Indoor navigation via multi-beam laser projection

• US 20140285631A1
• Filed: 06/20/2013
• Published: 09/25/2014
• Est. Priority Date: 03/20/2013
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Janky, James M., McCusker, Michael V., Ulman, Morrison, Sharp, Kevin A. I.
• Granted Patent: US 10,165,255 B2
• Time in Patent Office: Days
• US Class Current: 348/47
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: G05D 1/0248 in combination with a laser lasers per se H01S
• CPC Class Codes: G06T 7/596 from three or more stereo images
• CPC Class Codes: G06T 7/97 Determining parameters from multiple pictures depth or shape recovery from multiple images G06T7/55; stereo camera calibration G06T7/85
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence

Abstract

An indoor navigation system is based on a multi-beam laser projector, a set of calibrated cameras, and a processor that uses knowledge of the projector design and data on laser spot locations observed by the cameras to solve the space resection problem to find the location and orientation of the projector.

Claims

1. An indoor navigation system comprising:

a laser projector that emits one or more laser beams in four or more different directions during a time interval Δ

t;

two or more cameras that capture images of spots made by the laser beams on surfaces of an indoor space during Δ

t, the cameras calibrated such that three-dimensional locations of the spots can be estimated from images captured by at least two cameras; and

,

a processor in communication with the cameras, the processor estimating position of the laser projector in the indoor space by space resection given the four or more different directions and the three-dimensional locations of the spots.

2. The system of claim 1, the processor further in communication with the projector to determine orientation of the projector with respect to an object during Δ

t.

3. The system of claim 2, the projector attached to the object via a gimbal mount.

4. The system of claim 1, the projector comprising a rotating mirror;

and the processor further in communication with the projector to determine an angle of the rotating mirror during Δ

t.

5. The system of claim 1, the projector comprising a micro-electromechanical (MEMS) spatial light modulator;

and the processor further in communication with the projector to determine unit vectors representing directions of laser beams emitted by the projector during Δ

t.

6. The system of claim 1, each pair of directions of the four or more defining an angle different from that of any other pair.

7. The system of claim 1, the four or more different directions coinciding at a point.

8. The system of claim 1, the laser beams having an infrared wavelength and the cameras equipped with infrared filters to select the wavelength in preference to background light.

9. The system of claim 1, each laser beam modulated with a modulation signal that distinguishes it from all of the other laser beams, and each camera demodulating the signal to identify a correspondence between spots and laser beam directions.

10. The system of claim 9, the modulation signal being sinusoidal.

11. The system of claim 9, the modulation signal being a pseudorandom code.

12. The system of claim 9, the modulation signal further carrying information pertaining to the orientation of each laser beam with respect to an object.

13. A method for indoor navigation comprising:

capturing, with two or more cameras, images of spots made by one or more laser beams on surfaces of an indoor space, the laser beams emitted by a laser projector in four or more different directions during a time interval Δ

t;

estimating three-dimensional locations of the spots from images captured by at least two cameras during Δ

t; and

,

estimating position of the laser projector in the indoor space by space resection given the four or more different directions and the three-dimensional locations of the spots.

14. The method of claim 13 further comprising:

estimating an orientation of an object during Δ

t, given a relative orientation of the object and the projector.

15. The method of claim 14, the projector attached to the object via gimbal mount.

16. The method of claim 13 wherein the laser projector comprises a rotating mirror;

and further comprising;

estimating an orientation of an object during Δ

t, given an angle of the rotating mirror with respect to the object during Δ

t.

17. The method of claim 13 wherein the laser projector comprises a micro-electromechanical (MEMS) spatial light modulator;

and further comprising;

estimating an orientation of an object during Δ

t, given a set of unit vector coordinates describing directions of laser beams emitted by the projector with respect to the object during Δ

t.

18. The method of claim 13, the cameras calibrated by:

(a) capturing simultaneously with two or more cameras images of four or more spots on a planar surface;

(b) determining homographies between pairs of cameras by identifying corresponding spots in the images captured in step (a);

(c) determining from the homographies;

relative poses between pairs of cameras, and orientation of the planar surface with respect to the cameras;

(d) fitting the orientation of the planar surface to a model of the indoor space; and

,

(e) determining the location and pose of each camera in the indoor space.

