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AssigneeLeica Geosystems AG
InventorDietrich Meier
Estimating the term…
In a laser tracking system equipped for interferometric distance measurement there are provided at least two retroreflectors (3.1, 3.2, 3.3) which are connected to the target tracking mirror (1) in a manner such that their position changes when the spatial orientation of the target tracking mirror (1) is changed. Secondary measurement beams (4.1, 4.2, 4.3) deflected out of the primary measuring beam (4) of the laser tracking system are directed onto the retroreflectors (3.1, 3.2, 3.3.). Path length changes in the beam path of the secondary measurement beams (4.1, 4.2, 4.3) are interferometrically measured and the readings are used for computing the spatial orientation of the target tracking mirror (1).
A method for determining the spatial orientation of a movable target tracking mirror of a laser tracking system in which the direction of a primary measurement beam is changed by changing the spatial orientation of the target tracking mirror, direction changes of the primary measurement beam are detected by determining the spatial orientation of the target tracking mirror, and path length changes in the beam path of the primary measurement beam are detected with interferometric methods;
A laser tracking system comprising:
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
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Measuring arrangements characterised by the use of optical techniques: for measuring angles or tapers; for testing the alignment of axes
Common to transmitter and receiver: transmitted and received beams following a coaxial path
Systems determining position data of a target: for measuring distance only
Systems determining position data of a target: simultaneous measurement of distance and other co-ordinates
Term ended 13 Jun 2022 (estimated)
The invention relates to a method according to the preamble of the first independent patent claim. The method serves for determining the spatial orientation of a target tracking mirror in a laser tracking system. The system further relates to a mirror arrangement according to the corresponding independent patent claim, said mirror arrangement serving for carrying out the method.
The target tracking mirror is an essential component of laser tracking systems as they have been known for many years now in industry and are used for precise coordinate measurements on large subjects. Laser tracking systems permit the tracking of a moving target retroreflector with a tracking measurement beam, wherein by way of suitable measurements of the direction of the measurement beam and by way of interferometric measurements of the distance to the target retroreflector the coordinates (e.g. polar coordinates) of the target retroreflector are determined.
Directing the tracking measurement beam in a manner such that it always impinges the moving retroreflector is effected by suitably adjusting the target tracking mirror which usually is rotatable about two axes standing perpendicular to one another. The tracking measurement beam is reflected back by the retroreflector to the target tracking mirror and from this is deflected to the interferometer receiver. The interferometer receiver determines the distance of the target retroreflector to a defined zero position of the laser interferometer. The spatial orientation of the target tracking mirror is determined by measurement and from the readings the direction of the measurement beam is computed.
The method according to the invention and the device according to the invention are described in detail by way of the following Figs. wherein:
FIG. 1 shows the principle of determining the spatial orientation of a target tracking mirror using an exemplary embodiment of the method according to the invention;
FIGS. 2, 3 and 4 show for an exemplary embodiment of the mirror arrangement according to the invention, in various views, target tracking mirror, mirror suspension, drives for changing the mirror orientation and retroreflectors;
FIG. 1 illustrates on an exemplary embodiment the principle of the invention serving for determining the spatial orientation of a target tracking mirror. The Figure shows a target tracking mirror 1 rotatable about an axis A with a mirror surface perpendicular to the paper plane. Parallel to the mirror surface and perpendicular to the rotational axis A there runs a connection rod 2 which is rotatable with the mirror about the rotational axis A and on whose ends there is mounted in each case one retroreflector 3.1 and 3.2. The target tracking mirror 1, the connection rod 2 and the retroreflectors 3.1, and 3.2 are shown in two rotational positions, wherein the reference numerals of the parts are characterized in the one rotational position with an apostrophe.
A secondary measurement beam 4.1 (in front of the reflector brought to a diameter corresponding essentially to the reflector opening by way of beam widening optics 5.1) is directed tangentially to the circular arc described by the reflector 3.1 on rotation of the target tracking mirror 1 and advantageously such that in a middle reflector position it centrically impinges the reflector. The measurement beam 4 is reflected in the retroreflector 3.1 and in a manner yet to be shown together with a suitable secondary reference beam is led to an interferometer allocated to the retroreflector 3.1.
On pivoting mirror 1 and reflectors 3.1 and 3.2 the path length of the secondary measurement beam 4.1 changes, wherein path length changes between a predetermined zero position (e.g. defined by mechanical abutment or optically) and a momentary position are interferometrically detected and measured. The orientation of the mirror 1 (characterized by the rotation angle α) is unambiguously determined by the path length change of the secondary measurement beam 4.1 which is effected by a displacement of the retroreflector 3.1 from its zero position (for the zero orientation of the mirror) into another momentary position.