Laser tracker that combines two different wavelengths with a fiber-optic coupler

• US 8,908,154 B2
• Filed: 03/27/2012
• Issued: 12/09/2014
• Est. Priority Date: 04/15/2011
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E., Mertz, Jacob J.
• Primary Examiner(s): Ratcliffe, Luke
• Assistant Examiner(s): Abraham, Samantha K
• Application Number:
  US13/431,494
• Publication Number:
  US 20120262692A1
• Time in Patent Office: 987 Days
• Field of Search: 356/4.01, 356/5.01, 356/4.07, 356/5.09, 356/9, 356/625
• US Class Current: 356/3.1
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• 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 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4818 using optical fibres
• CPC Class Codes: G01S 7/491 Details of non-pulse systems
• CPC Class Codes: G06F 17/40 Data acquisition and logging for input to computer G06F3/00
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

Coordinate measurement device configured to send a first beam of light to a target includes first and second light sources configured to emit first and second lights having differing first and second wavelengths; fiber-optic coupler that includes three ports, a first port configured to accept a first portion of the first light, a second port configured to accept a second portion of the second light, a third port configured to transmit a third light which includes a portion of the first and second portions; first and second angle measuring devices configured to measure first and second angles of rotation; distance meter configured to measure a first distance from the device to the target based at least in part on a third portion of the second beam received by an optical detector; and a processor configured to provide 3D coordinates of the target.

Claims

1. A coordinate measurement device configured to send a first beam of light to a remote retroreflector target, the retroreflector target having a position in space, the retroreflector target returning a portion of the first beam as a second beam, the measurement device comprising:

a first light source configured to emit a first light having a first wavelength;

a second light source configured to emit a second light having a second wavelength, the second wavelength different than the first wavelength;

a fiber-optic coupler that includes at least a first port, a second port, and a third port, the first port configured to accept a first portion of the first light, the second port configured to accept a second portion of the second light, the third port configured to transmit a third light, the third light including a portion of the first portion and a portion of the second portion;

an optical system configured to transmit a portion of the third light out of the coordinate measurement device as the first beam;

a first motor and a second motor that together are configured to direct the first beam of light to a first direction, the first direction determined by a first angle of rotation about a first axis and a second angle of rotation about a second axis, the first angle of rotation produced by the first motor and the second angle of rotation produced by the second motor;

a first angle measuring device configured to measure the first angle of rotation and a second angle measuring device configured to measure the second angle of rotation;

a distance meter configured to measure a first distance from the coordinate measurement device to the retroreflector target based at least in part on a third portion of the second beam received by a first optical detector; and

a processor configured to provide three-dimensional coordinates of the retroreflector target, the three-dimensional coordinates based at least in part on the first distance, the first angle of rotation, and the second angle of rotation.

2. The coordinate measurement device of claim 1 further comprising:

a position detector assembly that includes a position detector, a fourth portion of the second beam passing onto the position detector, the position detector configured to produce a first signal in response to a position of the fourth portion on the position detector; and

a control system configured to send a second signal to the first motor and a third signal to the second motor, the second signal and the third signal based at least in part on the first signal, the control system configured to adjust the first direction of the first beam to the position in space of the retroreflector target.

3. The coordinate measurement device of claim 1 wherein the distance meter is an absolute distance meter.

4. The coordinate measurement device of claim 1 wherein the optical system is further configured to couple the third portion of the second beam into the third port of the fiber-optic coupler.

5. The coordinate measurement device of claim 1 wherein the fiber-optic coupler further includes a fourth port.

6. The coordinate measurement device of claim 5 wherein the fourth port is attached to a low-reflection termination.

7. The coordinate measurement device of claim 1 wherein the first wavelength is between 780 nm and 850 nm.

8. The coordinate measurement device of claim 1 wherein the second wavelength is a red wavelength or a green wavelength.

9. The coordinate measurement device of claim 1 wherein the first wavelength is an infrared wavelength and the second wavelength is a visible wavelength.

10. The coordinate measurement device of claim 1 wherein the first wavelength is a visible wavelength and the second wavelength is an infrared wavelength.

11. The coordinate measurement device of claim 1 wherein the first wavelength is a visible wavelength and the second wavelength is a visible wavelength.

