LASER-BASED COORDINATE MEASURING DEVICE AND LASER-BASED METHOD FOR MEASURING COORDINATES

• US 20120099119A1
• Filed: 01/03/2012
• Published: 04/26/2012
• Est. Priority Date: 04/05/1999
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E., Brown, Lawrence B., West, James K., Ackerson, D. Scott
• Granted Patent: US 8,958,055 B2
• Time in Patent Office: Days
• US Class Current: 356/620
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/02 for measuring length, width or thickness G01B11/08 takes precedence
• CPC Class Codes: G01B 11/026 by measuring distance between sensor and object G01B11/0608 takes precedence
• CPC Class Codes: G01B 11/03 by measuring coordinates of points
• CPC Class Codes: G01B 9/02012 using temporal intensity variation
• 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 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

A laser based coordinate measuring device measures a position of a remote target. The laser based coordinate measuring device includes a stationary portion, a rotatable portion, and at least a first optical fiber. The stationary portion has at least a first laser radiation source and at least a first optical detector, and the rotatable portion is rotatable with respect to the stationary portion. The first optical fiber system, which optically interconnects the first laser radiation source and the first optical detector with an emission end of the first optical fiber system, has the emission end disposed on the rotatable portion. The emission end emits laser radiation to the remote target and receives laser radiation reflected from the remote target with the emission direction of the laser radiation being controlled according to the rotation of the rotatable portion.

Claims

1. A laser tracker for measuring a location and an orientation of a patterned target that includes a pattern and a retroreflector, the laser tracker comprising:

a structure, rotatable about a first axis;

a mirror supported by the structure and rotatable about a second axis, from which a first beam is launched to the patterned target and to which a second beam is reflected from the patterned target,

a position detector that collects a portion of the second beam, the position detector generating a signal indicating a first direction the structure is to be rotated and a second direction the mirror is to be rotated in order to cause the first beam to track the patterned target;

a subsystem for measuring the location of the patterned target, the subsystem including a first encoder that measures a first angle of rotation of the structure about the first axis, a second encoder that measures a second angle of rotation of the mirror about the second axis, and a distance meter that measures a distance from the structure to the patterned target;

an optical system including a lens that forms an image of at least a portion of the patterned target on a photosensitive array;

a first electronics system that converts the image into a digital data set; and

a second electronics system that calculates the orientation of the patterned target, including a first orientation angle, based at least in part on the digital data set.

2. The laser tracker of claim 1 wherein:

the orientation of the patterned target further comprises a second orientation angle; and

the laser tracker measures at least five degrees of freedom.

3. The laser tracker of claim 2, wherein:

the orientation of the patterned target further comprises a third orientation angle; and

the laser tracker measures six degrees of freedom.

4. The laser tracker of claim 1, further comprising:

a motor coupled to the lens that adjusts the position of the lens to keep the image focused on or near the photosensitive array.

5. The laser tracker of claim 4, wherein the motor adjusts the position of the lens based at least in part on the distance.

6. The laser tracker of claim 1, wherein a transverse magnification of the optical system is essentially constant as a function of the distance.

7. The laser tracker of claim 1, wherein the optical system comprises an afocal subsystem.

8. The laser tracker of claim 11, wherein the distance meter measures an absolute distance.

9. The laser tracker of claim 1, wherein the retroreflector comprises a cube-corner retroreflector comprising three perpendicular reflecting surfaces.

10. The laser tracker of claim 9, wherein the retroreflector comprises a hollow-core cube-corner retroreflector.

11. The laser tracker of claim 9, wherein the retroreflector comprises a solid glass cube-corner retroreflector.

12. The laser tracker of claim 9, wherein the pattern is formed by at least a portion of three lines of intersection of the three perpendicular reflecting surfaces.

13. The laser tracker of claim 1, further comprising a probe tip attached to the patterned target.

14. The laser tracker of claim 11, further comprising a machine tool or robot end effector to which the patterned target is attached.

15. The laser tracker of claim 1, wherein the optical system is mounted on the structure.

16. The laser tracker of claim 1, wherein the retroreflector causes the second beam to include the pattern.