Determining coordinates of a target in relation to a survey instrument having at least two cameras

• US 9,189,858 B2
• Filed: 02/29/2008
• Issued: 11/17/2015
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: Trimble AB (Trimble Inc.)
• Original Assignee: Trimble AB (Trimble Inc.)
• Inventors: Svanholm, Set, Vogel, Michael, Grsser, Christian
• Primary Examiner(s): Lee, Y
• Assistant Examiner(s): CARTER, RICHARD BRUCE
• Application Number:
  US12/735,805
• Publication Number:
  US 20110043620A1
• Time in Patent Office: 2,818 Days
• Field of Search: 348/135, 382/106, 382/154, 356/5.1, 702/150, 332/90
• US Class Current: 1/1
• CPC Class Codes: G01C 1/04 combined with cameras
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G06T 7/55 from multiple images

Abstract

A method is disclosed for determining coordinates of a target in relation to a surveying instrument wherein a first image is captured using a first camera in a first camera position and orientation, a target is selected by identifying at least one object point in the first image, and first image coordinates of the object point in the first image are measured. In at least one embodiment, a second image is captured using a second camera in a second camera position and orientation, the object point identified in the first image is identified in the second image, and second image coordinates of the object point in the second image are measured. Target coordinates of the target in relation to the rotation center of the surveying instrument are then determined based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and first and second camera calibration data. Furthermore, a surveying instrument for performing the method is disclosed.

Claims

1. A method for determining three-dimensional coordinates of a target that is located remote from a surveying instrument, the three-dimensional coordinates determined in relation to the surveying instrument, the surveying instrument comprising a first camera in a first camera position and orientation, and a second camera in a second camera position and orientation, the first camera being eccentric to a rotation center of the surveying instrument, and the second camera position being spaced from the first camera position by a distance, the method comprising:

capturing a first image using the first camera, the first image including the target;

selecting the target by identifying at least one object point in the first image;

measuring first image coordinates of the at least one object point in the first image;

capturing a second image using the second camera, the second image including the target;

identifying, in the second image, the at least one object point identified in the first image, wherein the identifying, in the second image, includes,

selecting a minimum distance and a maximum distance from the first camera position along an imaging ray associated with the at least one object point, the imaging ray extending outward from the first camera position toward the target, between which minimum distance and maximum distance the target is located on the imaging ray,

determining a section of an epipolar line in the second image on which the at least one object point is located and that corresponds to the imaging ray, the section of the epipolar line determined based on the maximum distance, the minimum distance, the first camera position and orientation, the second camera position and orientation, the first image coordinates, and first and second camera calibration data, and

identifying, along the section of the epipolar line in the second image, the at least one object point identified in the first image;

measuring second image coordinates of the at least one object point in the second image; and

determining the three-dimensional coordinates of the target in relation to the rotation center of the surveying instrument based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and the first and second camera calibration data.

2. The method of claim 1, further comprising:

determining whether the epipolar line is completely inside the second image.

3. The method of claim 2, further comprising:

rotating, if the epipolar line is not completely inside the second image, the surveying instrument around the rotation center based on epipolar line data to move the second camera to a revised second camera position and orientation in order to position the epipolar line within a revised second image;

capturing the revised second image using the second camera in the revised second camera position and orientation; and

identifying, along the section of the epipolar line in the revised second image, the at least one object point identified in the first image.

4. The method of claim 1, wherein the minimum distance is selected as the distance between the first camera position and the second camera position.

5. The method of claim 1, wherein the at least one object point is identified in the first image by operator selection.

6. The method of claim 1, wherein the at least one object point is identified in the first image by automatic image analysis.

7. The method of claim 1, wherein the at least one object point identified in the first image is identified in the second image by automatic image analysis.

8. The method of claim 1, wherein the at least one object point identified in the first image is identified in the second image by user selection.

