Method and device for determining spatial positions and orientations

• US 6,667,798 B1
• Filed: 06/10/2002
• Issued: 12/23/2003
• Est. Priority Date: 07/28/1999
• Status: Expired due to Term

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Leica Geosystems AG (Hexagon AB)
• Inventors: Markendorf, Albert, Loser, Raimund
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US10/048,304
• Time in Patent Office: 561 Days
• Field of Search: 356/139.03, 356/141.1, 356/152.3, 356/141.5, 356/141.2, 356/601, 356/612, 702/153, 702/167
• US Class Current: 356/139.03
• CPC Class Codes: G01S 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

Using a laser-tracker (1) with an interferometer together with a retroreflector (3) in the form of a triple prism or a triple mirror arranged on an object and designed for parallel reflection of the laser beam (5) directed to the reflector (3), the position of the object is computed by way of measurement data with respect to the direction of the laser beam (5) and its path length. Additionally the spacial orientation of the object (2) is determined by producing additional measurement data with respect to the angle of incidence (α) of the laser beam into the reflector (3) and/or with respect to an adjustable orientation of the reflector (3) relative to the object (2) and by computing the position and spacial orientation of the object (2) by way of measurement data with respect to the direction and the path length of the laser beam (5) and by way of this additional measurement data. Thereby the measurement data of the direction measurement and of the interferometric measurement may be corrected by way of the additional measurement data with respect to the angle of incidence (α) such eliminating their dependency on the angle of incidence. For determining the angle of incidence (α), the reflector (3) is designed in a manner such that a central part of the laser beam (5) passes through the reflector (3) unreflected and behind the reflector (3) impinges a position sensor (12) arranged stationarily relative to the reflector, while a peripheral part of the laser beam (5) is reflected parallel and used for the interferometric measurement.

Claims

1. A method for determining a position and a spatial orientation of an object, in particular of a moving object, the method comprising the steps of:

mounting a reflector on the object, the reflector being able to reflect an incident laser beam parallelly independently of an angle of incidence;

pointing a laser beam from an essentially stationary source to the reflector and following the reflector with the laser beam during movement of the object by automatically changing the direction of the laser beam;

acquiring data defining the path length of the laser beam, the direction of the laser beam and the angle of incidence of the laser beam onto the reflector;

and calculating the position and the spatial orientation of the object from the acquired data and from data defining an orientation of the reflector relative to the object.

2. The method according to claim 1, characterized in that the data with respect to the angle of incidence of the laser beam onto the reflector is produced by a position sensor, said position sensor being stationarily arranged relative to the reflector in a manner such that an unreflected central part of the laser beam passes through a pass-through surface or passes through an opening of the reflector and impinges onto the position sensor and thereupon produces an image the position of which is correlated to the angle of incidence.

3. The method according to claim 1, characterized in that the reflector is stationarily arranged relative to the object.

4. The method according to claim 1, characterized in that the reflector has an adjustable orientation relative to the object and that data with respect to the orientation of the rejector relative to the object orientation are measured.

5. The method according to claim 4, characterized in that the reflector is arranged rotatable relative to the object about at least one axis perpendicular to its optical axis, and that data with respect to the reflector orientation relative to the object is produced by measuring at least one rotational angle of the reflector about said at least one axis.

6. The method according to claim 4, characterized in that the reflector is coarsely aligned with the laser beam by adjusting its orientation relative to the object, and that the position and spatial orientation of the object are computed by way of measurement data with respect to the direction and the path length of the laser beam and by way of the additional measurement data with respect to the angle of incidence as well as with respect to the reflector orientation relative to the object.

7. The method according to claim 1, characterized in that the measurement data with respect to the path length of the laser beam is produced by interferometry and that the measurement data with respect to the direction of the laser beam is produced by angle measurement.

8. The method according to claim 1, characterized in that measuring errors caused by a dependency of the path length or the direction of the laser beam on the angle of incidence are corrected using the measured data with respect to the angle of incidence.

9. The method according to claim 2, characterized in that the reflector is stationarily arranged relative to the object.

10. The method according to claim 2, characterized in that the reflector has an adjustable orientation relative to the object and that data with respect to the orientation of the reflector relative to the object orientation are measured.

11. The method according to claim 10, characterized in that the reflector is coarsely aligned with the laser beam by adjusting its orientation relative to the object and that the position and spatial orientation of the object is computed by way of measurement data with respect to the direction and the path length of the laser beam and by way of the additional measurement data with respect to the angle of incidence as well as with respect to the reflector orientation relative to the object.

12. An apparatus for determining a position and spatial orientation of an object, in particular of a moving object, the apparatus comprising:

a reflector mounted on the object and being able to reflect an incident laser beam in parallel to itself independently of an angle of incidence;

a substantially stationary laser tracker comprising a laser, means for pointing the laser beam produced by the laser to the reflector and following the reflector during movement of the object by automatically changing the direction of the laser beam and further comprising means for acquiring data defining a path length and a direction of the laser beam pointed to and reflected by the reflector;

means for acquiring data regarding the angle of incidence of the laser beam at the reflector;

and means for calculating the position and the spatial orientation of the object from the acquired data and data defining the orientation of the reflector.

13. The apparatus of claim 12, characterized in that the reflector is arranged with a non-adjustable orientation relative to the object.

14. The apparatus of claim 12, characterized in that the reflector is arranged with an adjustable orientation relative to the object and that the arrangement additionally comprises means for producing additional measurement data with respect to the adjustable orientation of the reflector relative to the object,

and means for computing the position and spatial orientation of the object by way of the measurement data with respect to the laser beam and by way of the additional measurement data.

15. The apparatus of claim 12, characterized in that the reflector is a triple prism with a pass-through surface or a triple mirror with a pass-through opening and that for measuring the angle of incidence and for producing corresponding measurement data, a position detector arranged stationarily relative the the reflector is provided.

16. The apparatus of claim 15, characterized in that for measuring the reflector orientation relative to the object and for producing corresponding measurement data, angle transmitters are provided.

17. The apparatus of claim 12, characterized in that it further comprises means for correcting the measurement data with respect to the direction of the laser bean or the path length of the laser beam by way of measurement data with respect to the angle of incidence of the laser beam into the reflector.

18. The apparatus of claim 15, characterized in that for measuring the reflector orientation relative to the object and for producing corresponding measurement data, angle transmitters are provided.