Fiber-optic transducer apparatus

• US 5,107,847 A
• Filed: 06/08/1990
• Issued: 04/28/1992
• Est. Priority Date: 05/25/1983
• Status: Expired due to Term

• Current Assignee: Camino Neurocare, Inc.
• Original Assignee: Camino Laboratories, Inc.
• Inventors: Knute, Wallace L., Bailey, Wilber H.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Lacyk, John P.
• Application Number:
  US07/535,974
• Time in Patent Office: 690 Days
• Field of Search: 128/665-667, 128/675, 128/748, 250/230, 250/232, 250/578.1, 73/703, 73/705, 73/715, 73/727
• US Class Current: 600/488
• CPC Class Codes: A61B 5/02154 by optical transmission
• CPC Class Codes: G01D 3/02 with provision for altering or correcting the law of variation
• CPC Class Codes: G01D 3/0365 the undesired influence being measured using a separate sensor, which produces an influence related signal
• CPC Class Codes: G01L 9/0039 using photoelectric means

Abstract

A fiber-optic transducer apparatus, and a related method of manufacturing it, for particular use in medical applications such as invasive blood pressure and body temperature measurement. The apparatus includes a catheter comprised of a sheath and an enclosed first set of optical fibers for transmitting a light beam to and from the remote end of the catheter, where a transducer modulates it in accordance with the variable to be measured, e.g., blood pressure. A photosensor located at the near end of the catheter measures the modulated intensity of the returned beam, to produce a corresponding measurement signal. The catheter is further comprised of a second set of optical fibers located within the sheath, for transmitting a reference light beam to and from the remote end of the catheter. A second photosensor measures the intensity of the returned reference light beam, to produce a correction signal indicative of variations in transmittance caused by bending of the catheter. It is presumed that the effects of such bending are the same for the second set of optical fibers as for the first set, so the apparatus adjusts the measurement signal in accordance with the correction signal, to produce an adjusted measurement signal that is substantially insensitive to the effects of such bending.

Claims

1. In a measurement system having a transducer for measuring a predetermined variable, an optical processing apparatus comprising:

a light source positioned at a location remote from the transducer;

a transducer coupling means for modulating a light beam in accordance with the predetermined variable measured by the transducer;

first optical fiber means for receiving light from the light source, forming said received light into a light beam, transmitting said light beam to said transducer coupling means, receiving the modulated light beam from said transducer coupling means, and conducting said received, modulated light;

first photosensor means for receiving said modulated light conducted by the first optical fiber means and for producing a measurement signal indicative of the modulation of the light received from the first optical fiber means;

a reflector fixed in a position near, but separate from the transducer coupling means;

a reference-emitter optical fiber means for receiving light from the light source, and transmitting from its remote end the received light to said reflector;

a reference-return optical fiber means for receiving at its remote end light reflected by the reflector and conducting said received light;

wherein the reference-emitter and reference-return fiber means are substantially coextensive with the first optical fiber means;

second photosensor means for receiving said light conducted by the reference-return optical fiber means and for producing a correction signal indicative of the intensity of the light received from the reference-return optical fiber means; and

correction means for receiving the correction signal and adjusting the measurement signal in response thereto;

wherein said reflector encloses the remote ends of the reference-emitter and the reference-return optical fiber means.

2. Optical processing apparatus as defined in claim 1, wherein:

the first optical fiber means includes an emitter fiber means for directing the light beam at the transducer coupling means and a return fiber means for receiving light modulated by the transducer coupling means.

3. Optical processing apparatus as defined in claim 1, wherein:

the first optical fiber means includes;

an emitter fiber means having proximal and remote ends, for receiving at its proximal end light from the light source, forming said received light into the light beam and transmitting from its source end the light beam to the transducer coupling means;

a return fiber means having proximal and remote ends, for receiving at its remote end the light beam modulated by the transducer coupling means and conducting said received modulated light to the first photosensor means; and

the apparatus further includes a sheath surrounding the emitter, return, reference-emitter and reference-return fiber means.

4. Optical processing apparatus as defined in claim 3, further comprising:

a rigid termination sleeve,

attachment means for attaching the remote ends of the emitter fiber means, return fiber means and sheath to the rigid termination sleeve; and

a wire means located within the sheath and attached by the attachment means to the rigid termination sleeve, the wire means for reducing tensile stress applied to the emitter fiber means, return fiber means and sheath.

5. Optical processing apparatus as defined in claim 4, wherein:

the attachment means includes an epoxy material located within the sleeve which adheres to the sleeve and to the emitter and the return fiber means.

6. The optical processing apparatus of claim 1 wherein the reflector is disposed such that it is in contact with the remote ends of both the reference-emitter and the reference-return fiber means.

7. The optical processing apparatus of claim 6 wherein the reflector comprises a first layer of reflective material disposed in contact with the remote ends of both the reference-emitter and reference-return fiber means and a second layer of material which is substantially opaque.

8. The optical processing apparatus of claim 1 wherein the transducer coupling means comprises a reflecting surface for modulating the light beam.

