Method and apparatus for locking onto a retroreflector with a laser tracker

• US 9,377,885 B2
• Filed: 11/03/2014
• Issued: 06/28/2016
• Est. Priority Date: 04/21/2010
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Bridges, Robert E., Park, Jennifer K.
• Primary Examiner(s): Punnoose, Roy M
• Application Number:
  US14/531,113
• Publication Number:
  US 20150049329A1
• Time in Patent Office: 603 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 21/047 Accessories, e.g. for positioning, for tool-setting, for measuring probes
• CPC Class Codes: G01B 5/004 for measuring coordinates of points
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G06F 3/017 Gesture based interaction, e.g. based on a set of recognized hand gestures interaction based on gestures traced on a digitiser G06F3/04883
• CPC Class Codes: G06F 3/0304 Detection arrangements using opto-electronic means constructional details of pointing devices not related to the detection arrangement using opto-electronic means G06F3/033; optical digitisers G06F3/042
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Abstract

A three-dimensional (3D) coordinate measurement system includes a communication device, a retroreflector, and a laser tracker. The communication device includes a first light source and an operator-controlled unit that controls emission from the first light source. The laser tracker includes a wide field-of-view (FOV) camera, a second light source, a narrow FOV camera next to the second light source, and a processor. The processor determines that a lock-in command has been given in response to the wide FOV camera capturing light emitted by the first light source. To lock onto the retroreflector, the processor captures with the narrow FOV camera light from the second light source reflected by the retroreflector and uses the image to lock onto the retroreflector with a beam of light from the tracker. It measures a distance and two angles with the tracker to get 3D coordinates of the retroreflector.

Claims

1. A three-dimensional (3D) coordinate measurement system, comprising:

a communication device that includes a first light source and an operator-controlled unit, the operator-controlled unit configured to control emission from the first light source;

a retroreflector separate from the communication device;

a laser tracker including;

a structure rotatable about a first axis and a second axis;

a first camera;

a second light source;

a second camera proximate the second light source, the second camera having a narrower field-of-view than the first camera; and

a processor responsive to executable instructions which when executed by the processor is operable to;

cause the first camera to capture a first light emitted by the first light source in a first digital image;

determine that a retroreflector lock-in command has been given based at least in part on the first digital image;

respond to the retroreflector lock-in command having been given by;

activating the second light source to produce a second light reflected by the retroreflector as a second reflected light;

capturing the second reflected light with the second camera to produce a second digital image; and

steering the structure based at least in part on the second digital image.

2. The system of claim 1 wherein the processor is further operable to respond to the retroreflector lock-in command having been given by steering the structure further based on the first digital image.

3. The system of claim 1 wherein:

the first light source is configured to emit visible light; and

the first camera is responsive to visible wavelengths of the first light source.

4. The system of claim 3 where the first camera is a color camera.

5. The system of claim 3 wherein:

the 3D coordinate measurement system further includes a display, the display configured to show image data obtained from the first camera; and

the processor is further configured to steer the structure to a user-selected position on the display.

6. The system of claim 1 wherein:

the second light source is configured to emit infrared light; and

the second camera is responsive to infrared wavelengths of the second light source.

7. The system of claim 1 wherein the laser tracker further includes:

a third light source that emits a third beam of light;

a distance meter; and

a position detector internal to the structure, the position detector having a surface area.

8. The system of claim 7 wherein the processor is further operable to respond to the retroreflector lock-in command having been given by obtaining from the position detector a position detector reading that indicates whether a first portion of the third light reflected by the retroreflector as a third reflected light is received by the position detector and, if so, a position on the surface area at which the first portion of the third reflected light is received.

9. The system of claim 8 wherein the processor is further operable to respond to the retroreflector lock-in command having been given by steering the structure further based on the position detector reading.

10. The system of claim 9 wherein the processor is further operable to respond to the retroreflector lock-in command having been given by:

capturing a plurality of third digital images with the second camera and taking a corresponding plurality of third position detector readings; and

steering the structure to direct the third light beam to the retroreflector further based on the plurality of the third digital images and the plurality of third position detector readings.

11. The system of claim 8 wherein the laser tracker further includes a first angular encoder and a second angular encoder.