12. A method for measuring three-dimensional coordinates of a retroreflector target located at a position in space, the method comprising steps of:

providing a coordinate measurement device that includes a first light source that produces a first light at a first wavelength, a second light source that produces a second light at a second wavelength different than the first wavelength, a fiber-optic coupler that includes at least a first port, a second port, and a third port, an optical system, a first motor, a second motor, a first angle measuring device, a second angle measuring device, a distance meter, and a processor;

coupling a first portion of the first light into the first port;

coupling a second portion of the second light into the second port;

transmitting a third light from the third port, the third light containing a portion of the first portion and a portion of the second portion;

transmitting a portion of the third light through the optical system out of the coordinate measurement device as a first beam of light;

directing the first beam of light in a first direction, the first direction determined by a first angle of rotation about a first axis and a second angle of rotation about a second axis, the first angle of rotation produced by the first motor and the second angle of rotation produced by the second motor;

measuring the first angle of rotation with the first angle measuring device;

measuring the second angle of rotation with the second angle measuring device;

reflecting a portion of the first beam from the retroreflector target as a second beam;

measuring a first distance from the coordinate measurement device to the retroreflector target with the distance meter, the measured distance based at least in part on a third portion of the second beam of light received by a first optical detector;

determining three-dimensional coordinates of the retroreflector target based at least in part on the first distance, the first angle of rotation, and the second angle of rotation; and

storing the determined three-dimensional coordinates.

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

providing a position detector assembly, the position detector assembly including a position detector;

sending a fourth portion of the second beam onto the position detector;

obtaining a first signal from the position detector, the first signal responsive to the position of the fourth portion on the position detector;

sending a second signal to the first motor and sending a third signal to the second motor, the second signal and the third signal based at least in part on the first signal; and

adjusting the first direction of the first beam to the position in space of the retroreflector target.

14. The method of claim 12, wherein the step of providing a coordinate measurement device further includes providing the distance meter as an absolute distance meter.

15. The method of claim 12, wherein the step of measuring a first distance from the coordinate measurement device to the retroreflector target with the distance meter further includes a step of coupling the third portion of the second beam into the third port of the fiber-optic coupler.

16. The method of claim 12, wherein the step of providing a coordinate measurement device further includes providing the fiber-optic coupler with a fourth port.

17. The method of claim 16, wherein the step of providing a coordinate measurement device further includes providing the fiber-optic coupler with the fourth port attached to a low-reflection termination.

18. A coordinate measurement device configured to send a first beam of light to a remote retroreflector target, the retroreflector target having a position in space, the retroreflector target returning a portion of the first beam as a second beam, the measurement device comprising:

a first light source configured to emit a first light having a first wavelength;

a second light source configured to emit a second light having a second wavelength, the second wavelength different than the first wavelength;

a fiber-optic coupler that includes a first port, a second port, a third port and a fourth port, the fiber-optic coupler further comprising a first fiber coupler configured to receive a first portion of the first light from the first port, a second fiber coupler having an input optically coupled to receive the first portion of the first light from the first fiber coupler, the second fiber coupler further configured to receive a second portion of the second light from the second port and transmit a third light through the third port, the third light including a portion of the first portion and a portion of the second portion, and a third fiber coupler optically disposed between the first fiber coupler and the second fiber coupler to allow the first portion of the first light to pass from the first fiber coupler to the second fiber coupler, the third fiber coupler having an output coupled to the fourth port;

an optical system configured to transmit a portion of the third light out of the coordinate measurement device as the first beam and receive the second beam returning from the retroreflector target;

a first motor and a second motor that together are configured to direct the first beam of light to a first direction, the first direction determined by a first angle of rotation about a first axis and a second angle of rotation about a second axis, the first angle of rotation produced by the first motor and the second angle of rotation produced by the second motor;

a first angle measuring device configured to measure the first angle of rotation and a second angle measuring device configured to measure the second angle of rotation;

a distance meter optically coupled to the fourth port, the distance meter configured to measure a first distance from the coordinate measurement device to the retroreflector target based at least in part on a third portion of the second beam received by a first optical detector, wherein the second beam passes through the first fiber coupler which is configured to form the third portion of the second beam having the first wavelength and a fourth portion of the second beam having the second wavelength;

an isolator device optically arranged between the second light source and the second port, the isolator device configured to prevent the fourth portion of the second beam from entering into the second light source; and

a processor configured to provide three-dimensional coordinates of the retroreflector target, the three-dimensional coordinates based at least in part on the first distance, the first angle of rotation, and the second angle of rotation.

19. The device of claim 18 wherein the second fiber coupler is a dichroic fiber coupler.

20. The device of claim 19 wherein the first fiber coupler, the second fiber coupler and the third fiber coupler are a fused type optical coupler having two cores configured to exchange light by evanescent coupling.