19. The method of claim 13, the space resection including:

creating a virtual point not coplanar with three actual spot locations used in resection;

using correspondences between locations of the three actual spots and the virtual point expressed with respect to the indoor space and the laser projector to establish a transformation matrix; and

,

using the transformation matrix to test a fourth actual spot to resolve geometric ambiguities in resection.

20. The method of claim 13, each laser beam modulated with a modulation signal that distinguishes it from all of the other laser beams, and each camera demodulating the signal to identify a correspondence between spots and laser beam directions.

21. The method of claim 20, the modulation signal being sinusoidal.

22. The method of claim 20, the modulation signal being a pseudorandom code.

23. The method of claim 13, each pair of directions of the four or more defining an angle different from that of any other pair.

24. The method of claim 13, the four or more different directions coinciding at a point.

25. The method of claim 13, the laser beams having an infrared wavelength and the cameras equipped with infrared filters to select the wavelength in preference to background light.

26. A method for indoor navigation comprising:

capturing, with two or more cameras, images of a first set of spots made by one or more laser beams on surfaces of an indoor space, the laser beams emitted by a laser projector in a first set of four or more different directions during a time interval Δ

t₁ and images of a second set of spots made by one or more laser beams on surfaces of the indoor space, the laser beams emitted by the laser projector in a second set of four or more different directions during a time interval Δ

t₂;

estimating three-dimensional locations of the spots from images captured by at least two cameras during Δ

t₁ and Δ

t₂; and

,

estimating a position of the laser projector in the indoor space during Δ

t₁ and Δ

t₂ by space resection given the first and second sets of four or more different directions and the three-dimensional locations of the spots.

27. The method of claim 26 further comprising:

estimating an orientation of an object during Δ

t₁ and Δ

t₂, given a relative orientation of the object and the projector.

28. The method of claim 27, the projector attached to the object via gimbal mount.

29. The method of claim 26 wherein the laser projector comprises a rotating mirror;

and further comprising;

estimating an orientation of an object during Δ

t₁ and Δ

t₂, given angles of the rotating mirror with respect to the object during Δ

t₁ and Δ

t₂.

30. The method of claim 26 wherein the laser projector comprises a micro-electromechanical (MEMS) spatial light modulator;

and further comprising;

estimating an orientation of an object during Δ

t₁ and Δ

t₂, given a set of unit vector coordinates describing directions of laser beams emitted by the projector with respect to the object during Δ

t₁ and Δ

t₂.

31. The method of claim 26, the cameras calibrated by:

(a) capturing simultaneously with two or more cameras images of four or more spots on a planar surface;

(b) determining homographies between pairs of cameras by identifying corresponding spots in the images captured in step (a);

(c) determining from the homographies;

relative poses between pairs of cameras, and orientation of the planar surface with respect to the cameras;

(d) fitting the orientation of the planar surface to a model of the indoor space; and

,

(e) determining the location and pose of each camera in the indoor space.

32. The method of claim 26, the space resection including:

creating a virtual point not coplanar with three actual spot locations used in resection;

using correspondences between locations of the three actual spots and the virtual point expressed with respect to the indoor space and the laser projector to establish a transformation matrix; and

,

using the transformation matrix to test a fourth actual spot to resolve geometric ambiguities in resection.

33. The method of claim 26, each laser beam modulated with a modulation signal that distinguishes it from all of the other laser beams, and each camera demodulating the signal to identify a correspondence between spots and laser beam directions.

34. The method of claim 33, the modulation signal being sinusoidal.

35. The method of claim 33, the modulation signal being a pseudorandom code.

36. The method of claim 26, each pair of directions of each set of four or more defining an angle different from that of any other pair.

37. The method of claim 26, each set of four or more different directions coinciding at a point.

38. The method of claim 26, the laser beams having an infrared wavelength and the cameras equipped with infrared filters to select the wavelength in preference to background light.