9. The method of claim 1, wherein the first and second images are captured while the target is illuminated by way of a light source, and two further images are captured with the light source turned off, and the method includes,

subtracting one of the two images of the first camera from the other one of the two images of the first camera in order to produce a first difference image, and

subtracting one of the two images of the second camera from the other one of the two images of the second camera in order to produce a second difference image, and wherein,

the selecting a target includes identifying at least one object point in the first difference image,

the measuring first image coordinates measures first image coordinates of the at least one object point in the first difference image,

the identifying, in the second image, identifies the at least one object point identified in the first difference image,

the measuring second image coordinates measures second image coordinates of the at least one object point in the second difference image, and

the determining three-dimensional coordinates of the target in relation to the rotation center of the surveying instrument determines the three-dimensional coordinates based on the first camera position and orientation, the first difference image coordinates, the second camera position and orientation, the second difference image coordinates, and first and second camera calibration data.

10. The method of claim 9, wherein said light source illuminates the target by way of a spot.

11. The method of claim 9, wherein said light source illuminates the target by way of a projected pattern.

12. The method of claim 1, wherein a number of images are captured with the two cameras in order to attain a scanning function, where an image of the first camera is processed with a corresponding image of the second camera in order to determine the three-dimensional coordinates for each pair of captured first and second images.

13. The method of claim 1, further comprising:

determining a direction from the rotation center of the surveying instrument towards the target based on the three-dimensional coordinates.

14. The method of claim 13, further comprising:

rotating the surveying instrument so that a line of sight of the surveying instrument is directed in the direction towards the target.

15. The method of claim 14, further comprising:

measuring a distance to the target using distance measuring capabilities within the surveying instrument.

16. The method of claim 1, further comprising:

determining a distance from the rotation center of the surveying instrument to the target based on the three-dimensional coordinates.

17. The method of claim 1, wherein the first image and the second image are captured simultaneously.

18. A method for determining three-dimensional coordinates of a target in relation to a surveying instrument, said method comprising:

determining the three-dimensional coordinates using the method of claim 1 at close range,

and

determining the three-dimensional coordinates using an electronic distance measurement at far range.

19. The method of claim 18, wherein the close range is between about 0 to 25 meters from the target.

20. A non-transitory computer readable medium comprising a computer program product, the computer program product comprising computer program code portions configured to perform the method of claim 1 when executed in a computer.

21. A surveying instrument for determining three-dimensional coordinates of a target in relation to the surveying instrument, comprising:

a first camera configured to capture images from a first position and orientation, the first camera being eccentric to a rotation center of the surveying instrument;

a second camera configured to capture images from a second position and orientation, the second camera position being spaced from the first camera position by a distance;

a display configured to display images captured by the first camera and the second camera;

at least one device configured to identify at least one object point corresponding to target in the displayed images;

at least one device configured to measure first image coordinates of the at least one object point in a first image captured by the first camera;

at least one device configured to measure second image coordinates of the at least one object point in a second image captured by the second camera, wherein the at least one device configured to identify the at least one object point is configured to,

select a minimum distance and a maximum distance from the first camera position along an imaging ray associated with the at least one object point, the imaging ray extending outward from the first camera position toward the target, between which minimum distance and maximum distance the selected target is located on the imaging ray,

determine a section of an epipolar line in the second image on which the at least one object point is located and that corresponds to the imaging ray, the section of the epipolar line determined based on the maximum distance, the minimum distance, the first camera position and orientation, the second camera position and orientation, the first image coordinates, and first and second camera calibration data, and

identify, along the section of the epipolar line in the second image, the at least one object point identified in the first image;

at least one device configured to determine the three-dimensional coordinates of the target in relation to the rotation center of the surveying instrument based on the first camera position and orientation, the first image coordinates, the second camera position and orientation, the second image coordinates, and the first and second camera calibration data.

22. The instrument of claim 21, wherein the at least one device configured to identify an object point is implemented as a cursor movable across the displayed images.

23. The instrument of claim 21, wherein the display is a touch display, and the at least one device configured to identify an object point is implemented using the touch display, the object point being identified by clicking or tapping on the touch display.

24. The instrument of claim 21, wherein the at least one device configured to identify an object point is further implemented using image processing software.

25. The instrument of claim 21, further comprising:

at least one device configured to emit light pulses towards the selected target in order to perform electronic distance measurements.

26. The instrument of claim 21, further comprising:

at least one device configured to illuminate the selected target.

27. The instrument of claim 26, wherein the at least one device configured to illuminate the selected target is arranged coaxially with at least one device configured to emit light pulses towards the selected target.