METHOD AND APPARATUS FOR AIR-COUPLED TRANSDUCER

• US 20090158851A1
• Filed: 05/24/2006
• Published: 06/25/2009
• Est. Priority Date: 05/24/2005
• Status: Active Grant

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: Song, Junho, Chimenti, Dale E.
• Granted Patent: US 7,759,842 B2
• Time in Patent Office: Days
• US Class Current: 73/644
• CPC Class Codes: B06B 1/0292 Electrostatic transducers, e.g. electret-type
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF
• CPC Class Codes: Y10T 29/49005 Acoustic transducer

Abstract

An air-coupled transducer includes a ultrasonic transducer body having a radiation end with a backing fixture at the radiation end. There is a flexible backplate conformingly fit to the backing fixture and a thin membrane (preferably a metallized polymer) conformingly fit to the flexible backplate. In one embodiment, the backing fixture is spherically curved and the flexible backplate is spherically curved. The flexible backplate is preferably patterned with pits or depressions.

Claims

1. A non-contact ultrasound transducer, comprising:

a ultrasonic transducer body having a radiation end;

a backing fixture at the radiation end;

a flexible backplate conformingly fit to the backing fixture; and

a thin metalized polymer membrane conformingly fit to the flexible backplate.

2. The non-contact ultrasound transducer of claim 1 wherein the backing fixture is spherically curved and the flexible backplate is spherically curved.

3. The non-contact ultrasound transducer of claim 1 wherein the thin metalized polymer membrane comprises a mylar film covered by an aluminum metallization.

4. The non-contact ultrasound transducer of claim 1 wherein the flexible backplate comprises a copper layer and a polymide foil.

5. The non-contact ultrasound transducer of claim 1 wherein the flexible backplate is patterned with depressions.

6. The non-contact ultrasound transducer of claim 5 wherein the depressions are circular depressions.

7. The non-contact ultrasound transducer of claim 5 wherein the depressions are fabricated by wet etching.

8. The non-contact ultrasound transducer of claim 5 wherein the depressions are sized and spaced to increase signal amplitude.

9. The non-contact ultrasound transducer of claim 5 wherein the depressions are pits having a center-to-center spacing, a pit diameter, and a pit depth.

10. The non-contact ultrasound transducer of claim 9 wherein the center-to-center spacing is about four times the center-to-center spacing is approximately equal to four times the pit diameter to thereby improve sensitivity of the non-contact ultrasound transducer.

11. The non-contact ultrasound transducer of claim 1 wherein the backplate is adhered to the backing fixture.

12. The non-contact ultrasound transducer of claim 1 wherein the non-contact ultrasound transducer is focused without use of mirrors or zone plates.

13. A method of manufacturing a capacitive air-coupled transducer having a backing fixture, comprising;

conformingly fitting a flexible backplate to the backing fixture;

conformingly fitting a thin metalized polymer membrane to the flexible backplate.

14. The method of claim 13 wherein the backing fixture is spherically shaped.

15. The method of claim 15 wherein the flexible backplate is fit over a warm spherical ball bearing to set the shape.

16. A non-contact ultrasound transducer, comprising:

a ultrasonic transducer body having a radiation end;

a backing fixture at the radiation end;

a flexible backplate conformingly fit to the backing fixture; and

a polymer membrane conformingly fit to the flexible backplate.

17. A method for optimizing performance characteristics of a capacitive air-coupled transducer back plate, comprising:

patterning the backplate with pits having a center-to-center spacing, and each pit having a pit diameter and a pit depth;

wherein the center-to-center spacing is selected to be substantially equal to four times the pit diameter.

18. The method of claim 17 wherein the backplate is a flexible backplate.

19. A non-contact ultrasound transducer, comprising:

a ultrasonic transducer body having a radiation end;

a backing fixture at the radiation end;

a flexible backplate conformingly fit to the backing fixture; and

a membrane operatively connected fit to the flexible backplate.

21. The non-contact ultrasound transducer of claim 19 wherein the membrane is an integral membrane.

22. The non-contact ultrasound transducer of claim 19 wherein the membrane is polarized through application of a high voltage.

23. The non-contact ultrasound transducer of claim 22 wherein the polarized membrane retains a permanent bias voltage on the membrane after the external voltage is removed.

24. The non-contact ultrasound transducer of claim 23 wherein the permanent bias eliminates the need for an external bias source during operation of the transducer thereby assisting in the ease and convenience of use of the transducer.

20. The non-contact ultrasound transducer wherein the membrane is a polymer membrane.

25. A non-contact ultrasound transducer, comprising:

a ultrasonic transducer body having a radiation end;

a backing fixture at the radiation end;

a flexible backplate conformingly fit to the backing fixture;

a thin metallized polymer membrane conformingly fit to the flexible backplate; and

the flexible backplate further comprising, a first and a second adjoining adjacent layers, the first layer having a top surface;

a pattern on the top surface; and

a plurality of adjacently spaced pits on the surface formed using the pattern.

26. A method of manufacturing a capacitive air-coupled transducer having a spherically shaped flexible backplate, comprising;

conformingly fitting a thin metalized polymer membrane to the flexible backplate by applying a biased voltage to the backplate;

conformingly fitting the flexible backplate having a first and second adjoining adjacent layers to a backing fixture;

the method of forming the backplate further comprising;

(a) providing a top surface on the first layer;

(b) forming a removable pattern on the top surface;

(c) creating a plurality of adjacently spaced pits on the top surface using the pattern; and

(d) removing the pattern from the top surface adjacent the pits.

27. The method of claim 26 further comprising conforming the thin metallized polymer membrane to a ball bearing having a radius of curvature equal to the top surface of the backplate.

28. The method of claim 27 further comprising heating the membrane conformingly fit to the ball bearing for creating a sphere.

29. The method of claim 28 wherein the membrane is conforming fit to the ball bearing using a panel member with an aperture radius equal to the ball bearing, pushing the bearing with the membrane into the aperture to evenly distribute hoop stress about the membrane to assist in removing wrinkles from the membrane.

30. The method of claim 29 wherein the first layer is a copper layer and the second layer is a polymide foil layer.