A 30-MHz, 3-D Imaging, Forward-Looking Miniature Endoscope Based on a 128-Element Relaxor Array

摘要

This work describes the design, fabrication, and characterization of a 128-element crossed electrode array in a miniature endoscopic form factor for real-time 3-D imaging. Crossed electrode arrays address some of the key challenges surrounding probe fabrication for 3-D ultra-sound imagingby reducing the number of elements required (2N compared with N-2). However, there remain practical challengesin packaginga high- frequencycrossedelectrode array into an endoscopic form factor. A process has been developed that uses a thinly diced strip of flex circuit to bring the back-side connections to common bond surface, which allows the final size of the endoscopetomeasure only 6mmx5 mm. An electrostrictive ceramic composite design was developed for the crossed electrode array. A laser dicing system was used to cut the 1-3 composite as well as etch the array electrodepattern. Asingle quarterwavelength Parylene matching layer made was vacuum deposited to finish the array. The electrical impedance magnitude of array elements on resonance was measured to be 49 Omega with a phase angle of -55.5 degrees. The finished array elements produced pulses with -6-dB two-way bandwidth of 60% with a 34-MHz center frequency. The average measured electrical crosstalk on the nearest neighboring element and next to nearest neighboring element was -37 and -29 dB, respectively. One- and two-way pulse measurements were completed to confirm the pulse polarity and fast switching speed. Preliminary 3-D images were generated of a wire phantom using the previously described simultaneous azimuth and Fresnel elevation (SAFE) compounding imaging technique.