Self-calibrating laser tracker and self-calibration method

Patent metadata

Field	Value
Publication number	US-9945938-B2
Application number	US-201314653802-A
Country	US
Kind code	B2
Filing date	Dec 19, 2013
Priority date	Dec 21, 2012
Publication date	Apr 17, 2018
Grant date	Apr 17, 2018

Abstract

Some embodiments of the invention relate to a laser tracker for determining the position of a target, comprising a beam source for generating measurement radiation; a base; a beam deflection unit which can pivot with respect to the base −4° C. about two axes in a motorized manner, for the emission and alignment of the measurement radiation and to capture at least one part of the measurement radiation reflected onto the target; a first position-sensitive surface detector and an evaluation and control unit for determining a point of impact of the reflected measurement on the surface detector for generating an output signal in order to determine the position of said target. Said laser tracker also comprises a calibration device for use with a self calibrating function to determine the calibration parameters thereof with respect to a position and/or direction of the measurement radiation.

First claim

What is claimed is:

1. A laser tracker for determining the position of a target and in particular for continuously tracking the target, comprising
a beam source for generating measurement radiation,
a base defining a vertical axis,
a support defining a tilting axis, which is substantially orthogonal to the vertical axis, wherein the support is pivotable in a motorized fashion about the vertical axis relative to the base and a horizontal pivoting angle is defined by an orientation of the support relative to the base,
a beam directing unit, which is pivotable in a motorized fashion about the tilting axis relative to the support, wherein a vertical pivoting angle is defined by an orientation of the beam directing unit relative to the support, for emission and orientation of the measurement radiation and for reception of at least part of the measurement radiation reflected at the target,
angle measuring functionality for determining the horizontal pivoting angle and the vertical pivoting angle,
distance measuring functionality,
a first position-sensitive surface detector, and
an evaluation and control unit for determining an impingement point of the reflected measurement radiation on the surface detector for generating an output signal for determining the position of the target,
wherein the laser tracker additionally comprises a calibration device for use with a self-calibration functionality, in the context of which calibration parameters are determinable with regard to a position and/or direction of the measurement radiation, wherein:
the calibration device has on the base a second position-sensitive surface detector, onto which measurement radiation is emittable by the beam directing unit, and
the evaluation and control unit is designed for determining an impingement point of measurement radiation impinging on the second position-sensitive surface detector, whereby at least one portion of the calibration parameters is determinable with regard to a position and/or direction of the measurement radiation, and

wherein the laser tracker comprises a first camera for capturing the spatial orientation of the target and at least one second camera for coarsely localizing the target, and/or wherein the measurement radiation is a laser beam, and the laser tracker comprises an absolute distance measuring device and/or an interferometer.

2. The laser tracker as claimed in claim 1 , wherein:
the evaluation and control unit is for controlling a target tracking functionality.

3. The laser tracker as claimed in claim 1 , wherein:
the calibration device has on the base a reflection means, onto which measurement radiation is emittable by the beam directing unit for reflecting the measurement radiation as reflected measurement radiation onto the first position-sensitive surface detector, wherein a servo control point is determinable as part of the calibration parameters.

4. A laser tracker for determining the position of a target and in particular for continuously tracking the target, comprising
a beam source for generating measurement radiation,
a base defining a vertical axis,
a support defining a tilting axis, which is substantially orthogonal to the vertical axis, wherein the support is pivotable in a motorized fashion about the vertical axis relative to the base and a horizontal pivoting angle is defined by an orientation of the support relative to the base,
a beam directing unit, which is pivotable in a motorized fashion about the tilting axis relative to the support, wherein a vertical pivoting angle is defined by an orientation of the beam directing unit relative to the support, for emission and orientation of the measurement radiation and for reception of at least part of the measurement radiation reflected at the target,
angle measuring functionality for determining the horizontal pivoting angle and the vertical pivoting angle,
distance measuring functionality,
a first position-sensitive surface detector, and
an evaluation and control unit for determining an impingement point of the reflected measurement radiation on the surface detector for generating an output signal for determining the position of the target,
wherein the laser tracker additionally comprises a calibration device for use with a self-calibration functionality, in the context of which calibration parameters are determinable with regard to a position and/or direction of the measurement radiation, wherein:
the calibration device has on the base a second position-sensitive surface detector, onto which measurement radiation is emittable by the beam directing unit,
the evaluation and control unit is designed for determining an impingement point of measurement radiation impinging on the second position-sensitive surface detector, whereby at least one portion of the calibration parameters is determinable with regard to a position and/or direction of the measurement radiation, and
a two-position measurement is implementable in the context of the self-calibration functionality by the laser tracker, wherein, in the context of the two-position measurement, measurement radiation is emittable onto the second position-sensitive surface detector in a first and a second orientation of the beam directing unit, wherein the beam directing unit is rotated by 180° with respect to the horizontal pivoting angle in the second orientation in comparison with the first orientation.

5. A laser tracker for determining the position of a target and in particular for continuously tracking the target, comprising
a beam source for generating measurement radiation,
a base defining a vertical axis,
a support defining a tilting axis, which is substantially orthogonal to the vertical axis, wherein the support is pivotable in a motorized fashion about the vertical axis relative to the base and a horizontal pivoting angle is defined by an orientation of the support relative to the base,
a beam directing unit, which is pivotable in a motorized fashion about the tilting axis relative to the support, wherein a vertical pivoting angle is defined by an orientation of the beam directing unit relative to the support, for emission and orientation of the measurement radiation and for reception of at least part of the measurement radiation reflected at the target,
angle measuring functionality for determining the horizontal pivoting angle and the vertical pivoting angle,
distance measuring functionality,
a first position-sensitive surface detector, and
an evaluation and control unit for determining an impingement point of the reflected measurement radiation on the surface detector for generating an output signal for determining the position of the target,
wherein the laser tracker additionally comprises a calibration device for use with a self-calibration functionality, in the context of which calibration parameters are determinable with regard to a position and/or direction of the measurement radiation, wherein:
the calibration device has on the base a second position-sensitive surface detector, onto which measurement radiation is emittable by the beam directing unit, and
the evaluation and control unit is designed for determining an impingement point of measurement radiation impinging on the second position-sensitive surface detector, whereby at least one portion of the calibration parameters is determinable with regard to a position and/or direction of the measurement radiation,
wherein the calibration device:
has an optical element arranged upstream of the second position-sensitive surface detector in the beam direction of the measurement radiation, wherein the optical element
is provided on the base in a known spatial relation with respect to the second position-sensitive surface detector, and
is fashioned and arranged in such a way that calibration parameters

Assignees

• Leica Geosystems Ag

Inventors

• Markendorf Albert

Classifications

• G01S7/4817

  relating to scanning · CPC title

• G01S7/4972 Primary

  Alignment of sensor · CPC title

• G01S17/66

  Tracking systems using electromagnetic waves other than radio waves · CPC title

• G01S17/86

  Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders · CPC title

• G01S17/023

  Physics · mapped topic