Automatic measurement of dimensional data within an acceptance region by a laser tracker

• US 9,400,170 B2
• Filed: 05/20/2015
• Issued: 07/26/2016
• Est. Priority Date: 04/21/2010
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Steffey, Kenneth
• Primary Examiner(s): Nguyen, Tu
• Application Number:
  US14/716,971
• Publication Number:
  US 20150253124A1
• Time in Patent Office: 433 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 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: G01C 15/004 Reference lines, planes or sectors
• 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 7/4811 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

An automatic method for measuring three-dimensional coordinates by a laser tracker includes determining whether a retroreflector is accessible within an acceptance region of an inspection location and, if not, taking corrective action.

Claims

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

providing 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, an absolute distance meter, a tracking system, a position detector, a camera, a first lens system, a first 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 camera including the first lens system and the first photosensitive array, the camera having a field of view, the second light source providing a second light beam that cooperates with the camera, the camera fixed with respect to the structure, the memory operably coupled to the processor, and the processor configured to operate the laser tracker;

providing an inspection plan having a plurality of inspection locations;

providing a plurality of acceptance regions, each acceptance region corresponding to an inspection location, the plurality of acceptance regions including a first acceptance region;

rotating the first motor and the second motor to point the camera to view one of the plurality of acceptance regions;

emitting the second light beam;

capturing with the camera a first image of the acceptance region illuminated by the second light beam;

determining by the processor whether a retroreflector is present in the first acceptance region based at least in part on the first image;

when the retroreflector is not present in the first acceptance region the method stops to await further instructions;

when the retroreflector is present in the first acceptance region, then the method continues by;

determining a position of the retroreflector based at least in part on the first image;

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 image, and the 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 first light beam;

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

tracking the retroreflector using the tracking system;

measuring a first distance to the retroreflector with the absolute distance meter;

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

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

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

2. The method of claim 1, wherein the step of stopping to await further instructions further includes determining by an operator whether the retroreflector is present at the inspection location and placing the retroreflector at the inspection location when the retroreflector is not present.

3. The method of claim 1, wherein the step of stopping to await further instructions further includes determining whether an obstruction is preventing illumination of the retroreflector by the second light beam and removing the obstruction when the obstruction is present.

4. The method of claim 1, wherein the step of stopping to await further instructions further includes determining whether the retroreflector is rotated to a fourth angle that prevents reflection of the second light beam into the camera and rotating the retroreflector to enable reflection of the second light beam into the camera when the retroreflector is rotated to the fourth angle.

5. The method of claim 1 wherein the first acceptance region corresponds to an area.

6. The method of claim 5 wherein the first acceptance region corresponds to the area enclosed by a circle.

7. The method of claim 5 wherein the first acceptance region corresponds to the area enclosed by a square.