Calibration of magnetic and optical sensors in a virtual reality or augmented reality display system

• US 10,534,043 B2
• Filed: 09/25/2017
• Issued: 01/14/2020
• Est. Priority Date: 09/26/2016
• Status: Active Grant

• Current Assignee: Magic Leap, Inc.
• Original Assignee: Magic Leap, Inc.
• Inventors: Woods, Michael, Nortman, Scott David
• Primary Examiner(s): Nguyen, Tung X
• Application Number:
  US15/714,905
• Publication Number:
  US 20180088185A1
• Time in Patent Office: 841 Days
• CPC Class Codes: G01R 33/0035 Calibration of single magnetic sensors, e.g. integrated calibration
• CPC Class Codes: G01R 35/00 Testing or calibrating of apparatus covered by the other groups of this subclass
• CPC Class Codes: G06F 1/163 Wearable computers, e.g. on a belt
• CPC Class Codes: G06F 3/011 Arrangements for interaction with the human body, e.g. for user immersion in virtual reality blind teaching G09B21/00
• CPC Class Codes: G06F 3/012 Head tracking input arrangements
• CPC Class Codes: G06F 3/0304 Detection arrangements using opto-electronic means constructional details of pointing devices not related to the detection arrangement using opto-electronic means G06F3/033; optical digitisers G06F3/042
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06T 19/006 Mixed reality object pose determination, tracking or camera calibration for mixed reality G06T7/00

Abstract

A system for calibrating alignment of magnetic and optical sensors in a virtual reality (VR) or augmented reality (AR) device. The system can include a controller, a waveform generator, and an electrical driver. The waveform generator can produce calibration waveforms under control of the controller. The system can also include conductive loops which are energized with electrical currents corresponding to the calibration waveforms. The controller can cause the waveform generator to generate a first calibration waveform to calibrate a first type of magnetic sensor in the display device, and to generate a second calibration waveform to calibrate a second type of magnetic sensor in the display device. The system may also include one or more optical fiducial markers in a known spatial relationship with respect to the conductive loops. The optical fiducial markers can be used to calibrate the alignment direction of one or more optical sensors.

Claims

1. A system for calibrating alignment of two or more magnetic sensors in a virtual reality (VR) or augmented reality (AR) display device, the system comprising:

a controller;

a waveform generator configured to generate a first calibration waveform and a second calibration waveform under control of the controller;

a first conductive loop oriented in a first plane orthogonal to a first axis passing through the first conductive loop;

a second conductive loop oriented in a second plane parallel to the first plane and spaced apart from the first conductive loop along the first axis; and

an electrical driver connected to the waveform generator to receive the first and second calibration waveforms, to generate corresponding first and second electrical output currents, and to provide the first and second electrical output currents to the first conductive loop and the second conductive loop,

wherein the controller is configured to cause the waveform generator to generate the first calibration waveform to calibrate a first type of magnetic sensor in the display device, and to generate the second calibration waveform to calibrate a second type of magnetic sensor in the display device.

2. The system of claim 1, wherein the controller is configured to communicate with the display device to identify the magnetic sensors to be calibrated, and to select the first and second calibration waveforms based on the identification of the magnetic sensors.

3. The system of claim 1, wherein the first type of magnetic sensor comprises an inductive magnetometer and the first calibration waveform comprises an alternating current waveform.

4. The system of claim 1, wherein the second type of magnetic sensor comprises a static field magnetometer and the second calibration waveform comprises a direct current waveform.

5. The system of claim 1, wherein the first conductive loop and the second conductive loop are connected to the electrical driver such that the electrical output current travels in the same direction around both the first conductive loop and the second conductive loop.

6. The system of claim 1, wherein the first conductive loop and the second conductive loop have the same shape.

7. The system of claim 1, wherein the first conductive loop and the second conductive loop have the same size.

8. The system of claim 7, wherein the first conductive loop and the second conductive loop are circular and have a radius, the first conductive loop and the second conductive loop being spaced apart along the first axis by a distance corresponding to the radius.

9. The system of claim 1, further comprising a mount configured to attach to the display device and to support it in a first predetermined spatial relationship with respect to the first and second conductive loops.

10. The system of claim 9, further comprising an actuator connected to the mount and configured to move the display device to a second predetermined spatial relationship with respect to the first and second conductive loops.

