Gain factor and position determination system

• US 6,990,427 B2
• Filed: 07/22/2003
• Issued: 01/24/2006
• Est. Priority Date: 06/26/2001
• Status: Expired due to Term

• Current Assignee: Northern Digital Inc. (Roper Technologies, Inc.)
• Original Assignee: Northern Digital Inc. (Roper Technologies, Inc.)
• Inventors: Kirsch, Stefan R., Schild, Hans R., Schilling, Christian J.
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US10/624,917
• Publication Number:
  US 20050049820A1
• Time in Patent Office: 917 Days
• Field of Search: 702/150, 702/151, 702/152, 702/153, 702/154, 600/229, 600/230, 600/407, 600/424, 32420712-20717, 324/318, 324/322, 606/108, 606/130
• US Class Current: 702/150
• CPC Class Codes: A61B 5/062 using magnetic field
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00

Abstract

A system for determining the position, orientation and system gain factor of a probe includes a plurality of magnetic field sources and at least one magnetic field sensor, such that a combination of a magnetic field sensor and a magnetic field source generates a unique measured magnetic field value. The system includes a probe whose gain, position, and orientation affect these unique measured magnetic field values. A processor is configured to receive and iteratively process these unique measured magnetic field values to determine a system gain factor indicative of the gain of the probe and a plurality of location factors indicative of the position and orientation of the probe. The number of unique measured magnetic field values generated must be at least equal to the sum of the number of gain and location factors calculated.

Claims

1. A system for determining the position, orientation and system gain factor of a probe comprising:

a plurality of magnetic field sources;

at least one magnetic field sensor, wherein a combination of a magnetic field sensor and a magnetic field source generates a unique measured magnetic field value;

a probe whose gain, position, and orientation affects said unique measured magnetic field values; and

a processor, configured to receive and iteratively process said unique measured magnetic field values, for determining a system gain factor indicative of the gain of said probe and a plurality of location factors indicative of the position and orientation of said probe, wherein said iterative process is configured to determine a function of the differences between said measured magnetic field values and a plurality of predicted magnetic field values.

2. The system for determining the position, orientation and system gain factor of claim 1 wherein the number of unique measured magnetic field values generated is at least equal to the sum of the number of gain and location factors calculated.

3. The system for determining the position, orientation and system gain factor of claim 2 wherein said processor includes a calculated location process for calculating said predicted magnetic field values, wherein said calculated location process guesses an initial gain, position, and orientation for said probe, and calculates said predicted magnetic field values based on a physical model and said initial gain, position, and orientation.

4. The system for determining the position, orientation and system gain factor of claim 3 wherein said initial position and orientation is a predetermined fixed point.

5. The system for determining the position, orientation and system gain factor of claim 3 wherein said initial position and orientation is a randomly selected fixed point.

6. The system for determining the position, orientation and system gain factor of claim 3 wherein said processor includes an optimization function for determining an extremum indicative of said differences between said measured magnetic field values and said predicted magnetic field values.

7. The system for determining the position, orientation and system gain factor of claim 6 wherein said optimization function is a least squares sum function.

8. The system for determining the position, orientation and system gain factor of claim 6 wherein said processor includes a repositioning process for adjusting said initial gain, position, and orientation of said probe in response to said extremum being in a predefined range of unacceptable values, which is indicative of an unacceptable level of difference between said measured magnetic field values and said plurality of predicted magnetic field values.

9. The system for determining the position, orientation and system gain factor of claim 1 wherein said location factors include spatial coordinates.

10. The system for determining the position, orientation and system gain factor of claim 1 wherein said location factors include spherical coordinates.

11. The system for determining the position, orientation and system gain factor of claim 1 wherein said location factors include rotational coordinates.

12. A system for determining the position, orientation and system gain factor of a probe comprising:

one of a plurality of magnetic field sensors and a plurality of magnetic field sources;

at least one of the other of the magnetic field sensors and magnetic field sources, wherein a combination of a magnetic field sensor and a magnetic field source generates a unique measured magnetic field value,

a probe whose gain, position, and orientation affects said unique measured magnetic field values; and

a processor, configured to receive and iteratively process said unique measured magnetic field values, for determining a system gain factor indicative of the gain of said probe and a plurality of location factors indicative of the position and orientation of said probe;

wherein said iterative process is configured to determine a function of the differences between said measured magnetic field values and a plurality of predicted magnetic field values.

13. The system for determining the position, orientation and system gain factor of claim 12 wherein the number of unique measured magnetic field values generated is at least equal to the sum of the number of gain and location factors calculated.

14. The system for determining the position, orientation and system gain factor of claim 13 wherein said processor includes a calculated location process for calculating said predicted magnetic field values, wherein said calculated location process guesses an initial gain, position, and orientation for said probe, and calculates said predicted magnetic field values based on a physical model and said initial gain, position, and orientation.

15. The system for determining the position, orientation and system gain factor of claim 14 wherein said initial position and orientation is a predetermined fixed point.

16. The system for determining the position, orientation and system gain factor of claim 14 wherein said initial position and orientation is a randomly selected fixed point.

17. The system for determining the position, orientation and system gain factor of claim 14 wherein said processor includes an optimization function for determining an extremum indicative of said differences between said measured magnetic field values and said predicted magnetic field values.

18. The system for determining the position, orientation and system gain factor of claim 17 wherein said optimization function is a least squares sum function.

19. The system for determining the position, orientation and system gain factor of claim 17 wherein said processor includes a repositioning process for adjusting said initial gain, position, and orientation of said probe in response to said extremum being in a predefined range of unacceptable values, which is indicative of an unacceptable level of difference between said measured magnetic field values and said plurality of predicted magnetic field values.

20. The system for determining the position, orientation and system gain factor of claim 12 wherein said location factors include spatial coordinates.

21. The system for determining the position, orientation and system gain factor of claim 12 wherein said location factors include spherical coordinates.

22. The system for determining the position, orientation and system gain factor of claim 12 wherein said location factors include rotational coordinates.