Probe that cooperates with a laser tracker to measure six degrees of freedom

• US 10,126,415 B2
• Filed: 12/29/2015
• Issued: 11/13/2018
• Est. Priority Date: 12/31/2014
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Becker, Bernd-Dietmar, Heidemann, Rolf, Zweigle, Oliver, Wolke, Matthias
• Primary Examiner(s): Ratcliffe, Luke D
• Application Number:
  US14/982,259
• Publication Number:
  US 20160187470A1
• Time in Patent Office: 1,050 Days
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/4863 Detector arrays, e.g. charge-transfer gates
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A system includes a measurement device configured to measure a distance, a first angle, and a second angle to a retroreflector target. The system further includes a probe having the retroreflector target, an inclinometer sensor, a camera, and a processor, the inclinometer sensor configured to determine a two-dimensional inclination of the probe relative to a gravity vector, the camera configured to capture an image of a light emitted from or reflected by the measurement device, the processor configured to determine six degrees of freedom of the probe based at least in part on the distance, the first angle, the second angle, the two-dimensional inclination, and the captured image of the camera.

Claims

1. A system comprising:

a measurement device configured to send a first beam of light to a retroreflector target and to measure a distance, a first angle, and a second angle to the retroreflector target; and

a probe assembly including the retroreflector target, an inclinometer sensor, and a camera, the inclinometer sensor configured to determine a two-dimensional inclination of the probe assembly relative to a gravity vector, the retroreflector configured to reflect the first beam of light as a first reflected light, the camera configured to capture an image of a second light, the system being configured to determine six degrees of freedom of the probe assembly based at least in part on the measured distance, the measured first angle, the measured second angle, the measured two-dimensional inclination, and the captured image of the camera,

wherein the second light is either a light emission from a light source on the measurement device or a reflection of the first reflected light off an window of the measurement device.

2. The system of claim 1 wherein the retroreflector target is a cube-corner retroreflector.

3. The system of claim 1 wherein the measurement device is a laser tracker configured to emit the first beam of light at a first wavelength and to track movement of the retroreflector target.

4. The system of claim 1 wherein the inclinometer sensor includes a first one-axis inclinometer sensor and a second one-axis inclinometer sensor.

5. The system of claim 1 wherein the inclinometer sensor includes a first inclinometer assembly, the first inclinometer assembly having a first one-axis sensor, a second one-axis sensor, and a third one-axis sensor, the inclinometer assembly being configured to measure over 360 degrees of rotation about a first axis.

6. The system of claim 5 further wherein the inclinometer sensor further includes a second inclinometer assembly, the second inclinometer assembly having a fourth one-axis sensor, a fifth one-axis sensor, and a sixth one-axis sensor, the second inclinometer assembly being configured to cooperate with the first inclinometer assembly to measure over 360 degrees of rotation about each of the first axis and a second axis, the first axis and the second axis being mutually perpendicular.

7. The method of claim 4 wherein the first one-axis sensor and the second one-axis sensor are mounted on daughter boards configured to attach to connectors on a motherboard, each daughter board being perpendicular to the motherboard.

8. The system of claim 1 wherein the inclinometer sensor includes a first two-axis inclinometer sensor.

9. The system of claim 1 wherein the inclinometer sensor includes a first inclinometer assembly that measures inclination about a first axis of rotation, a second inclinometer assembly that measures inclination about a second axis of rotation, and a third inclinometer assembly that measures inclination about a third axis of rotation, wherein the first axis, the second axis and the third axis are mutually perpendicular.

10. The system of claim 9 wherein the first inclinometer assembly, the second inclinometer assembly, and the third inclinometer assembly each measure over an angle of 360 degrees.

11. The system of claim 1 wherein the inclinometer sensor includes a two-axis pendulum having two angular encoders, the two angular encoders together configured to measure a pitch angle and a roll angle of the inclinometer sensor.

12. The system of claim 3 wherein the camera is configured to image first reflected light reflected or scattered off a tracker window through which light from the retroreflector target is returned into the tracker, the first reflected light being at the first wavelength.

13. The system of claim 3 wherein the camera includes a lens coated to selectively pass light at the first wavelength.

14. The system of claim 1 wherein the light emitted from or reflected by the measurement device is a light emitted by a light source affixed to the measurement device.

15. The system of claim 2 wherein the cube-corner retroreflector is a glass prism.

16. The system of claim 1 wherein the retroreflector target is one of a plurality of retroreflector targets, each retroreflector target of the plurality of retroreflector targets located on different face of the probe assembly.

17. The system of claim 16 wherein the probe assembly includes a plurality of cameras, each camera located on a different face of the probe assembly.

18. The system of claim 1 wherein the probe assembly is attached to a tactile probe.

19. The system of claim 18 wherein the tactile probe is configured to rotate about a first axis relative to the probe assembly, the system further including a first angular encoder configured to measure a first angle of rotation about the first axis.

20. The system of claim 19 wherein the tactile probe is further configured to rotate about a second axis relative to the probe assembly, the second axis perpendicular to the first axis, the system further including a second angular encoder configured to measure a second angle of rotation about the second axis.

21. The system of claim 1 wherein the probe assembly is attached to a six-DOF triangulation scanner having a projector configured to project a pattern of light and the camera is configured to image the pattern projected onto an object, the projector and the camera separated by a baseline distance.

22. The system of claim 21 wherein the triangulation scanner is a structured light scanner configured to project a pattern of light over an area.

23. The system of claim 21 wherein the triangulation scanner is a line scanner configured to project a line of light.

24. The system of claim 21 wherein the triangulation scanner is configured to rotate about a first axis relative to the probe assembly, the system further including a first angular encoder configured to measure a first angle of rotation about the first axis.

25. The system of claim 24 wherein the triangulation scanner is further configured to rotate about a second axis relative to the probe assembly, the system further including a second angular encoder configured to measure a second angle of rotation about the second axis.

26. The system of claim 1 wherein the probe assembly is attached to a six-DOF projector configured to project a pattern of light onto an object.

27. The system of claim 1 wherein the probe assembly further includes an inertial measurement unit configured to be used in combination with a Kalman filter to account, at least in part, for the effect of probe velocity and acceleration.

28. The system of claim 27 wherein the inertial measurement unit includes a three-axis gyroscope.

29. The system of claim 28 wherein the inertial measurement unit further includes a three-axis accelerometer.

30. The system of claim 1 wherein the system further includes one or more processors configured to determine position and orientation of the probe assembly.

31. The system of claim 30 wherein the one or more processors are included in one or more of the probe assembly, the measurement device, and an external computing device.

32. The system of claim 31 wherein the measurement device and the probe assembly transfer information through wireless communication.

33. The system of claim 31 wherein the measurement device and the probe assembly transfer information through wired communication.