11. The system of claim 1, further comprising:

a third conductive loop oriented in a third plane orthogonal to a second axis passing through the third conductive loop, the second axis being orthogonal to the first axis;

a fourth conductive loop oriented in a fourth plane parallel to the third plane and spaced apart from the third conductive loop along the second axis.

12. The system of claim 11, further comprising:

a fifth conductive loop oriented in a fifth plane orthogonal to a third axis passing through the fifth conductive loop, the third axis being orthogonal to the first and second axes;

a sixth conductive loop supported by the frame and oriented in a sixth plane parallel to the fifth plane and spaced apart from the fifth conductive loop along the third axis.

13. The system of claim 1, wherein the system is further configured to calibrate alignment of an optical sensor, the system further comprising one or more optical fiducial markers oriented in a predetermined spatial relationship with respect to the first conductive loop and the second conductive loop.

14. The system of claim 13, wherein the optical sensor comprises a camera.

15. The system of claim 13, wherein the one or more optical fiducial markers include two-dimensional or three-dimensional features.

16. A system for calibrating alignment of one or more magnetic sensors and one or more optical sensors in a virtual reality (VR) or augmented reality (AR) display device, the system comprising:

a first conductive loop oriented in a first plane orthogonal to a first axis passing through the first conductive loop;

a second conductive loop oriented in a second plane parallel to the first plane and spaced apart from the first conductive loop along the first axis; and

one or more optical fiducial markers supported in a predetermined spatial relationship with respect to the first conductive loop and the second conductive loop.

17. The system of claim 16, wherein the one or more optical fiducial markers are mounted to the first conductive loop or the second conductive loop.

18. The system of claim 16, further comprising:

a controller;

a waveform generator configured to generate a calibration waveform under control of the controller; and

an electrical driver connected to the waveform generator to receive the calibration waveform, to generate a corresponding electrical output current, and to provide the electrical output current to the first conductive loop and the second conductive loop.

19. A method for calibrating alignment of two or more magnetic sensors in a virtual reality (VR) or augmented reality (AR) display device, the method comprising:

generating a first calibration waveform;

energizing, with the first calibration waveform, a first conductive loop oriented in a first plane orthogonal to a first axis passing through the first conductive loop and a second conductive loop oriented in a second plane parallel to the first plane and spaced apart from the first conductive loop along the first axis;

determining a first measurement, using a first type of magnetic sensor of the display device, indicative of an orientation of a magnetic field produced by the first and second conductive loops when energized with the first calibration waveform;

generating a second calibration waveform;

energizing the first and second conductive loops with the second calibration waveform;

determining a second measurement, using a second type of magnetic sensor of the display device, indicative of an orientation of a magnetic field produced by the first and second conductive loops when energized with the second calibration waveform; and

comparing the first measurement with the second measurement.

20. The method of claim 19, further comprising determining a calibration value based on the comparison of the first and second measurements.

21. The method of claim 20, further comprising storing the calibration value in a memory of the display device.

22. The method of claim 21, further comprising modifying readings from the first or second magnetic sensor based on the calibration value while executing an application using the display device.

23. A method for calibrating alignment of one or more magnetic sensors and one or more optical sensors in a virtual reality (VR) or augmented reality (AR) display device, the method comprising:

generating a calibration waveform;

energizing, with the calibration waveform, a first conductive loop oriented in a first plane orthogonal to a first axis passing through the first conductive loop and a second conductive loop oriented in a second plane parallel to the first plane and spaced apart from the first conductive loop along the first axis;

determining a first measurement, using a magnetic sensor of the display device, indicative of an orientation of a magnetic field produced by the first and second conductive loops when energized with the calibration waveform;

determining, with an optical sensor of the display device, a second measurement indicative of a spatial relationship of an optical fiducial marker with respect to the first conductive loop and the second conductive loop; and

comparing the first measurement with the second measurement.

24. The method of claim 23, wherein determining the measurement indicative of the spatial relationship of the optical fiducial marker comprises determining the position or orientation of the optical fiducial marker.

25. The method of claim 23, further comprising determining a value indicative of an alignment direction of the optical sensor based on the measurement indicative of the spatial relationship of the optical fiducial marker.

26. The method of claim 23, further comprising determining a calibration value based on the comparison of the first and second measurements.

27. The method of claim 26, further comprising storing the calibration value in a memory of the display device.

28. The method of claim 27, further comprising modifying readings from the magnetic sensor or the optical sensor based on the calibration value while executing an application using the display device.