Automatic measurement of dimensional data with a laser tracker

• US 9,146,094 B2
• Filed: 12/10/2014
• Issued: 09/29/2015
• Est. Priority Date: 04/21/2010
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Steffey, Kenneth, Steffensen, Nils P., Bridges, Robert E.
• Primary Examiner(s): NGUYEN, TU T
• Application Number:
  US14/565,624
• Publication Number:
  US 20150092199A1
• Time in Patent Office: 293 Days
• Field of Search: 356/614
• US Class Current: 1/1
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/14 for measuring distance or clearance between spaced objects or spaced apertures G01B11/26 takes precedence; rangefinders G01C3/00
• CPC Class Codes: G01B 21/045 Correction of measurements G01B9/02055 takes precedence
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• 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 7/481 Constructional features, e.g. arrangements of optical elements
• CPC Class Codes: G01S 7/4811 common to transmitter and receiver
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4815 using multiple transmitters
• CPC Class Codes: G01S 7/4972 Alignment of sensor

Abstract

Measuring with a system having retroreflector targets and a laser tracker includes storing a list of coordinates for three targets and at least one added point; capturing on a photosensitive array a portion of the light emitted by a light beam and reflected off the targets; obtaining spot positions on a photosensitive array of a tracker camera from the reflected light; determining a correspondence between three spot positions on the photosensitive array and the coordinates of the targets; directing a beam of light from the tracker to the targets based at least in part on the coordinates of the first target and the first spot position; measuring 3-D coordinates of the targets with the tracker; determining 3-D coordinates of the at least one added point based at least in part on the measured 3-D coordinates of the targets and the coordinates of the at least one added point.

Claims

1. A method for measuring with a system, the method comprising steps of:

providing the system including a first retroreflector target and a laser tracker, the laser tracker having a structure, a first angular transducer, a second angular transducer, a first motor, a second motor, a first light source, a second light source, a third light source, an absolute distance meter, a tracking system, a position detector, a first camera, a second camera, a first lens system, a second lens system, a first photosensitive array, a second photosensitive array, a processor, and a memory, the structure rotatable about a first axis by the first motor and a second axis by the second motor, the first light source producing a first light beam that cooperates with the absolute distance meter to measure a distance based at least in part on a speed of the first light beam, the first angular transducer measuring a first angle of rotation about the first axis, the second angular transducer measuring a second angle of rotation about the second axis, the tracking system configured to move the first light beam to a center of the first retroreflector target in response to a portion of the first light beam reflected by the first retroreflector target and received by the position detector, the first camera including the first lens system and the first photosensitive array configured to have a first field of view, the second light source providing a second light beam that cooperates with the first camera, the second camera including the second lens system and the second photosensitive array configured to have a second field of view, the third light source providing a third light beam that cooperates with the second camera, the first field of view being greater than the second field of view, the first camera and the second camera fixed with respect to the structure, the memory operably coupled to the processor, and the processor configured to operate the laser tracker;

emitting the second light beam;

capturing on the first photosensitive array a portion of the second light beam reflected by the first retroreflector target;

obtaining a first spot position on the first photosensitive array from the portion of the second light beam reflected by the first retroreflector target;

measuring the first angle of rotation and the second angle of rotation as a first pair of measured angles;

determining by the processor a second pair of estimated angles based at least in part on the first pair of measured angles, the first spot position, and the first field of view;

rotating the structure by the first motor and the second motor to cause the first angle of rotation and the second angle of rotation to correspond to the determined second pair of estimated angles;

emitting the third light beam;

capturing on the second photosensitive array a portion the third light beam reflected by the first retroreflector target;

obtaining a second spot position on the second photosensitive array from the portion of the third light beam reflected by the first retroreflector target;

measuring the first angle of rotation and the second angle of rotation as a third pair of measured angles;

determining by the processor a fourth pair of estimated angles based at least in part on the third pair of measured angles, the second spot position, and the second field of view;

rotating the structure by the first motor and the second motor to cause the first angle of rotation and the second angle of rotation to correspond to the determined fourth pair of estimated angles;

emitting the first light beam;

receiving by the position detector a portion of the first light beam reflected by the first retroreflector target;

tracking the first retroreflector target using the tracking system;

measuring a first distance by the absolute distance meter;

measuring the first angle of rotation and the second angle of rotation as a fifth pair of measured angles;

determining by the processor a first set of three-dimensional coordinates of the center of the first retroreflector target based at least in part on the first distance and the fifth pair of measured angles; and

storing the first set of three-dimensional coordinates in the memory.

2. The method of claim 1, wherein in the step of providing the system, the first field of view is offset with respect to the first light beam.

3. The method of claim 1, wherein in the step of providing the system, the second field of view is offset with respect to the first light beam.

4. The method of claim 1, wherein:

in the step of providing the system, the laser tracker further comprises a third camera, a third lens system, a third photosensitive array, and a fourth light source, the third camera including the third lens system and the third photosensitive array configured to have a third field of view, the fourth light source providing a fourth light beam that cooperates with the third camera.

