# US 2017/0287219 A1 · Electromagnetic tracking of objects for mixed reality > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2017/0287219 A1 - Document ID: US20170287219A1 - Status: Published application - Kind: A1 - Application number: 15/087,833 - Filed: 2016-03-31 - Published: 2017-10-05 - Earliest claimed: 2016-03-31 - Inventors: Adam G. Poulos; Daniel Joseph McCulloch; Nicholas Gervase Fajt; Arthur Tomlin; Brian Mount; Lev Cherkashin; Lorenz Henric Jentz - Web page: https://patentgrep.com/patent/US20170287219A1 ## CPC - G06T 19/006: {Mixed reality (object pose determination, tracking or camera calibration for mixed reality G06T7/00)} - G02B 27/017: {Head mounted} - G02B 27/0172: {characterised by optical features} - G06F 3/011: {Arrangements for interaction with the human body, e.g. for user immersion in virtual reality (blind teaching G09B21/00)} - G06F 3/0346: with detection of the device orientation or free movement in a three-dimensional [3D] space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors - G02B 2027/0138: {comprising image capture systems, e.g. camera} - G02B 2027/014: {comprising information/image processing systems} - G02B 2027/0174: {holographic} - G02B 2027/0178: {Eyeglass type (eyeglass details G02C)} - G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A mixed reality system may comprise a head-mounted display (HMD) device with a location sensor from which the HMD device determines a location of the location sensor in space and a base station mounted a predetermined offset from the location sensor and configured to emit an electromagnetic field (EMF). An EMF sensor affixed to an object may be configured to sense a strength of the EMF. The HMD device may determine a location of the EMF sensor relative to the base station based on the sensed strength and determine a location of the EMF sensor in space based on the relative location, the predetermined offset, and the location of the location sensor in space. In some aspects, the HMD device may comprise a see-through display configured to display augmented reality images and overlay a hologram that corresponds to the location of the EMF sensor in space over time. ## Claims ### Claim 1 A mixed reality system comprising: a head-mounted display (HMD) device comprising: a location sensor from which the HMD device determines a location of the location sensor in space; and a base station mounted at a fixed position relative to the HMD device a predetermined offset from the location sensor and configured to emit an electromagnetic field; and an electromagnetic field sensor affixed to an object and configured to sense a strength of the electromagnetic field; wherein the HMD device includes a processor configured to: determine a location of the electromagnetic field sensor relative to the base station based on the sensed strength; and determine a location of the electromagnetic field sensor in space based on the relative location, the predetermined offset, and the location of the location sensor in space. ### Claim 2 (depends on 1) The mixed reality system of claim 1, wherein the HMD device further comprises an at least partially opaque display configured to display virtual reality images. ### Claim 3 (depends on 1) The mixed reality system of claim 1, wherein the HMD device further comprises an at least partially see-through display configured to display augmented reality images. ### Claim 4 (depends on 3) The mixed reality system of claim 3, wherein the display is further configured to overlay a hologram that corresponds to the location of the electromagnetic field sensor in space over time. ### Claim 5 (depends on 1) The mixed reality system of claim 1, wherein the electromagnetic field sensor is configured to communicate the sensed strength to the base station and the base station is configured to determine the location of the electromagnetic field sensor relative to the base station based on the sensed strength. ### Claim 6 (depends on 1) The mixed reality system of claim 1, wherein the electromagnetic field sensor is configured to determine the location of the electromagnetic field sensor relative to the base station based on the sensed strength and communicate the location of the electromagnetic field sensor relative to the base station, to the base station. ### Claim 7 (depends on 1) The mixed reality system of claim 1, wherein the object is a handheld input device configured to provide user input to the HMD device. ### Claim 8 (depends on 1) The mixed reality system of claim 1, wherein the location sensor is at least one camera. ### Claim 9 (depends on 1) The mixed reality system of claim 1, wherein the electromagnetic field sensor comprises a transceiver to wirelessly communicate with the base station. ### Claim 10 (depends on 1) The mixed reality system of claim 1, wherein the base station is positioned in a front portion of a housing of the HMD device. ### Claim 11 (depends on 1) The mixed reality system of claim 1, wherein, to determine the location of the electromagnetic field sensor in space, the processor is configured to: offset the location of the location sensor in space by the predetermined offset to determine a location of the base station in space; and offset the location of the base station in space by the location of the electromagnetic field sensor relative to the base station. ### Claim 12 A method of locating an object in a mixed reality system, the method comprising: determining a location of a location sensor of a head-mounted display (HMD) device in space; emitting an electromagnetic field from a base station mounted at a fixed position relative to the HMD device a predetermined offset from the location sensor; sensing a strength of the electromagnetic field with an electromagnetic field sensor affixed to the object; determining, with a processor of the HMD device, a location of the electromagnetic field sensor relative to the base station based on the sensed strength; and determining, with the processor, a location of the electromagnetic field sensor in space based on the relative location, the predetermined offset, and the location of the location sensor in space. ### Claim 13 (depends on 12) The method of claim 12, further comprising displaying augmented reality images on an at least partially see-through display of the HMD device. ### Claim 14 (depends on 13) The method of claim 13, further comprising overlaying on the display a hologram that corresponds to the location of the electromagnetic field sensor in space over time. ### Claim 15 (depends on 12) The method of claim 12, further comprising communicating the sensed strength to the base station and determining, at the base station, the location of the electromagnetic field sensor relative to the base station based on the sensed strength. ### Claim 16 (depends on 12) The method of claim 12, wherein the object is a handheld input device and the method further comprises providing user input to the HMD device via the input device. ### Claim 17 (depends on 12) The method of claim 12, wherein the electromagnetic field sensor comprises a transceiver and the method further comprises wirelessly communicating between the electromagnetic field sensor and the base station. ### Claim 18 (depends on 12) The method of claim 12, further comprising positioning the base station in a front portion of a housing of the HMD device. ### Claim 19 (depends on 12) The method of claim 12, wherein determining the location of the electromagnetic field sensor in space comprises: offsetting the location of the location sensor in space by the predetermined offset to determine a location of the base station in space; and offsetting the location of the base station in space by the location of the electromagnetic field sensor relative to the base station. ### Claim 20 A mixed reality system comprising: an electromagnetic field sensor affixed to an object and configured to sense a strength of an electromagnetic field; and a head-mounted display (HMD) device comprising: a location sensor from which the HMD device determines a location of the location sensor in space; a base station mounted at a fixed position relative to the HMD device a predetermined offset from the location sensor and configured to emit the electromagnetic field; a processor configured to: determine a location of the electromagnetic field sensor relative to the base station based on the sensed strength; and determine a location of the electromagnetic field sensor in space based on the relative location, the predetermined offset, and the location of the location sensor in space; and an at least partially see-through display configured to display augmented reality images and overlay a hologram that corresponds to the location of the electromagnetic field sensor in space over time.