Method for using a handheld appliance to select, lock onto, and track a retroreflector with a laser tracker

• US 8,724,119 B2
• Filed: 03/27/2013
• Issued: 05/13/2014
• Est. Priority Date: 04/21/2010
• Status: Active Grant

• Current Assignee: Faro Technologies Incorporated
• Original Assignee: Faro Technologies Incorporated
• Inventors: Steffey, Kenneth, Pease, Gregory D., Bridges, Robert E.
• Primary Examiner(s): Punnoose, Roy M
• Application Number:
  US13/851,221
• Publication Number:
  US 20130229512A1
• Time in Patent Office: 412 Days
• Field of Search: 356/614
• US Class Current: 356/614
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• 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: 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: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• 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

Abstract

A method for locking onto and tracking a selected retroreflector target with a laser tracker includes steps of: actuating by the operator the handheld appliance and sending a wireless signal; responding to the wireless message by repetitively carrying out steps in the following loop and exiting the loop when an exit condition is met: reflecting part of the cone of light by the at least one retroreflector target and capturing an array image on the photosensitive array; determining which retroreflector target meets the retroreflector target criterion; determining whether the position detector is receiving the reflected beam; establishing that the exit condition is met when the position detector receives the reflected beam and the reflected beam comes from the selected retroreflector target; and steering the first light beam toward the selected retroreflector target.

Claims

1. A method for locking onto and tracking a selected retroreflector target with a laser tracker, the locking onto and tracking carried out under direction of an operator, the method including steps of:

providing at least one retroreflector target;

providing the laser tracker, the laser tracker having a structure, a first light source, a distance meter, a first angular transducer, a second angular transducer, a position detector, a camera, a second light source, and a processor, the structure rotatable about a first axis and a second axis;

the first light source configured to produce a first light beam that cooperates with the distance meter, the first angular transducer configured to measure a first angle of rotation about the first axis, the second angular transducer configured to measure a second angle of rotation about the second axis, the position detector configured to receive a reflected beam, the reflected beam being the first light beam reflected by a retroreflector target, the camera including a lens system and a photosensitive array, the second light source configured to provide a cone of light, the first light beam and the cone of light being fixed in relation to the structure, the second light source configured to cooperate with the camera, the camera having a field of view, the processor configured to operate the laser tracker;

providing a tracker transceiver coupled to the laser tracker or coupled to a computer in communication with the laser tracker, the tracker transceiver including a receiver and optionally a transmitter;

providing a handheld appliance having an appliance transceiver affixed to the handheld appliance, the appliance transceiver configured to wirelessly communicate with the tracker transceiver, the appliance transceiver configured to emit a wireless signal selected from the group consisting of an RF signal, a microwave signal, and an infrared signal;

positioning the at least one retroreflector target within the field of view of the camera;

actuating by the operator the handheld appliance and in response to the actuation sending a first wireless signal from the appliance transceiver to the tracker transceiver;

in response to reception of the first wireless signal by the tracker receiver, determining a retroreflector target criterion;

responding to the first wireless signal by repetitively carrying out steps in a loop including the following steps (a)-(e) and exiting the loop when an exit condition is met;

(a) reflecting part of the cone of light by the at least one retroreflector target and capturing an array image on the photosensitive array;

(b) determining which of the at least one retroreflector target meets the retroreflector target criterion, the determining based at least in part on the array image, the retroreflector target that meets the retroreflector target criterion referred to as the selected retroreflector target;

(c) measuring a signal level with the position detector and determining, based on the signal level, whether the position detector is receiving the reflected beam;

(d) establishing whether the exit condition is met, the exit condition being met if and only if the position detector receives the reflected beam and the reflected beam comes from the selected retroreflector target;

(e) activating the first motor and the second motor to steer the first light beam toward the selected retroreflector target;

activating the first motor and the second motor to steer the reflected beam so as to keep the reflected beam on the position detector; and

measuring to the selected retroreflector target a distance with the distance meter, a third angle with the first angular transducer, and a fourth angle with the second angular transducer.

2. The method of claim 1, wherein, in the step of providing a handheld appliance, the handheld appliance is a handheld phone.

3. The method of claim 1, wherein, in the step of providing a handheld appliance, the handheld appliance is a remote control.

4. The method of claim 1, wherein the step of determining a retroreflector target criterion further includes choosing by the operator a retroreflector target criterion with the handheld appliance.

5. The method of claim 1, wherein the step of determining a retroreflector target criterion further includes providing and using a default retroreflector target criterion.

6. The method of claim 4, wherein the criterion is selected from the group consisting of:

the retroreflector target having an image nearest a center of the photosensitive array, the retroreflector target having an image nearest an edge of the photosensitive array, the retroreflector target having an image having the greatest speed from among the retroreflector target images as determined from successive array images, the retroreflector target image corresponding to the retroreflector target located nearer an inertial measurement unit than any other retroreflector target in the field of view of the camera, the retroreflector target having an image corresponding to the retroreflector target located nearer than any other retroreflector target to a line originating at the inertial measurement unit and projecting toward the retroreflector target, and the retroreflector target selected by the operator from among retroreflector targets represented by images in the array image sent from the transceiver to the handheld appliance.

7. The method of claim 1, wherein the step of providing a handheld appliance further includes steps of:

providing an inertial measurement unit affixed to the handheld appliance, the inertial measurement unit configured to measure inertial quantities, the inertial measurement unit in communication with the appliance transceiver;

placing the inertial measurement unit in the proximity of a second retroreflector target;

measuring with the laser tracker a first position of the second retroreflector;

measuring initial inertial quantities with the inertial measurement unit;

wirelessly transmitting initial inertial quantities from the appliance transceiver to the tracker transceiver; and

setting an initial position of the inertial measurement unit to the first position of the second retroreflector.

8. The method of claim 7, wherein, in the step of providing a handheld appliance, the inertial measurement unit includes a three-dimensional accelerometer and a three-dimensional gyroscope, the three-dimensional accelerometer configured to measure acceleration in three dimensions and the three-dimensional gyroscope configured to measure changes in angular orientation about three axes.

9. The method of claim 7, wherein the step of actuating by the operator the handheld appliance further includes steps of:

placing the inertial measurement unit in proximity of a third retroreflector target;

measuring second inertial quantities with the inertial measurement unit;

wirelessly transmitting second inertial quantities from the appliance transceiver unit to the tracker transceiver;

obtaining an approximate position of the third retroreflector target based at least in part on the second inertial quantities received by the tracker transceiver; and

determining that the third retroreflector target is the selected retroreflector target, the determining based at least in part on the approximate position of the inertial measurement unit.

10. The method of claim 7, wherein the step of actuating by the operator the handheld appliance further includes steps of:

aiming by the operator the handheld appliance in the direction of a third retroreflector target;

measuring second inertial quantities with the inertial measurement unit;

wirelessly transmitting second inertial quantities from the appliance transceiver to the tracker transceiver;

obtaining an approximate line on which the third retroreflector target lies, the approximate line based at least in part on the second inertial quantities received by the tracker transceiver; and

determining that the third retroreflector target is the selected retroreflector target, the determining based at least in part on a line on which the third retroreflector target lies.