated by the conventional transmitter shown in fig. 5 distributes its energy field not only in the ROI 640, but also in the non-ROI regions, as shown in fig. 5. Utilizing reflective elements such as reflective elements 620 and 622 will produce a modified electromagnetic field pattern that is concentrated in ROI 640. In this modified pattern, the distortion caused by the metal in the areas where the magnet wires are minimal will be minimal. Thus, the reflective elements 620 and 622 shield the transmitter's coil and the sensor's coil from deformation caused by metal on the other side of the reflective elements 620 and 622. For the configurations shown in fig. 6, and fig. 7-9, the controller 106 can calculate the position and orientation based on the modified field pattern.

FIG. 7 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a segmented reflector according to some embodiments. A segmented reflector 720 is placed near one side of the emitter 510. The segmented reflector 720 includes a first distal reflective element 722, a central reflective element 724, and a second distal reflective element 726. Since the elements of the segmented reflector 720 reflect the electromagnetic field established along the negative z-direction, the electromagnetic field lines 710 form a single lobe oriented along the positive z-direction. The dimensions (e.g., lengths) of the reflective elements 720, 724, 726, as well as the angle between the first distal reflective element 722 and the central reflective element 724, and the angle between the second distal reflective element 726 and the central reflective element 724, may be selected to control the distribution of the electromagnetic field lines 710.

In some embodiments, the length of the central reflective element 724 is equal to the length of the emitter 510 in the x-direction, and the angles between the distal reflective elements 722, 726 and the central reflective element 724 are both 45 °. The length of the distal reflective elements 722, 726 can be selected based on the length of the central reflective element 724. It will be apparent to those skilled in the art that an increase in the length of the distal reflective elements 722, 726 will result in less electromagnetic field being present in the area behind the distal reflective elements 722, 726 (as opposed to the centerline of the electromagnetic field pattern). However, the increased length of the distal reflective elements 722, 726 may result in increased system weight and cost. In a similar manner, the angle between the central reflective element 724 and the pair of distal reflective elements 722, 726 may be varied as appropriate for a particular application. Thus, although an equal angle of 45 ° is shown in fig. 7, embodiments are not limited to this implementation and configurations having other angles may also be utilized. Further, the angles need not be equal, and may be different. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

FIG. 8 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a trihedral reflector according to some embodiments. In FIG. 8, only electromagnetic field lines lying in the x-z plane are shown for clarity, but those skilled in the art will appreciate that there will be a three-dimensional lobe pattern with the center of the lobe extending away from the electromagnetic transmitter along a direction orthogonal to the x-axis and at an angle of 45 relative to the x-z plane.

Referring to fig. 8, three reflective elements are shown. The first reflective element 812 and the second reflective element 814 are positioned adjacent to the emitter 510. A third reflective element 816, located in the x-z plane, is shown by the dashed line. In the embodiment shown in FIG. 8, the three reflective elements 812, 814, 816 are orthogonal to each other, forming one half of a cube structure, where the intersection of the three reflective elements forms the angular vertex of the cube. The emitter 510 is oriented at 45 deg. relative to the orientation shown in fig. 6. Thus, in this embodiment, the plates of the emitter 510 are oriented at 45 ° with respect to the x-axis.

Since the first, second, and third reflective elements 620, 622, 816 reflect the electromagnetic fields established along the negative z-direction and the positive y-direction, the electromagnetic field lines 810 form a single lobe oriented outward from the plane of the figure along the positive z-direction and the negative y-direction. In some embodiments, the presence of the reflective elements 812, 814, 816 in the half-cube configuration results in an efficiency increase of up to eight times and a power consumption reduction of up to one-eighth. Alternatively, the size of the transmitter 510 may be reduced to achieve a given efficiency/power consumption. Furthermore, in some embodiments, the size of the transmitter 510 is reduced while achieving improved efficiency/power consumption performance. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

Fig. 9 is a plan view of an electromagnetic emitter and corresponding electromagnetic field lines incorporating a hemispherical reflector according to some embodiments. In fig. 9, a portion of hemispherical reflector 920 located in the x-z plane is shown as a circular arc. It will be appreciated that rotation of the illustrated arc about the z-axis will define the hemispherical shape of the hemispherical reflector. Since hemispherical reflector 920 reflects the electromagnetic field established along the negative z-direction, the electromagnetic field lines 910 form a single lobe oriented along the positive z-direction.

FIG. 10A is a perspective view illustrating integration of an electromagnetic transmitter incorporating a trihedral reflector with a handheld controller according to some embodiments. Referring to FIG. 10A, a handheld controller 1000 includes an electromagnetic emitter 1010 (generally referred to as "emitter 1010") integrated with a three-sided cube reflector 1020. In this example, the three sides of the reflector lie in the following planes, respectively: first side 1022 lies in the x-z plane, second side 1024 lies in the x-y plane, and third side 1026 lies in the y-z plane. Reflection of the electromagnetic field generated by the emitter 1010 by the dihedral cube reflector 1020 results in the center of the three-dimensional lobe pattern generated by the emitter 1010 being aligned with a vector 1030, the vector 1030 being aligned with a direction away from the intersection of the three reflector planes (in a direction of a principal line equidistant from the three axes of the dihedral cube reflector, where each axis corresponds to the intersection of two reflectors). As shown in FIG. 10A, the vector 1030 points from the origin in x-y-z coordinate space along a line pointing to a point (1,1,1) in x-y-z coordinate space that corresponds to the center of the three-dimensional lobe pattern. When such a dihedral cube reflector is applied to a sensor, it will make the sensor sense most effectively along a main line directed to the ROI.

