Method of making a miniature, high efficiency dual frequency ultrasonic transducer

• US 5,740,596 A
• Filed: 12/02/1996
• Issued: 04/21/1998
• Est. Priority Date: 01/06/1994
• Status: Expired due to Term

• Current Assignee: Volcano Corporation (Koninklijke Philips N.V.)
• Original Assignee: Cardiometrics, Inc. (JOMED NV)
• Inventors: Corl, Paul D., Chechelski, Victor, Pao, Michael C., Barletta, Vincent A.
• Primary Examiner(s): Hall, Carl E.
• Application Number:
  US08/759,054
• Time in Patent Office: 505 Days
• Field of Search: 310/369, 310/334, 29/25.35
• US Class Current: 29/25.35
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: B06B 1/0644 using a single piezoelectric element B06B1/0688 takes precedence
• CPC Class Codes: B06B 1/0655 of cylindrical shape
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

Ultrasonic transducer with a selectable beamwidth comprising a body of piezoelectric material in the form of an annulus having an outer diameter D and a thickness T. The body has proximal and distal generally planar parallel surfaces and a centrally disposed hole extending therethrough. The body has a cylindrical wall with a width W extending from the hole to the outer diameter. The transducer is capable-of operating at low and high resonance frequencies with the low frequency resonance being determined by the diameter D and an aspect ratio of D/T and the high frequency resonance being determined by the thickness T and an aspect ratio of W/T.

Claims

1. In a method of manufacturing a miniature ultrasonic transducer for use in a liquid carrying vessel, the steps of:

forming a body of piezoelectric material in the shape of an annulus having a central opening, an outer diameter D no greater than about 0.018 inch, and a pair of annular end surfaces of width W separated by a thickness T, dimensioning the diameter D and an aspect ratio D/T to provide a strong low frequency resonant mode of operation, and dimensioning the thickness T and an aspect ratio W/T to provide a strong high frequency resonant mode of operation.

2. The method of claim 1 wherein the diameter D and the aspect ratio D/T are selected to provide low frequency resonance at a frequency on the order of 6.0 to 6.5 MHz.

3. The method of claim 1 wherein the thickness T and the aspect ratio W/T are selected to provide high frequency resonance at a frequency on the order of 10 to 15 MHz.

4. The method of claim 1 wherein the body is formed with a generally cylindrical outer surface and generally planar proximal and distal end surfaces.

5. The method of claim 4 wherein the body is cut by a laser from a sheet of piezoelectric material, and the generally cylindrical outer surface and the hole are tapered.

6. The method of claim 1 wherein the diameter D and the aspect ratio D/T to are dimensioned to produce a beam having a width of approximately 60°

at the low frequency resonance, and the thickness T and the aspect ratio W/T to are dimensioned to produce a beam having a width of approximately 30°

at the high frequency resonance.

7. The method of claim 1 further including the steps of connecting means to the body for selectively supplying low frequency excitation signals and high frequency excitation signals to the transducer to control the width of a beam produced by the transducer.

8. The method of claim 7 wherein the width of the beam produced by the high frequency resonance is on the order of 30°

and the width of the beam produced by the low frequency resonance is on the order of 60°

.

9. The method of claim 1 further including the steps of positioning the transducer in a vessel, selecting a first frequency for operation of the transducer to provide a first beamwidth and thereafter selecting a second frequency for excitation of the transducer to provide a second beamwidth which subtends a greater angle than the first beamwidth.

10. The method of claim 9 wherein first and second beamwidths are utilized to ensure that the sample volume being measured includes the center of the vessel in which the measurement is being made.