Geodetic instruments and methods of operating geodetic instruments

Patent metadata

Field	Value
Publication number	US-2016305778-A1
Application number	US-201615172013-A
Country	US
Kind code	A1
Filing date	Jun 2, 2016
Priority date	Dec 5, 2013
Publication date	Oct 20, 2016
Grant date	—

Abstract

Embodiments provide for a geodetic instrument comprising a scanning head, a reflecting optical element, a radiation source, a control unit and an electronic distance measurement (EDM) unit. The scanning head is rotatable about a first axis. The reflecting optical element mounted in the scanning head and rotatable about the same first axis. The radiation source is adapted to emit light to be output along a light beam path from the geodetic instrument via light reflection against the reflecting optical element. The control unit is adapted to adjust an angular displacement profile of the reflecting optical element about the first axis relative to an angular displacement profile of the scanning head such that an angular displacement of the light beam path about the first axis as a function of time presents a stair-like profile. The EDM unit is adapted to determine a distance to a target during a flat portion of the stair-like profile.

First claim

1 . A method of operating a geodetic instrument, comprising:
rotating a scanning head of the geodetic instrument about a first axis according to a first angular displacement profile; rotating about the same first axis a reflecting optical element mounted in the scanning head according to a second angular displacement profile, wherein a light beam path for outputting light from the geodetic instrument is provided via light reflection against the reflecting optical element; adjusting the second angular displacement profile relative to the first angular displacement profile such that an angular displacement of the light beam path about the first axis as a function of time presents a stair-like profile; and determining a distance to a target during a flat portion of the stair-like profile.

2 . The method of claim 1 , wherein the scanning head is rotated continuously forward and the reflecting optical element is rotated back and forth.

3 . The method of claim 1 , wherein the first angular displacement profile is linear in a first angular direction while the second angular displacement profile includes linear portions in a second angular direction opposite to the first angular direction, a rotation speed of the reflecting optical element in said linear portions being equal to a rotation speed of the scanning head.

4 . The method of claim 1 , wherein the second angular displacement profile is a saw-tooth pattern.

5 . The method of claim 1 , wherein the determining a distance to a target is based on time-of-flight measurements or phase-shift measurements.

6 . The method of claim 1 , wherein the determining a distance includes averaging values repetitively obtained during a flat portion of the stair-like profile.

7 . A geodetic instrument comprising:
a scanning head rotatable about a first axis; a reflecting optical element mounted in the scanning head and rotatable about the same first axis; a radiation source adapted to emit light to be output along a light beam path from the geodetic instrument via light reflection against the reflecting optical element; a control unit adapted to adjust an angular displacement profile of the reflecting optical element relative to an angular displacement profile of the scanning head such that an angular displacement of the light beam path about the first axis as a function of time presents a stair-like profile; and an electronic distance measurement, EDM, unit adapted to determine a distance to a target during a flat portion of the stair-like profile.

8 . The geodetic instrument of claim 7 , wherein the control unit is adapted to cause rotation of the scanning head continuously forward and to cause rotation of the reflecting optical element back and forth.

9 . The geodetic instrument of claim 7 , wherein the control unit is adapted to cause the scanning head to rotate about the first axis at a constant rotation speed in a first angular direction and to cause the reflecting optical element to periodically rotate about the first axis at the same constant speed in an angular direction opposite to the first angular direction.

10 . The geodetic instrument of claim 7 , wherein the angular displacement profile of the reflecting optical element is a saw-tooth pattern.

11 . The geodetic instrument of claim 7 , wherein the EDM unit is adapted to determine the distance by averaging values repetitively obtained during a flat portion of the stair-like profile.

12 . The geodetic instrument of claim 7 , further comprising at least one of a galvanometer, a piezoelectric actuator and a magnetostrictive actuator for rotating the reflecting optical element.

13 . The geodetic instrument of claim 7 , wherein the reflecting optical element is a scanning mirror or a scanning prism.

14 . A method of operating a geodetic instrument, comprising:
rotating about either one of a first axis and a second axis a center unit mounted on a base of the geodetic instrument; rotating about the same first or second axis a reflecting optical element rotationally mounted in the center unit, wherein light reflection at the reflecting optical element provides a light beam path along which light is to be output from the geodetic instrument; controlling the respective rotations of the center unit and the reflecting optical element such that an angular displacement of the light beam path about either one of the first axis and the second axis as a function of time results in a stair-like profile; and measuring a distance to a target based on detection of a signal representative of reflection of the light against the target during a flat portion of the stair-like profile.

15 . The method of claim 14 , wherein the stair-like profile is obtained by controlling the rotation of the center unit at a constant speed in a first rotational direction about either one of the first axis and the second axis and periodically controlling the rotation of the reflecting optical element, at the same constant speed, in a rotational direction opposite to the first rotational direction about the same axis.

16 . A geodetic instrument, comprising:
a center unit rotationally mounted on a base for rotation about a first axis and a second axis; a reflecting optical element rotationally mounted in the center unit for rotation about the first axis and the second axis; a light source for emission of light to be output along a light beam path from the geodetic instrument via light reflection at the reflecting optical element; a control unit adapted to control the respective rotations of the center unit and the reflecting optical element such that an angular displacement of the light beam path about either one of the first axis and the second axis as a function of time results in a stair-like profile; and a processing unit for measurement of a distance to a target based on detection of a signal representative of reflection of the light against the target during a flat portion of the stair-like profile.

17 . The geodetic instrument of claim 16 , wherein the control unit is adapted to control the rotation of the center unit at a constant speed in a first rotational direction about either one of the first axis and the second axis and to periodically control the rotation of the reflecting optical element at the same constant speed in a direction opposite to the first rotational direction about the same axis.

18 . The geodetic instrument of claim 16 , wherein the control unit is configured to synchronize emission of light from the light source, or the radiation source, with the determination or measurement of the distance to the target during a flat portion of the stair-like profile.

19 . The method of claim 1 , wherein light is emitted from the geodetic instrument during a flat portion of the stair-like profile.

20 . A non-transitory computer-readable digital storage medium comprising a computer program product comprising computer-executable components adapted to, when executed on a processing unit, perform a method according to claim 1 .

Assignees

• Trimble Ab

Inventors

• Berg Ulf

Classifications

• G01C15/002 Primary

  Active optical surveying means (optical plumbing G01C15/105) · CPC title

• G01C9/06 Primary

  Electric or photoelectric indication or reading means · CPC title