In typical use, the handheld controller 1000 is placed in front of the user with the surface 1050 generally orthogonal to a line pointing toward the user's head and the AR headset worn by the user. The line connecting surface 1050 and the user's head and normal to surface 1050 is generally parallel to vector 1030. As a result, a stronger field is generated along vector 1030 and near the user's head and the AR headset worn by the user due to the increased directivity of the electromagnetic field generated by transmitter 1010. Similarly, as described below with respect to fig. 10B, the headset may include sensors with corresponding three-sided corner cube reflectors (or other suitable integrated reflectors described herein) configured such that maximum reception occurs in the ROI that is desired to include the emitter. Thus, improved system performance is provided relative to embodiments that do not utilize reflective elements.

Figure 10B is a perspective view illustrating integration of an electromagnetic sensor incorporating a trihedral reflector with a headset according to some embodiments. As shown in fig. 10B, the AR headset 301 includes a sensor housing 1075, in some embodiments, the sensor housing 1075 is mounted below the right temple (temple) of the AR headset 301. Fig. 10C is a perspective view showing an expanded view of the sensor housing 1075 shown in fig. 10B. Sensor housing 1075 includes an electromagnetic sensor 1070 (generally referred to as "sensor 1070") integrated with a three-sided corner cube reflector 1072. The three-sided corner cube reflector reflects the electromagnetic field received by sensor 1070, such reflection resulting in the center of the three-dimensional lobe pattern received by sensor 1070 being aligned with vector 1074, vector 1074 being oriented along a direction away from the intersection of the three reflector planes (in a direction of a main line equidistant from the three axes of the three-sided corner cube reflector, where each axis corresponds to the intersection of two reflectors). As shown in FIG. 10B, the vector 1074 points from the origin of the x-y-z coordinate space along a line pointing to a point (1,1,1) in the x-y-z coordinate space that corresponds to the center of the three-dimensional lobe pattern. It is noted that the x-y-z coordinate space shown in FIG. 10B is different from the coordinate space shown in FIG. 10A for clarity. As shown in fig. 10B, by applying a three-sided corner cube reflector 1072 to sensor 1070, sensor 1070 is allowed to sense most efficiently along a main line directed toward the emitter.

In typical use, since the handheld controller 1000 shown in fig. 10A is placed in front of and below the head of the user, the electromagnetic field received by the sensor housing 1075 from the emitters will be enhanced by the presence of the three-sided corner cube reflector 1072. The positioning of a three-sided cube reflector 1072 next to sensor 1070 results in an increased directionality of the electromagnetic field received by sensor 1070. Thus, the sensitivity of the sensor increases along the line connecting the handheld controller 1000 and the AR headset 301. Thus, the sensor 1070 has a higher sensitivity to electromagnetic fields generated near the handheld controller. Thus, improved system performance is provided relative to embodiments that do not utilize reflective elements.

FIG. 11 is a simplified flow diagram illustrating a method of operating an electromagnetic tracking system incorporating an integrated reflector according to an embodiment of the present invention. The method 1100 in which the electromagnetic tracking system includes one or more integrated electromagnetic reflectors includes generating an electromagnetic field using an electromagnetic transmitter (1100). The electromagnetic emitter may be provided in a handheld controller as one element of an electromagnetic tracking system that includes the handheld controller, an auxiliary unit that may include the controller, and a head-mounted augmented reality display. The integrated electromagnetic reflector may be used with the emitter and/or sensor and may be any of the integrated electromagnetic reflectors shown in fig. 6-9 of the present specification.

The method also includes reflecting the electromagnetic field using a first electromagnetic reflector to form a modified electromagnetic field pattern (1112). The first electromagnetic reflector may be positioned adjacent to the electromagnetic emitter. The first electromagnetic reflector may include reflective elements having various geometric characteristics, including two or more reflective plates that may be joined at an apex. In other embodiments, three reflective plates are utilized and arranged to define the angular vertices of a cube. In an alternative embodiment, the first electromagnetic reflector is formed as a single reflector element. As an example, the single reflector element may be a segmented reflector as discussed and illustrated with respect to fig. 7, or a hemispherical reflector as discussed and illustrated with respect to fig. 9.

The method also includes reflecting a portion of the modified electromagnetic field pattern using a second electromagnetic reflector (1114) and sensing the reflected portion of the modified electromagnetic field pattern using an electromagnetic sensor adjacent to the second electromagnetic reflector (1116). The method further includes controlling, with the controller, timing of generating the electromagnetic field and sensing the reflected portion of the modified electromagnetic field, and digitally calculating a position and orientation of the electromagnetic emitter and the electromagnetic sensor based on the modified electromagnetic field pattern.

It should be appreciated that the specific steps illustrated in FIG. 11 provide a particular method of operating an electromagnetic emitter incorporating an integrated reflector in accordance with an embodiment of the present invention. Other sequences of steps may also be performed according to alternative embodiments. For example, alternative embodiments of the present invention may perform the steps outlined above in a different order. Moreover, the various steps shown in FIG. 11 may include multiple sub-steps that may be performed in various sequences as appropriate to the individual step. In addition, additional steps may be added or deleted depending on the particular application. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.