Microfabricated ultrasonic transducer array for 3-D imaging and method of operating the same
A capacitive microfabricated transducer array used for 3-D imaging, with a relatively large elevation dimension and a bias control of the elevation aperture in space and time, confers the same benefits of mechanical translation, except that image cross-sections are electronically rather than mechanically scanned, and are registered very accurately in space. The 3-D cMUT, when combined with elevation bias control and convex curvature in elevation, increases the volume interrogated by the electronic scanning, thus improving field of view. Further still, the 3-D cMUT can be combined Fresnel focusing of the elevation section to improve the elevation focus.
1. A method of obtaining imaging data for rendering a 3-d image using a capacitive microfabricated transducer array having a plurality of transducer elements, and a plurality of transducer sub-elements within each transducer element that correspond to a plurality of elevation apertures, wherein adjacent sub-elements within the plurality of transducer elements correspond to the same elevation aperture and wherein each transducer sub-element includes at least one transducer cell, the method comprising the steps of:
selecting at least one of the plurality of elevation apertures;
scanning the transducer array at the selected one elevation aperture, the step of scanning including:
biasing transducer sub-elements in order to substantially turn off elevation apertures other than the selected elevation apertures;
detecting image data from the selected one elevation aperture; and
outputting the detected image data; and
repeating the steps of selecting and scanning for a plurality of different elevation apertures in order to provide the imaging data required for rendering of the 3-d image.
2. The method according to claim 1 , wherein the step of selecting selects only one of the plurality of elevation apertures, and the step of scanning includes biasing transducer sub-elements in order to substantially turn off all elevation apertures other than the selected one elevation aperture.
3. The method according to claim 2 wherein the biasing of each elevation aperture applies a zero bias to each transducer cell that is not associated with the selected one elevation aperture.
4. The method according to claim 2 wherein the biasing of each elevation aperture applies a large bias to pin a vibrating drum associated with each transducer cell that is not associated with the selected one elevation aperture.
5. The method according to claim 2 wherein the biasing of each elevation aperture applies an alternating bias to elevation row bias lines associated with the selected one elevation aperture.
6. The method according to claim 1 , wherein a size of the selected at least one elevation aperture increases over a period of time during which the step of detecting takes place.
7. The method according to claim 6 , wherein an adjacent elevation aperture is used to increase the size of the selected one elevation aperture.
8. The method according to claim 1 , wherein the step of outputting uses a same output circuitry for output of the image data associated with each different elevation aperture.
9. The method according to claim 1 wherein the step of scanning the selected one elevation aperture further includes Fresnel focusing to improve the elevation focus, the Fresnel focusing inverting by 180 degrees the bias amplitude of certain elevation row bias lines associated with the selected one elevation aperture.
10. The method according to claim 1 , wherein the step of selecting selects a plurality of different elevation apertures, and, wherein each of the selected elevation apertures encode received data differently.
11. The method according to claim 10 , wherein the step of scanning further includes transmit firings of differing frequency bands for each of the different elevation apertures, and each different elevation aperture encodes receive data by frequency band.
12. The method according to claim 1 , further including a step of curving the transducer array such that a same curvature is maintained during the steps of scanning and detecting.
13. An apparatus capable of obtaining image data for rendering a 3-d image comprising:
a capacitive microfabricated transducer array having a plurality of transducer elements, and a plurality of transducer sub-elements within each transducer element that correspond to a plurality of elevation apertures, wherein adjacent sub-elements within the plurality of transducer elements correspond to the same elevation aperture and wherein each transducer sub-element includes at least one transducer cell, and wherein each of the plurality of transducer sub-elements has an aperture size that allows for obtaining a slice of image data for a predetermined frequency band of interest; and
means for scanning the array at different elevational apertures to obtain slices of the image data required for rendering of the 3-d image;
wherein the means for scanning includes a biasing circuit that biases certain transducer sub-elements within the elevation aperture currently being scanned, and substantially turns off elevation apertures other than the elevation aperture currently being scanned.
14. The apparatus according to claim 13 further including output circuitry that outputs detected image data, the same output circuitry being used for the output of the image data associated with each different elevation aperture.
15. The apparatus according to claim 13 wherein the transducer array is curved.
16. The apparatus according to claim 13 further including a plurality of elevation row bias lines associated with each sub-element, and wherein the bias amplitude of certain of the elevation row bias lines is inverted by 180 degrees to achieve Fresnel focusing.
17. The apparatus according to claim 13 wherein the means for scanning includes means for increasing the aperture size over a period of time during which detection of the image data associated with one elevation aperture takes place.