12. The system of claim 11 wherein the processor is further operable to:

receive by the distance meter a second portion of the third reflected light;

determine a first distance based at least in part on the second portion of the third reflected light;

measure with the first angular encoder a first angle of rotation about the first axis;

measure with the second angular encoder a second angle of rotation about the second axis; and

determine 3D coordinates of the retroreflector based at least in part on the first distance, the first angle of rotation, and the second angle of rotation.

13. The system of claim 1 wherein the processor is further operable to:

cause the first camera to capture a plurality of fourth digital images; and

determine that the lock-in command has been given further based on the plurality of fourth digital images.

14. The system of claim 1 wherein the communication device further includes a battery.

15. The system of claim 14 wherein the battery is rechargeable.

16. The system of claim 1 wherein the operator-controlled unit includes a first actuator that when activated causes the first light source to illuminate.

17. The system of claim 13 wherein the first light source is illuminated in a first temporal pattern.

18. The system of claim 17 wherein the processor determines that the lock-in command has been given is further based on a correspondence between the first temporal pattern and the lock-in command.

19. The system of claim 16 wherein the actuator is selected from the group consisting of a button and a selection from a touch screen display.

20. The system of claim 16 wherein the communication device further includes a second actuator configured to send a wireless signal to the tracker when the second actuator is activated, the wireless signal indicative of a second command.

21. The system of claim 20 wherein the communication device is a remote control unit.

22. The system of claim 20 wherein the communication device is a smart device configured for communication with the laser tracker.

23. The system of claim 22 wherein the smart device is selected from the group consisting of a tablet, a mobile phone, a laptop computer, and a wearable device.

24. The system of claim 22 wherein the smart device is configured to provide a user interface, the user interface including a display configured to provide a selection of tracker commands, the selection of tracker commands including the retroreflector lock-in command and a measure command.

25. The system of claim 24 wherein the smart device is configured to download software from an Internet.

26. The system of claim 8 wherein the processor is further configured to send a warning indication to the communication device in response to obtaining a position detector reading indicating that the first portion of the third reflected light has not been received.

27. The system of claim 26 wherein the operator-controlled unit is controlled by a control selected from the group consisting of a voice command, a button push, and a menu selection on a touch screen display.

28. A method for locking on a retroreflector with a laser tracker, the method comprising:

providing a communication device, the retroreflector, and the laser tracker,

the communication device including a first light source and an operator-controlled unit, the operator-controlled unit configured to control emission of a first light from the first light source,

the retroreflector separate from the communication device,

the laser tracker including a structure, a distance meter, a first angular encoder, a second angular encoder, a first camera, a second camera, a second light source, a position detector, a processor, and third light source, the structure rotatable about a first axis and a second axis, the second camera proximate the second light source, the second camera having a narrower field-of-view than the first camera, the first camera and the second camera affixed to an external portion of the structure, the position detector internal to the tracker;

emitting the first light from the communication device;

capturing the first light with the first camera to produce a first digital image;

determining by the processor, based at least in part on the first digital image, that a lock-in command has been given and in response activating the second light source to produce second light;

reflecting from the retroreflector a portion of the second light as second reflected light;

capturing the second reflected light with the second camera to produce a second digital image;

launching a third light beam from the third light source;

steering the structure to direct the third light beam to the retroreflector, the steering based at least in part on one of the second digital image and a reading of the position detector;

reflecting a portion of the third light beam as a third reflected light;

capturing a first part of the third reflected light with the position detector;

capturing a second part of the third reflected light with the distance meter;

determining with the processor a first distance to the retroreflector based at least in part on the second part of the third reflected light;

measuring with the first angular encoder a first angle of rotation about the first axis;

measuring with the second angular encoder a second angle of rotation about the second axis;

determining with the processor three-dimensional (3D) coordinates of the retroreflector based at least in part on the first distance, the first angle of rotation, and the second angle of rotation; and

storing the 3D coordinates.

29. The method of claim 28 wherein:

the step of capturing the second reflected light with the second camera to produce a second digital image further includes capturing a plurality of third digital images and taking a corresponding plurality of third position detector readings; and

the step of steering the structure to direct the third light beam to the retroreflector is further based on the plurality of third digital images and the plurality of third position detector readings.

30. The method of claim 29 wherein:

the step of capturing the first light with the first camera to produce a first digital image further includes capturing a plurality of fourth digital images; and

the step of determining by the processor that the lock-in command has been given, the determining further based on the plurality of fourth digital images.