Optical position sensors

• US 6,223,066 B1
• Filed: 01/15/1999
• Issued: 04/24/2001
• Est. Priority Date: 01/21/1998
• Status: Expired due to Term

• Current Assignee: Biosense, Inc. (Cardinal Health, Inc.)
• Original Assignee: Biosense, Inc. (Cardinal Health, Inc.)
• Inventors: Govari, Assaf
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US09/232,499
• Time in Patent Office: 830 Days
• Field of Search: 600/424
• US Class Current: 600/424
• CPC Class Codes: G01R 33/032 using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12

Abstract

An elongate medical probe, having proximal and distal ends, whose position is tracked within the body of a subject includes a magnetic-field responsive optical element adjacent to the distal end, which modulates light passing therethrough responsive to an externally-applied magnetic field. The probe also includes a fiberoptic coupled to receive modulated light from the optical element and convey it to the proximal end of the probe for analysis of the modulation.

Claims

1. Apparatus for determining the position of an object, comprising:

a light source;

a magnetic-field responsive optical element, coupled to the object, which receives light from the light source and modulates the light responsive to an external AC magnetic field, having a predetermined frequency;

a detector, which receives at least a portion of the modulated light from the magnetic-field responsive optical element and generates signals responsive thereto; and

signal processing circuitry, which receives the signals from the detector and processes the signals to determine the position of the object.

2. Apparatus according to claim 1, and comprising a fiberoptic which couples the light source to the optical element.

3. Apparatus according to claim 2, and comprising a reference detector which receives light that is substantially not modulated by the magnetic-field responsive element and which provides reference signals responsive thereto to the circuitry.

4. Apparatus according to claim 3, and comprising a reference fiberoptic coupled to the reference detector.

5. Apparatus according to claim 4, wherein the light source emits light at a detection wavelength, which is modulated by the magnetic-field responsive element, and element, and a reference wavelength, which is substantially not modulated thereby, and wherein the reference detector receives the light at the reference wavelength and provides the reference signal responsive thereto.

6. Apparatus according to claim 5, wherein the fiberoptic comprises a polarization preserving fiberoptic.

7. Apparatus according to claim 2 wherein the magnetic-field responsive optical element comprises a magneto-optic crystal.

8. Apparatus according to claim 7, and comprising a polarizing element for analyzing polarization rotation of the light by the magneto-optic crystal.

9. Apparatus according to claim 1, and comprising a magnetic field generator, which generates the external AC magnetic field together with a DC magnetic field.

10. Apparatus according to claim 1, wherein the signal processing circuitry processes the signals to measure a modulation thereof at the predetermined frequency.

11. Apparatus according to claim 1, wherein the signal processing circuitry tracks and records hysteresis of the magnetic-field responsive element.

12. Apparatus according to claim 1, wherein the object comprises a catheter inserted into the body of a subject.

13. A method for determining the position of an object, comprising:

fixing a magnetic field-responsive optical element to the object;

injecting light into the magnetic field-responsive optical element;

applying a modulated magnetic field to the object;

receiving light from the magnetic field-responsive optical element and detecting a modulation in the light responsive to the magnetic field;

analyzing the modulation to determine the position of the object.

14. A method according to claim 13, wherein fixing the magnetic field-responsive element to the object comprises fixing a magneto-optic material to the object.

15. A method according to claim 14, wherein injecting light into the magnetic field-responsive element comprises injecting polarized light into the magnetic field-responsive element.

16. A method according to claim 15, wherein detecting the modulation in the light comprises analyzing a polarization rotation of the light due to the material.

17. A method according to claims 16, wherein injecting light into the magnetic field-responsive element comprises coupling a light source to the magnetic field-responsive element with a fiberoptic.

18. An elongate medical probe, having proximal and distal ends, whose position is tracked within the body of a subject, comprising:

a magnetic-field responsive optical element adjacent to the distal end, which modulates light passing therethrough responsive to an externally-applied magnetic field; and

a fiberoptic coupled to receive modulated light from the optical element and convey it to the proximal end of the probe for analysis of the modulation.

19. A probe according to claim 18, wherein the optical element comprises a magneto-optical crystal.