9. In a measurement system having a transducer for measuring a predetermined variable, an optical processing apparatus comprising:

a light source positioned at a location remote from the transducer;

a transducer coupling means for modulating a light beam in accordance with the predetermined variable measured by the transducer;

a sheath;

first optical fiber means located within the sheath and including an emitter fiber means having proximal and remote ends for receiving at its proximal end light from the light source, forming said received light into a light beam and transmitting from its remote end said light beam at said transducer coupling means, and a return fiber means having a remote end for receiving the modulated light beam from the transducer coupling means and conducting said received modulated light;

first photosensor means for sensing the modulation of the light received by the return fiber means of the first optical fiber means and for producing a corresponding measurement signal;

light directing means fixed in position near but separate from the transducer coupling means for redirecting received light;

second optical fiber means located within the sheath and including a reference-emitter fiber means having proximal and remote ends for receiving at its proximal end light from the light source, and transmitting from its remote end said received light to the light directing means, and a reference-return fiber means having a remote end for receiving at its remote end light directed by the light directing means and conducting said received, directed light;

wherein the reference-emitter and reference-return fiber means are substantially coextensive with the first optical fiber means;

second photosensor means for sensing the intensity of the light conducted by the reference-return fiber means of the second optical fiber means and for producing a corresponding correction signal therefrom; and

correction means for adjusting the measurement signal in accordance with the correction signal thereby minimizing errors in the measurement signal caused by variations in the transmittance of the first optical fiber means;

wherein said light directing means encloses the remote ends of the reference-emitter and the reference-return optical fiber means.

10. Optical processing apparatus as defined in claim 9, further comprising:

a sleeve having an inside surface and an outside surface; and

epoxy means for rigidly securing the remote ends of the emitter fiber and return fiber of the first optical fiber means to the inside surface of the sleeve and for rigidly securing the remote end of the sheath to the outside surface of the sleeve.

11. Optical processing apparatus as defined in claim 10, wherein:

the sleeve is located beyond the remote ends of the reference-emitter fiber means and reference-return fiber means of the second optical fiber means;

the light directing means includes translucent epoxy means for bonding together the remote ends of the reference-emitter fiber means and the reference-return fiber means of the second optical fiber means.

12. Optical processing apparatus as defined in claim 10, and further including a wire located within the sheath and rigidly secured to the inside surface of the sleeve by the epoxy means, the wire being shorter in length than both the sheath and the first optical fiber means such that any tensile stress applied to the apparatus is withstood primarily by the wire.

13. The optical processing apparatus of claim 9 wherein the reflector is disposed such that it is in contact with the remote ends of both the reference-emitter and the reference-return fiber means.

14. The optical processing apparatus of claim 13 wherein the light directing means comprises a first layer of reflective material disposed in contact with the remote ends of both the reference-emitter and reference-return fiber means and a second layer of material which is substantially opaque.

15. The optical processing apparatus of claim 9 wherein the transducer coupling means comprises a reflecting surface for modulating the light beam.

16. In a measurement system having a transducer for measuring a predetermined variable, a fiber-optic processing apparatus comprising:

an elongated, generally cylindrical sheath having a remote end;

a light source positioned at a located remote from the transducer;

a first reflector means coupled to the transducer for used in modulating a light beam in accordance with the predetermined variable measured by the transducer;

first optical fiber means located within the sheath and including an emitter fiber means having proximal and remote ends for receiving at its proximal end a light beam from the light source, conducting said received light beam to the first reflector, and transmitting from its remote end the light beam to said first reflector, and a return fiber means having a remote end, for receiving at its remote end and returning reflected, modulated light from the first reflector;

a sleeve having an inside surface and an outside surface;

epoxy means for rigidly securing the remote end of the sheath to the outside surface of the sleeve and for rigidly securing the remote ends of the emitter fiber means and return fiber means of the first optical fiber means to the inside surface of the sleeve, in confronting relationship with the first reflector;

first photosensor means for sensing the intensity of the light returned by the return fiber means of the first optical fiber means and for producing a corresponding measurement signal;

a second reflector;

second optical fiber means located within the sheath and including a reference emitter fiber means having proximal and remote ends, for receiving at its proximal end a second beam from the light source, conducting said second beam and transmitting from its remote end the second light beam to the second reflector, and a reference-return fiber means having a remote end, for returning light reflected from the second reflector;

wherein the second optical fiber means are substantially coextensive with the first optical fiber means;

wherein the second reflector contacts and encloses the remote ends of the reference-emitter and reference-return fiber means of the second optical fiber means for directing a predetermined proportion of the second light beam from the reference-emitter fiber means to the reference-return fiber means;

wherein the sleeve is located beyond the remote ends of the reference-emitter fiber means and reference-return fiber means of the second optical fiber means;

second photosensor means for sensing the intensity of the reflected light beam returned by the second optical fiber means and for producing a corresponding correction signal;

correction means connected to the light source for controllably adjusting the intensity of the first and second light beams it produces in accordance with the correction signal, such that the second light beam returned by the second optical fiber means has a substantially constant intensity, thereby minimizing errors in the measurement signal caused by variations in the transmittance of the first optical fiber means; and

a wire located within the sheath and rigidly secured to the inside surface of the sleeve by the epoxy means, the wire being shorter in length than both the sheath and the first optical fiber means such that any tensile stress applied to the apparatus is withstood primarily by the wire.

17. The optical processing apparatus of claim 16 wherein the second reflector includes translucent epoxy means bonding together the remote ends of the reference-emitter fiber means and reference-return fiber means of the second optical fiber means.

18. The optical processing apparatus of claim 16 wherein the second reflector comprises a first layer of reflective material in contact with and facing towards the reference-return fiber means and a second layer of material which is substantially opaque.