SYSTEM AND METHOD FOR SYNCHRONIZING FIDUCIAL MARKERS

• US 20160005174A1
• Filed: 06/30/2015
• Published: 01/07/2016
• Est. Priority Date: 07/01/2014
• Status: Active Grant

• Current Assignee: Tilt Five, Inc.
• Original Assignee: Technical Illusions, Inc.
• Inventors: Ellsworth, Jeri J., Clements, Ken
• Granted Patent: US 9,626,764 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2027/0138 comprising image capture systems, e.g. camera
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 2027/0187 slaved to motion of at least a part of the body of the user, e.g. head, eye
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G06T 11/60 Editing figures and text; Combining figures or text
• CPC Class Codes: G06T 2207/30208 Marker matrix
• CPC Class Codes: G06T 2207/30244 Camera pose
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

A system of active fiducial markers for pose calculation of head mounted displays is described in which information is exchanged among said markers for the purpose of synchronization. Fiducial patterns are made more easily identifiable by selective duty cycles of sub groups of synchronized emitters and means is described to propagate pose information among markers.

Claims

1. A system of fiducial markers for movable device pose calculation comprising:

a plurality of fixtures with one or more light emitters;

said fixtures having light detecting and demodulating means;

synchronization means active through information exchanged between said emitters and detectors;

said fixtures further having control and activation circuitry in order to turn on said light emitters for display of fiducial patterns during active duty cycle periods as determined by said synchronization.

2. The system of claim 1 in which said markers comprise a plurality of sets of said emitters with duty cycles independently adjusted to provide different images as seen by a camera or cameras.

3. The system of claim 1 in which said markers emit infrared light.

4. The system of claim 1 in which said markers communicate by means of local area wireless network technology.

5. The system of claim 1 in which said movable device comprises a camera or cameras having means to image one or more said markers and further having means to calculate an estimate of the pose of said camera or cameras with respect to said marker or markers.

6. The system of claim 5 further comprising light or radio frequency or ultrasonic means by which said camera may transmit pose estimate information to one or more said markers.

7. The system of claim 6 further comprising means to use the pose estimate calculated at said camera or cameras from images of two or more said markers to calculate the pose of said markers relative to each other.

8. The system of claim 7 in which said movable device comprises a head mounted display.

9. The system of claim 7 in which said movable device comprises a hand held control.

10. The system of claim 7 further comprising means to transmit said relative pose information to said imaged markers by techniques of light modulation or wireless local area networking or ultrasonic signaling.

11. The system of claim 10 further comprising means in said markers to exchange stored relative pose information by light transmission and reception or wireless local area networking or ultrasonic signaling.

12. A method of active fiducial marker synchronization comprising the steps:

(a) providing a plurality of light emitting fiducial markers having means to modulate emitted light, or radio frequency, patterns and to receive and demodulate information encoded as light, or radio frequency, patterns;

(b) encoding synchronization time stamps as modulated light patterns at a first marker and transmitting said patterns from said first marker to secondary markers;

(c) receiving and demodulating said time stamps at one or more said secondary markers;

(d) using said received time stamps to set schedules for emission of patterns of light from said markers.

13. The method of claim 12. further comprising the steps:

(a) providing a camera or cameras having the means to image said markers;

(b) calculating the pose of said camera or cameras relative to said markers from said images;

(c) providing communicating means for said cameras to encode and transmit said relative pose information to said markers and providing communication means at said markers to receive and decode said information;

(d) sending said relative pose information to said markers and receiving said pose information at said markers;

(e) storing said relative pose information at said markers.

14. The method of claim 13. further comprising the steps:

(a) providing communication means for said markers to exchange said relative pose information;

(b) exchanging said relative pose information among said markers.

15. The method of claim 13. further comprising the steps:

(a) providing a motion sensor at said camera or cameras;

(b) using said motion sensor to track the motion of said camera or cameras when images of said markers are out of view.

16. The method of claim 15. further comprising using said tracked motion to calculate estimates of the relative pose of markers when said markers are brought into view.

17. The method of claim 13. further comprising using averaging or other statistical means to combine pose estimates so as to reduce pose uncertainty.