Magnetic tracker with dual-transmit frequency

Patent metadata

Field	Value
Publication number	US-10416333-B2
Application number	US-201715600357-A
Country	US
Kind code	B2
Filing date	May 19, 2017
Priority date	May 19, 2017
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A system of a transmitter and a receiver uses magnetic fields to determine the relative position and orientation, or pose, of the two devices. For example, the transmitter could be a handheld control device and the receiver could be an augmented reality or other computing solution. The transmitter transmits two magnetic fields of differing frequencies and differing amplitudes. The receiver selects the one of the magnetic fields with the higher signal to noise ratio to determine the relative pose of the transmitter. By using two magnetic fields of different amplitudes, the pose can be determined over a wider range of separations.

First claim

We claim:

1. A method, comprising:
transmitting, from a transmitter, a first magnetic field signal at a first power level while concurrently transmitting a second magnetic field signal at a second power level that is less than the first power level, wherein the first magnetic field signal is transmitted at a first frequency, and wherein the second magnetic field signal is transmitted at a second frequency that differs from the first frequency;
receiving, at a receiver, the first magnetic field signal while concurrently receiving the second magnetic field signal, wherein:
the first power level results in the first magnetic field signal having a first useful range over which the first magnetic field signal that is being transmitted from the transmitter does not saturate the receiver,
the second power level results in the second magnetic field signal having a second useful range over which the second magnetic field signal that is being transmitted from the transmitter does not saturate the receiver, and
the second useful range being closer to the receiver than the first useful range;

determining which particular magnetic field signal, of the first magnetic field signal and the second magnetic field signal, corresponds to a higher signal to noise ratio at the receiver; and
determining, while the first magnetic field signal and the second magnetic field signal are being concurrently transmitted, a relative pose between the transmitter and the receiver based on the particular magnetic field signal that corresponds to the higher signal to noise ratio.

2. The method of claim 1 , wherein the transmitter includes a first plurality of coils each aligned along one of a first plurality of axes, and wherein transmitting the first magnetic field signal and the second magnetic field signal includes generating the first magnetic field signal and the second magnetic field signal by the first plurality of coils, and
wherein the receiver includes a second plurality of coils each aligned along one of a second plurality of axes by which the first magnetic field signal and the second magnetic field signal are received.

3. The method of claim 2 , wherein each coil of the first plurality of coils generates both the first magnetic field signal and the second magnetic field signal, and wherein each coil of the second plurality of coils receives both the first magnetic field signal and the second magnetic field signal.

4. The method of claim 2 , wherein the first plurality of coils are three coils aligned along orthogonal axes and the second plurality of coils are three coils aligned along orthogonal axes.

5. The method of claim 1 , further comprising:
determining, while the first magnetic field signal is being transmitted concurrently with the second magnetic field signal, whether both of the first magnetic field signal and the second magnetic field signal have at least a sufficiently high signal to noise ratio for determining the relative pose; and
in response to determining that both of the first magnetic field signal and the second magnetic field signal have at least the sufficiently high signal to noise ratio for determining the relative pose, determining the relative pose between the transmitter and the receiver based on both of the first magnetic field signal and the second magnetic field signal.

6. The method of claim 1 , wherein the receiver determines that the particular magnetic field signal has the higher signal to noise ratio without gain control.

7. The method of claim 1 , wherein the receiver is a component of an augmented reality device.

8. The method of claim 1 , wherein the transmitter is a hand-held device.

9. A method, comprising:
causing a transmitter to transmit a first magnetic field signal at a first power level while concurrently transmitting a second magnetic field signal at a second power level that is less than the first power level, and wherein the first magnetic field signal is transmitted at a first frequency and the second magnetic field is concurrently transmitted at a second frequency that differs from the first frequency;
detecting, via a receiver, the first magnetic field signal concurrently with the second magnetic field signal, wherein:
the first power level results in the first magnetic field signal having a first useful range of distances from the receiver over which the first magnetic field signal does not saturate the receiver,
the second power level results in the second magnetic field signal having a second useful range of distances from the receiver over which the second magnetic field signal does not saturate the receiver, and
the second useful range being closer to the receiver than the first useful range;

selecting a particular magnetic field signal, from the first magnetic field signal and the second magnetic field signal, based on the particular magnetic field signal having a highest signal to noise ratio of the first magnetic field signal and the second magnetic field signal;
determining a relative pose between the transmitter and the receiver based on the particular magnetic field signal that has the highest signal to noise ratio.

10. The method of claim 9 , wherein selecting the particular magnetic field signal includes:
determining a first signal to noise ratio that corresponds to the first magnetic field signal;
determining a second signal to noise ratio that corresponds to the second magnetic field signal; and
selecting the particular magnetic field signal based on a comparison between the first signal to noise ratio and the second signal to noise ratio.

11. The method of claim 9 , wherein the transmitter is integrated into a hand-held control device that corresponds to a head mounted display device, and wherein the receiver is integrated into the head mounted display device.

12. The method of claim 9 , wherein the receiver is integrated into a hand-held control device that corresponds to a head mounted display device, and wherein the transmitter is integrated into the head mounted display device.

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Fullam Scott F
• Cherkashin Lev

Classifications

• H04W88/06

  adapted for operation in multiple networks {or having at least two operational modes}, e.g. multi-mode terminals · CPC title

• H04W4/029

  Location-based management or tracking services · CPC title

• H04W4/026

  using orientation information, e.g. compass · CPC title

• G02B2027/0187

  slaved to motion of at least a part of the body of the user, e.g. head, eye · CPC title

• G02B2027/014

  comprising information/image processing systems · CPC title