Systems and methods implementing frequency-steered acoustic arrays for 2D and 3D imaging
View Patent ↗Frequency-steered acoustic arrays transmitting and/or receiving multiple, angularly dispersed acoustic beams are used to generate 2D and 3D images. Input pulses to the arrays are generally non-linear, frequency-modulated pulses. Frequency-steered acoustic arrays may be provided in one-dimensional linear and two dimensional planar and curvilinear configurations, may be operated as single order or multiple order arrays, may employ periodic or non-periodic transducer element spacing, and may be mechanically scanned to generate 2D and 3D volumetric data. Multiple imaging fields of view may generated in different directions by switching the polarity of phase-shifted array transducer elements. Multiple frequency-steered arrays arranged in an X-configuration provide a wide, contiguous field of view and multiple frequency steered arrays arranged in a T-configuration provide orthogonally oriented fields of view. Methods and systems for operating acoustic arrays in a frequency-steered mode in combination a mechanical beam steering mode, electronic time-delay and phase shift beam forming modes, and phase comparison angle estimation modes are also provided.
1. A multiple beam acoustic imaging system comprising: an acoustic pulse generator; a frequency steerable acoustic array comprising a plurality of acoustic transducer elements capable of transmitting and/or receiving frequency-steered acoustic beams having a field of view adjustable by frequency band selection, each transducer element being phase shifted with respect to neighboring elements; and an electronics structure electrically connected to the acoustic array that provides a common connection for multiple elements and communication with transmit and/or receiver control systems and electrodes; wherein signals generated by neighboring elements are phase shifted by 90° and the transmit system comprises a two channel arbitrary pulse generator/power amplifier subsystem to generate two signals and transformers to produce the phase-shifted signals from the two signals, and the receive system comprises transformers to combine sets of phase-shifted signals and an analog circuit to combine the resulting phase-shifted signals.
2. A multiple beam acoustic imaging system comprising:
an acoustic pulse generator;
a frequency steerable acoustic array comprising a plurality of acoustic transducer elements capable of transmitting and/or receiving frequency-steered acoustic beams having a field of view adjustable by frequency band selection, wherein the acoustic array comprises multiple sets of elements including a first set of elements arranged with a constant spacing d 1 between each element of the set and a second set of elements arranged with a constant spacing d 2 between each element of the set, wherein d 1 and d 2 are different; and
an electronics structure electrically connected to the acoustic array that provides a common connection for multiple elements and communication with transmit and/or receiver control systems and electronics.
3. A multiple beam acoustic imaging system of claims 1 , or 2 , wherein the acoustic pulse generator is capable of producing a broadband pulse selected from the group consisting of: an FM pulse, a scale-swept wavelet pulse train, a multi-wavelet pulse train, a multi-frequency pulse, and a pseudo-random, appended or overlapped series of sub-pulses matched to the array's scaled aperture function.
4. A multiple beam acoustic imaging system of claim 1 , wherein the frequency steerable acoustic array is formed as multiple stacked layers.
5. A multiple beam acoustic imaging system of claims 1 , or 2 , wherein the frequency steerable acoustic array has a configuration selected from the group consisting of: a one dimensional linear array having a flat profile; a one dimensional linear array having a curved profile; a two dimensional planar array having a generally flat profile; and a two dimensional curvilinear array having a curved profile.
6. A multiple beam acoustic imaging system of claims 1 , or 2 , wherein the electronics structure provides shading of transducer elements in the frequency steerable array and the array is operable as a shaded array in which a reduction in signal amplitude is applied moving from the center toward outer elements of the array.
7. A multiple beam acoustic imaging system of claims 1 , or 2 , wherein the array comprises a plurality of element sets and the electronics structure comprises a plurality of electronics channels, and wherein the electronics structure provides for switching interconnections between electronics channels and element sets within the frequency steerable array.
8. A multiple beam acoustic imaging system of claims 1 , or 2 , wherein the array is operable in an unshaded mode in which equivalent amplitude signals are applied to the array elements.
9. A multiple beam acoustic imaging system of claims 1 , or 2 , capable of generating a two dimensional image.
10. A multiple beam acoustic imaging system of claims 1 , or 2 , capable of generating a three dimensional image.
11. A multiple beam acoustic imaging system of claims 1 , or 2 , additionally comprising a matched filter bank to generate angular and range information from received signals.
12. A multiple beam acoustic imaging system of claims 1 or 2 , additionally comprising a signal processor capable of performing short-time Fourier Transform (STFT) signal analysis techniques.
13. A multiple beam acoustic imaging system of claims 1 or 2 , wherein the frequency steerable acoustic array has an order selected from the group consisting of m=½; m=¼; m=⅛, m= 1/16 and m=1/n, wherein m is the number or fraction of coherent wavelengths between two consecutive elements of the array and n is any positive or negative number.
14. A multiple beam acoustic imaging system of claims 1 or 2 , wherein the frequency steerable acoustic array is multi-order and has a combination of at least two orders selected from the group consisting of m=½; m=¼; m=⅛, m= 1/16 and m=1/n, wherein m is the number or fraction of coherent wavelengths between two consecutive elements of the array and n is any positive or negative number.
15. A multiple beam acoustic imaging system of claims 1 or 2 , additionally comprising a mechanical beam steering mechanism capable of scanning the array.