Miniature transducer

• US 4,305,399 A
• Filed: 08/04/1980
• Issued: 12/15/1981
• Est. Priority Date: 10/31/1978
• Status: Expired due to Term

• Current Assignee: University of Western Australia
• Original Assignee: University of Western Australia
• Inventors: Beale, David G.
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US06/175,040
• Time in Patent Office: 498 Days
• Field of Search: 128/645, 128/646, 128/635, 128/652, 128/653, 128/676, 128/745, 128/748, 73/722, 73/728, 336/115-118
• US Class Current: 600/398
• CPC Class Codes: A61B 3/16 for measuring intraocular pressure, e.g. tonometers

Abstract

A pressure or force transducer capable of miniaturization. Preferably, the transducer takes the form of a "contact lens" and is applied to the eyeball to permit intra-ocular pressure to be measured.

Claims

1. A miniature pressure transducer, comprising:

a container forming a housing;

an aperture in said container;

first and second parallel, planar, and co-axial coils arranged in proximity to one another in said container and having a common permeable core passing therethrough;

said core being axially aligned with said aperture;

said second coil being secured to a member fixed relative to said housing;

said first coil being secured to said core and movable therewith relative to said aperture, said fixed member and said coil; and

resilient mounting means positioned between said core and said housing, supporting said core and said first coil for movement thereof relative to said fixed member and second coil without changing the volume within said container and maintaining said coils parallel and co-axial, and urging said core into a rest position relative to said fixed member and second coil in which one end of said core protrudes past said aperture;

said one end of said core being movable towards the interior of said container as said core moves from said rest position in response to a force applied to said one end of said core, said force being caused by pressure outside of said container whereby the change in spacing of said coils, and hence their remotely determinable resonant frequency, is directly proportional to a change in said outside pressure.

2. A transducer as claimed in claim 1, wherein:

said container comprises a cup-shaped cap adapted to be positioned on an eyeball;

said cup-shaped cap having a concave surface;

said fixed member forms part of said container and comprises an annular shelf centrally located on said concave surface of said cap; and

said aperture is centrally located in said shelf.

3. A transducer as claimed in claim 2, wherein:

said first coil is secured to the other end of said core; and

said second coil is interposed between said shelf and said first coil.

4. A transducer as claimed in claim 3, wherein:

said resilient mounting means comprises a membrane of resilient material secured to said shelf and said one end of said core, which membrane extends across and closes said aperture.

5. A transducer as claimed in claim 4, wherein:

said resilient material is selected from the group consisting of synthetic rubber and silicone rubber gel.

6. A transducer as claimed in claim 3, wherein:

said resilient mounting means comprises a body of resilient material interconnecting said first coil and the other end of said core with the interior of said container.

7. A transducer as claimed in claim 6, wherein:

said resilient material is selected from the group consisting of synthetic rubber and silicone rubber gel.

8. A transducer as claimed in claim 1, wherein:

said container includes vent means and the interior of said container communicates with the exterior of said container via said vent means.

9. An intra-ocular pressure transducer for the measurement of intra-ocular pressure in vivo, said transducer comprising:

a container forming a housing having an interior, and first and second co-axial coils and a co-axial substantially cylindrical permeable core therein;

said container comprising a cup-shaped cap having a concave surface adapted to be positioned on an eyeball, said concave surface having a central annular shelf with a central opening therethrough;

said core being located within said opening, having one end thereof extending through said opening and beyond said annular shelf, and having the other end thereof located interiorly of said container;

said first coil being secured to said other end of said core;

said second coil being secured to said annular shelf interiorly of said container, said coils being substantially planar and parallel; and

a mass of resilient material inter-connecting said core and said container, said core being longitudinally movable, in response to a force applied to said one end of said core by said eyeball, away from a rest position in which said coils abut each other to a position in which said coils are spaced apart but remain parallel to each other, said force being caused by pressure outside said container whereby the change in spacing of said coils, and hence their remotely determinable resonant frequency, is directly proportional to a change in said outside pressure.

10. A transducer as claimed in claim 9, wherein:

said mass of resilient material comprises a membrane covering said opening and enveloping said one end of said core, the material of said membrane being selected from the group consisting of synthetic rubber and silicone rubber gel.

11. A transducer as claimed in claim 9, wherein:

said mass of resilient material is disposed between the interior of said container and said other end of said core.

12. A transducer as claimed in claim 9, wherein:

said container includes a vent communicating the interior of said container with the exterior of said container.