5. The method of claim 4, further comprising steps of:

emitting the fourth light beam;

capturing on the third photosensitive array a portion of the fourth light beam reflected by the first retroreflector target; and

obtaining a third spot position on the third photosensitive array from the portion of the fourth light beam reflected by the first retroreflector target;

wherein in the step of determining by the processor the second pair of estimated angles, the determining is further based on the third spot position and the third field of view.

6. The method of claim 4, further comprising steps of:

emitting the fourth light beam;

capturing on the third photosensitive array a portion the fourth light beam reflected by the first retroreflector target; and

obtaining a third spot position on the third photosensitive array from the portion of the fourth light beam reflected by the first retroreflector target;

wherein in the step of determining by the processor the fourth pair of estimated angles, the determining is further based on the third spot position and the third field of view.

7. The method of claim 4, wherein the third field of view is greater than the second field of view.

8. The method of claim 4, wherein the second field of view is greater than the third field of view.

9. A measuring system comprising:

a first retroreflector target and a laser tracker;

the laser tracker having a structure, a first angular transducer, a second angular transducer, a first motor, a second motor, a first light source, a second light source, a third light source, an absolute distance meter, a tracking system, a position detector, a first camera, a second camera, a first lens system, a second lens system, a first photosensitive array, a second photosensitive array, a processor, a memory, and computer readable media with instructions executable by the processor;

the structure rotatable about a first axis by the first motor and a second axis by the second motor, the first light source producing a first light beam that cooperates with the absolute distance meter to measure a distance based at least in part on a speed of the first light beam, the first angular transducer measuring a first angle of rotation about the first axis, and the second angular transducer measuring a second angle of rotation about the second axis;

the tracking system configured to move the first light beam to a center of the first retroreflector target in response to a portion of the first light beam reflected by the first retroreflector target and received by the position detector, the first camera including the first lens system and the first photosensitive array configured to have a first field of view, the second light source providing a second light beam that cooperates with the first camera, the second camera including the second lens system and the second photosensitive array configured to have a second field of view, the third light source providing a third light beam that cooperates with the second camera, the first field of view being greater than the second field of view, and the first camera and the second camera fixed with respect to the structure;

the memory operably coupled to the processor, and the processor configured to operate the laser tracker, the instructions configured such that when executed by the processor causes the laser tracker to execute steps of;

emitting the second light beam;

capturing on the first photosensitive array a portion of the second light beam reflected by the first retroreflector target;

obtaining a first spot position on the first photosensitive array from the portion of the second light beam reflected by the first retroreflector target;

measuring the first angle of rotation and the second angle of rotation as a first pair of measured angles;

determining by the processor a second pair of estimated angles based at least in part on the first pair of measured angles, the first spot position, and the first field of view;

rotating the structure by the first motor and the second motor to cause the first angle of rotation and the second angle of rotation to correspond to the determined second pair of estimated angles;

emitting the third light beam;

capturing on the second photosensitive array a portion of the third light beam reflected by the first retroreflector target;

obtaining a second spot position on the second photosensitive array from the portion of the third light beam reflected by the first retroreflector target;

measuring the first angle of rotation and the second angle of rotation as a third pair of measured angles;

determining by the processor a fourth pair of estimated angles based at least in part on the third pair of measured angles, the second spot position, and the second field of view;

rotating the structure by the first motor and the second motor to cause the first angle of rotation and the second angle of rotation to correspond to the determined fourth pair of estimated angles;

emitting the first light beam;

receiving by the position detector a portion of the first light beam reflected by the first retroreflector target;

tracking the first retroreflector target using the tracking system;

measuring a first distance by the absolute distance meter;

measuring the first angle of rotation and the second angle of rotation as a fifth pair of measured angles;

determining by the processor a first set of three-dimensional coordinates of the center of the first retroreflector target based at least in part on the first distance and the fifth pair of measured angles; and

storing the first set of three-dimensional coordinates in the memory.

10. The measuring system of claim 9, wherein the first field of view is offset with respect to the first light beam.

11. The measuring system of claim 9, wherein the second field of view is offset with respect to the first light beam.

12. The measuring system of claim 9, wherein the laser tracker further comprises a third camera, a third lens system, a third photosensitive array, and a fourth light source, the third camera including the third lens system and the third photosensitive array configured to have a third field of view, the fourth light source providing a fourth light beam that cooperates with the third camera.

13. The measuring system of claim 12, wherein the instructions further comprise steps of:

emitting the fourth light beam, capturing on the third photosensitive array a portion of the fourth light beam reflected by the first retroreflector target, and obtaining a third spot position on the third photosensitive array from the portion of the fourth light beam reflected by the first retroreflector target, wherein in the step of determining by the processor the second pair of estimated angles, the determining is further based on the third spot position and the third field of view.

14. The measuring system of claim 12, wherein the instructions further comprise steps of:

emitting the fourth light beam, capturing on the third photosensitive array a portion of the fourth light beam reflected by the first retroreflector target, and obtaining a third spot position on the third photosensitive array from the portion of the fourth light beam reflected by the first retroreflector target, wherein in the step of determining by the processor the fourth pair of estimated angles, the determining is further based on the third spot position and the third field of view.

15. The measuring system of claim 12, wherein the third field of view is greater than the second field of view.

16. The measuring system of claim 12, wherein the second field of view is greater than the third field of view.