Claims
- 1. A transducer device for transmitting acoustic waves in response to an electrical signal comprising:
- a piezoelectric element having first and second surfaces and a first acoustic impedance, and further having an operating frequency; and
- means having an interface with said first surface for establishing a desired pattern of wave interference for acoustic waves that are originally directed toward said first surface and then redirected toward said second surface;
- said means including first and second sections having dissimilar acoustic impedances, said first acoustic impedance being more closely matched to said acoustic impedance of said second sections than to said acoustic impedance of said first sections;
- said first and second sections having generally planar proximal sides at said interface with said first surface of said piezoelectric element, said second sections having generally planar distal sides opposite to said proximal sides, each said distal side being parallel to said proximal side and separated therefrom by a distance equal to an integral odd multiple of a one-quarter wavelength of said operating frequency of said piezoelectric element;
- whereby said desired pattern of wave interference is formed such that acoustic energy reflected at said proximal sides of said first section is substantially 180.degree. out of phase with respect to acoustic energy reentering said piezoelectric element after being reflected at said distal sides of said second section.
- 2. The transducer of claim 1 wherein said proximal and distal sides of said second sections have a maximum width of two times a wavelength of said operating frequency.
- 3. The transducer of claim 1 wherein said proximal sides of said first and second sections at said interface are uniformly sized and define an alternating pattern.
- 4. The transducer of claim 3 wherein said alternating pattern is a checkerboard pattern of said proximal sides of said first and second sections.
- 5. The transducer of claim 1 wherein said first sections include a backing layer having a thickness extending from said interface and beyond said distal sides of said second sections, thereby containing said second sections within said backing layer.
- 6. A transducer device comprising:
- a piezoelectric element having an operating frequency;
- a backing member having a contact surface and having a rear surface opposite to said contact surface; and
- a plurality of delay elements embedded within said backing member, each said delay element having a first surface intersecting and being coplanar with said contact surface, thereby dividing said contact surface into areas exposing said backing member and areas exposing said delay elements;
- said contact surface being coupled to a side of said piezoelectric element and defining a first generally planar interface between said side of said piezoelectric element in contact with said areas exposing said backing member;
- each said delay element being coupled to said backing member at a generally planar second interface defined between said each delay element and said backing member, said second interfaces being parallel to said first interface, said second interfaces further being separated from said first interface by a distance less than a distance between said contact and rear surfaces of said backing member and being substantially equal to an integral odd multiple of a one-quarter wavelength of said operating frequency;
- said delay elements having an acoustic impedance that is different than an acoustic impedance of said backing member and that is substantially equal to an acoustic impedance of said piezoelectric element;
- whereby a portion of the acoustic energy of acoustic waves directed at said backing member is reflected at said first interface and at said second interfaces, said acoustic energy propagating through said piezoelectric element after being reflected at said first interface being substantially 180.degree. out of phase with respect to said acoustic energy reflected at said second interfaces.
- 7. The device of claim 6 wherein said delay elements are uniformly sized, each said delay element having a maximum width measurement of two times a wavelength of said operating frequency.
- 8. The device of claim 6 wherein said delay elements are uniformly spaced apart within said backing member such that said areas exposing said backing member and said areas exposing said delay elements have an alternating pattern.
- 9. The device of claim 8 wherein said areas exposing said backing member and said areas exposing said delay elements have a uniformly spaced checkerboard arrangement.
- 10. The device of claim 8 wherein said alternating pattern is an alternating pattern of stripes.
- 11. The device of claim 6 wherein said delay elements have a maximum width of two times a wavelength of said operating frequency.
CROSS REFERENCE TO RELATED APPLICATION
This is a continuation of application Ser. No. 08/198,727 filed on Feb. 18, 1994, now abandoned.
US Referenced Citations (3)
Foreign Referenced Citations (1)
Number |
Date |
Country |
0005857 |
Dec 1979 |
EPX |
Non-Patent Literature Citations (1)
Entry |
Hossack, J. A., et al., "Multiple Layer Transducers for Broadband Applications," 1991 Ultrasonics Symposium, IEEE, pp. 605-610. |
Continuations (1)
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Number |
Date |
Country |
Parent |
198727 |
Feb 1994 |
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