Method for determining the position and rotational position of an object

• US 6,671,058 B1
• Filed: 09/21/2000
• Issued: 12/30/2003
• Est. Priority Date: 03/23/1998
• Status: Expired due to Term

• Current Assignee: Leica Geosystems AG (Hexagon AB)
• Original Assignee: Leica Geosystems AG (Hexagon AB)
• Inventors: Appius, Raphael, Braunecker, Bernard, Aebischer, Beat
• Primary Examiner(s): Nguyen, Tu T.
• Application Number:
  US09/666,834
• Time in Patent Office: 1,195 Days
• Field of Search: 356/3-1-, 356/4-1-, 356/3--, 356/5-1-, 356/5-1-, 356/6-22, 356/614-640
• US Class Current: 356/616
• CPC Class Codes: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• CPC Class Codes: G01S 5/163 Determination of attitude using inertial means G01C9/00; control of attitude G05D1/49

Abstract

The invention relates to a method for determining the spatial and rotational positions of an object. With the assistance of an imaging optical system, the object is mapped and detected on a high-sensitivity resolution optoelectronic detector. The location parameter of the object, such as the position vector ({overscore (r)}₀), the direction vector ({overscore (ν)}) of the object axis, and the angle (κ) of rotation of the object around the object axis is determined from the planar position of the mapped object structures in the coordinate system (X_Det, Y_Det) of the detector by means of geometric optical relationships and mathematical evaluation methods. With this, the spatial position of the object is determined in a quick and contactless manner.

Claims

1. A method for determining the position and rotational position of an object with object structures of known dimension in three-dimensional space using an optical measuring head having an imaging optical system with imaging properties, an optoelectronic detector which is position-resolving in two dimensions, and an evaluation system, said method comprising the steps of collecting on the detector a focused image of that part of the object which is present in the field of view of the imaging optical system, feeding detected image information from the detector to the evaluation system, and using the evaluation system to determine at least one of the position and rotational position of the object in space, described by position parameters, by determining the position of focused object structures on the detector using the detected image information, determining an imaging scale based on the position of focused object structures on the detector relative to known dimensions of the object structures, and determining the position parameters by at least one of the following:

(1) calculating theoretical detector images for at least one set of position parameters using the imaging scale and imaging properties of the optical system, and choosing the position parameters which result in a calculated detector image which agrees with the detected image information; and

(2) calculating the position parameters directly using the imaging properties of the optical system, the imaging scale, and geometric vector equations.

2. The method according to claim 1, wherein at least one of geometric shape of the object and marks on the object are recorded and evaluated as object structure by the measuring head.

3. The method according to claim 1, wherein a code pattern is applied to the object and is recorded and evaluated as object structure by the measuring head.

4. The method according to claim 1, wherein the object structures are applied as a code pattern on a separate body which is mechanically connected to the object.

5. The method according to claim 4, wherein a plurality of bodies provided with a code pattern are used and are mechanically connected to the object.

6. The method according to claim 1, wherein at least one of the object and the body are tubular.

7. The method according to claim 6, wherein the object structures are rotationally symmetrical with respect to the longitudinal axis of at least one of the object and the body.

8. The method according to claim 6, wherein the object structures are rotationally symmetrical with respect to, and parallel to, the longitudinal axis of at least one of the object and the body.

9. The method according to claim 1, wherein the object structures have a spiral shape.

10. The method according to claim 1, wherein the object structures are completely irregular but are unambiguously formed with respect to their position on at least one of the object and the body.

11. The method according to claim 1, wherein in order to improve the accuracy of measurement, the fundamental spatial frequency or a higher harmonic spatial frequency of the intensity distribution produced by the object structures on the detector forms, together with the fundamental spatial frequency of the radiation-sensitive structures of the detector, a low-frequency superposition pattern.

12. The method according to claim 1, wherein the object is illuminated.

13. The method according to claim 1, wherein a plurality of optical measuring heads for determining the spatial position of at least one object are simultaneously used.

14. The method according to claim 1, wherein the object is stereoscopically mapped.

15. The method according to claim 14, wherein the stereoscopic map is produced by one of (1) two optical measuring heads which are oriented relative to one another, and (2) one optical measuring head and at least more mirror which are aligned relative thereto.

16. The method according to claim 1, wherein the distance to the object is determined with the aid of a distance measuring instrument.

17. The method according to claim 16, wherein the distance measuring instrument is an electrooptic distance measuring instrument.

18. The method according to claim 1, wherein the position parameters describing at least one of the position and rotational position of the object are transformed into a superior coordinate system.

19. The method according to claim 1, wherein the object is an aid used in one chosen from medical diagnostics, therapy and operations.

20. The method according to claim 19, wherein the aid is one of a surgical microscope, a surgical tool, a frame connected to a patient, and a radiation source for tumour treatment.

21. The method according to claim 1, wherein the object is a levelling staff.

22. The method according to claim 1, wherein the object is one of a gun barrel, a directional aerial, and a radar aerial.

23. The method according to claim 1, wherein at least one of the object and the object structures is luminescent.

24. The method according to claim 1, wherein the imaging optical system includes a zoom, and further comprising the step of using the zoom to vary the field of view.

25. The method according to claim 1, wherein the imaging optical system has a field of view, and further comprising the step of moving the optical measuring head to scan a larger field of view.

26. The method according to claim 1, wherein the imaging optical system has a field of view, and further comprising the step of imaging a larger field of view by using a plurality of prisms, said prisms each imaging a portion of the larger field of view.

27. The method according to claim 26, wherein the prisms are configured such that imaged portions overlap one another.

28. The method according to claim 1, wherein a mathematical optimization method is used to vary the position parameters so that the calculated detector image agrees with the detected image information.